U.S. patent application number 10/037630 was filed with the patent office on 2003-06-26 for incorporation of drilling cuttings into stable load-bearing structures.
Invention is credited to Scott, J. Blake.
Application Number | 20030116887 10/037630 |
Document ID | / |
Family ID | 26714325 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030116887 |
Kind Code |
A1 |
Scott, J. Blake |
June 26, 2003 |
Incorporation of drilling cuttings into stable load-bearing
structures
Abstract
Cuttings from drilling through or into natural rock and/or soil
can be incorporated into useful, high quality load-bearing
structures such as vehicle roads and pads for deep drilling rigs.
This process recycles a material previously regarded as valueless
at best and often as a pollution hazard. The cuttings, optionally
mixed with drilling mud and/or soil, are converted to the useful
structures by pozzolanic and/or cementitious reactions after being
mixed with suitable other materials and/or are bonded into the
useful structures by asphaltic materials.
Inventors: |
Scott, J. Blake; (Longview,
TX) |
Correspondence
Address: |
DANN DORFMAN HERRELL & SKILLMAN
SUITE 720
1601 MARKET STREET
PHILADELPHIA
PA
19103-2307
US
|
Family ID: |
26714325 |
Appl. No.: |
10/037630 |
Filed: |
January 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60311439 |
Aug 10, 2001 |
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Current U.S.
Class: |
264/333 |
Current CPC
Class: |
Y02W 30/91 20150501;
C04B 18/049 20130101 |
Class at
Publication: |
264/333 |
International
Class: |
C04B 007/00 |
Claims
The invention claimed is:
1. A process for constructing load-bearing structures incorporating
drilling cuffings, said process comprising operations of: (1)
forming a particulate mixture comprising drilling cuttings; and (2)
at least one of groups (2.1) and (2.2) of suboperations, said group
(2.1) comprising suboperations of: (2.1.1) mixing said particulate
mixture comprising drilling cuttings in a specified proportion with
at least one stabilizer selected from the group consisting of: (A)
quicklime; (B) hydrated lime; (C) Portland Cement; (D) Class C fly
ash; (E) cement kiln dust; (F) lime kiln dust; (G) Class F fly ash;
and (H) other pozzolans to form a cementitious second mixture;
(2.1.2) forming said cementitious second mixture into the shape and
size of the desired load-bearing structure; and (2.1.3) causing the
shaped and sized second mixture formed in suboperation (2.1.2) to
undergo a pozzolanic reaction to form said load-bearing structure;
and said group (2.2) comprising suboperations of: (2.2.1) mixing
said particulate mixture comprising drilling cuttings in a
specified proportion with at least one of foamed asphalt and
emulsified asphalt to form an asphaltic second mixture; (2.2.2)
forming said asphaltic second mixture into the shape and size of
the desired load-bearing structure; and (2.2.3) causing the shaped
and sized asphaltic second mixture formed in suboperation (2.2.2)
to form the load-bearing structure by removal from said shaped
asphaltic second mixture of a sufficient fraction of the gas
dispersed in any foamed asphalt incorporated into said second
mixture and of the liquid continuous phase in which any emulsified
asphalt incorporated into said shaped second mixture is
emulsified.
2. A process according to claim 1, wherein at least 10 percent by
mass of said particulate mixture are deep drilling cuttings that
have been generated by a process comprising the following
suboperations: (1.1) providing drilling means, drilling driving
means that cause the drilling means to operate at the bottom of a
borehole, and drilling mud; and (1.2) causing said drilling driving
means to drive said drilling means while said drilling mud flows
into and out of said borehole through separate passageways disposed
so as to insure that mud pumped into the borehole must reach the
near vicinity of the drilling means that is deepening, widening,
and/or otherwise increasing the volume of said borehole before the
mud can enter any passageway through which a mixture of mud and
cuttings flows out of the borehole during drilling, said mixture of
mud and cuttings, optionally after removal therefrom of all or part
of the constituents of said mixture that are not cuttings,
constituting said deep drilling cuttings.
3. A process according to claim 2, wherein at least part of the
deep drilling cuttings have been produced by drilling with a
water-based drilling mud.
4. A process according to claim 3, said process comprising group
(2.1) of suboperations.
5. A process according to claim 4, wherein said stabilizer is
selected from the group consisting of quicklime, hydrated lime,
Portland Cement, Class C fly ash, and mixtures of Class C fly ash
with Portland Cement.
6. A process according to claim 5, wherein: said stabilizer is a
mixture of Class C fly ash with Portland Cement; and suboperation
(2.1.1) is accomplished in two stages, in the first of which Class
C fly ash is mixed with said particulate mixture comprising
drilling cuttings and in the second of which Portland Cement is
mixed into the mixture previously formed by mixing Class C fly ash
with said particulate mixture comprising drilling cuttings.
7. A process according to claim 6, wherein, based on the
particulate mixture comprising drilling cuttings to be stabilized:
the amount of Portland Cement used as a stabilizer is at least
1.0%; the amount of Class C fly ash used as a stabilizer is at
least 2.0%; and the ratio of the amount of Class C fly ash used as
a stabilizer to the amount of Portland Cement used as a stabilizer
is at least 0.50:1.0 but is not more than 10:1.0.
8. A process according to claim 2, wherein at least part of the
deep drilling cuttings have been produced by drilling with an
oil-based drilling mud.
9. A process according to claim 8, said process comprising group
(2.1) of suboperations.
10. A process according to claim 9, wherein said stabilizer is
selected from the group consisting of quicklime, hydrated lime,
Portland Cement, Class C fly ash, fluidized bed fly ash, and
mixtures of either Class C or fluidized bed fly ash with Portland
Cement.
11. A process according to claim 10, wherein: said stabilizer is a
mixture of Class C or fluidized bed fly ash with Portland Cement;
and suboperation (2.1.1) is accomplished in two stages, in the
first of which C fly ash is mixed with said particulate mixture
comprising drilling cuttings and in the second of which Portland
Cement is mixed into the mixture previously formed by mixing fly
ash with said particulate mixture comprising drilling cuttings.
12. A process according to claim 11, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
13. A process according to claim 10, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
14. A process according to claim 7, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
15. A process according to claim 6, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
16. A process according to claim 5, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
17. A process according to claim 4, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
18. A process according to claim 3, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
19. A process according to claim 2, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
20. A process according to claim 1, wherein said load-bearing
structure has an unconfined compressive strength of at least 100
psi and has a thickness of: at least 8 inches if constructed on a
subgrade with a resilient modulus that is at least 15.0 kpsi; at
least 12 inches if constructed on a subgrade with a resilient
modulus that is at least 10.0 kpsi but less than 15.0 kpsi; and, at
least 16 inches if constructed on a subgrade with a resilient
modulus that is at least 5.0 kpsi but less than 10.0 kpsi.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Priority under 35 U.S.C. .sctn. 119(e) from application Ser.
No. 60/311,439 filed Aug. 10, 2001 is claimed for this
application.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] Drilling through or into natural soil and/or rock is
performed in a variety of ways to serve practical ends. Any such
drilling converts initially continuous solid soil and/or rock into
particulate solid matter called "drilling cuttings," which have
heretofore been generally regarded in the art as waste material to
be disposed of as inexpensively as possible. Hereinafter, the term
"drilling cuttings" and any of its grammatical variations shall be
understood to mean such cuttings produced by drilling through
and/or into natural soil or rock.
[0004] For practical reasons, drilling through or into natural soil
and/or rock is commonly divided into two kinds: "shallow" and
"deep." Relatively shallow drilling with a variety of means known
in the art is used, for example, in construction of building
foundations and mining excavations and in making water wells in
areas where the water table is no more than a few tens of feet
below the natural soil surface. Shallow drilling, simply because it
is shallow, produces relatively low petroleum and/or natural gas
often generates large volumes of cuttings. Therefore, even the most
inexpensive possible disposition of the cuttings as waste,
specifically burial of the cuttings in soil, often incurs a
substantial expense.
[0005] Practical deep drilling normally requires more elaborate
equipment than is usually used for shallow drilling. More
specifically, deep drilling equipment normally comprises at least
the following three conceptual entities:
[0006] drilling means, which, after the first few meters of
drilling are within the hole being drilled (the "borehole") and are
in physical contact with the solid soil and/or rock at the portion
of the borehole that is to be enlarged during the next interval of
drilling, and which, when suitably driven, convert the volume of
solid material that corresponds to the enlargement of the borehole
during this particular interval of drilling into particles
sufficiently small to be readily removed from the borehole and
transported to the earth's surface;
[0007] drilling driving means that supply the energy needed to
cause the drilling means to provide actual drilling; and
[0008] a fluid lubricant for the drilling means.
[0009] (Although these entities are conceptually distinct, the same
physical material may serve as all or part of two or more of them,
and in practice the lubricant is probably more often than not also
a hydraulic fluid that acts as part of the drilling driving means.)
The phrase "deep drilling" when used hereinafter in this
specification shall be understood to mean drilling performed by
equipment comprising said drilling means, drilling driving means,
and fluid lubricant for the drilling means.
[0010] The currently most commonly used deep drilling means are
various types of rotary drill bits well known in the drilling art.
In once widely practiced and still sometimes used "cable tool"
drilling, the drilling means are essentially a hammer that is
repeatedly lifted and dropped within the borehole in order to
deepen it. In some laboratories today, laser light is being tested
as a drilling means, and shock waves propagated through air or
other fluids could reasonably be used as drilling means.
[0011] Typical deep drilling driving means may be: a solid
structure of pipe or cable connected mechanically to the drilling
means and rotated, or alternatively lifted and dropped, by motive
power supplied at the surface so that the motion of the solid
connecting structure is mechanically transferred to the drilling
means; a combination of a hydraulic fluid, fluid transport means,
and a pump that drives the hydraulic fluid, so that the motion of
the hydraulic fluid, by its passage through suitably designed
passageways in a rotary drill bit, forces the components of the bit
to move in a manner that converts any coherent solid material
adjacent to the rotary drill bit into particulates; a source of
radiation that is absorbed by the surface of a volume of solid to
be added to the volume of the borehole, the absorbing solid surface
and part of the solid underlying it being thereby rapidly heated
and caused to fracture by heating-induced expansion; and/or means
for propagating mechanical shock waves through a fluid in contact
with the surface of a volume of solid to be added to the volume of
the borehole.
[0012] The least expensive possible deep drilling lubricant is the
air of the natural atmosphere, and this is actually used in
practice in some instances. Another established deep drilling
lubricant is a foam of air in a continuous liquid phase, usually
preponderantly of water. However, practical deep drilling for oil
and/or natural gas in most locations in the world that are now
being explored requires use of a viscous liquid lubricant that
comprises, preferably consists essentially of, or more preferably
consists of at least one continuous liquid phase and at least one
type of dispersed solid particles, most often a clay (such as
sodium montmorillonite) that has a sufficiently fine particle size
and sufficiently hydrophilic particle surfaces that the clay
spontaneously disperses in most aqueous based liquids. (In
oil-based lubricants and some water-based ones, additional
surfactants are usually added to promote suspension of the clay
and/or other solid constituents such as high density,
water-insoluble "wetting agents" in the fluid.) Additional detailed
information about deep drilling fluids is given in, e.g., H. C. H.
Darley and George R. Gray, Composition and Properties of Drilling
and Completion Fluids, 5th Ed. (Gulf Publishing Co., Houston,
1988), the entire disclosure of which, except for any part that may
be contrary to an explicit statement herein, is hereby incorporated
herein by reference. This deep drilling lubricant, when
preponderantly liquid and often even when preponderantly gaseous,
is generally called "drilling mud" or simply "mud" by those who use
it, and the word "mud" when used below in this specification shall
be understood to mean deep drilling mud or another deep drilling
fluid unless expressly stated to the contrary or required by the
context.
[0013] Mud normally is pumped continuously into and flows
continuously out of a borehole whenever deep drilling is underway.
The mud flows into and out of the borehole through separate
passageways that are disposed so as to insure that mud pumped into
the borehole must reach the near vicinity of the drilling means
that is actually cutting a borehole deeper during drilling before
the mud can enter any passageway through which mud flows out of the
borehole during drilling. The mud serves to cool and lubricate the
drilling means and to remove from the borehole soil and/or rock in
the form of particles cut by the drilling means, such particles
being commonly called "cuttings". (If these cuttings were not
removed from the borehole, they would eventually clog the drilling
means and make continued drilling impossible.)
[0014] The oufflowing mixture of mud and cuttings from deep
drilling is normally subjected to at least one separation process
intended to separate the relatively large particle size cuttings
from the relatively fine clay and any other suspended particles
deliberately added as part of the drilling mud before it flows into
the borehole. The cuttings from this separation are generally more
or less wet with the fluid phase of the mixture of mud and cuttings
from which they were separated and may contain relatively small
portions of the dispersed and/or dissolved solids deliberately
added to the drilling mud before it flows into the borehole. Also,
the cuttings as thus separated may be and often are remixed with
all or part of the drilling mud used when deep drilling of a
particular hole has been completed. The solids volume of the
cuttings or mixture of the cuttings with no longer needed drilling
mud is usually at least several hundred cubic meters for each well
drilled to a depth of five thousand meters.
[0015] A major object of this invention is to convert and/or
incorporate mixtures of drilling cuttings, optionally mixed with
other constituents such as those of deep drilling mud, into stable
load-bearing structures.
BRIEF SUMMARY OF THE INVENTION
[0016] It has been found that drilling cuttings and mixtures of the
cuttings with drilling mud can be converted and/or incorporated
into excellent high-load-bearing civil engineering structures such
as vehicle roads and drilling pads by one or more processes as
described in detail below. Embodiments of the invention include
processes for such conversion, extended processes including
additional operations that may be conventional in themselves, and
the load-bearing structures made by a process according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
[0017] A shaped load-bearing structure according to the invention
is made by a process comprising, preferably consisting essentially
of, or more preferably consisting of, the following operations:
[0018] (1) forming a particulate mixture comprising drilling
cuttings; and
[0019] (2) at least one of groups (2.1) and (2.2) of suboperations,
said group (2.1) comprising suboperations of:
[0020] (2.1.1) mixing said particulate mixture comprising drilling
cuttings in a specified proportion with at least one material
selected from the group consisting of:
[0021] (A) quicklime;
[0022] (B) hydrated lime;
[0023] (C) Portland Cement;
[0024] (D) Class C fly ash;
[0025] (E) cement kiln dust;
[0026] (F) lime kiln dust;
[0027] (G) Class F fly ash; and
[0028] (H) other pozzolans to form a cementitious second
mixture;
[0029] (2.1.2) forming said cementitious second mixture into the
shape and size of the desired load-bearing structure; and
[0030] (2.1.3) causing the shaped and sized second mixture formed
in suboperation (2.1.2) to undergo a pozzolanic reaction to form
said load-bearing structure; and said group (2.2) comprising
suboperations of:
[0031] (2.2.1) mixing said particulate mixture comprising drilling
cuttings in a specified proportion with at least one of foamed
asphalt and emulsified asphalt to form an asphaltic second
mixture;
[0032] (2.2.2) forming said asphaltic second mixture into the shape
and size of the desired load-bearing structure; and
[0033] (2.2.3) causing the shaped and sized asphaltic second
mixture formed in suboperation (2.2.2) to form the load-bearing
structure by removal from said shaped asphaltic second mixture of a
sufficient fraction of the gas dispersed in any foamed asphalt
incorporated into said second mixture and of the liquid continuous
phase in which any emulsified asphalt incorporated into said shaped
second mixture is emulsified.
[0034] Any material as described above that is mixed with the
particulate mixture comprising drilling cuttings in suboperation
(2.1.1) or (2.2.1) is denoted herein as a "stabilizer." Following
are the believed mechanism of stabilization for each stabilizer and
the basic advantages and limitations for each of the types of
stabilizers listed above, those types of stabilizers listed
explicitly above being preferred over other pozzolanic
stabilizers.
[0035] QUICK LIME AND HYDRATED LIME
[0036] Whether hydrated lime, i.e., Ca(OH).sub.2, or quick-lime,
i.e., CaO, is selected as a source of stabilization, it is believed
that hydrated lime is more effective for stabilization. Therefore,
if quicklime is selected as the source of stabilization, at an
early stage during the formation of the second mixture as described
in suboperations (2.1.1) and (2.2.1) above, the quicklime
preferably is transformed to hydrated lime through reaction with
adequate quantities of water. This water may derive from the
particulate mixture comprising drilling cuttings as described above
or may be added separately. Since the gram-molecular weight of
Ca(OH).sub.2 is approximately 74 and the gram-molecular weight of
CaO is approximately 56, the minimum mass of water required for
hydration is 34 percent of the mass of the CaO to be hydrated.
Practically, however, hydration, also called "slaking," of
quicklime is not usually 100 percent efficient within a reasonable
time. Under most conditions, therefore, the mass of the water
available for slaking any mass of quicklime used as a stabilizer in
a process according to the invention preferably is at least, with
increasing preference in the order given, 50, 60, 70, 80, 90, or
99% of the mass of the quicklime.
[0037] Lime is believed to stabilize primarily the clay fraction of
the first mixture of mud and cuttings to be stabilized with which
it is mixed to form a second mixture as described above. Therefore,
when lime is an important or the sole component of the stabilizing
agent used in a process according to this invention, the
particulate mixture comprising drilling cuttings to be stabilized
preferably comprises clay as a percentage of its solids content
that is at least, with increasing preference in the order given, 2,
4, 6, 8, 10, 12, 15, 20, or 25%. Independently, the particulate
mixture comprising drilling cuttings to be stabilized with lime in
a process according to the invention preferably has a Plasticity
Index (hereinafter usually abbreviated as "PI" and determined
according to American Society for Testing and Materials
(hereinafter usually abbreviated as "ASTM") Procedure D-4318) that
is at least, with increasing preference in the order given, 3, 5,
7, 9, 11, 13, 15, 20, 25, or 30 percent. Lime is believed to react
with the clay in the high pH environment created when lime and
water are mixed. In this environment, the silica and alumina
contents of the clay are believed to become sufficiently soluble,
as pozzolans, to react with the calcium and water to form
calcium-silicate-hydrates and calcium-aluminate-hydrates that are
cementitious products. (A pozzolan is defined as a high surface
area siliceous or alumino-siliceous material that in the presence
of an alkaline earth-containing alkali such as lime produces a
cementitious reaction.) This postulated reaction, along with
calcium exchange on clay surfaces, reduces the plasticity of,
improves the workability of, improves the drying and drainage of,
and provides a substantial strength gain for, the particulate
mixture comprising drilling cuttings to be stabilized.
[0038] The major advantages of lime are that: it vastly improves
the workability of highly plastic mixtures comprising cuttings to
be stabilized; and it reacts slowly enough to allow plenty of
mixing time -up to four days. The major limitation is that lime
does not react with soils that do not contain a reactive clay
fraction. Therefore, lime is not reactive with gravelly and sandy
soils without clay. Lime may not be reactive with sandy,
silty-sandy, and silty soils without reactive clay. However,
combinations of lime and fly ash can be effectively used to
stabilize these soils.
[0039] Portland Cement
[0040] The basic reactions in stabilization with Portland Cement
(hereinafter usually abbreviated as "PC") stabilization are
believed to be the cementitious, hydration reaction that occurs
when calcium silicates and calcium aluminates present in the
Portland Cement hydrate with added water. The strength gain is
independent of soil mineralogy, e.g., whether any clay is present
in the soil. However, some pozzolanic reaction between lime
released during the cementitious reaction and any clay that is
present in the particulate mixture comprising drilling cuttings to
be stabilized can and is believed to occur. Portland Cement
provides workability and strength improvements similar to those
achieved with lime. The major differences are that: PC usually
works better with low PI, granular soils, whereas lime works better
with higher PI, clayey soils; strength gain with PC is quicker than
with lime; and PC will usually provide a higher final strength than
lime in any structure made by stabilization in a process according
to this invention. The faster strength gain can be either an
advantage or a disadvantage, depending on circumstance; it can be
an advantage in meeting a short construction schedule, but the
construction/shaping time is usually limited to four hours after
mixing in order to avoid significant strength loss. A second
limitation is a greater prevalence of significant shrinkage
cracking in structures stabilized with high percentages of PC.
[0041] Class C Fly Ash
[0042] Class C fly ash is a non-combustible residue of coal. This
residue is composed primarily of high surface area silicates and
aluminates and often contains calcium from calcium oxide naturally
present in the coal and/or added to abate air pollution by reacting
with gaseous oxides of sulfur generated by the combustion of some
coal. When water is added to Class C fly ash, any silicates and
aluminates in the fly ash that have been fused with calcium oxide
are believed to react as with PC to form cementitious products,
while the silicates and aluminates that have not previously been
fused with lime are believed to react as pozzolans if an outside
source of lime is added. Class C fly ash is accordingly believed to
stabilize cementitious second mixtures as described above through
combined processes of hydration and pozzolanic reactions that
result in improved workability of the second mixtures during
shaping and sizing and in increased shear strength in the cured
structure.
[0043] Fly ashes are quite variable and source dependent. Class C
fly ash for use in a process according to this invention preferably
has the following characteristics, each of these characteristics
being independently preferred and combinations of the
characteristics being still more preferred, the preference being
greater the greater the number of preferred characteristics
combined:
[0044] the percentage of the mass of the fly ash retained on a No.
325 sieve preferably is not more than, with increasing preference
in the order given, 34, 32, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12,
10, 8, 6, 4, or 2%;
[0045] the total content of
SiO.sub.2+Al.sub.2O.sub.3+Fe.sub.2O.sub.3 preferably constitutes a
percentage of the total mass of the fly ash that is at least, with
increasing preference in the order given, 50, 60, 65, 70, 75, 80,
85, 90, 95, or 99%;
[0046] the total content of sulfur, measured as its stoichiometric
equivalent as SO.sub.3, preferably is not more than, with
increasing preference in the order given, 5.0, 4.0, 3.0, 2.5, 2.0,
1.5, 1.0, 0.5, 0.3, or 0.1%; and
[0047] the loss on ignition of the fly ash preferably is not more
than, with increasing preference in the order given, 10, 8, 6, 4,
2.0, 1.5, 1.0, 0.5, 0.3, or 0.1%.
[0048] Class C fly ash is similar to PC in its ability to provide
high strength, its ability to provide stabilization even in the
absence of clay in the particulate mixture comprising drilling
cuttings to be stabilized, and in its fast strength development.
The principal advantage of Class C fly ash is that it can be
considerably less expensive than PC or lime if available from a
source near where a process according to the invention is
performed, and the principal disadvantage of Class C fly ash is its
variability in setting time, which requires more frequent testing
than with PC except in relatively rare instances where a
sufficiently large supply of the fly ash with consistent properties
is available.
[0049] Combinations of Lime and Fly Ash
[0050] Class F fly ash is a more or less pure pozzolan which
contains little or no alkaline earth metal content. Lime reacts
with Class F ash as it does with clay to produce a pozzolanic
reaction which can be of substantial value in strength development
in a shaped and sized secondary mixture as described above. Class F
ash and lime can be effectively used together to stabilize mixtures
of mud and cuttings with a wide range of mineralogical contents
ranging from clays to sands and gravels. Since a pozzolan is
contributed by the ash, clay is not required to react with the
lime.
[0051] Like Class C ash, Class F ash is variable from source to
source. Class F fly ash for use in a process according to this
invention preferably has the following characteristics, each of
these characteristics being independently preferred and
combinations of the characteristics being still more preferred, the
preference being greater the greater the number of preferred
characteristics combined:
[0052] the percentage of the mass of the fly ash retained on a No.
325 sieve preferably is not more than, with increasing preference
in the order given, 34, 32, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12,
10, 8, 6, 4, or 2%;
[0053] the total content of
SiO.sub.2+Al.sub.2O.sub.3+Fe.sub.2O.sub.3 preferably constitutes a
percentage of the total mass of the fly ash that is at least, with
increasing preference in the order given, 70, 75, 80, 85, 90, 95,
or 99%;
[0054] the total content of sulfur, measured as its stoichiometric
equivalent as SO.sub.3, preferably is not more than, with
increasing preference in the order given, 5.0, 4.0, 3.0, 2.5, 2.0,
1.5, 1.0, 0.5, 0.3, or 0.1%;
[0055] the loss on ignition of the fly ash preferably is not more
than, with increasing preference in the order given, 10, 8, 6, 4,
2.0, 1.5, 1.0, 0.5, 0.3, or 0.1%; and
[0056] the unconfined compressive strength (hereinafter usually
abbreviated as "UCS"), measured as described below, preferably is
at least, with increasing preference in the order given, 800, 850,
900, 950, 1000, 1050, 1100, 1, 1200, 1250, 1300, 1350, 1400, 1450,
or 1500 pounds per square inch (hereinafter usually abbreviated as
"psi").
[0057] The unconfined compressive strength of the fly ash is
measured on samples that have previously been mixed with lime
and/or Portland Cement in the same proportion between the fly ash
and lime and/or Portland Cement as is intended for the combination
to be used in stabilization. Tests on these mixtures are performed
in accordance with ASTM Procedure C-593 to determine the UCS
value.
[0058] Combinations of Class F fly ash and lime have advantages and
disadvantages similar to those of lime, except that: the need for
reactive clay in the particulate mixture comprising drilling
cuttings to be stabilized is removed by using Class F fly ash; the
variability of characteristics of all fly ash is introduced; and
the method of application can be varied to advantage in some
instances: Lime can be added first to clay-containing mixtures,
with the fly ash added later. The initial mixing of lime with the
clay will reduce plasticity and improve workability while the later
addition of fly ash will enhance strength. This may be superior to
lime stabilization alone in mixtures of mud and cuttings to be
stabilized, which, even though they may contain clay, do not react
rapidly enough with lime to produce sufficient pozzolanic strength
development for the purpose of a process according to this
invention.
[0059] Combinations of Class C or Fluidized Bed Fly Ash and
Portland Cement
[0060] These combinations are particularly advantageous in
two-stage processes according to the invention, in which the fly
ash is used as a drier in the first stage and the cement as an
activator in the second stage.
[0061] Other Cementitious and Pozzolanic Stabilizers
[0062] Besides lime, PC, and fly ash, other cementitious and
pozzolanic stabilizers which may be candidates for stabilization in
a process according to this invention include cement kiln dust
(hereinafter usually abbreviated as "CKD") and lime kiln dust
(hereinafter usually abbreviated as "LKD"). These materials are
by-products of cement and lime manufacture, respectively. CKD and
LKD are similar to a Class C fly ash in that they both contain some
self-cementing calcium-silicate (hereinafter usually abbreviated as
"CS") and calcium-aluminate (hereinafter usually abbreviated as
"CA") compounds. However, both types of kiln dust may have
considerable free lime, "free lime" being defined for this usage as
the total amount of calcium hydroxide and calcium oxide, both
measured as their stoichiometric equivalent as CaO, that are
present in the material in a form free to react cementitiously with
additional silicates and/or aluminates that may be mixed with the
material. LKD is generally higher in free lime and lower in CS and
CA products than CKD. The only advantage of CKD or LKD over lime,
PC, or fly ash is a lower cost. To provide a substantial cost
advantage in a process according to this invention, CKD and/or LKD
usually must be locally available near the process site. Both CKD
and LKD are quite variable.
[0063] Asphalt Emulsions and Foams
[0064] Asphalt emulsions consist essentially of fine particles of
asphalt emulsified in water. The emulsion is a sufficiently low
viscosity liquid to be mixed with a particulate mixture comprising
drilling cuttings to be stabilized at normal ambient field
temperatures (i.e., from about 0 to 50.degree. C.), whereas a
normal unemulsified asphalt would have to be heated to around
300.degree. C. in order to mix intimately with soil or aggregate.
The emulsified particles of asphalt preferably have an average
particle size (largest linear dimension) that is at least, with
increasing preference in the order given, 0.2, 0.5, 0.7, 1.0, 1.2,
1.4, 1.6, 1.8, or 2.0 micrometres (hereinafter usually abbreviated
as "m") and independently preferably is not more than, with
increasing preference in the order given, 30, 20, 15, 13, 11, 9, 7,
or 5 m. Dispersion in water is maintained by using at least one
emulsifying agent, the emulsifying-effective moieties of which may
have a positive or a negative charge or be electrically neutral.
Ordinarily, cationic emulsions (i.e., those in which the emulsified
asphalt particles have a positive charge) are preferred for use
with alkaline mixtures of mud and cuttings to be stabilized, while
anionic emulsions in which the emulsified asphalt particles have a
negative charge are preferred if the particulate mixture comprising
drilling cuttings to be stabilized are acidic. However, climatic
conditions also affect preferences because in a high humidity
environment, an anionic emulsion will not normally cure properly,
and curing of emulsions is very important to their success. Curing
involves first properly coating the aggregate or soil with the
emulsion and then removing the water in which the asphalt had been
dispersed from the asphalt by draining and/or evaporating the water
and leaving behind an asphalt coating of the aggregates. Adequate
curing occurs when the proper asphalt emulsion is selected and
proper construction methods are used to effect aeration of the
mixture during mixing. The residual asphalt then coats the
aggregate to provide a cohesive "glue" which in turn provides
stability and durability to the mixture.
[0065] Asphalt stabilization may, in some circumstances, be cheaper
than chemical stabilization. Asphalt is often preferred for
stabilizing relatively rare mixtures of mud and cuttings to be
stabilized that have little or no plasticity and/or have such a
high organic content that they cannot be stabilized with
economically practical amounts of pozzolanic or cementitious
materials. Foamed asphalt and emulsified asphalt should produce
essentially the same result. However, the technology for the use of
foamed asphalt is not widely developed.
[0066] A major limitation with asphalt stabilization is that if or
when it is desired to recycle a structure made in a process
according to this invention with asphalt stabilization to its
original or near original state, recycling will usually be more
complicated and correspondingly more expensive because of the
presence of the organic binder. On the other hand, calcium-based
pozzolanic stabilizers can be recycled to a near virgin state by
pulverization and mixing. The material will retain a relatively
high pH, between about 8 and 11, but this can be reduced through
dilution (mixing with virgin soil) if necessary. If the initial pH
is near the higher end of this range, the pH will even be
spontaneously reduced, at least in well-aerated parts of the
recycled material, by gradual conversion of more alkaline
calcium-containing substances to calcium carbonate by reaction with
atmospheric carbon dioxide.
[0067] Because of the highly variable nature of the particulate
mixtures comprising drilling cuttings to be stabilized and of some
of the stabilizers used (the fly ashes and kiln dusts), the
preferred amounts of stabilizers can be explicitly specified herein
only in rather broad terms as shown in Table 1 below for the most
important and preferred single and combination stabilizers.
However, with minimal experimentation that is well within ordinary
skill in the art, considerably narrower preferences for each
particular instance can be readily determined by one of the testing
protocols set forth below. The most desirable stabilizer(s) to be
tested initially can be readily determined by those skilled in the
art by consideration of the advantages and disadvantages of the
various stabilizers as described above, the required civil
engineering properties of the load-bearing structure to be made in
a process according to the invention, and the costs of the various
stabilizers at the site of the fabrication of the structure.
1TABLE 1 BROAD PREFERENCES FOR AMOUNTS OF PREFERRED STABILIZERS TO
BE USED Preferred Amount of Stabilizer, as a Percentage of Solids
in the Stabilizer to Solids in the Particulate Mixture Comprising
Drilling Stabilizer Cuttings to Be Stabilized Portland Cement (as
the At least, with increasing preference in the order given, 0.5,
1.0, 1.5, 2.0, 2.5, sole stabilizer) or 2.9% and independently
preferably not more than, with increasing preference in the order
given, 15, 12, 10, 8, or 6.0% Lime (as the sole At least, with
increasing preference in the order given, 1.0, 2.0, 2.5, 3.0, 3.5,
stabilizer) or 4.0% and independently preferably not more than,
with increasing preference in the order given, 20, 15, 12, 10, or
8% Lime and fly ash (as the Lime that is at least, with increasing
preference in the order given, 0.2, 0.5, sole stabilizers) 0.8,
1.0, 1.2, 1.4, 1.6, 1.8, or 2.0% and independently preferably is
not more than, with increasing preference in the order given, 9, 7,
5, or 3%; fly ash that is at least, with increasing preference in
the order given, 0.2, 0.5, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, or 2.0%
and independently preferably is not more than, with increasing
preference in the order given, 20, 17, 14, 12, 10, 8, or 6%; and,
independently, a ratio of fly ash to lime that is at least, with
increasing preference in the order given, 0.3:1.00, 0.5:1.00,
0.7:1.00, or 0.9:1.00 and independently preferably is not more
than, with increasing preference in the order given, 5:1.00,
3.0:1.00, 2.5:1.00, or 2.0:1.00 Class C and/or fluidized Fly ash
that is at least, with increasing preference in the order given,
0.2, 0.5, bed fly ash and Portland 0.8, 1.2, 1.6, 2.0, 2.4, 2.8,
3.2, 3.6, 4.0, 4.4, or 4.8% and independently Cement (as the sole
preferably is not more than, with increasing preference in the
order given, 50, stabilizers) 35, 30, 25, or 20, 17, 14, 11, or 9%:
Portland Cement that is at least, with increasing preference in the
order given, 0.5, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6,
or 2.8% and independently preferably is not more than, with
increasing preference in the order given, 15, 10, 8.5, 8.0, 7.5,
7.0, or 6.5%; and, independently, a ratio of fly ash to cement that
is at least, with increasing preference in the order given,
0.10:1.0, 0.20:1.00, 0.30:1.00, 0.35:1.00, 0.40:1.00, or 0.45:1.00
and independently preferably is not more than, with increasing
preference in the order given, 10:1.00, 8.0:1.00, 7.0:1.00,
6.0:1.00; 5.0:1.00, 4.5:1.00, 4.0:1.00, 3.5:1.00, 3.2:1.00,
3.0:1.00, or 2.8:1.00. Class C fly ash, lime At least, with
increasing preference in the order given, 0.5, 1.0, 1.5, 2.0, 2.5,
kiln dust, and/or cement or 3.0% and independently preferably not
more than, with increasing kiln dust (as the sole preference in the
order given, 30, 25, 20, 15, or 10% stabilizer(s)) Asphalt,
emulsified or At least, with increasing preference in the order
given, 0.5, 1.0, 1.5, 2.0, 2.5, foamed or 3.0% and independently
preferably not more than, with increasing preference in the order
given, 25, 20, 15, 12, 10, or 8%
TEST PROTOCOLS
Preliminary Tests--Visual Evaluation and Concentrations of
Interfering Constituents
[0068] The major objectives of visual evaluation are to estimate
the moisture content of the particulate mixture comprising drilling
cuttings to be stabilized, this moisture content being normally
quite high when a mud with an aqueous liquid continuous phase is
used, and to determine the presence or absence in the particulate
mixture comprising drilling cuttings to be stabilized of any
foreign, non-soil-like material such as organics, salt crystals,
especially sulfate salts, and/or the like. Thus the visual
identification screens the material for any constituents that are
unusual and/or require special stabilization strategies.
[0069] Sulfates can interfere with pozzolanic reactions and
cementitious reactions when calcium-based stabilizers are used,
causing a severely expansive reaction and loss of density and often
strength. For this reason, it is necessary to screen the cuttings
for the presence of soluble sulfates. If soluble sulfates are found
to be less than or equal to 3 parts per thousand by mass of the
solids content of the particulate mixture comprising drilling
cuttings to be stabilized, this unit of concentration being
hereinafter usually abbreviated as "ppt", there is no significant
risk of these adverse effects from sulfates during stabilization.
(The concentration of sulfates preferably should be determined on
the basis of Texas Department of Transportation Test Methods
TEX-620-J and TEX-619-J. The partitioning of soluble sulfates from
the cuttings that is part of these test procedures preferably is
done with ten parts water to one part soil.) If soluble sulfates
are present in a higher concentration than 3 ppt, there is some
risk of such adverse effects. Nevertheless, a process according to
the invention can still be used to stabilize high sulfate mixtures.
For example, a highly sulfate tolerant type of Portland Cement can
be used. Additional details on this and other methods of coping
with high sulfate content soil and/or rock are given in Little,
"The Effect of Sulfates on Lime-Soil Interactions" in Handbook for
Stabilization of Pavement Subgrades and Base Courses with Lime
(Candle-Hunt Publishing Company, Dubuque, Iowa, 1995), pp 51-52 and
references cited therein, and in Searcher, S. L. and Little, D. N.,
"Microstructural Stability of Sulfate-Contaminated Crushed Concrete
Treated with Cementitious Materials", 1999 Annual Meeting of the
Transportation Research Board, all of which, except for any part
which may be inconsistent with any explicit statement herein, are
hereby incorporated herein by reference.
[0070] It is also known that organic material in excess of one
percent by weight may be deleterious to pozzolanic and cementitious
reactions in calcium-based stabilizers. If organics are present in
levels that interfere with calcium-based stabilization, they will
prevent strength development. Therefore, the simplest way to
evaluate the effect of organics is to assess the rate and level of
strength gain, a test that is preferred for other purposes in any
event and is described below. However, even though fairly high
concentrations of organic material may be tolerated in the
particulate mixture comprising drilling cuttings provided in
operation (1) as described above of a process according to this
invention, they will require larger amounts of calcium-based
stabilizer, and therefore be more expensive to treat, whenever
calcium-based stabilizers are used. Accordingly, the concentration
of organic material in the particulate mixture comprising drilling
cuttings provided in operation (1) as described above of a process
according to this invention that employs group (2.1) of
suboperations as described above preferably does not exceed, with
increasing preference in the order given, 15, 13, 11, 9, 7, 5, 3,
or 1% by mass of said particulate mixture comprising drilling
cuttings.
[0071] If a mixture desired to be treated according to the
invention contains too much of sulfate, organic material, or any
other constituent that interferes with attaining the desired degree
of stabilization, it may nevertheless be treated by a process
according to this invention by diluting the initially unsuitable
mixture with other sources of particulate rock and/or soil in
sufficient quantity to bring the concentrations of interfering
material to a adequately low level in the diluted mixture.
[0072] One of the most common "interfering constituents" of a
mixture to be treated in a process according to this invention is
water from aqueous based drilling muds. This particular
constituent, when present in a mixture desired to be utilized in a
process according to the invention, is rarely if ever preferably
reduced in concentration by dilution with another source of soil
and/or rock. Instead, any large excess of water is preferably
separated from the mixture by a less expensive technique, such as
allowing the suspensions to settle and drawing off accumulated
water from above the settled bed of solids, spreading the wet
mixture over a large outdoor area to promote evaporation of the
water, mixing with a solid drying agent, or the like. A
particularly preferred technique, when the concentration of water
in the mixture and the nature of the soil and/or rock to be treated
are suitable, is to utilize a relatively inexpensive drying agent,
such as fly ash and/or kiln dust, that also has a stabilizing
effect as described above. Any such material added should be
regarded as part of the stabilizer when the amount of stabilizer is
selected along the guidelines in Table 1. This technique is
particularly advantageous when mixtures of lime with fly ash and/or
kiln dust are to be used as the preponderant stabilizer, because
the lime can be added at a later stage of mixing, when it is not so
readily bound by excessive amounts of water in the mixture to be
stabilized and thereby prevented, or at least delayed, from
promoting desired pozzolanic stabilization reactions.
Mixture of Cutting with Other Sources of Particulate Rock and/or
Soil for Purposes other than Dilution of Interfering
Constituents
[0073] Dilution of cuttings with other sources of particulate soil
and/or rock is a very useful supplemental technique in a process
according to the invention in many instances, even when no dilution
is required to reduce the concentrations of interfering substances.
For example, often suitable soil is available at very low cost in
the near vicinity of a site where a structure is to be built by a
process according to the invention. In such an instance, the cost
of such a structure can often be considerably reduced by mixing
some low cost soil with the cuttings, because most naturally formed
soils will need less stabilizer per unit volume than most cuttings
to be used in a process according to the invention, and the
stabilizer is usually more costly than either cuttings or natural
soil. Furthermore, a mixture of natural soil and cuttings often
forms a stronger structure in a process according to the invention
than could be obtained from stabilizing nearby natural soil alone
with the same amount of stabilizer. Still further, of course, one
object of the invention is to convert drilling cuttings to useful
structures, particularly when such conversion will reduce potential
liability for environmental pollution by the cuttings. Accordingly,
it is preferred that particulate rock and/or soil produced by
drilling constitute at least, with increasing preference in the
order given, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by mass of the
particulate mixture comprising drilling cuttings provided in
operation (1) as described above of a process according to this
invention, unless the use of such a high fraction of cuttings leads
to results inconsistent with other preferences expressed herein for
characteristics of the finished structures built by a process
according to the invention. (For example, the use of cuttings and
stabilizer only in a structure built by a process according to the
invention could in some cases result in a structure more
susceptible to cracking or other deterioration during aging of the
structure than if some other source of particulate rock and/or soil
were incorporated into the structure.)
[0074] Alternatively or additionally, the fraction of cuttings in
the particulate mixture comprising drilling cuttings provided in
operation (1) as described above of a process according to this
invention preferably is such that the unconfined compressive
strength of a structure built by a process according to the
invention is greater by at least, with increasing preference in the
order given, 3, 6, 9, 12, 15, 18, 21, 24, 27, or 30 percent than
the unconfined compressive strength of a reference structure built
by a process that is identical, except that all of the cuttings
included in the particulate mixture comprising drilling cuttings
provided in operation (1) as described above for the process
according to this invention are substituted by an equal volume of
the constituents other than cuttings that are present in said
particulate mixture.
Lime and/or Hydrated Lime Stabilization
[0075] The degree of stabilization normally desired requires that
if lime is the sole or greatly predominant stabilizer, a sufficient
amount of lime be added not only to reduce plasticity of clay fines
(improve workability) but also to achieve a substantial pozzolanic
reaction between clay fines and hydrated lime. This test protocol
ensures that an appropriate amount of lime is added to achieve the
desired engineering properties.
[0076] Step 1
[0077] Determine the pH of mixtures of the particulate mixture
comprising drilling cuttings to be stabilized with lime in amounts
varying in Ca(OH).sub.2 content from 0 to 10 percent. Select a
target lime content in accordance with ASTM C-977.
[0078] Step 2
[0079] Prepare samples according to ASTM D-698 to determine a
predicted optimum moisture content for samples with the target
percentage of hydrated lime determined in Step 1, with at least one
of 1.0 and 2.0 percent below, and with at least one of 1.0 and 2.0
percent above the target lime content determined in Step 1. Samples
should be intimately mixed with the specific type of lime and/or
hydrated lime intended for use in a process according to this
invention and allowed to mellow for two hours prior to
compaction.
[0080] Step 3
[0081] Fabricate three samples at and/or within 2% of the predicted
optimum moisture content determined in Step 2 for each trial lime
content. Condition the samples at 100 percent relative humidity and
at a temperature of 40.degree. C. (The approximate 100 percent
relative humidity environment is difficult to achieve in many high
temperature chambers. In order to maintain the level of moisture
required for pozzolanic reaction and cementitious reaction, it is
advisable to wrap the sample in plastic and then to place the
sample with approximately 10 grams of water in a readily sealable
and unsealable moisture-proof plastic bag.)
[0082] Step 4
[0083] Determine the UCS of the samples prepared in Step 3 after
these samples have been compacted in accordance with ASTM D-698.
ASTM Procedure D-5102 is used to determine UCS. The test should be
performed on the standard-sized samples used in compaction density
evaluation. Prior to UCS testing, the samples are wrapped in a
fibrous geofabric capable of transporting moisture along the
circumference of the sample, placed on a porous stone covered to
the top with water, and allowed to absorb moisture through
capillary soak for a period of 24 hours.
[0084] Step 5
[0085] Plot the compressive strengths of the three samples at each
of the three lime contents determined in Step 4 on a chart of
compressive strength versus stabilizer content. Select the lime
content that provides both the highest compressive strength and an
acceptable compressive strength based on the section below titled,
"Target Engineering Properties and Structural Thickness
Requirements".
Portland Cement Stabilization
[0086] Step 1
[0087] Select three trial PC contents based on Table 1. If these
stabilizer contents do not provide acceptable strength, then
additional trials may be made.
[0088] Step 2
[0089] Prepare samples according to ASTM D-698 to determine a
predicted optimum moisture content for a sample with each PC
percentage selected in Step 1. The particulate mixture comprising
drilling cuttings to be stabilized should be intimately mixed with
PC and then immediately compacted.
[0090] Step 3
[0091] Fabricate three samples at and/or within 2% of the predicted
optimum moisture content determined in Step 2 for each trial PC
content. Cure the samples by placing them in a sealed plastic bag
and place the bagged samples in a curing room at a temperature of
25.degree. C. for 7 days.
[0092] Step 4
[0093] Determine the UCS of the samples fabricated in Step 3 by the
same procedures as for Step 4 under the heading "Lime and/or
Hydrated Lime Stabilization" above.
[0094] Step 5
[0095] Plot the compressive strengths of the three samples at each
of the three PC contents on a chart of compressive strength versus
stabilizer content. Select the PC content in the same manner as
used for selecting lime content in Step 5 under the heading "Lime
and/or Hydrated Lime Stabilization" above.
Class C Fly Ash, Lime Kiln Dust, and/or Cement Kiln Dust
Stabilization
[0096] Step 1
[0097] Select three trial ash and/or dust contents from Table 1. If
these stabilizer contents are not satisfactory, then additional
testing may be required.
[0098] Step 2
[0099] Prepare samples according to ASTM D-698 to determine a
predicted optimum moisture content for a sample with each
percentage of ash and/or dust selected in Step 1. Samples should be
intimately mixed with the ash and/or dust and then compacted
immediately.
[0100] Step 3
[0101] Fabricate three samples at and/or within 2% of the predicted
optimum moisture content determined in Step 2 for each trial ash
and/or dust content. Cure the samples by placing them in a sealed
plastic bag and placing the bagged samples in a curing room at a
temperature of 25.degree. C. for 7 days.
[0102] Step 4
[0103] Determine the UCS of the samples cured in Step 3 by the same
procedures as for Step 4 under the heading "Lime and/or Hydrated
Lime Stabilization" above.
[0104] Step 5
[0105] Plot the compressive strengths of the three samples at each
of the three ash and/or dust contents on a chart of compressive
strength versus stabilizer content. Select the ash and/or dust
content in the same manner as used for selecting lime content in
Step 5 under the heading "Lime and/or Hydrated Lime Stabilization"
above.
Stabilization with Combinations of Portland Cement, Lime, and/or
Hydrated Lime with Fly Ash, Cement Kiln Dust, and/or Lime Kiln
Dust
[0106] 1. Single Stage Type
[0107] Step 1.1
[0108] Based on Table 1, determine target contents for each of the
lime group and the ash/dust group. The combinations of lime and
Class F fly ash in Table 1 are based on the amount of fly ash
required to provide a pozzolan source and, secondly, the amount of
lime required to sufficiently activate the Class F ash. However, if
more plastic cuttings are encountered and do not react with the
lime group alone to provide sufficient strength gain, then the lime
group content may have to be increased above that listed in Table 1
in order to modify the clay content of the particulate mixture
comprising drilling cuttings to be stabilized prior to activating
the pozzolanic reaction with the Class F ash.
[0109] Step 1.2
[0110] Prepare samples according to ASTM D-698 to determine a
predicted optimum moisture content for a sample with each
combination of lime group and ash/dust group content selected in
Step 1. Samples should be intimately mixed with both the lime group
and the ash/dust group stabilizers. The stabilizers of both groups
may be added at the same time unless the plasticity index of the
cuttings as determined according to ASTM Procedure D-4318 exceeds
15 percent. In that instance, the lime group stabilizer should be
mixed first with the particulate mixture comprising drilling
cuttings to be stabilized, immediately followed by the ash/dust
group stabilizer.
[0111] Step 1.3
[0112] Fabricate three samples at and/or within 2% of the predicted
optimum moisture content determined in Step 2 for each trial
content combination. Cure the samples by placing them in a sealed
plastic bag and place the bagged samples in an oven or curing room
at a temperature of 40.degree. C. for 7 days.
[0113] Step 1.4
[0114] Determine the unconfined compressive strength (UCS) of the
samples cured in Step 3 by the same procedures as for Step 4 under
the heading "Lime and/or Hydrated Lime Stabilization" above.
[0115] Step 1.5
[0116] Plot the compressive strengths of the three samples at each
of the three contents combinations on a chart of compressive
strength versus stabilizer content. Select the lime group and
ash/dust group contents in the same manner as used for selecting
lime content in Step 5 under the heading "Lime and/or Hydrated Lime
Stabilization" above.
[0117] 2. Two Stage Type
[0118] Step 2.1
[0119] The purpose of the initial step is to select a drying and
pre-stabilization agent (hereinafter usually abbreviated as "DPSA")
that has the capability of drying the drill cuttings to a level of
acceptable workability and of initiating the stabilization process.
Typical candidates for DPSA include fly ash, lime kiln dust, cement
kiln dust, and quicklime. The DPSA candidates should be able to
produce a high enough pH to initiate a pozzolanic reaction between
silica and alumina in the cuttings and calcium from the DPSA. This
pozzolanic reaction accomplishes part of the drying process and
begins the strength gain process. Proper selection of the DPSA
permits successful drying and stabilization. Within these
constraints, the selection of the appropriate DPSA is largely based
on site-specific availability and cost effectiveness.
[0120] Step 2.2
[0121] Mix trial amounts of the candidate DPSA with the cuttings in
their natural moisture state. The mixing process should simulate
the level of preliminary mixing that can be achieved in the field.
A reasonable process is to mix the DPSA with the cuttings in a
mixing bowl with a spatula. Then allow the mixture of cuttings and
DPSA to dry overnight and test the resulting moisture content. A
satisfactory level of drying is achieved when the cuttings can be
molded into a cohesive mass in the palm of a normal human hand.
(This is typically at about three to five percentage points above
optimum moisture for compaction according to American Association
of State Highway and Transportation Officials Procedure T-99, if
some soil is to be blended with the mixture in the final structure
to be built according to the invention.)
[0122] Step 2.2'
[0123] (Used Only When Soil is to be Added to the Mixture in the
Final Structure to be Built According to the Invention.)
[0124] Blend samples of the dried mixture from step 2.2 with
several proportions of the soil to be used. Determine the moisture
density relationship of the blend of cuttings, DPSA, and soil. A
reasonable moisture-density relationship according to American
Association of State Highway and Transportation Officials Procedure
T-99 normally should be achieved with about five samples.
[0125] Step 2.3
[0126] Determine the type and amount of second stage stabilizer,
alternatively denoted as "activator", to be used. The activator can
be the same material as the DPSA, but typically will be Portland
Cement or lime (calcium oxide or calcium hydroxide). The primary
role of the activator is to react with the soil and/or DPSA
pozzolans to complete the pozzolanic reaction and to augment the
pozzolanic reaction by a hydration cementitious reaction as
required to achieve the desired compressive strength. The activator
not only completes the stabilization process but also completes the
drying process.
[0127] Step 2.4
[0128] Determine the amount of the activator selected in Step 2.3
that is needed to achieve the required unconfined compressive
strength. The determination can usually be effectively begun by
molding three samples at the predicted optimum moisture content
determined in step 2.2 (including 2.2' if this step is used) and
three additional samples at each of one percent less than optimum
and one percent in excess of optimum. Nine samples according to
this procedure should be made for each of the mixtures without
activator and for activator contents of each of 3.0, 5.0, and 7.0
percent. The UCS of these samples is tested after curing and
conditioning as described for Steps 3 and 4 under the heading "LIME
AND/OR HYDRATED LIME STABILIZATION" above.
[0129] Step 2.5
[0130] Select an appropriate mixture design based on the results of
UCS Testing in Step 2.4. The UCS is used in a layered elastic model
of the structure to be built according to the invention as
described in the section of this description below after the
heading "TARGET ENGINEERING PROPERTIES AND STRUCTURAL THICKNESS
REQUIREMENTS".
Stabilization with Asphalt (Emulsidied and/or Foamed)
[0131] Step 1
[0132] Select a slow setting (hereinafter usually abbreviated as
"SS") emulsion for cuttings having greater than 15 percent by mass
of material passing a sieve with openings 0.075 millimeter(s)
(hereinafter usually abbreviated as "mm"). Otherwise, select a
medium setting (hereinafter usually abbreviated as "MS") emulsion.
(A determination of whether an anionic or cationic emulsion should
be used is based on coating and adhesion tests described in
subsequent steps).
[0133] Step 2
[0134] Determine a trial emulsion and/or foam content for the
particulate mixture comprising drilling cuttings to be stabilized
as follows:
% emulsion and/or
foam=[(0.06.times.B)+(0.01.times.C].times.100)/A,
[0135] where A is percent residue by ASTM D-244, B is percent of
dried particulate mixture comprising drilling cuttings to be
stabilized that passes a No. 4 sieve, and C is (100-B).
[0136] Step 3
[0137] The trial emulsion and/or foam content determined in Step 2
is combined with the particulate mixture comprising drilling
cuttings to be stabilized, corrected to a dry weight, and formed
into a coating, which is visually estimated as satisfactory or
unsatisfactory for its intended use of the mix. The procedure for
forming the coating consists of the following operations: (3.1)
Determine the moisture content of a representative particulate
mixture comprising drilling cuttings to be stabilized; (3.2) mix in
water by hand for 10 seconds or until visually uniformly dispersed,
the amount of water being determined by visual inspection of the
mixture; (3) add the selected weight of the trial emulsion and/or
foam content to the moist aggregate at the anticipated use
temperature and mix vigorously by hand for 60 seconds or until
sufficient dispersion has occurred throughout the mixture; and (4)
place the mixture on a flat surface and visually estimate the
degree of coating.
[0138] Step 4
[0139] Prepare three or more specimens each at a minimum of three
different emulsion and/or foam contents. If the mixture in the
coating test of Step 3 appears satisfactory, use one specimen with
the same emulsion and/or foam concentration as used for Step 3,
with one other specimen below and one other specimen above the
trial emulsion and/or foam content. If the mixture in the coating
test of Step 3 appears to be dry, use one specimen with the foam
and/or emulsion content used for Step 3 and increase the foam
and/or emulsion content for each of the other two specimens.
Conversely, if the mixture in the coating test of Step 3 appears
too wet, reduce the foam and/or emulsion content for the second and
third specimens. (A normal difference between the emulsion and/or
foam contents is one percent, or a residual asphalt content
difference of 0.65 percent for an emulsion and/or foam with a 65
percent residual content.)
[0140] Step 5
[0141] Determine adhesion by the following sequence of operations:
(1) Cure a 100 gram portion of the mix from Step 4 in a shallow
container for 24 hours in a forced draft oven at 60.degree. C.; (2)
put the oven-cured mix in a 600 milliliter (hereinafter usually
abbreviated as "ml") size beaker containing 400 ml of boiling
distilled water; (3) bring to a boil again, and maintain boiling
and stir at one revolution per second; (4) pour off water and place
the mix on a piece of white absorbent paper, and (5) after the mix
has dried, visually evaluate the amount of retained asphalt
coating. If satisfactory, continue the mix design or if not
acceptable, then the amount of emulsion and/or foam used should be
modified or another grade selected.
[0142] Step 6
[0143] Compact a freshly prepared specimen of the most satisfactory
mixture(s) from Step 5 according to ASTM D 59 or D 1560. (Aeration
or drying of a dense-graded mixture is often required prior to
specimen compaction. If the total liquid volume exceeds the voids
in the mineral aggregate plus any absorbed liquid volume, proper
compaction cannot be achieved.)
[0144] Step 7
[0145] Determine volumetrics and stability of the compacted
mixtures. Volumetrics such as air voids, voids filled with bitumen,
and voids in the mineral aggregate, can be determined by properly
accounting for moisture and following appropriate ASTM testing
procedures, including D-70, D-1188, D-2726, and D-3203. Marshall
stability and flow should be determined following the procedures of
ASTM D-1559 beginning at paragraph five (Procedure), except that
the compacted specimens preferably are placed in an air bath for a
minimum of two hours at the test temperature of 25.degree. C.
(.+-.1.degree. C.). A stability value of 2,224 N or greater has
been found to be satisfactory for most pavements with low to
moderate traffic volume. Hveem stability preferably is determined
following ASTM D-1560 (paragraphs four through nine), except that
the compacted specimens preferably are placed in an air bath for a
minimum of two hours at the test temperature of 25.degree. C.
(.+-.1.degree. C.). A stability value of 30 or greater has been
found to be satisfactory for most pavements with low to moderate
traffic volume.
Target Engineering Properties and Structural Thickness
Requirements
[0146] The combination of thickness and physical properties, e.g.,
stiffness and strength, of the stabilized particulate mixture
comprising drilling cuttings must be capable of supporting all of
the continuous and/or varying loads applied to it during its
designed use. For example, if the structure to be built by a
process according to the invention is a drilling pad, the pad must
be able to support heavy equipment hauled in and out of the site
during the drilling operations. However, stiffness and strength
values far greater than those needed are disadvantageous for at
least two reasons: very high stiffness and strength values result
in greater susceptibility to cracking and similar forms of brittle
deterioration that can substantially shorten the useful life of a
structure, and achieving very high strength and stiffness usually
requires considerably larger fractions of stabilizer in a
structure, thereby increasing its cost.
[0147] To assess the required engineering properties and thickness
combinations required of the stabilized particulate mixture
comprising drilling cuttings, a layered elastic structural
evaluation is preferred. In this type of evaluation, the structure
to be built is modeled as a succession of layers. Each layer is
modeled by a modulus and a Poisson's ratio with an assigned
thickness. A load configuration is modeled to simulate the critical
traffic applied to the structure and includes consideration of the
wheel load, load geometries, and tire contact pressure. The layered
elastic model (hereinafter usually abbreviated as "LEM") calculates
stresses and strains within the pavement system. Stresses and
strains at critical points, e.g., compressive strains at the top of
the natural subgrade, and shearing stresses within the structural
layer are calculated and compared to criteria used to assess
performance in terms of the number of applications of such a design
load that the structure can withstand.
[0148] A factorial LEM analysis was performed considering the
effects of four variables: the number of load applications,
subgrade strength, structural layer thickness, and structural layer
strength and modulus. The design load was defined as an 18,000
pound single axle load, which is expected to result in a structure
that is fully satisfactorily strong, stiff, and durable for a
normal deep drilling pad or lease road needed in connection with
deep drilling. Table 2 illustrates some results of the factorial
analysis. "E" in Table 2 represents the resilient modulus. The
value for E given in Table 2 was calculated by the most
conservative of established empirical correlations between
resilient modulus and UCS, specifically that:
E (in thousands of psi).gtoreq.0.12 (UCS {in PSI})+9.98.
[0149] The unit "thousands of psi" is hereinafter usually
abbreviated as "kpsi".
[0150] The UCS values shown in Table 2 are for samples that have
been moisture-conditioned for 7 days. If unconditioned samples are
used instead, the UCS values should be 100 psi higher than those
shown in Table 2.
[0151] The control in Table 2 is a compacted crushed limestone
gravel base with a UCS value of 45 psi and a modulus that is
expected to be within a range from 13 to 18 kpsi, based on typical
properties of unbound aggregate bases under a stress representative
of that on a structural pad or a lease road.
[0152] A considerably higher UCS value than the maximum value of
300 psi shown in Table 2 can be achieved by using high stabilizer
percentages. However, the 300 psi value is considered to be the
upper limit practically required of most stabilized bases subjected
to moisture conditioning that simulates the deep drilling field
environment. In fact, if a stabilized layer can maintain at least
100 psi following moisture conditioning, it normally should provide
adequate field durability when used in the thicknesses shown for
that UCS value in Table 2. However, if the structure is being built
in an area with a continuously high water table or an area where
there are large seasonal fluctuations in water table, a higher UCS
value may be advantageous to prevent deterioration from these
environmental influences. In a normal deep drilling field
environment, however, for the reasons given above, the UCS values
obtained after 7 days of aging of the actual mixture of materials
to be used in building a structure by a process according to this
invention preferably does not exceed the value given in Table 2 for
the structure thickness and subgrade strength values as shown in
Table 2 by a percentage of said value given in Table 2 that is more
than, with increasing preference in the order given, 300, 250, 200,
190, 180, 170, 160, 150, 140, 130, 120, 110, 100, 90, 80, 70, 60,
50, 40, 30, or 20 percent. For example, if the subgrade strength is
at least 5,000 psi but less than 10,000 psi and the thickness of
the structure to be built is 16 inches, the conditioned UCS value
preferably is at least 100 psi but need not be more than 120 psi,
but if the thickness is only 10 inches, the conditioned UCS value
preferably is at least 300 psi and need not be more than 360
psi.
2TABLE 2 FACTORS AND VALUES THEREOF CONSIDERED IN FACTORIAL
ANALYSIS AND RESULTING THICKNESS REQUIREMENTS Strength and
Stiffness of the Stabilized Particulate Mixture Recommended
Comprising Particles of "Control" or Thickness, Subgrade Strength
of Soil, Rock, or Both Rock and Soil inches Soft (E.sub.subgrade =
5.0 kpsi) Control (E = 13-18 kpsi) 18 UCS = 100 psi (E = 22 kpsi)
16 UCS = 200 psi (E = 35 kpsi) 12 UCS = 300 psi (E = 47 kpsi) 10
Moderate (E.sub.subgrade = 10.0 kpsi) Control (E = 13-18 kpsi) 13
UCS = 100 psi (E = 22 kpsi) 12 UCS = 200 psi (E = 35 kpsi) 9 UCS =
300 psi (E = 47 kpsi) 8 Strong (E.sub.subgrade = 15.0 kpsi) Control
(E = 12.6-18 kpsi) 8 UCS = 100 psi (E = 22 kpsi) 8 UCS = 200 psi (E
= 35 kpsi) 8 UCS = 300 psi (E = 47 kpsi) 8
[0153] The thickness values recommended in Table 2 can accommodate
at least 10,000 applications of the design load with less than 1
inch depth of rutting. (These values were compared to those found
using the U.S. Army Corps of Engineers granular base rutting model
and found to be at least as large as those recommended by that
model.)
[0154] The thicknesses in Table 2 are exact only for the specified
purposes and conditions. Each instance of use of a process
according to this invention should be evaluated by the methods
outlined above using the actual stabilizer(s) and particulate
mixture comprising drilling cuttings to be stabilized and the
particular strength, stiffness, and durability requirements of the
actual structure to be built.
[0155] In a particularly preferred embodiment of the invention, the
mixture comprising drilling cuttings provided in operation (1) of a
process according to the invention as described above is a mixture
that has been produced by drilling through the surface of the earth
to form a borehole by a process comprising suboperations of:
[0156] (1.1) providing drilling means, drilling driving means that
cause the drilling means to operate at the bottom of said borehole,
and drilling mud; and
[0157] (1.2) causing said drilling driving means to drive said
drilling means while said drilling mud flows into and out of said
borehole through separate passageways disposed so as to insure that
mud pumped into the borehole must reach the near vicinity of the
drilling means that is deepening, widening, and/or otherwise
increasing the volume of said borehole before the mud can enter any
passageway through which a mixture of mud and cuttings flows out of
the borehole during drilling, said mixture of mud and cuttings,
optionally after removal therefrom of all or part of the
constituents of said mixture that are not cuttings and/or additions
thereto of other particulate material, constituting said mixture
that has been produced by drilling through the surface of the earth
to form a borehole.
[0158] The invention may be further appreciated by consideration of
the following examples, at least some, but not necessarily all, of
which are according to the invention.
EXAMPLES OF DEVELOPMENT OF STRUCTURAL STRENGTH IN MIXTURES
INCORPORATING DRILLING CUTTINGS
Example 1
[0159] In this example, the cuttings used were obtained during
drilling in the vicinity of Buffalo in Freestone County, Texas,
using water-based drilling mud. The native soil in this area is
described as follows by government sources: "Edge Fine Sandy Loam,
5 to 12% Slopes. The Edge Series consists of deep over siltstone,
well drained, very slowly permeable upland soils. The surface to 11
inches is fine sandy loam. The subsoil is reddish and clay loam 11
to 29 inches." Cuttings from drilling through this soil with a
water-based drilling mud were collected in a waste pit on the
drilling site and allowed to settle for a period of at least
several months. Settled and moist sediment of this type was used as
the cuttings to be stabilized during this example. These cuttings
were determined by ASTM D 4318 to have an Atterberg Liquid Limit of
25, Plastic Limit of 16, and Plasticity Index of 9, while the
native surface soil was independently determined to have an
Atterberg Liquid Limit of 18 and Plastic Limit of 19.
[0160] Based on the principles given above, concentrations of 3, 5,
and 7% of Type 1 Portland Cement and a concentration of 10% of
Class C Fly Ash were chosen as candidate stabilizers for a mixture
of the selected cuttings with twice its own mass of the native soil
taken from the top 12 inches thereof. In accordance with the Test
Protocols given above for both these stabilizers, a predicted
optimum moisture content for each mixture was determined according
to ASTM D 698 for each mixture, with the results shown in Table 3
below.
3TABLE 3 Predicted Optimum Moisture Concentration and Type of
Stabilizer Percent 3% Cement 11.4 5% Cement 10.6 7% Cement 11.0 10%
Class C Fly Ash 9.6
[0161] Samples incorporating the predicted optimum moisture percent
and moisture percents differing from the predicted optimum by 2%
both greater and less were then prepared and cured as described
above in the test protocols. The UCS values for these samples are
shown in Table 4 below.
4 TABLE 4 UCS Value in psi with Percents of Moisture: Concentration
and Predicted Predicted Predicted Type of Stabilizer Optimum - 2
Optimum Optimum + 2 3% Cement 159 181 136 5% Cement 196 336 219 7%
Cement 243 389 358 10% Class C Fly Ash 28 54 40
[0162] In this instance, a UCS value expected to be satisfactory
for very heavy duty service is readily achieved with 5% or 7%
cement and a value satisfactory for slightly lighter duty service
was achieved with 3% cement. The particular type of Class C Fly Ash
used was not as effective in achieving strength gain as the
cement.
Example 2
[0163] In this example, the cuttings used were obtained during
drilling in Midland County, Texas, using water-based drilling mud.
The native soil in this area is of two types, which are described
as follows by government sources: "Miles Loamy Fine Sand, 0 to 3%
Slopes . . . The Miles Series consists of deep, moderately drained
soils on uplands . . . [From] 0 to 14 inches [the soil is/has]
reddish-brown (5YR 5/4) loamy fine sand, dark reddish-brown (5YR
3/4) when moist; weak, very fine, subangular blocky structure;
soft, very friable; common roots; neutral; gradual, smooth
boundary" and "Sharvana Fine Sandy Loam, 0 to 3% Slopes. The
Sharvana [S]eries consists of moderately permeable soils on
uplands. These soils are shallow to indurated caliche . . . . In a
representative profile the surface layer is reddish-brown fine
sandy loam about 6 inches thick. The next layer is reddish-brown
sandy clay loam about 8 inches thick." Cuttings from drilling
through this soil with a water-based drilling mud were collected in
a waste pit on the drilling site and allowed to settle for a period
of at least several months. Settled and moist sediment of this type
was used as the cuttings to be stabilized during this example.
[0164] Based on the principles given above, concentrations of 3, 5,
and 7% of Type 1 Portland Cement and a concentration of 10% of
Class C Fly Ash were chosen as candidate stabilizers for a mixture
of the selected cuttings with twice its own mass of the native soil
taken from the top 12 inches thereof. In accordance with the Test
Protocols given above for both these stabilizers, a predicted
optimum moisture content for each mixture was determined according
to ASTM D 698 for each mixture, with the results shown in Table 5
below.
5TABLE 5 Predicted Optimum Moisture Concentration and Type of
Stabilizer Percent 3% Cement 11.0 5% Cement 11.5 7% Cement 11.0 10%
Class C Fly Ash 10.5
[0165] Samples incorporating the predicted optimum moisture percent
and moisture percents differing from the predicted optimum by 2%
both greater and less were then prepared and cured as described
above in the test protocols. The UCS values for these samples are
shown in Table 6 below.
6 TABLE 6 UCS Value in psi with Percents of Moisture: Concentration
and Predicted Predicted Predicted Type of Stabilizer Optimum - 2
Optimum Optimum + 2 3% Cement 132 122 80 5% Cement 221 156 127 7%
Cement 254 223 161 10% Class C Fly Ash 115 80 63
[0166] In this instance, a UCS value expected to be satisfactory
for very heavy duty service is readily achieved with 5% or 7%
cement and a value satisfactory for slightly lighter duty service
was achieved with 3% cement. The particular type of Class C Fly Ash
used was not quite as effective in achieving strength gain as even
the lowest percentage of the cement, but was much more effective
than in Example 1.
Examples 3 to 9
[0167] In all of these examples, the cuttings used were obtained
during drilling at various sites in Latimer County, Oklahoma using
oil-based drilling mud. Cuttings from drilling through these soils
with an oil-based drilling mud were passed over a shaker table and
through a centrifuge in tandem to separate the cuttings from the
drilling mud, which was recycled to drilling. Separated cuttings of
this type were used as the cuttings to be stabilized during these
examples. These cuttings for Examples 5 to 9 were determined by
ASTM D 4318 to have Atterberg Liquid Limits, Plastic Limits, and
Plasticity Indices as shown in Table 7 below, while the nearby
surface soil was independently determined to have values for the
same characteristics at the time of mixing with the cuttings used
in the various examples as also shown in Table 7.
[0168] Based on the principles given above, concentrations of 3, 5,
and 7% of Type 1 Portland Cement and a concentration of a
combination of 10% of Class C Fly Ash and 2% of Portland Cement
were chosen as candidate stabilizers for the mixtures of the
selected cuttings with twice their own masses of the native soil
taken from the top 12 inches thereof. In accordance with the Test
Protocols given above for both these stabilizers, an estimated
optimum moisture content for each mixture was determined according
to ASTM D 698 for each mixture, with the results shown in Table 8
below.
7TABLE 7 Cuttings or Atterberg Test Values for: Example No. Soil?
Liquid Limit Plastic Limit Plasticity Index 5 Soil 31 22 9 Cuttings
55 45 10 6 Soil 56 28 28 Cuttings 31 26 5 7 Soil 20 71 3 Cuttings
55 42 13 8 Soil 35 20 15 Cuttings 65 50 15 9 Soil 24 17 7 Cuttings
48 39 9
[0169] Samples incorporating the predicted optimum moisture percent
and moisture percents differing from the predicted optimum by 2%
both greater and less were then prepared and cured as described
above in the test protocols. The UCS values for these samples are
shown in Table 9 below.
[0170] In most of these instances, a UCS value expected to be
satisfactory for moderately heavy duty service is readily achieved
with 5% or 7% cement. The combination of cement and the particular
type of Class C Fly Ash used, along with 3% cement only, was not as
effective in achieving strength gain as the cement in most
instances, but the combination was nearly as good for Example 4.
These results emphasize that the exact materials to be used need to
be tested and optimized in order to achieve very highly
satisfactory structures.
Examples 10 to 15
[0171] In these examples, the cuttings always included some
cuttings that have been obtained by drilling with water-based mud.
Therefore, in accordance with the preferences indicated above, the
processes according to the invention were divided into two stages.
In the first stage, the cuttings and any mud of the same type used
to produce them that had previously been mixed for storage were
mixed with a Class C Fly Ash, a type of stabilizer that is also a
relatively inexpensive drying agent, to form a preliminary mixture.
In the second stage, the preliminary mixture was itself mixed with
soil from within the top 2 feet of naturally occurring soil near
the site of the drilling operation that had generated the cuttings
and with Type I Portland Cement to form the final mixtures that
were conditioned for several days
8TABLE 8 Concentration and/or Predicted Optimum Moisture Example
Number Type of Stabilizer Percent 3 3% Cement only 18.7 5% Cement
only 17.0 7% Cement only 18.4 Fly Ash + Cement 18.0 4 3% Cement
only 20.4 5% Cement only 19.5 7% Cement only 19.9 Fly Ash + Cement
18.6 5 3% Cement only 20.5 5% Cement only 19.9 7% Cement only 18.8
Fly Ash + Cement 18.6 6 3% Cement only 18.9 5% Cement only 17.3 7%
Cement only 14.0 Fly Ash + Cement 9.8 7 3% Cement only 15.0 5%
Cement only 13.6 7% Cement only 14.1 Fly Ash + Cement 13.7 8 3%
Cement only 16.0 5% Cement only 18.2 7% Cement only 17.9 Fly Ash +
Cement 15.5 9 3% Cement only 14.7 5% Cement only 14.6 7% Cement
only 13.5 Fly Ash + Cement 12.8
[0172]
9 TABLE 9 UCS Value in psi with Percents of Moisture: Example
Concentration and/or Type of Predicted Predicted Predicted Number
Stabilizer Optimum - 2 Optimum Optimum + 2 3 3% Cement only 73 82
63 5% Cement only 152 113 80 7% Cement only 215 229 160 Fly Ash +
Cement 94 87 61 4 3% Cement only 104 128 93 5% Cement only 128 172
160 7% Cement only 191 226 184 Fly Ash + Cement 190 220 200 5 3%
Cement only 92 75 50 5% Cement only 156 104 92 7% Cement only 172
122 119 Fly Ash + Cement 44 37 32 6 3% Cement only 46 53 35 5%
Cement only 48 66 72 7% Cement only 89 62 141 Fly Ash + Cement 17
33 55 7 3% Cement only 105 73 60 5% Cement only 218 166 119 7%
Cement only 294 189 157 Fly Ash + Cement 117 90 57 8 3% Cement only
84 55 44 5% Cement only 116 97 76 7% Cement only 142 147 101 Fly
Ash + Cement 140 80 58 9 3% Cement only 87 59 57 5% Cement only 118
125 82 7% Cement only 172 142 127 Fly Ash + Cement 170 109 102
[0173] before strength testing as described above. Except for
Examples 11, 14, and 15, the nearby surface soil that was used in
the immediately previously described mixtures was also mixed with
Class C Fly Ash and with at least some of the same fractions of the
same type of Portland Cement as had been used to make these
immediately previously described mixtures, in order to determine
whether the incorporation of cuttings would change the strength
values that could be obtained with soil, fly ash, and cement alone.
(These mixtures that contained no drilling cuttings are not
examples according to the invention.)
[0174] Table 10 below gives further details of Examples. 10-15.
10TABLE 10 Location % by Mass of All Constituents in Conditioned
Mixture Except Ex- (North Portland Cement am- Latitude.vertline.
Soil Only or Water-Based Cuttings Oil-Based Cuttings ple West
Mixture with and Any Mud Mixed and Any Mud Mixed Fly No. Longitude)
Cuttings? Soil with Them in Storage with Them in Storage Ash 10
30.degree.36.0'.vertline. Soil 80 0 0 20 91.degree.30.5' Mixture 50
30 12 8 11 32.degree.58.3'.vertline. Mixture 71 24 0 5
97.degree.23.1' 12 33.degree.8.1'.vertline. Soil 65 0 0 35
97.degree.22.2' Mixture 71 21 0 7 13 33.degree.10.6'.vertline. Soil
70 0 0 30 97.degree.18.4' Mixture 71 22 0 7 14
33.degree.10.0'.vertline. Mixture 71 26 0 3 97.degree.18.2' 15
32.degree.58.3'.vertline. Mixture 72 25 0 4 97.degree.22.5'
[0175] Some of the mixtures as described in Table 10 were then
mixed with 3.0, 5.0, and 7.0 percent of their own mass of Type I
Portland Cement. The predicted optimum moisture percent values for
some of these mixtures were determined in accordance with the
procedures specified above. Results are shown in Table 11
below.
11TABLE 11 Concentration of Predicted Optimum Moisture Example
Number Cement Percent 10 3% 22.0 5% 20.9 7% 20.3 11 5% 24.1 12 5%
24.2 13 5% 19.5 14 5% 18.8 15 5% 23.1
[0176] Samples incorporating the predicted optimum moisture percent
and moisture percents differing from the predicted optimum by 2%
both greater and less were then prepared and cured as described
above in the test protocols. For Examples 11 through 15, the
predicted optimum for a mixture with 5% of cement was used
irrespective of the actual percent of cement in the sample tested.
The UCS values for these samples are shown in Table 12 below. These
values were determined after 7 days of conditioning for Examples
10, 14, and 15 and after 5 days of conditioning for Examples 11
through 13.
[0177] In Examples 10 and 12, the mixtures containing cuttings
developed substantially greater UCS values under most of the
conditions tested than the compared mixtures without cuttings, even
though the latter contained more of the fly ash stabilizer.
12TABLE 12 Cuttings Present UCS Value in psi with Percents of
Moisture: Example Concentration of in Conditioned HPredicted
Predicted Predicted Number Cement Mixture? Optimum - 2 Optimum
Optimum + 2 10 3% No 109 77 55 Yes 128 107 84 5% No 160 103 59 Yes
153 127 113 7% No 164 90 63 Yes 169 135 117 11 3% Yes 113 135 80 5%
Yes 161 170 155 7% Yes 217 189 198 12 5% No 166 144 163 Yes 264 264
223 7% Yes 342 318 249 13 3% Yes 129 83 not tested 5% No 278 257
not tested Yes 148 113 85 7% Yes 137 113 75 14 3% Yes 133 123 71 5%
Yes 181 169 156 7% Yes 219 219 150 15 3% Yes 133 107 64 5% Yes 223
155 147 7% Yes 250 207 146
CONSTRUCTION OF A WORKING LEASE ROAD INCORPORATING CUTTINGS BY A
PROCESS ACCORDING TO THE INVENTION
[0178] A volume of about 573 cubic meters (hereinafter usually
abbreviated as "m.sup.3") that was constituted preponderantly of
cuttings formed by drilling with an oil-based drilling mud and also
included some fluidized bed fly ash (a material containing about
16% stoichiometric equivalent as SO.sub.3 of sulfur) that had been
added to the cuttings as a drying agent was used as the initial
mixture comprising soil, rock, or both rock and soil to begin the
process according to this invention. Analysis showed that this
initial mixture contained 9.9 ppt of soluble sulfate and 86 ppt of
total petroleum hydrocarbons and had a bulk density of 1.4
megagrams per cubic meter (hereinafter usually abbreviated as
"Mg/m.sup.3"). Because this initial mixture contained too much
sulfate for direct use in a process according to the invention as
described above, the initial mixture was diluted with some of the
native soil in this area, which is described as "Bengal-Denman
association, moderately steep" by the U.S. Department of
Agriculture Soil Conservation Service, (now named the Natural
Resources Conservation Service). Further details about this soil
are available in Soil Survey of Latimer County, Oklahoma, Issue of
December 1981. This soil was analyzed and found to contain 1.23 ppt
of soluble sulfate and 15 ppt of total organic carbon and to have a
bulk density 1.5 Mg/m3. Calculation shows that this soil can be
mixed in a bulk volume ratio of 7:3 with the initial mixture of
cuttings and fluidized bed fly ash to form an amended initial
mixture with no more than 3 ppt of sulfate. Because this is still
near the upper limit of sulfate that can be treated in a process
according to this invention without concern, Portland Cement was
selected as the stabilizer for use in the process according to the
invention, inasmuch as Portland Cement is the most tolerant of
sulfate of all the lime-based stabilizers shown in Table 1, and in
particular "ASTM C 150, Type II" cement, a sulfate-tolerant type of
cement, was selected. Consideration of Table 1 shows that 6.0 ppt
of the cement should produce a satisfactory final structure.
[0179] Accordingly, the Bengal-Denman soil noted above was mixed
with a volume fraction of 4% of the soil volume with this type of
cement to form a combined stabilizer-diluent mixture. This mixture,
because the cement has a bulk specific gravity of 3.14, contained
7.8 ppt of the cement.
[0180] A layer of the initial mixture containing oil-based cuttings
and high sulfate as noted above, the layer being about 0.15 meters
in depth and from 11 to 14 meters in width, was deposited along the
line of the road to be constructed, and then covered with a second
layer of the stabilizer-diluent mixture described above, this
second layer being about 0.46 meters in depth and the same width as
the first layer. The entire particulate contents of these two
layers were then mixed with a soil stabilizer machine, a machine
that is known in the art to achieve excellent mixing throughout the
entire depth of particulates mixed. Sufficient water was then added
atop this mixture to provide an amount of water by mass equal to 12
to 14% of the mass of the mixture, and after a pause of 30 minutes
to allow the water to permeate through the depth of the particulate
bed, the top of the bed was successively rolled with a "sheep's
foot roller" that applied a pressure of 200 to 300 pounds per
square inch, bladed, and rolled with a smooth roller which applied
very little pressure and acted essentially as a finishing tool. A
thickness of 0.4 centimeter of gravel was then spread over the top
of the thus prepared road bed. All of these operations for the
entire road construction were completed within three hours after
the mixing of the stabilizer-diluent mixture with the initial
mixture had begun.
[0181] Within two days after the construction as described above of
a structure intended to serve as a road was completed, the
structure began to be used as a road, and in over four months of
service it has shown no evidence of deterioration of any type,
including rutting, despite frequent passage over the road of
tractor-trailer trucks and their loads totaling about eighty
thousand pounds for each truck. There was heavy rain during this
period, and conventional lease roads, consisting essentially of
several inches thickness of gravel, that were in the same area and
subjected to the same level of traffic loads needed frequent
re-graveling to reduce rutting. Thus the road constructed by a
process according to the invention demonstrated clearly superior
quality.
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