U.S. patent application number 11/192712 was filed with the patent office on 2006-02-02 for injection process and system for earth stabilization.
Invention is credited to Leonard E. Jowell, Michael L. Jowell, Craig T. Tarrant.
Application Number | 20060024136 11/192712 |
Document ID | / |
Family ID | 35732385 |
Filed Date | 2006-02-02 |
United States Patent
Application |
20060024136 |
Kind Code |
A1 |
Jowell; Michael L. ; et
al. |
February 2, 2006 |
Injection process and system for earth stabilization
Abstract
Injection systems and processes may improve earth stability of a
site. In one implementation, an injection system and process
include the ability to insert an array of liquid-conveying probes
into the ground of a site to a predetermined depth, the probes
spaced substantially less than five feet apart from each other, and
to supply a predominantly-aqueous solution to the probes. The
system and process also include the ability to insert the probes a
predetermined further distance into the ground and supply
additional solution.
Inventors: |
Jowell; Michael L.; (North
Richland Hills, TX) ; Jowell; Leonard E.; (Fort
Worth, TX) ; Tarrant; Craig T.; (Grand Prairie,
TX) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
35732385 |
Appl. No.: |
11/192712 |
Filed: |
July 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60592995 |
Jul 30, 2004 |
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Current U.S.
Class: |
405/269 ;
405/263 |
Current CPC
Class: |
E02D 3/12 20130101 |
Class at
Publication: |
405/269 ;
405/263 |
International
Class: |
E02D 5/18 20060101
E02D005/18; E02D 3/12 20060101 E02D003/12 |
Claims
1. A method for earth stabilization, the method comprising:
inserting an array of liquid-conveying probes into the ground of a
site to a predetermined depth, the probes spaced substantially less
than five feet apart from each other; supplying a
predominantly-aqueous solution to the probes; inserting the probes
a predetermined further distance into the ground; and supplying
additional solution.
2. The method of claim 1, further comprising: determining whether a
sufficient amount of solution has been supplied; and inserting the
probes a predetermined further distance into the ground when a
sufficient amount of solution has been supplied.
3. The method of claim 2, further comprising: extracting the array
from the ground; moving the array a second predetermined distance;
and inserting the array into the ground to the predetermined
depth.
4. The method of claim 3, wherein the second predetermined distance
is approximately equal to the spacing of the probes.
5. The method of claim 2, wherein determining whether a sufficient
amount of solution has been supplied comprises determining whether
refusal has been achieved.
6. The method of claim 1, wherein the spacing of the probes is
approximately two and one-half feet.
7. The method of claim 1, wherein the array is linear and comprises
seven probes, each probe having a three-hundred and sixty degree
spray pattern.
8. The method of claim 1, wherein the predetermined further
distance is approximately one foot.
9. The method of claim 1, further comprising continuing to insert
the array into the ground at different locations until the site is
covered.
10. The method of claim 9, further comprising: measuring the
potential movement of the treated ground; determining whether the
potential movement of the treated ground is acceptable; and if the
potential movement of the treated ground is not acceptable,
performing another injection pass over the site.
11. The method of claim 1, wherein the predominantly-aqueous
solution comprises a surfactant that is mixed at a rate of
approximately one gallon per three-thousand five-hundred gallons of
water.
12. The method of claim 1, wherein supplying a
predominantly-aqueous solution to the probes comprises supplying
the solution to the probes at a pressure above two-hundred pounds
per square inch.
13. A system for earth stabilization, the system comprising: an
array of liquid conveying probes, the probes spaced substantially
less than five feet apart from each other and operable to convey a
predominantly-aqueous solution into the ground; and a system for
driving the probes into the ground.
14. The system of claim 13, wherein the drive system is operable to
individually drive each probe into the ground.
15. The system of claim 13, further comprising a solution supply
system for supplying a predominantly-aqueous solution to the
probes.
16. The system of claim 15, wherein the solution supply system is
operable to control the solution flow to each probe.
17. The system of claim 13, further comprising a transport unit
operable to move the array and the driving system.
18. A method for earth stabilization, the method comprising
injecting a predominantly-aqueous solution into the ground of a
site by inserting an array of liquid conveying probes spaced at
substantially less than five feet apart at a plurality of locations
of the site and supplying a predominantly-aqueous solution to the
probes.
19. The method of claim 18, further comprising: inserting the
probes to a plurality of depths at each location of the site; and
injecting the solution at each depth.
20. The method of claim 19, further comprising determining whether
a sufficient amount of solution has been supplied at a depth before
inserting the probes to another depth at a location.
21. The method of claim 18, wherein the spacing of the probes is
approximately two and one-half feet.
22. The method of claim 18, further comprising: measuring the
potential movement of the treated ground; determining whether the
potential movement of the treated ground is acceptable; and if the
potential movement of the treated ground is not acceptable,
performing another injection pass over the site.
23. The method of claim 18, wherein the predominantly-aqueous
solution comprises a over ninety-eight percent water.
24. A site treated by injecting a predominantly-aqueous solution
into the ground at simultaneous injection points spaced at
substantially less than five feet apart at a plurality of locations
of the site to achieve earth stabilization.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of and incorporates by
reference U.S. Provisional Patent Application No. 60/592,995,
entitled "Injection Process and System for Earth Stabilization" and
filed on Jul. 30, 2004.
TECHNICAL FIELD
[0002] This invention relates to geophysics and, more particularly,
to a process and system for earth stabilization.
BACKGROUND
[0003] As the population continues to grow, more land is needed for
homes, commercial buildings, industrial plants, and the like. Land
with low-activity soils, however, is fast being consumed, and
possibly even already exhausted, in at least several major
metropolitan areas. Thus, land with higher-activity soils (e.g.,
clay) is being, or at least soon will be, used.
[0004] Unfortunately, higher-activity soils can lead to substantial
problems. Because higher-activity soils expand and contract
significantly, they often cause wall cracks and sticking doors in
buildings. Higher-activity soils can also cause more serious
problems, such as cracked foundations. The Federal Housing
Administration (FHA) and the Veteran's Administration (VA) have
tightened requirements for remediating higher-activity soils in an
attempt to reduce these problems.
[0005] Many techniques have been used to try to prevent the
problems caused by higher-activity soils. One common technique is
to suspend a structural slab on piers to prevent post-construction
movement. However, this technique can be costly--up to three times
the cost of normal slab construction, depending on area. If some
post-construction movement can be accepted, other techniques are
available.
[0006] One technique that allows some post-construction movement is
to remove existing soil at the site and replace it with select
fill. However, as fill resources around major metropolitan areas
decline, suitable materials have to be trucked in at higher
cost.
[0007] Decreasing supplies and consequent increased cost of select
fill resources have resulted in on-site remediation of
higher-activity soils, which is typically more costly than
excavation and replacement with select fill. Several typical
techniques for on-site remediation include injecting a water, lime,
and/or fly-ash slurry into the ground. For a water/lime slurry,
lime is typically mixed with the water at a rate of two and
one-half to three pounds per gallon of water. The water/lime slurry
is often used in sites that require an increase in soil bearing
capacities, as the injected lime forms thin lime-soil seams
throughout the soil mass, which create a moisture resistant
membrane that is locked into the mass. Also, the surface lime acts
as a seal, removing the cost of another surface seal. A
water/lime/fly-ash slurry is advantageous because of its
re-cementing ability across cracks and seams. These self-healing
properties make the soil less susceptible to deterioration under
repeated loads and greatly increase the compression and shear
strengths of the soil.
[0008] In these methods, the slurry is typically injected into the
ground through a linear array of probes spaced at approximately
five-foot intervals. A rectangular grid of injection points is
formed over the site and allowed to cure for a given time (e.g.,
twenty-four hours). Then, another injection pass is made over the
site at an orthographic offset from the original injection points.
Once several injection passes and cure periods have been performed,
the soil is examined to determine whether the activity, often
measured as potential vertical rise (PVR), has been sufficiently
reduced. If the activity has not been sufficiently reduced, more
injection passes are made over the site. Typically, these injection
processes require several passes and cure periods before initial
testing is performed and five to seven passes before the soil
activity is acceptable.
SUMMARY
[0009] Injection systems and processes may improve earth stability
of a site by simultaneously injecting a predominantly-aqueous
solution into the ground at a number of relatively closed-spaced
points. In one general aspect, a process for earth stabilization
includes inserting an array of liquid-conveying probes into the
ground of a site to a predetermined depth, the probes spaced
substantially less than five feet apart from each other, and
supplying a predominantly-aqueous solution to the probes. The
probes may, for example, be spaced at approximately two and
one-half feet. The process also includes inserting the probes a
predetermined further distance (e.g., one foot) into the ground and
supplying additional solution. The solution may, for example, be
supplied to the probes at a pressure above two-hundred pounds per
square inch.
[0010] The process may also include determining whether a
sufficient amount of solution has been supplied and inserting the
probes a predetermined further distance into the ground when a
sufficient amount of solution has been supplied. Determining
whether a sufficient amount of solution has been supplied may, for
example, include determining whether refusal has been achieved. The
process may additionally include extracting the array from the
ground, moving the array a second predetermined distance, and
inserting the array into the ground to the predetermined depth. The
second predetermined distance may, for example, be approximately
equal to the spacing of the probes.
[0011] The array may, for example, be linear and include seven
probes, which may each have a three-hundred and sixty degree spray
pattern. The predominantly-aqueous solution may, for example,
include a surfactant that is mixed at a rate of approximately one
gallon per three-thousand five-hundred gallons of water.
[0012] The process may also include continuing to insert the array
into the ground at different locations until the site is covered.
The process may additionally include measuring the potential
movement of the treated ground, determining whether the potential
movement of the treated ground is acceptable, and if the potential
movement of the treated ground is not acceptable, performing
another injection pass over the site.
[0013] In another general aspect, a system for earth stabilization
includes an array of liquid conveying probes and a system for
driving the probes into the ground. The probes are spaced
substantially less than five feet apart from each other and are
operable to convey a predominantly-aqueous solution into the
ground. The drive system may, for example, be operable to
individually drive each probe into the ground.
[0014] The system may also include a solution supply system and a
transport unit. The solution supply system may supply a
predominantly-aqueous solution to the probes, and the transport
unit may move the array and the driving system. The solution supply
system may be operable to control the solution flow to each
probe.
[0015] In another aspect, a process for earth stabilization
includes injecting a predominantly-aqueous solution into the ground
of a site by inserting an array of liquid conveying probes spaced
at substantially less than five feet apart at a plurality of
locations of the site and supplying a predominantly-aqueous
solution to the probes. The solution may, for example, be composed
of over ninety-eight percent water.
[0016] The process may also include inserting the probes to a
plurality of depths at each location of the site and injecting the
solution at each depth. The process may additionally include
determining whether a sufficient amount of solution has been
supplied at a depth before inserting the probes to another depth at
a location. The spacing of the probes may be approximately two and
one-half feet.
[0017] The process may further include measuring the potential
movement of the treated ground, determining whether the potential
movement of the treated ground is acceptable, and if the potential
movement of the treated ground is not acceptable, performing
another injection pass over the site.
[0018] In yet another aspect, an earth-stabilized site is achieved
by injecting a predominantly-aqueous solution into the ground at
simultaneous injection points spaced at substantially less than
five feet apart at a plurality of locations of the site to achieve
earth stabilization.
[0019] Various injection systems and processes may have one or more
features. For example, an injection system and process may allow as
few as one injection pass to be made over a site before testing for
activity remediation. This saves time and money and conserves
resources. Furthermore, an injection system and process may achieve
an average PVR of less than one percent in fewer than four
injection passes, which again saves times and money and conserves
resources. An injection system and process may also allow for
completing operations for nearby sites before moving to different
sites, which also saves time and money and conserves resources.
Saving time and money and conserving resources is important not
only to the contractor, it also allows relatively stable sites to
be made available to businesses, municipalities, and home owners at
cheaper prices.
[0020] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other features
will be apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0021] FIGS. 1A-C are line drawings illustrating one implementation
of a system for earth stabilization.
[0022] FIG. 2 is a conceptual drawing illustrating one example of
an injection pattern for earth stabilization.
[0023] FIGS. 3A-B are line drawings illustrating another
implementation of a system for earth stabilization.
[0024] FIG. 4 is a flow chart illustrating one implementation of a
process for earth stabilization.
[0025] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0026] Earth stabilization may be achieved by repeatedly injecting
a predominantly-aqueous solution into the ground of a site (e.g., a
home site, a building site, or any other parcel of land) through
simultaneous injection points spaced at substantially less than
five feet apart. In particular implementations, the injection
points are made by probes of a linear probe array. The injection
process decreases the potential vertical rise (PVR) in soils via
increased in-site soil moisture content. This may be especially
useful for remediating higher-activity soils.
[0027] FIGS. 1A-C illustrate one implementation of a system 100 for
earth stabilization. FIG. 1A provides a front oblique view of
system 100, and FIG. 1B provides a rear oblique view of the system.
FIG. 1C provides a front view of a component of the system.
[0028] As illustrated, system 100 includes a transportation unit
110, a linear probe array 120, and an aqueous solution supply
system 140. System 100 may be used to inject a
predominantly-aqueous solution into the ground of a site to
pre-swell higher-activity soils (e.g., clay) prior to construction
to achieve earth stabilization.
[0029] Transportation unit 110 is a track-mounted rig capable of
traversing a wet sub grade while loaded with linear probe array 120
and aqueous solution supply system 140. Typically, this will
require the transportation unit to have a minimum gross weight of
five tons (e.g., a D3B from Caterpillar, Inc. of Peoria, Ill.). The
transportation unit also has the capability of inserting linear
probe array 120 into a sub grade so as to limit lateral movement of
the linear probe array, to prevent blow-by at the probes.
[0030] Linear probe array 120 includes seven probes 122 that are
inserted into the ground. Probes 122 may, for example, be hollow
steel pipes with tapered ends, to assist in their insertion into
the ground. At or near the tapered ends, probes 122 may have ports,
typically in a 360.degree. pattern, to eject the solution from the
probes. Probes 122 are spaced at approximately two and one-half
feet from each other, although in other implementations, the
spacing between the probes may range from approximately one to four
feet. Probes 122 may be inserted into the ground from approximately
seven to sixteen feet in this implementation, depending on what the
particular ground formation being stabilized dictates.
[0031] Linear probe array 120 also includes probe guides 124 and a
probe driver 126. Probe guides 124 assist in maintaining the
spacing and alignment of probes 122 as they are inserted into the
ground. Probe driver 126 imparts force to the probes to insert them
into the ground. Probe guides 124 and probe driver 126 may be made
of steel or other appropriate material.
[0032] Linear probe array 120 additionally includes a probe drive
system 128. Probe drive system 128 is responsible for actuating
probe driver 126. Probe drive system 128 includes a hydraulic
cylinder 130 that is driven by a hydraulic motor 132. In this
implementation, hydraulic cylinder 130 is a two-stage cylinder,
although it may have any number of stages in other implementations.
Probe drive system 128 also includes guides 134. In this
implementation, guides 134 are chains that circulate around pulleys
and couple to probe driver 126 to stabilize the probe driver as it
is moved, although they may have any other appropriate
configuration in other implementations.
[0033] Aqueous solution supply system 140 includes a network of
supply lines 142 (e.g., hoses), one for each probe 122 in this
implementation. The supply lines may be composed or rubber, steel,
or any other appropriate material. Supply lines 142 are coupled to
manifold 144, which may be coupled to a high-pressure pumping unit
or other appropriate water source (e.g., a fire hydrant). A pumping
unit may use one or more centrifugal pumps, whether stationary or
mounted on the transportation unit, capable of producing between
approximately fifty and two-hundred and fifty pounds per square
inch of pressure at probes 122. The proper pressure to use may
depend on the soil at the site. A pressure gauge 146 on manifold
144 informs the system operator of the current supply pressure.
Pressure gauge 146 may, for example, be capable of indicating up to
two-hundred and fifty psi.
[0034] The aqueous solution delivered to manifold 144 is composed
of predominantly water, which may be non-potable. In certain
implementations, the aqueous solution is greater than ninety-nine
percent water. The aqueous solution may include certain additives,
such as, for example, a surfactant, which acts as a carrying agent
for the water, promoting better moisture penetration into a soil
mass, or other non-ionic wetting agent. One example of a suitable
additive is the NP 9.5 Mol surfactant from Advance Blending of
Mansfield, Tex. A surfactant may be added to the water at the rate
of approximately one gallon of surfactant per three-thousand
five-hundred gallons of water. Different surfactants, however, may
call for different rates.
[0035] In one mode of operation, system 100 achieves earth
stabilization by pumping a water/surfactant solution into a sub
grade at high pressure, preferably between approximately
two-hundred and two-hundred and fifty psi. Probes 122 are inserted
into the ground at a location of the site at eighteen inch
intervals, waiting for refusal at each insertion increment. Refusal
is typically achieved once the injected solution begins to return
to the surface. When refusal is achieved, probes 122 are advanced
to the next depth. The solution, following the path of least
resistance, is forced vertically and laterally into desiccated
fissures, tension cracks, and available voids to form a system of
supplementary moisture. Also, due to the high pressure, the
solution may break up the soil, providing additional paths for the
solution to reach and, hence, be absorbed by the soil.
[0036] Once probes 122 have been inserted to the appropriate depth
at a location of the site, probe drive system 128 extracts the
probes, and transportation unit 110 advances to the next location,
which is typically perpendicular to the linear probe array,
although other movements may be used. The distance of movement is
often approximately equal to the probe spacing, although other
appropriate distances can be used.
[0037] Typically, the probes are incrementally inserted into the
ground to depths ranging from approximately eight to fifteen feet.
Other depths, however, are possible. The incremental depth is
typically between one to two feet. Coverage of a site may include
injecting outside of a building footprint, typically between five
feet to ten feet.
[0038] Once a solution injection pass is completed over a site, the
site is allowed to cure for a period of time (e.g., twenty-four
hours), allowing time for moisture absorption. After the cure time
has elapsed, the soil may be tested, or a secondary injection pass
may be performed, with the consecutive injection points positioned
to provide enhanced distribution of the solution. Clay soils
containing a tremendous number of fractures due to an extreme lack
of moisture may require one or two passes without refusal to allow
soil swelling so the fissures will close.
[0039] FIG. 2 illustrates one example of an injection pattern 200
for use with system 100. As shown, injection pattern 200 includes a
first series of injection points 210 and a second series of
injection points 220. During stabilization, injection points 210a
are simultaneously made by a linear probe array 120. Then,
injection points 210b are simultaneously made by the linear probe
array, followed by injection points 210c and injection points 210d.
In the next pass over the site, injection points 220 are offset
orthographically from injection points 210. Thus, injection points
220a are simultaneously made by the linear probe array, followed by
injection points 220b and injection points 220c. The second pass
may be made before or after testing for remediation.
[0040] Post-injection tests may play a key role in the earth
stabilization process. The purpose of the tests is to establish
whether the injection has improved the soil conditions as
specified. The establishment of a pass/fail criterion may
facilitate the success of an injection project. Typically, a good
starting point is evaluating the existing moisture content and the
soil's liquid limit (LL). Assumptions can then be made about the
increased soil moisture content due to every injection pass; for
two and one-half foot centers, for example, a six-percent to
seven-percent moisture increase has been achieved per injection
pass. This will give a minimum number of injection passes to
perform before testing.
[0041] Testing a site's soil activity may be accomplished by any
one of a variety of techniques. Two common metrics for measuring a
site's soil activity are probable vertical movement (PVM) and
probable vertical rise (PVR).
[0042] Testing a site's PVM may be accomplished by the technique
prescribed by Texas Department of Transportation Method Tex-124-E.
This technique determines the maximum swell potential from very wet
conditions to very dry conditions.
[0043] PVR may be measured by a swell test. In a swell test, core
samples are taken using a three-inch, seamless Shelby tube advanced
to the depth of injection. Once in the lab, core samples are
subjected to the one-dimensional swell test described in ASTM
D-4546 method B. Basically, the procedure calls for placing a small
sample in a confining ring, placing the confining ring on a porous
stone, covering the confining ring by another porous stone, and
directly loading the sample to mimic overburden pressure. The
sample is then inundated with water, and a dial indicator is
affixed to measure the change in sample height. Once the indicator
has ceased to move, typically in thirty-six to seventy-two hours,
the change is recorded, the free swell percent is determined, and
the moisture gain is recorded. Typically, a one-percent swell
average with a two-percent maximum swell is allowed per core hole.
Core holes are often spaced at the rate of one per five-thousand
square feet, with typically at least two core holes per site.
[0044] Pocket penetrometer readings of each core sample may also be
taken on-site for a rudimentary analysis. Sometimes, pocket
penetrometer readings are used as a pass/fail criterion for
aqueous-solution injection. In such cases, readings of 3.0 T/SF or
lower are typically considered acceptable. These results, however,
can be misleading. A non-homogenous soil mass can contain
iron-laced material, calcareous particles, or unseen gravel that
will result in high readings even though the free swell potential
may be low. On the other hand, some of the plastic, yellow to
yellow-brown clays can produce a low reading and still have a high
swell potential. Thus, pocket penetrometer readings are typically
not as reliable as a free swell test.
[0045] Another technique for analyzing PVR examines soil suction.
Soil suction test results are available quickly, reducing
turn-around time for a failed sample. Currently, however, the soil
suction test is accepted as a failure only test. But the
relationship between soil suction and free swell is being examined,
and it is possible that once more data is acquired, the soil
suction test may replace the free swell test. Thus, swell results
could be provided in hours instead of days.
[0046] A common concern regarding aqueous-solution injection is
that moisture in the injected soils will be wicked into the
adjoining material, leaving a foundation vulnerable to settlement
or impending vertical swell. For fat clay, aqueous-solution
injection is typically continued until the moisture content is
increased to approximately one half the LL and the PVR is at or
below one-percent swell average. The very low permeability rate of
saturated clays and the strong bond that exists between hydrogen
atoms and clays resist potential moisture change in the treated
soil. Aqueous-solution injection is typically extended five to ten
feet beyond the planned perimeter of the structure to create a
sub-surface moisture barrier outside the structure's boundary.
[0047] Another concern in dealing with expansive soils is the
potential for low plasticity index (PI) fill to cause a bathtub
effect under the structure. Even with a clay seal over the fill,
moisture may collect in the select material, settle to the bottom,
and swell underlying expansive material. The structure may
experience whatever swell potential is available. When proper
drainage is provided for the fill, this problem is reduced. On
sites that require deep fill, however, providing proper drainage
may be costly. Select fill, in smaller quantities, may be used in
conjunction with aqueous-solution injection to combat these
effects. Materials below the select fill are pre-swelled, and the
moisture content is at or above optimal. This reduces the potential
for post-construction movement due to moisture permeation.
[0048] An important consideration of foundation design is
post-construction maintenance. This is especially true for
structural fill and soils that have been treated by
aqueous-solution injection. Exposed soils are susceptible to
increasing or decreasing surface moisture availability. It is
generally accepted that clay soils at or above the optimum moisture
content will neither absorb nor release their moisture easily. It
is recommended, therefore, that a moisture control program be
instituted for a five to ten foot zone around structures. If the
perimeter of the building is encased in concrete or another
moisture resistant material is present, the need for this program
is reduced.
[0049] Evaprotransportation is another major concern. Trees and
other plants that consume large quantities of water should be kept
away from the structure. It is estimated that a large tree can
consume as much as 150 gallons of water per day.
[0050] As damaging as a loss of moisture can be, excessive moisture
can cause heave that may not be repairable through remedial
foundation repair techniques. Under-slab utility line leaks and
poor drainage are the primary culprits of post-construction heave.
However, once the soil has been pre-swelled to achieve a low PVR,
the potential swell effect on the in-site soil is greatly reduced.
In particular implementations, an average potential swell of
one-percent or less over the profile of a sample is preferred.
[0051] Because an exposed soil surface may be susceptible to
drastic seasonal moisture changes, a moisture barrier may be
installed to prevent desiccation of the deeper soil mass. There are
a variety of acceptable moisture barriers. For example, a select
fill cap may be used. Once injection operations are accepted,
select fill is installed at a minimum of one-foot thick in six-inch
to eight-inch lifts. As another example, a concrete slab may be
used, if placed within three weeks of completed aqueous-solution
injection operations. As an additional example, a six-inch
lime-soil mix may be used. The lime may be mixed at a rate of four
to six percent at six to eight inches deep and compacted. An added
benefit of using a lime-soil mix is that a stable working platform
is created for other construction trades that follow. As a further
example, a six to eight mil polyethylene sheeting may be used.
Prior to aqueous-solution injection, approximately one foot of
material is excavated and stored on site. When the injection
operations are complete, the sub-grade is re-compacted, and the
sheeting is installed. The excavated fill is placed over the
sheeting to prevent wind and UV damage. Of course, adding water to
the surface soils on a regular basis in quantities sufficient to
maintain optimal moisture content is also a solution.
[0052] For a particular application, the following technique may be
used. In general, the technique includes preparing the site,
injecting the predominantly-aqueous solution, and testing the
site.
[0053] Site preparation includes clearing and grubbing the site. As
part of this, organic materials are removed from the area to be
injected. The area to be injected is then brought to grade minus
the thickness of the moisture barrier. Allowances also may be made
for the vertical movement that will occur due to the injection
process. Measures may be taken to provide for drainage of water
runoff as a result of the injection process. Injection operations
are typically completed before the installation of underground
utilities and foundation elements.
[0054] Application of the solution includes spacing the injections
on approximately two and one-half foot centers, each way.
Subsequent injections are offset orthographically one and
one-quarter foot from the previous pass. Previously used injection
holes are not used for subsequent injections. The area to be
injected extends a minimum of five feet beyond the general building
line.
[0055] Injection is made to the required depth or to impenetrable
material. Impenetrable material is defined as the point at which
two injection probes cannot be forced to the prescribed depth.
Injection shall be made in twelve to eighteen inch intervals to the
prescribed depth. The probes are held at each interval until
refusal, which is typically the point at which water flows from
fractures or previous injection holes.
[0056] A minimum of twenty-four hours is allowed between each
injection pass. Once the initial injection operations are complete,
the swell potential, moisture content, and/or other soil properties
are evaluated to determine acceptance of the injected areas. Test
results determine if additional injections are required.
[0057] During injection operations, a laboratory technician is
present at the site. Undisturbed samples are taken in one to two
foot intervals to the total injection depth, at a rate of one test
hole per five thousand square feet of injection area. A minimum of
three free swell tests are performed per test hole. Samples are
tested to represent overburden pressures of the sample depth.
[0058] Upon acceptance of the injection process, the exposed
surface is scarified to a depth of six inches and recompacted to
between ninety-five and one-hundred percent of standard Proctor
density (ASTM D 698) and a moisture content between zero and four
percentage points above the material's optimum value. The moisture
content of the injected soil is maintained until the slab is
placed. Loss of moisture is prevented by watering or a moisture
barrier. Open trenches are sealed or kept wet to prevent moisture
loss. Trenches are also backfilled with the excavated material. The
moisture content of the backfill is maintained in the range of zero
to four percentage points above the material's optimum moisture
content.
[0059] System 100 provides a variety of features. For example, the
system allows as few as one injection pass to be made over a site
before testing for activity remediation. This saves time and money
and conserves resources. Furthermore, the system can typically
achieve an average PVR of less than one percent in less than four
injection passes, which again saves times and money and conserves
resources.
[0060] The system also allows for completing operations for nearby
sites before moving to different sites, which also saves time and
money and conserves resources. With a conventional system, two
five-thousand square foot sites may typically be worked in one day.
But with a typical one-day cure period, two additional sites would
be worked the next day. Then, the system would have to be returned
to the original sites on the third day. With the current system,
however, one five-thousand square foot site may typically be worked
in day. The next day, an adjacent site may be worked, with the
system returning to the first site the next day. For four adjacent
sites, for example, this can result in twenty to thirty percent
less movement of the system.
[0061] Saving time and money and conserving resources is important
not only to the contractor. It also allows stable sites to be made
available to companies, municipalities, and home owners at a
cheaper price.
[0062] While system 100 has a variety of features, it is counter to
the accepted industry practice, which is to perform
predominantly-aqueous-solution injection on no less five-foot
centers. Moreover, at closer spacings, it is the commonly believed
that the injected aqueous solution will readily return to the
surface through the already established insertion points without
saturating the ground into which the water is being injected. Field
testing, however, has shown this not to be the case. The closer
spacing appears to lead to a super saturation of the soil, which
allows an introduction of more water at one time. For example,
using five-foot centers for injection points, it is assumed that a
two-percent to three-percent moisture content increase may be
achieved per injection pass. However, for two and one-half foot
centers, a six-percent to seven-percent moisture content increase
has been achieved per injection pass. Using high pressures (e.g.,
above two-hundred psi) also may facilitate saturation by breaking
down the soil so that additional paths for the solution are
available.
[0063] Using closer spacings also produces an effect that is
seemingly undesirable--it reduces the surface coverage rate,
assuming the probe array is advanced a distance approximately equal
to the probe spacing for each insertion. For example, a system
having four probes on five-foot centers may typically work two
five-thousand square-foot sites in one day. But a system having
seven probes on two and one-half foot centers may typically work
one five-thousand square-foot site in one day. Thus, not as much
progress is made on a one day basis. The increased soil moisture
content per injection pass, however, more than makes up for this
apparent shortcoming, by leading to fewer injection passes and/or
tests and, hence, to a faster site completion rate.
[0064] Although system 100 illustrates one implementation of a
system for earth stabilization, other implementations may include
fewer, additional, and/or a different arrangement of components.
For example, in other implementations, the transportation unit may
be any of a variety of other appropriate types of rigs (e.g., a
tractor). As another example, any number of probes may be used in
the array, and the probes may be inserted to any appropriate depths
(e.g., from five to fifty feet), depending on the application. As
an additional example, in certain implementations, probes may be
independently driven into the ground. In these implementations, the
probes may be inserted until impenetrability is achieved by two
probes. Furthermore, the probes may be driven by chains or other
appropriate driving mechanisms. As a further example, the manifold
of the solution supply system may be provided with separate
pressure gauges and/or shut-off valves for each probe.
[0065] FIGS. 3A-B illustrate another implementation of a system 300
for earth stabilization. FIG. 3A provides a front view of system
300, and FIG. 3B provides a front view of a component of the
system.
[0066] As illustrated, system 300 includes a transportation unit
310, a linear probe array 320, and an aqueous solution supply
system 340. System 300 may achieve earth stabilization by injecting
a predominantly-aqueous solution to a site to pre-swell expansive
soils prior to construction.
[0067] Transportation unit 310 is responsible for moving linear
probe array 320 and aqueous solution supply system 340 across a
site and holding it relatively stationary during an injection
sequence. As illustrated, transportation unit 310 is a
track-mounted rig (e.g., a bull dozer), but may be any other
appropriate vehicle capable of moving linear probe array 320 and
aqueous solution supply system 340 across a wet sub-grade.
[0068] Linear probe array 320 includes probes 322, frame elements
324, and probe towers 326. Frame elements 324 support probe towers
326 relative to transportation unit 310 and each other, and probe
towers 326 house and drive probes 322 into the ground. In this
implementation, probe towers 326 are spaced apart from each other
approximately two and one-half feet center-line to center-line,
although other appropriate spacings (e.g., one to four feet) may be
used. Linear probe array 320 also includes probe drive systems 328,
one for each probe tower 326. In this implementation, each of probe
drive systems 328 includes a hydraulic motor at the base of the
associated probe tower 326 and a drive chain system (not shown for
clarity) for advancing probes 322 into the ground. The drive chain
system loops from the hydraulic motor to the top of the associated
probe tower and interacts with the probe to drive it into the
ground. Each of probe drive systems 328 also has a pair of supply
lines 330 (only one pair of which are demarcated in FIG. 3A for
clarity) to supply hydraulic fluid. Supply lines 330 may, for
example, be hoses and are coupled to a hydraulic source under the
control of an operator of the transportation unit for use during
operation. Supply lines 330 are also coupled to quick disconnects
332 (only one of which is demarcated in FIG. 3A for clarity), which
allow ease of assembly and servicing of linear probe array 320.
[0069] Aqueous solution supply system 340 includes supply lines 342
(only one of which is demarcated in FIG. 3A for clarity) and fluid
connectors 344 (only one of which is demarcated in FIG. 3A for
clarity), one set for each of each of probes 322. Supply lines 342
may, for example, be hoses and are coupled to a manifold (not shown
for clarity) under control of the operator of the transportation
unit for use during operation. Supply lines 342 are also coupled to
quick disconnects 338 (only one of which is demarcated in FIG. 3A
for clarity), which allow ease of assembly and servicing of linear
probe array 320. Supply lines 342 and fluid connectors 344 (e.g.,
sleeves) are operable to move with probes 322 as they are inserted
into the ground.
[0070] In one mode of operation, system 300 achieves earth
stabilization by injecting a predominantly-aqueous solution (e.g.,
greater than ninety-eight percent water) into a sub grade at high
pressure, preferably between approximately two-hundred and
two-hundred and fifty psi. The aqueous solution may penetrate and
saturate the soil as described previously. Probes 322 are inserted
into the ground at eighteen inch intervals, waiting for refusal at
each insertion increment. When refusal is achieved, hydraulic
motors 328 are activated to advance probes 322 to the next
depth.
[0071] Because each probe 322 has its own associated probe drive
system 328, system 300 may independently drive the probes into the
ground. This may be beneficial when one of the probes encounters an
object (e.g., a rock) that it cannot penetrate, because the other
probes may continue to be advanced. When a number of the probes
cannot be advance anymore, the injection process at a particular
location of the site may be complete.
[0072] Once probes 322 have been inserted to the appropriate depth,
probe drive systems 328 are activated to extracts the probes, and
transportation unit 310 advances to the next location on the site.
The probes are then inserted again, and the solution injection
begins for that location.
[0073] Typically, the array is incrementally inserted into the
ground to depths ranging from approximately eight feet to fifteen
feet. Other depths, however, are possible. The incremental depth is
typically between one to two feet.
[0074] After injection at a particular location of the site, the
array is typically moved perpendicular to the array, although other
movements may be used. Also, the distance of movement is typically
the spacing of the array probes, although other spacings may be
used. Coverage of a site may include injecting outside of a
building footprint, typically between five feet to ten feet.
[0075] Although system 300 illustrates one implementation of a
system for earth stabilization, other systems may include fewer,
additional, and/or a different arrangement of components. For
example, although seven probe towers are shown, any other
appropriate number of probe towers may be used. As another example,
the quick-disconnect feature for the hydraulic lines and/or the
solution supply lines does not have to be implemented. As a further
example, electric motors could be used in place of the hydraulic
motors. As an additional example, a ram system could be used to
insert the probes into the ground.
[0076] FIG. 4 illustrates one implementation a process 400 for
earth stabilization. In particular, process 400 illustrates earth
stabilization for a particular site, such as a building site.
Process 400 may, for example, be one example of a process performed
with system 100.
[0077] Process 400 begins with inserting a linear probe array into
the ground (operation 404). The probes of the array may, for
example, be spaced approximately two and one-half feet apart from
each other.
[0078] After inserting the linear probe array into the ground,
process 400 calls for supplying a predominantly-aqueous solution to
the probes (operation 408). The solution may be composed of ninety
percent or more water, which may be potable or non-potable. Process
400 continues with determining whether a sufficient amount of the
solution has been supplied (operation 412). A sufficient amount of
the solution may have been supplied, for example, if refusal is
achieved, which may be determined by a visual inspection.
[0079] If a sufficient amount of the solution has not been
supplied, process 400 calls for continuing to supply the solution
(operation 408). Once a sufficient amount of the solution has been
supplied, however, process 400 calls for ceasing to supply the
solution (operation 416). Process 400 also calls for determining
whether the linear probe array has been inserted deep enough into
the ground (operation 420). The distance to insert the linear probe
array into the ground may be predetermined based on geophysical
reports regarding the ground at the site and the amount of
stabilization to be achieved. Typical distances include six to
forty feet, but other distances may be used depending on the
application.
[0080] If the linear probe array has not been inserted deep enough
into the ground, the linear probe array is inserted deeper into the
ground (operation 424), and the solution is supplied again
(operation 408). The incremental depth to insert the linear probe
array is typically between one to two feet.
[0081] If, however, the linear probe array has been inserted deep
enough into the ground, process 400 calls for extracting the linear
probe array from the ground (operation 428) and determining whether
the site has been covered (operation 432). A site may be covered,
for example, when a ten-foot perimeter has been created around a
projected building footprint or the entire parcel of land has been
treated.
[0082] If the site has not been covered, process 400 calls for
moving the linear probe array (operation 436). The linear probe
array may, for example, be moved in a direction perpendicular to
the linear probe array for a distance equal to the spacing between
the probes (e.g., two and one-half feet). Process 400 then calls
for inserting the linear probe array into the ground again
(operation 404) and again supplying the solution (operation
408).
[0083] If, however, the site has been covered, process 400 calls
for measuring the movement potential of the treated ground
(operation 440). Measuring the movement potential of the treated
ground may be accomplished by field test, laboratory tests, or
otherwise. Sometimes, the measurements may take several days to
perform; in the interim, other sites may be worked.
[0084] Process 400 also calls for determining whether the movement
potential is acceptable (operation 444). The movement potential may
be acceptable, for example, if no test point has a potential swell
of greater than 2% and the overall average potential swell is less
than 1%. If the potential movement is not acceptable, process 400
calls for inserting the linear probe array into the ground
(operation 404) to begin another injection pass over the site. If,
however, the potential movement is acceptable, the process is at an
end for that site.
[0085] Although FIG. 4 illustrates one implementation of a process
for earth stabilization, other processes may include fewer,
additional, and/or a different arrangement of operations. For
example, a process may have more than one injection pass over a
site before measuring movement potential. As another example, the
linear probe array may be offset orthographically on subsequent
passes over the site. As an additional example, a process may call
for determining whether the linear probe array has been inserted
deep enough into the ground before ceasing to supply the aqueous
solution or even before supplying the aqueous solution.
Furthermore, a determination of whether the site has been covered
may be made before extracting the linear probe array from the
ground or even before the linear probe array is inserted into the
ground. As a further example, a process may include site
preparation and/or finishing.
[0086] Several implementations have been discussed in detail, and a
number of other implementations have been mentioned or suggested.
Furthermore, a variety of additions, deletions, modifications, and
substitutions to these implementations will be readily apparent to
those skilled in the art while still achieving earth stabilization.
For at least these reasons, the scope of the invention is to be
measured by the appended claims, which may encompass one or more
aspects of one or more of the implementations.
* * * * *