U.S. patent application number 13/810159 was filed with the patent office on 2013-07-18 for base seal for a dump, in particular a residual salt dump.
This patent application is currently assigned to K+S Aktiengesellschaft. The applicant listed for this patent is Ines Feldberg, Hans-Joachim Kind, Matthias Kockx, Michael Lesch, Albrecht Palm, Martin Westphal. Invention is credited to Ines Feldberg, Hans-Joachim Kind, Matthias Kockx, Michael Lesch, Albrecht Palm, Martin Westphal.
Application Number | 20130183103 13/810159 |
Document ID | / |
Family ID | 44653913 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130183103 |
Kind Code |
A1 |
Feldberg; Ines ; et
al. |
July 18, 2013 |
BASE SEAL FOR A DUMP, IN PARTICULAR A RESIDUAL SALT DUMP
Abstract
The invention relates to a base seal of a dump, in particular a
residual salt dump, said seal comprising two layers disposed on top
of one another. The upper layer has a mixture of gravel, sand and
bentonite or powered clay with a permeability coefficient of
k.ltoreq.10.sup.-9 m/s and the lower layer has a mixture of sand
and bentonite or powered clay with a permeability coefficient of
k.ltoreq.5*10.sup.-10 m/s.
Inventors: |
Feldberg; Ines;
(Haldensleben, DE) ; Kind; Hans-Joachim;
(Hohenwarthe, DE) ; Kockx; Matthias; (Magdeburg,
DE) ; Lesch; Michael; (Steinfeld, DE) ; Palm;
Albrecht; (Garlipp, DE) ; Westphal; Martin;
(Wolmirstedt, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Feldberg; Ines
Kind; Hans-Joachim
Kockx; Matthias
Lesch; Michael
Palm; Albrecht
Westphal; Martin |
Haldensleben
Hohenwarthe
Magdeburg
Steinfeld
Garlipp
Wolmirstedt |
|
DE
DE
DE
DE
DE
DE |
|
|
Assignee: |
K+S Aktiengesellschaft
Kassel
DK
|
Family ID: |
44653913 |
Appl. No.: |
13/810159 |
Filed: |
May 17, 2011 |
PCT Filed: |
May 17, 2011 |
PCT NO: |
PCT/DE2011/001077 |
371 Date: |
March 27, 2013 |
Current U.S.
Class: |
405/263 ;
252/194 |
Current CPC
Class: |
E02D 31/002 20130101;
B09B 1/00 20130101 |
Class at
Publication: |
405/263 ;
252/194 |
International
Class: |
E02D 31/00 20060101
E02D031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2010 |
DE |
10 2010 026 863.1 |
Claims
1. A base seal of a dump, more specifically of a residual salt dump
comprising two layers disposed on top of one another, the upper
layer having a mixture of gravel, sand and bentonite or powdered
clay with a permeability coefficient of k.ltoreq.10.sup.-9 m/s, and
the lower layer having a mixture of sand and bentonite or powdered
clay with a permeability coefficient of k.ltoreq.5*10.sup.-10.
2. The base seal of a dump according to claim 1, characterized in
that the friction angle of the upper layer amounts to
.phi..gtoreq.35.degree..
3. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the friction angle of the lower layer
amounts to .phi..gtoreq.30.
4. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the mixture of the lower layer
comprises a polymer for improving the sealing properties.
5. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the sand has a grain range of 0-2
mm.
6. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the gravel has a grain range of 8-16
mm.
7. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the proportion of bentonite or
powdered clay in the mixture for the upper layer amounts to ca.
2-10 weight percent, preferably 3-5 weight percent.
8. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the proportion of bentonite or
powdered clay in the mixture for the lower layer amounts to
.gtoreq.11 weight percent.
9. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the upper layer has a thickness of
.gtoreq.0.2 m.
10. The base seal of a dump according to one of the afore-mentioned
claims, characterized in that the lower layer has a thickness of
.gtoreq.0.1 m.
Description
[0001] Dumps or surface landfills of a whole variety of types are
known, for example also residual salt dumps. Such residual salt
dumps frequently have a height of more than 120 m and generate
corresponding distributed loads and shear stresses. This means that
due to the great weight, high normal and tangential forces are
applied onto the substrate of the support surface. The consequence
of this is a deformation at the base of the dump, i.e. the
occurrence of subsidences and vertical displacements. In the area
of the deformation, extensions and compressions of the seal system
can occur. In the center of the dump, these deformations, here
subsidences, are greater than in the edge area in consequence of
the extra load. In the edge areas, vertical displacements also
occur in addition to the subsidences. These deformations must be
absorbed by the base seal system under the respective local dump
conditions.
[0002] The prior art for sealing the dump basis are clay seals,
which are also used in residual salt dumps. Hereby, a layer of clay
with a thickness of about 0.3 m is applied onto the subsoil, onto
which the dump is piled. The permeability coefficient of such a
clay layer is of k.ltoreq.10.sup.-9 m/s. Another variant consists
in a so-called enrichment of the surface soil. An enriched surface
soil is a soil into which powdered clay or bentonite is
incorporated with a corresponding weight proportion. Depending on
the composition of the soil, the proportion of powdered clay
amounts to between 3 and 10 weight percent.
[0003] In this context, it is known from EP 0 456 035 A2 in a road
surfacing for drivable traffic areas, primarily in the area of gas
stations, to provide below the roadbed a sealing layer made of a
mixture of clay minerals, for example montmorillonite and other
mineral materials. The mixture is composed of fractions of
different grain sizes in such a manner that the volume of the
respectively finer graining is greater than the pore volume of the
respectively coarser graining and the coarsest grain of the finer
graining is equal or smaller than about 1/10 of the smallest grain
of the coarser graining.
[0004] From EP 0 453 619 A1, a multilayered ground is moreover
known for areas in which water-polluting substances, more
specifically hydrocarbons, are poured and transferred, which has a
barrier layer containing bentonite.
[0005] Due to the conditions specific to the dump (high load,
accumulation of salted dump water, solubility, and viscoplastic
behavior of the dump material), the base seal must have a
corresponding solidity that resists to the mechanical stresses and
does not negatively influence the stability of the dump body. On
the other hand, it must be sufficiently deformable to absorb the
deformations of the ground and of the base seal caused by the extra
load, without losing its effectiveness.
[0006] The object underlying the invention is therefore to provide
an alternative base seal for a dump, more specifically a residual
salt dump that can resist to deformations under local conditions,
without a substantial deterioration of the permeability
coefficient.
[0007] In order to solve the object, it is proposed according to
the invention, that in a base seal of a dump, more specifically a
residual salt dump, the base seal comprises two layers disposed on
top of one another, the upper layer comprising a mixture of gravel,
sand and bentonite or powdered clay with a permeability coefficient
of k.ltoreq.10.sup.-9 m/s, and the lower layer has a mixture of
sand and bentonite or powdered clay with a permeability coefficient
of k.ltoreq.5*10.sup.-10 m/s. The choice between bentonite or
powdered clay as a part of the mixture for forming the layer of the
base seal depends on which material is actually available in
sufficient quantity. When using bentonite, the proportion of
smectite amounts to more than 50%, the powdered clay contains
illite and smectite in different proportions. A base seal that is
configured in this manner acts in the following way under the load
of the dump: the upper layer of the base seal with a mixture of
gravel, sand and bentonite or powdered clay constitutes a so-called
graded, mineral seal, wherein the grain range of the sand amounts
to between 0 and 2 mm and the grain range of the gravel between 8
and 16 mm. The lower layer that is made of sand and bentonite or
powdered clay has a more ductile consistency than the upper layer.
Due to the weight of the dump, stresses appear at the base, which
can lead to extensions and compressions. If such a deformation
occurs, it has turned out that in case of an extension of the base
seal, the upper layer penetrates into the lower layer and ensures
there that the base seal continues to fulfill its function. This
means that the base seal regenerates itself in the course of the
deformation.
[0008] Advantageous features and embodiments of the invention can
be gathered from the sub-claims.
[0009] Thus, it is more specifically provided that the angle of
friction of the upper layer amounts to .phi..gtoreq.35.degree. and
that of the lower layer to .phi..gtoreq.30.degree.. During a
deformation of the base seal, which can occur vertically as well as
horizontally, as a consequence of the load, the material of the
mixture of the lower layer can penetrate into the underside of the
upper layer and in this manner provides for a substantially
unchanged permeability coefficient. In order to reduce the
permeability coefficient, a polymer (for example, a long carbon
chain with a high molecular weight and correspondingly active side
chains) can be added to the mixture of the lower layer, which also
improves salt resistance.
[0010] Furthermore, it has turned out that for the upper layer the
proportion of bentonite or powdered clay in the mixture amounts to
ca. 2 to 10 weight-percent, preferably 3 to 5 weight-percent of the
entire mixture. The proportion of bentonite or powdered clay in the
mixture for the lower layer amounts to .gtoreq.11 weight-percent in
relation to the entire mixture. Moreover it has turned out to be
advantageous if the upper layer has a thickness of .gtoreq.0.2 m,
whereas the lower layer has a thickness of .gtoreq.0.1 m. At this
point, it must be pointed out that the amount of powdered clay or
bentonite in the mixture of the upper layer depends substantially
on the grain distribution of the gravel portion. This means that
the addition of powdered clay or bentonite depends on the grain
distribution. In the prior art, the grain distribution is
determined in laboratory tests and the bentonite or powdered clay
proportion is matched with it. Therefore, it must be noted that due
to the stresses, the individual layers seal off one another due to
the press-fitting.
[0011] In the following, the invention is exemplarily described and
submitted in more detail based on the drawings:
[0012] FIG. 1 shows a schematic section of a residual salt
dump;
[0013] FIG. 2 schematically shows a two-layered base seal in the
initial condition;
[0014] FIG. 3 shows a base seal according to FIG. 2 after a
deformation.
[0015] The residual salt dump labeled 1 stands on the subsoil 2,
the base seal labeled 10 being located between the residual salt
dump I and the subsoil 2. The base seal labeled 10 comprises the
upper layer 11 and the lower layer 15. The upper layer 11 comprises
a mixture of gravel, sand and bentonite or powdered clay, whereas
the lower layer is thinner and comprises sand and bentonite or
powdered clay. In the representation according to FIG. 2, the
initial condition of the base seal is shown.
[0016] It is known that the base seal can be deformed under the
action of the stresses. The effectiveness of the base seal is not
influenced in the deformed areas, which are compressed and
compacted. In the areas that are extended and compacted, the
effectiveness can increase, i.e. the permeability coefficient
remains constant or decreases. The principle of the base seal
according to the invention consists in that the lower layer 15,
which is formed thinner and more ductile than the lower layer 16,
is pressed into the lower part of the upper layer and the
effectiveness of the entire base seal thus remains the same or
increases.
* * * * *