CA1112466A - Foundation with liquid tight joints, and method of forming the same - Google Patents
Foundation with liquid tight joints, and method of forming the sameInfo
- Publication number
- CA1112466A CA1112466A CA310,813A CA310813A CA1112466A CA 1112466 A CA1112466 A CA 1112466A CA 310813 A CA310813 A CA 310813A CA 1112466 A CA1112466 A CA 1112466A
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- Prior art keywords
- water
- section
- trench
- sections
- slurry
- Prior art date
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Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/18—Bulkheads or similar walls made solely of concrete in situ
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- Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Bulkheads Adapted To Foundation Construction (AREA)
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
Abstract
Abstract of the Disclosure A method of constructing an in-ground liquid barrier in separate sections with liquid tight joints between the sections, and the barrier formed thereby. A barrier area is excavated and the sections formed therein, preferably by initially filling the excavation with a liquid sealing slurry and sequentially displacing portions of the slurry with a liquid impermeable barrier material to form barrier sections which are mutually abutting along leaky interfaces. A bore is drilled between adjacent sections in a direction generally transverse to the direction of leakage, and filled with a liquid sealing material to seal the joint. The sealing material preferably comprises a dry, hydro-expandable bentonite composition which expands to form a slurry sealant by permitting liquid to seep between the barrier sections into the bore and contact the bentonite therein.
Description
This invention relates to the construction art, and more particularly to a method of forming underground foundations with liquid tight joints and to the foundation walls constructed thereby.
There are numerous requirements for in-ground, water impermeable foundations in the construction trade. For example, trenches can be dug in the ground and filled with concrete to halt water seepage, or to allow an ex-cavation to proceed without seriously upsetting the geology of the surrounding land. Water tight construction is also highly desirable for building founda-tions. When the trenches or foundation sites are dug through solid clay or rock, the sides of the excavation are usually solid enough to enable the achievement of a considerable depth with either a back hoe or a drag-line digging machine. However, such conditions do not ordinarily exist where the ground is saturated with water and is composed of silt, sand and/or gravel.
If the water table is reached while attempting to dig a deep, narrow trench in a saturated sandy soil, the movement of water into the trench loosens the sand and collapses the structure, causing the entire formation to fall.
In order to reach the desired depth, the trench may ultimately have to be made so wide on the surface as to render the cost of filling prohibitive.
This problem has been substantially overcome in the past by a tech-nique commonly known as slurry trenching or diaphragm wall construction. Thisconstruction technique involves keeping the trench filled during digging with a slurry formed from a mixture of bentonite and water. As digging proceeds and more slurry is added, a tough, flexible seal forms on the inside of the trench and stops the flow of water through the trench walls. This film, to-gether with the pressure of the slurry behind it, holds the walls upright and water tight. During continued digging, the slurry moves into the freshly ex-posed dirt and commences i~s sealing action.
When the trench has been dug to the desired depth and filled with ,, _ 1 --slurry, metal pipes spanning the width of the trench are lowered into one sec-tion and act as lateral stops to isolate the section during its subsequent formation. The section is then filled with a water impermeable material such as concrete, clay, or a mixture of clay, sand and gravel while slurry is simul-taneously displaced from the trench section, preferably for recovery and re-use. The foundation material is then allowed to harden until the pipes at either end can be removed without the newly formed wall collapsing into the remainder of the trench. After removal of the pipes, another section adjacent to the first section is formed by placing a pipe at the far end of the new section, and filling the new section with foundation material while simultane-ously placing the slurry therein. After the new section has hardened suffi-ciently, additional sections can be formed in the same manner until the de-sired wall length is attained. With the use of this method and sophisticated digging equipment, depths of several hundred feet have been achieved.
Bentonite, and specifically sodium bentonite, has a property which makes it particularly useful as the agent for forming the slurry. When dis-persed in water, sodium bentonite adsorbs water onto the surface of its plate-lets, giving rise to a multitude of individual platelets of clay, each sur-rounded by a water jacket. This water jacket gives bentonite the ability to develop viscosity in water, and also to line the trench walls with a tough, thin film which reduces water permeability.
Nhile the above technique represents a marked advance over previous methods, there is still room for further improvement. Specifically, when a new section of concrete is poured it does not form a perfect bond with the previ-ously poured section, at least partly because the previous section retains a slurry coating. This creates an area of potential leakage in which water can seep through the wall along the 30int between ad3acent sections. In some cases the seepage problem has been severe enough to require the construction
There are numerous requirements for in-ground, water impermeable foundations in the construction trade. For example, trenches can be dug in the ground and filled with concrete to halt water seepage, or to allow an ex-cavation to proceed without seriously upsetting the geology of the surrounding land. Water tight construction is also highly desirable for building founda-tions. When the trenches or foundation sites are dug through solid clay or rock, the sides of the excavation are usually solid enough to enable the achievement of a considerable depth with either a back hoe or a drag-line digging machine. However, such conditions do not ordinarily exist where the ground is saturated with water and is composed of silt, sand and/or gravel.
If the water table is reached while attempting to dig a deep, narrow trench in a saturated sandy soil, the movement of water into the trench loosens the sand and collapses the structure, causing the entire formation to fall.
In order to reach the desired depth, the trench may ultimately have to be made so wide on the surface as to render the cost of filling prohibitive.
This problem has been substantially overcome in the past by a tech-nique commonly known as slurry trenching or diaphragm wall construction. Thisconstruction technique involves keeping the trench filled during digging with a slurry formed from a mixture of bentonite and water. As digging proceeds and more slurry is added, a tough, flexible seal forms on the inside of the trench and stops the flow of water through the trench walls. This film, to-gether with the pressure of the slurry behind it, holds the walls upright and water tight. During continued digging, the slurry moves into the freshly ex-posed dirt and commences i~s sealing action.
When the trench has been dug to the desired depth and filled with ,, _ 1 --slurry, metal pipes spanning the width of the trench are lowered into one sec-tion and act as lateral stops to isolate the section during its subsequent formation. The section is then filled with a water impermeable material such as concrete, clay, or a mixture of clay, sand and gravel while slurry is simul-taneously displaced from the trench section, preferably for recovery and re-use. The foundation material is then allowed to harden until the pipes at either end can be removed without the newly formed wall collapsing into the remainder of the trench. After removal of the pipes, another section adjacent to the first section is formed by placing a pipe at the far end of the new section, and filling the new section with foundation material while simultane-ously placing the slurry therein. After the new section has hardened suffi-ciently, additional sections can be formed in the same manner until the de-sired wall length is attained. With the use of this method and sophisticated digging equipment, depths of several hundred feet have been achieved.
Bentonite, and specifically sodium bentonite, has a property which makes it particularly useful as the agent for forming the slurry. When dis-persed in water, sodium bentonite adsorbs water onto the surface of its plate-lets, giving rise to a multitude of individual platelets of clay, each sur-rounded by a water jacket. This water jacket gives bentonite the ability to develop viscosity in water, and also to line the trench walls with a tough, thin film which reduces water permeability.
Nhile the above technique represents a marked advance over previous methods, there is still room for further improvement. Specifically, when a new section of concrete is poured it does not form a perfect bond with the previ-ously poured section, at least partly because the previous section retains a slurry coating. This creates an area of potential leakage in which water can seep through the wall along the 30int between ad3acent sections. In some cases the seepage problem has been severe enough to require the construction
- 2 -` ---of additional wall sections parallel to the primary foundation and adjacent each joint to stop leakage through the joints. Accordingly, there is still a need for an in-ground foundation that is internally waterproof, and a method of forming the same.
In view of the above problems associated with the prior art, the present invention provides a method of constructing a liquid impermeable barrier within a liquid permeable base, comprising the seq~ential steps of forming a first laterally extending liquid impermeable barrier section in the base to a predetermined depth, forming a second laterally extending liquid impermeable barrier section in the base, with a substantially continuous lateral boundary thereof abutting a lateral boundary of the first section along an interface which extends over substantially the entire surface area of said first section lateral boundary, forming a common void between the sections by removing barrier material from adjacent sides of the interface to substantially the full depths of sa;d sections, and substantially filling the void with a liquid sealing material to inhibit liquid leakage through said ba.rier along said interface.
The method is particularly suited to the slurry trenching technique.
In this application, the method of constructing a water impermeable wall, com-2Q prises excavating a generally vertical trench, substantially filling the - trench with a water sealing slurry simultaneously with excavation thereof, placing a pair of spaced generally vertically disposed isolating members in the trench, the members extending across substantially the full width of the trench to isolate a first trench section therebetween, one of the members supporting a detachable guide member adjacent its side which ~aces the trench section, the guide member being generally vertically disposed and substantially parallel to its supportive isolating member, introducing a setta~le water
In view of the above problems associated with the prior art, the present invention provides a method of constructing a liquid impermeable barrier within a liquid permeable base, comprising the seq~ential steps of forming a first laterally extending liquid impermeable barrier section in the base to a predetermined depth, forming a second laterally extending liquid impermeable barrier section in the base, with a substantially continuous lateral boundary thereof abutting a lateral boundary of the first section along an interface which extends over substantially the entire surface area of said first section lateral boundary, forming a common void between the sections by removing barrier material from adjacent sides of the interface to substantially the full depths of sa;d sections, and substantially filling the void with a liquid sealing material to inhibit liquid leakage through said ba.rier along said interface.
The method is particularly suited to the slurry trenching technique.
In this application, the method of constructing a water impermeable wall, com-2Q prises excavating a generally vertical trench, substantially filling the - trench with a water sealing slurry simultaneously with excavation thereof, placing a pair of spaced generally vertically disposed isolating members in the trench, the members extending across substantially the full width of the trench to isolate a first trench section therebetween, one of the members supporting a detachable guide member adjacent its side which ~aces the trench section, the guide member being generally vertically disposed and substantially parallel to its supportive isolating member, introducing a setta~le water
-3-impermeable material into the first trench section, and substantially simul-taneously therewith displacing the slurry therefrom, permitting the water impermeable material to harden sufficiently to assume the lateral contours of the isolating members, detaching the guide member from its supportive isolating member and removing the isolating members from the trench, placing a ger.erally vertically disposed isolating member in the trench on the guide member side of and laterally spaced from the first section, thereby isolating a second trench section, introducing a settable water impermeable material into the second trench section, and substantially simultaneously therewith displacing the 1~ slurry therefrom, permitting the water impermeable material to harden to form a second wall section having a common latera1 boundary with the first wall section, drilling through the guide member and adjacent water impermeable material with a drill of sufficient diameter to form a bore which substantially overlaps the boundary along its full vertical extent, and introducing a water sealar.t material into the bore to establish a water tight joint between said sections.
The water sealant material preferably comprises a bentonite slurry.
The step of introducing the bentonite slurry may comprise the steps of introducing into the bore a sufficient quantity of dry hydro-expandable bentonite material adapted, upon the addition of water, to form a water sealing slurry in the bore~ and permitting water to leak into the bore along the boundary between adjacent wall sections to form a slurry with the bentonite and there~y establiah a water tight joint between the sections.
A water impermeable wall manufactured according to the invention comprises a plurality of generally ~ertically disposed wall sections formed from a water impermea~le material, the sections extending in lateral succession with a lateral end of each section forming a su~stantially continuous interface ~"~
~ L~-Ç;b with a lateral end of the next adjacent section, a plurality of bores extending generally vertically along each of the interfaces, respectively, and projecting into the wall material on both sides of the interfaces, and a water sealing slurry, such as a hydrated bentonite suspension, substantially filling each of said bores to prevent transverse water leakage through said wall along said interfaces.
Further advantages and features of the invention will be apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof, taken together with the accompanying drawings, in which:
Figures 1 and 2 are plan views showing two stages in the construction of an inground foundation wall in accordance with the prior art;
Figures 3 and 4 are plan views showing two stages in the construction of an inground foundation wall in accordance with the present invention;
Figures 5, 6 and 7 are cross-sectional elevation views taken respec-tively along the lines 5 - 5, 6 - 6, and 7 - 7 of Figure 4;
Figure 8 is a plan view of an inground foundation wall at a construc-tion stage following the stage shown in Figure 4;
Figure 9 is a cross-sectional view taken along the lines 9-9 of Figure 8;
Figures 10 - 13 are fragmentary cross-sectional views showing succes-sive steps in the formation of a liquid tight joint between adjacent sections of the foundation wall, all taken along line 10 - 13 - 10 - 13 of Figure 8; and Figure 14 is a fragmentary cross-sectional view taken along the line 14 - 14 of Figure 8, showing a completcd joint.
~eferring first to Figure 1, an initial stage in the construction of an inground foundation wall or liquid barrier in accordance with the slurry trenching techni~ue described above is shown. A ~rench 2 has been dug to a desired depth and simultaneously filled with a slurry 4 comprising a mixture of bentonite and water. ~he proportionate quantities of the two ingredients for the particular application is generally recommended by the bentonite sull-_~_ ~.
plier. The factors to be considered in selecting a proper mixing ratio in-clude the purity of the water, in particular the calcium, magnesium or salt content; the temperature of the water; and the chemical composition of the soil. In general, the slurry should be of a sufficient viscosity to maintain the suspension of fine solids as excavation of the trench progresses, to mini-mize loss of water from the trench to the surrounding strata, and to be easily displaced by the concrete fill.
Isolating members such as metal pipes 6 and 8, having diameters suf-ficient to completely span the width of the trench and act as stops in isolat-ing an intermediate trench section 10, are lowered into the trench after it isflooded with slurry. Once the stage shown in Figure 1 has been reached, con-crete is poured into trench section 10, displacing the slurry therein which is preferabl~ pwmped away and reused. When the concrete has hardened enough for the wall section to retain its shape without collapsing into the trench, pipes 6 and 8 are removed and another pipe inserted into the trench, spaced another section distance to the right of section 10. Concrete is then poured into the space between section 10 and the new pipe, displacing the slurry therein and forming a second section. Additional sections are constructed by the same pro-cess of successively moving the pipe laterally and pouring concrete into the section between the new pipe location and the existing wall.
Figure 2 shows the condition of the wall with two sections 10 and 12 completed, and a pipe 14 placed in the trench laterally spaced to the right of section 12 to form the right hand boundary of a third section. Laterally ad-jacent wall sections 10 and 12 abut each other and are commonly bounded along a curved joint or interface 16, the exact shape of which is determined by the cross-section of the metal pipes. This interface is generally not water tight, and seepage can occur between the sections from ons side of the wall to the other. Should the lea~age pro~lem be serious supplementary wall 18, constructed alongside the primary wall adjacent the intersectional joints and indicated bydashed lines, were resorted to in the prior art to stem leakage flow.
The leakage problem is solved in a simpler and less expensive manner by the construction technique provided by the present invention. Referring to Figure 3, the same isolation pipes 6 and 8 are used to form section boundaries as in the prior art. However, in the preferred embodiment a drill guide mem-; ber 20 is detachably secured to the side of pipe 8 which faces the section to be poured. Guide member 20 preferably comprises a plastic pipe secured to pipe 8 by means of detachable or breakable clips or a relatively weak adhesive.
Member 20 is carried either in contact with the outer surface of pipe 8 orclosely adjacent thereto so as to be generally vertically oriented in the trench, as are pipes 6 and 8.
Construction of the wall proceeds generally as in the prior art.
However, before removing an isolating pipe from the trench, its attached guide member is first detached and left embedded in the concrete adjacent or slightly spaced from the lateral boundary of the section. A hole or bore of sufficient diameter to extend across the boundary between sections and into the concrete of each section is then drilled, using member 20 as a guide. Following this step the bore is at least partially filled with dry, hydro-expandable bento-nite. The bentonite can be provided in numèrous forms. For example, pelletscan be formed under high pressure and dropped into the bore, or lumps of an appropriate size may simply be taken from a dryer normally used for drying bentonite. Also, the bentonite can be placed in the bore either loose or in packaged form, such as inside a cardboard tube of the mailing tube variety ; which would deteriorate over a period of time once inside the box. Whatever form the bentonite takes, the formation of an effective liquid seal proceeds along similar lines. Assuming pellets are used, water ~hich subsequently ~eaks between ad3acent sections into the bore is absorbed by the pellets there--in, causing them to expand and form a slurry within the bore which seals off the intersectional joint from any leakage. The invention thus actually em-ploys an initial leakage partially through the wall to form a water tight joint.
Figure 4 shows a wall at an intermediate stage of contruction. Two sections 22 and 24 have already been filled with concrete, while a third sec-tion 26 is still filled with slurry and bounded laterally on the left by sec-tion 24 along interface 28, and on the right by metal isolating pipe 30 and attached plastic guide member 32. Section 24 is shown after the metal pipe forming its right-hand boundary has been detached from its associated guide member 34 ant removed, leaving member 34 secured in the concrete adjacent in-terface 28. Construction of an intersectional joint is shown advanced to completion between sections 22 and 24. A bore 36 has been drilled across the interface 38 between the two sections, using a guide member embedded in con-crete on the right hand side of section 22 as a drilling guide A sufficient quantity of bentonite pellets is then introduced into bore 36 to form a water sealing slurry 40 as water gradually seeps through interface 38 into bore 36.
Figures 5 - 7 illustrate the trench at various stages of construc-tion. In Figure 5 the trench section 42 to the right of isolating pipe 30 has been dug to a substantial depth relative to its width, and is flooded with slurry 4 to prevent the side walls from collapsing. Figure 6 shows section 26 at a later stage of construction, after it has been isolated and a cage 44 of reinforcing steel lowered through the slurry to rest on the bottom of the trench. Figure 7 shows completed section 22 filled with concrete 46 which has hardened and set to form a water impermeable barrier. Steel reinforcement 47 is cemented in place within the wall and adds to its structural strength. By comparing Figures 5, 6 and 7, it can be seen that the cross-sectional dimen-sions of the trench are substantially unchanged during the various stages of construction.
Referring now to Figure 8, the wall of Figure 4 is depicted at a somewhat more advanced stage, with section 26 filled with concrete. Figure 9 shows the metal pipe 30 and drill guide member 32 which form the right hand lateral boundary of section 26. Guide member 32 comprises a plastic pipe hav-ing a plurality of annular rings or flares 48 spaced along its length to assist in holding it in the concrete when pipe 30 is removed. Member 32 is shown se-cured to pipe 30 at the top by a band 50, which is removed prior to lifting pipe 30 out of the trench. Other means of attachment such as a weak adhesive bond or breakable coupling could also be used to hold the pipe and guide mem-ber together, the important factor being that the guide member remain in the trench while the pipe is being removed. In the embodiment shown, member 32 is slightly spaced from the section boundary formed by the left hand outer wall of pipe 30.
The cross-sectional appearance of interface 28 between sections 24 and 26, after removal of the isolation pipes and filling of section 26 with concrete, is shown in Figure 10. Guide member 32 extends out of the trench parallel to and slightly offset to the left of interface 28. In the next step of the method, illustrated in Figure 11, a concrete drill 52 is used to drill a vertical bore along the entire depth of the wall, using member 32 as a guide.
Drill bit 52 is larger in diameter than guide member 32, and overlaps inter-face 28 to extend the drill hole into section 26 as well as into section 24.
Guide member 32 is preferably about one inch to one and one half inches in diameter, while drill bit 52 is preferably about 4 inches in diameter.
The drilling operation forms a bore 54, which extends across boundary 2~ into both adiacent wall sections, as shown in Figure 12. The interface be-tween each successive pair of sections may thus be viewed as being character-ized in a direction transverse to the flow of water along the interface by end _ g _ .
portions 56 and 58 (seen in ~igure 8) at which the two wall sections are mutually abutting, and by an intermediate portion comprising the drilled bore.
In the next step, illustrated in Figure 13, bore 54 is filled with bentonite in the form of pellets 60 which have preferably been formed under high pressure to a diameter of approximately one centimeter. A preferred ben-tonite is sodium bentonite which is basically a hydratable montmorillonite clay having a sodium as its predominant exchangeable ion. As noted above, sodium bentonite will swell in water and is therefore the type of bentonite which is most useful in the present invention. However, the bentonite utilized in the present invention may also contain other cations such as magnesium or iron.
` The bentonite is preferably prepared in the form of a contaminant resistant composition in accordance with the teachings of United States Patent No. 3,949,560 by Arthur G. Clem, issued April 13, 1976 and assigned to the assignee of the present invention. This composition resists contamination from water which has acquired contaminants by passing over the concrete during transit along the interface to bore 54. The preferred composition as described in the referenced patent consists essentially of (A) bentonite; (B) a water-soluble dispersing agent selected from the group consisting of a water-soluble salt of phosphoric acid, a water-soluble suifate of the formula ROSO3X where R
is hydrocarbon of from 8 to 32 carbon atoms and X is a member selected from the group consisting of an alkaline metal or ammonium, and a water-soluble salt of leonardite; and (C) a water-soluble polymer selected from the group consisting of polyacrylic acid, water-soluble salts of polyacrylic acid, hydrolyzed poly-; acrylonitrile, polyvinyl ace~ate, polyvinyl alcohol, copolymers of the fore-going, and a &opolymer of acrylic acid and maleic anhydride, the amount of water-soluble polymer in said soil sealant composition being from 0.1% to 3.0%
by weight, and the amount of water-soluble dispersant in said sealant composi-b tion being from 0 1% to 3.0% by weight, the weight ratio of water-soluble dis-persant to water-soluble polymer being from 6:1 - 36.
Once a bore has been filled with bentonite pellets, water seeping transversely through the wall along the joint between wall sections enters the bore and causes the pellets therein to gradually hydrate and swell. Figure 14 shows a completed joint in which a suitable quantity of water has entered bore 36 to form a slurry with the bentonite pellets therein. The slurry es-tablishes an intermediate liquid tight seal which pre~ents any liquid flow between the opposite end portions 56 and 58 (seen in Figure 8) of interface 38 between sections 22 and 24. The leakage problem is thereby solved in an efficient and inexpensive manner, without having to extend the excavation beyond the limits of the primary wall.
While a particular embodiment of the invention has been shown and described, numerous additional modifications and variations are possible in light of the above teachings. For example, instead of filling the bores with dry bentonite pellets and allowing the pellets to expand and form a slurry under the influence of water seeping in ~hrough the joints, a slurry could be premixed and poured into the bore wet. Also, a number of different ways to provide a drilling guide may be envisioned, or the guide member may be dis-pensed with entirely and drilling performed~only with the use of externalguidance if the drilling equipment is suitable. In addition, while the prefer-red embodiment involves the construction of a liquid impermeable barrier in the ground, the invention could be applied to the construction of such barriers in bases other than soil. It is therefore intended that the scope of the in-vention be limited only in and by the terms of the appended claims.
The water sealant material preferably comprises a bentonite slurry.
The step of introducing the bentonite slurry may comprise the steps of introducing into the bore a sufficient quantity of dry hydro-expandable bentonite material adapted, upon the addition of water, to form a water sealing slurry in the bore~ and permitting water to leak into the bore along the boundary between adjacent wall sections to form a slurry with the bentonite and there~y establiah a water tight joint between the sections.
A water impermeable wall manufactured according to the invention comprises a plurality of generally ~ertically disposed wall sections formed from a water impermea~le material, the sections extending in lateral succession with a lateral end of each section forming a su~stantially continuous interface ~"~
~ L~-Ç;b with a lateral end of the next adjacent section, a plurality of bores extending generally vertically along each of the interfaces, respectively, and projecting into the wall material on both sides of the interfaces, and a water sealing slurry, such as a hydrated bentonite suspension, substantially filling each of said bores to prevent transverse water leakage through said wall along said interfaces.
Further advantages and features of the invention will be apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof, taken together with the accompanying drawings, in which:
Figures 1 and 2 are plan views showing two stages in the construction of an inground foundation wall in accordance with the prior art;
Figures 3 and 4 are plan views showing two stages in the construction of an inground foundation wall in accordance with the present invention;
Figures 5, 6 and 7 are cross-sectional elevation views taken respec-tively along the lines 5 - 5, 6 - 6, and 7 - 7 of Figure 4;
Figure 8 is a plan view of an inground foundation wall at a construc-tion stage following the stage shown in Figure 4;
Figure 9 is a cross-sectional view taken along the lines 9-9 of Figure 8;
Figures 10 - 13 are fragmentary cross-sectional views showing succes-sive steps in the formation of a liquid tight joint between adjacent sections of the foundation wall, all taken along line 10 - 13 - 10 - 13 of Figure 8; and Figure 14 is a fragmentary cross-sectional view taken along the line 14 - 14 of Figure 8, showing a completcd joint.
~eferring first to Figure 1, an initial stage in the construction of an inground foundation wall or liquid barrier in accordance with the slurry trenching techni~ue described above is shown. A ~rench 2 has been dug to a desired depth and simultaneously filled with a slurry 4 comprising a mixture of bentonite and water. ~he proportionate quantities of the two ingredients for the particular application is generally recommended by the bentonite sull-_~_ ~.
plier. The factors to be considered in selecting a proper mixing ratio in-clude the purity of the water, in particular the calcium, magnesium or salt content; the temperature of the water; and the chemical composition of the soil. In general, the slurry should be of a sufficient viscosity to maintain the suspension of fine solids as excavation of the trench progresses, to mini-mize loss of water from the trench to the surrounding strata, and to be easily displaced by the concrete fill.
Isolating members such as metal pipes 6 and 8, having diameters suf-ficient to completely span the width of the trench and act as stops in isolat-ing an intermediate trench section 10, are lowered into the trench after it isflooded with slurry. Once the stage shown in Figure 1 has been reached, con-crete is poured into trench section 10, displacing the slurry therein which is preferabl~ pwmped away and reused. When the concrete has hardened enough for the wall section to retain its shape without collapsing into the trench, pipes 6 and 8 are removed and another pipe inserted into the trench, spaced another section distance to the right of section 10. Concrete is then poured into the space between section 10 and the new pipe, displacing the slurry therein and forming a second section. Additional sections are constructed by the same pro-cess of successively moving the pipe laterally and pouring concrete into the section between the new pipe location and the existing wall.
Figure 2 shows the condition of the wall with two sections 10 and 12 completed, and a pipe 14 placed in the trench laterally spaced to the right of section 12 to form the right hand boundary of a third section. Laterally ad-jacent wall sections 10 and 12 abut each other and are commonly bounded along a curved joint or interface 16, the exact shape of which is determined by the cross-section of the metal pipes. This interface is generally not water tight, and seepage can occur between the sections from ons side of the wall to the other. Should the lea~age pro~lem be serious supplementary wall 18, constructed alongside the primary wall adjacent the intersectional joints and indicated bydashed lines, were resorted to in the prior art to stem leakage flow.
The leakage problem is solved in a simpler and less expensive manner by the construction technique provided by the present invention. Referring to Figure 3, the same isolation pipes 6 and 8 are used to form section boundaries as in the prior art. However, in the preferred embodiment a drill guide mem-; ber 20 is detachably secured to the side of pipe 8 which faces the section to be poured. Guide member 20 preferably comprises a plastic pipe secured to pipe 8 by means of detachable or breakable clips or a relatively weak adhesive.
Member 20 is carried either in contact with the outer surface of pipe 8 orclosely adjacent thereto so as to be generally vertically oriented in the trench, as are pipes 6 and 8.
Construction of the wall proceeds generally as in the prior art.
However, before removing an isolating pipe from the trench, its attached guide member is first detached and left embedded in the concrete adjacent or slightly spaced from the lateral boundary of the section. A hole or bore of sufficient diameter to extend across the boundary between sections and into the concrete of each section is then drilled, using member 20 as a guide. Following this step the bore is at least partially filled with dry, hydro-expandable bento-nite. The bentonite can be provided in numèrous forms. For example, pelletscan be formed under high pressure and dropped into the bore, or lumps of an appropriate size may simply be taken from a dryer normally used for drying bentonite. Also, the bentonite can be placed in the bore either loose or in packaged form, such as inside a cardboard tube of the mailing tube variety ; which would deteriorate over a period of time once inside the box. Whatever form the bentonite takes, the formation of an effective liquid seal proceeds along similar lines. Assuming pellets are used, water ~hich subsequently ~eaks between ad3acent sections into the bore is absorbed by the pellets there--in, causing them to expand and form a slurry within the bore which seals off the intersectional joint from any leakage. The invention thus actually em-ploys an initial leakage partially through the wall to form a water tight joint.
Figure 4 shows a wall at an intermediate stage of contruction. Two sections 22 and 24 have already been filled with concrete, while a third sec-tion 26 is still filled with slurry and bounded laterally on the left by sec-tion 24 along interface 28, and on the right by metal isolating pipe 30 and attached plastic guide member 32. Section 24 is shown after the metal pipe forming its right-hand boundary has been detached from its associated guide member 34 ant removed, leaving member 34 secured in the concrete adjacent in-terface 28. Construction of an intersectional joint is shown advanced to completion between sections 22 and 24. A bore 36 has been drilled across the interface 38 between the two sections, using a guide member embedded in con-crete on the right hand side of section 22 as a drilling guide A sufficient quantity of bentonite pellets is then introduced into bore 36 to form a water sealing slurry 40 as water gradually seeps through interface 38 into bore 36.
Figures 5 - 7 illustrate the trench at various stages of construc-tion. In Figure 5 the trench section 42 to the right of isolating pipe 30 has been dug to a substantial depth relative to its width, and is flooded with slurry 4 to prevent the side walls from collapsing. Figure 6 shows section 26 at a later stage of construction, after it has been isolated and a cage 44 of reinforcing steel lowered through the slurry to rest on the bottom of the trench. Figure 7 shows completed section 22 filled with concrete 46 which has hardened and set to form a water impermeable barrier. Steel reinforcement 47 is cemented in place within the wall and adds to its structural strength. By comparing Figures 5, 6 and 7, it can be seen that the cross-sectional dimen-sions of the trench are substantially unchanged during the various stages of construction.
Referring now to Figure 8, the wall of Figure 4 is depicted at a somewhat more advanced stage, with section 26 filled with concrete. Figure 9 shows the metal pipe 30 and drill guide member 32 which form the right hand lateral boundary of section 26. Guide member 32 comprises a plastic pipe hav-ing a plurality of annular rings or flares 48 spaced along its length to assist in holding it in the concrete when pipe 30 is removed. Member 32 is shown se-cured to pipe 30 at the top by a band 50, which is removed prior to lifting pipe 30 out of the trench. Other means of attachment such as a weak adhesive bond or breakable coupling could also be used to hold the pipe and guide mem-ber together, the important factor being that the guide member remain in the trench while the pipe is being removed. In the embodiment shown, member 32 is slightly spaced from the section boundary formed by the left hand outer wall of pipe 30.
The cross-sectional appearance of interface 28 between sections 24 and 26, after removal of the isolation pipes and filling of section 26 with concrete, is shown in Figure 10. Guide member 32 extends out of the trench parallel to and slightly offset to the left of interface 28. In the next step of the method, illustrated in Figure 11, a concrete drill 52 is used to drill a vertical bore along the entire depth of the wall, using member 32 as a guide.
Drill bit 52 is larger in diameter than guide member 32, and overlaps inter-face 28 to extend the drill hole into section 26 as well as into section 24.
Guide member 32 is preferably about one inch to one and one half inches in diameter, while drill bit 52 is preferably about 4 inches in diameter.
The drilling operation forms a bore 54, which extends across boundary 2~ into both adiacent wall sections, as shown in Figure 12. The interface be-tween each successive pair of sections may thus be viewed as being character-ized in a direction transverse to the flow of water along the interface by end _ g _ .
portions 56 and 58 (seen in ~igure 8) at which the two wall sections are mutually abutting, and by an intermediate portion comprising the drilled bore.
In the next step, illustrated in Figure 13, bore 54 is filled with bentonite in the form of pellets 60 which have preferably been formed under high pressure to a diameter of approximately one centimeter. A preferred ben-tonite is sodium bentonite which is basically a hydratable montmorillonite clay having a sodium as its predominant exchangeable ion. As noted above, sodium bentonite will swell in water and is therefore the type of bentonite which is most useful in the present invention. However, the bentonite utilized in the present invention may also contain other cations such as magnesium or iron.
` The bentonite is preferably prepared in the form of a contaminant resistant composition in accordance with the teachings of United States Patent No. 3,949,560 by Arthur G. Clem, issued April 13, 1976 and assigned to the assignee of the present invention. This composition resists contamination from water which has acquired contaminants by passing over the concrete during transit along the interface to bore 54. The preferred composition as described in the referenced patent consists essentially of (A) bentonite; (B) a water-soluble dispersing agent selected from the group consisting of a water-soluble salt of phosphoric acid, a water-soluble suifate of the formula ROSO3X where R
is hydrocarbon of from 8 to 32 carbon atoms and X is a member selected from the group consisting of an alkaline metal or ammonium, and a water-soluble salt of leonardite; and (C) a water-soluble polymer selected from the group consisting of polyacrylic acid, water-soluble salts of polyacrylic acid, hydrolyzed poly-; acrylonitrile, polyvinyl ace~ate, polyvinyl alcohol, copolymers of the fore-going, and a &opolymer of acrylic acid and maleic anhydride, the amount of water-soluble polymer in said soil sealant composition being from 0.1% to 3.0%
by weight, and the amount of water-soluble dispersant in said sealant composi-b tion being from 0 1% to 3.0% by weight, the weight ratio of water-soluble dis-persant to water-soluble polymer being from 6:1 - 36.
Once a bore has been filled with bentonite pellets, water seeping transversely through the wall along the joint between wall sections enters the bore and causes the pellets therein to gradually hydrate and swell. Figure 14 shows a completed joint in which a suitable quantity of water has entered bore 36 to form a slurry with the bentonite pellets therein. The slurry es-tablishes an intermediate liquid tight seal which pre~ents any liquid flow between the opposite end portions 56 and 58 (seen in Figure 8) of interface 38 between sections 22 and 24. The leakage problem is thereby solved in an efficient and inexpensive manner, without having to extend the excavation beyond the limits of the primary wall.
While a particular embodiment of the invention has been shown and described, numerous additional modifications and variations are possible in light of the above teachings. For example, instead of filling the bores with dry bentonite pellets and allowing the pellets to expand and form a slurry under the influence of water seeping in ~hrough the joints, a slurry could be premixed and poured into the bore wet. Also, a number of different ways to provide a drilling guide may be envisioned, or the guide member may be dis-pensed with entirely and drilling performed~only with the use of externalguidance if the drilling equipment is suitable. In addition, while the prefer-red embodiment involves the construction of a liquid impermeable barrier in the ground, the invention could be applied to the construction of such barriers in bases other than soil. It is therefore intended that the scope of the in-vention be limited only in and by the terms of the appended claims.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. The method of constructing a liquid impermeable barrier within a liquid permeable base, comprising the sequential steps of:
forming a first laterally extending liquid impermeable barrier section in said base to a predetermined depth;
forming a second laterally extending liquid impermeable barrier sec-tion in said base, with a substantially continuous lateral boundary thereof abutting a lateral boundary of said first section along an interface which extends over substantially the entire surface area of said first section lat-eral boundary;
forming a common void between said sections by removing barrier material from adjacent sides of said interface to substantially the full depths of said sections, and substantially filling said void with a liquid sealing material to inhibit liquid leakage through said barrier along said interface.
forming a first laterally extending liquid impermeable barrier section in said base to a predetermined depth;
forming a second laterally extending liquid impermeable barrier sec-tion in said base, with a substantially continuous lateral boundary thereof abutting a lateral boundary of said first section along an interface which extends over substantially the entire surface area of said first section lat-eral boundary;
forming a common void between said sections by removing barrier material from adjacent sides of said interface to substantially the full depths of said sections, and substantially filling said void with a liquid sealing material to inhibit liquid leakage through said barrier along said interface.
2. The method of claim 1, wherein said liquid sealing material comprises a hydrated bentonite.
3. The method of claim 2, wherein the step of introducing said liquid sealing material comprises the first step of introducing dry hydro-expandable bentonite material into said void, and the second step of permitting liquid to leak along the boundary between sections into said void to hydrate the bento-nite therein.
4. The method of constructing a water impermeable wall, comprising:
excavating a generally vertical trench;
substantially filling said trench with a water sealing slurry simul-taneously with excavation thereof;
placing a pair of spaced generally vertically disposed isolating mem-bers in said trench, said members extending across substantially the full width of said trench to isolate a first trench section therebetween, one of said members supporting a detachable guide member adjacent its side which faces the trench section, said guide member being generally vertically disposed and sub-stantially parallel to its supportive isolating member;
introducing a settable water impermeable material into said first trench section, and substantially simultaneously therewith displacing the slurry therefrom;
permitting the water impermeable material to harden sufficiently to assume the lateral contours of said isolating members;
detaching said guide member from its supportive isolating member and removing said isolating members from said trench;
placing a generally vertically disposed isolating member in said trench:
on the guide member side of and laterally spaced from said first section, there-by isolating a second trench section;
introducing a settable water impermeable material into said second trench section, and substantially simultaneously therewith displacing the slurry therefrom;
permitting the water impermeable material to harden to form a second wall section having a common lateral boundary with said first wall section;
drilling through said guide member and adjacent water impermeable material with a drill of sufficient diameter to form a bore which substantially overlaps said boundary along its full vertical extent; and introducing a water sealant material into said bore to establish a water tight joint between said sections.
excavating a generally vertical trench;
substantially filling said trench with a water sealing slurry simul-taneously with excavation thereof;
placing a pair of spaced generally vertically disposed isolating mem-bers in said trench, said members extending across substantially the full width of said trench to isolate a first trench section therebetween, one of said members supporting a detachable guide member adjacent its side which faces the trench section, said guide member being generally vertically disposed and sub-stantially parallel to its supportive isolating member;
introducing a settable water impermeable material into said first trench section, and substantially simultaneously therewith displacing the slurry therefrom;
permitting the water impermeable material to harden sufficiently to assume the lateral contours of said isolating members;
detaching said guide member from its supportive isolating member and removing said isolating members from said trench;
placing a generally vertically disposed isolating member in said trench:
on the guide member side of and laterally spaced from said first section, there-by isolating a second trench section;
introducing a settable water impermeable material into said second trench section, and substantially simultaneously therewith displacing the slurry therefrom;
permitting the water impermeable material to harden to form a second wall section having a common lateral boundary with said first wall section;
drilling through said guide member and adjacent water impermeable material with a drill of sufficient diameter to form a bore which substantially overlaps said boundary along its full vertical extent; and introducing a water sealant material into said bore to establish a water tight joint between said sections.
5. The method of claim 4, wherein said water sealant material comprises a bentonite slurry.
6. The method of claim 5, wherein the step of introducing the bentonite slurry comprises the steps of:
introducing into said bore a sufficient quantity of dry hydro-expandable bentonite material adapted, upon the addition of water, to form a water sealing slurry in said bore; and permitting water to leak into said bore along the boundary between adjacent wall sections to form a slurry with said bentonite and thereby es-tablish a water tight joint between said sections.
introducing into said bore a sufficient quantity of dry hydro-expandable bentonite material adapted, upon the addition of water, to form a water sealing slurry in said bore; and permitting water to leak into said bore along the boundary between adjacent wall sections to form a slurry with said bentonite and thereby es-tablish a water tight joint between said sections.
7. A water impermeable wall, comprising:
a plurality of generally vertically disposed wall sections formed from a water impermeable material, said sections extending in lateral succes-sion with a lateral end of each section forming a substantially continuous interface with a lateral end of the next adjacent section;
a plurality of bores extending generally vertically along each of said interfaces, respectively, and projecting into the wall material on both sides of said interfaces; and a water sealing slurry substantially filling each of said bores to prevent transverse water leakage through said wall along said interfaces.
a plurality of generally vertically disposed wall sections formed from a water impermeable material, said sections extending in lateral succes-sion with a lateral end of each section forming a substantially continuous interface with a lateral end of the next adjacent section;
a plurality of bores extending generally vertically along each of said interfaces, respectively, and projecting into the wall material on both sides of said interfaces; and a water sealing slurry substantially filling each of said bores to prevent transverse water leakage through said wall along said interfaces.
8. The water impermeable wall of claim 7, wherein said slurry comprises a hydrated bentonite composition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US83135877A | 1977-09-08 | 1977-09-08 | |
| US831,358 | 1977-09-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1112466A true CA1112466A (en) | 1981-11-17 |
Family
ID=25258859
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA310,813A Expired CA1112466A (en) | 1977-09-08 | 1978-09-07 | Foundation with liquid tight joints, and method of forming the same |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1112466A (en) |
| DE (1) | DE2838363A1 (en) |
| GB (1) | GB2003965B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4784522A (en) * | 1986-11-14 | 1988-11-15 | Dennis Mraz | Method and apparatus for effecting high pressure isolation of liquids |
| US4818144A (en) * | 1986-11-14 | 1989-04-04 | Dennis Mraz | Flood isolation dam |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3218516A1 (en) * | 1982-05-17 | 1983-11-24 | Philipp Holzmann Ag, 6000 Frankfurt | SHUTDOWN DEVICE FOR SLOT WALL LAMPS |
| DE3717885C3 (en) * | 1987-05-27 | 1994-12-15 | Dyckerhoff & Widmann Ag | Method and device for producing a sealing layer from mineral sealing materials |
| AT388404B (en) * | 1987-09-14 | 1989-06-26 | Niv Spezial Grundbaugesellscha | Method of producing a seal in the joint between two segments of an underground wall produced in a diaphragm-wall type of construction, and apparatus for carrying out this method |
| DE3823874C1 (en) * | 1988-07-14 | 1989-11-16 | Dyckerhoff & Widmann Ag, 8000 Muenchen, De | Dry mixture for producing a flat-spread sealing layer |
| GB9204927D0 (en) * | 1992-03-06 | 1992-04-22 | Finic Bv | Process for farming water-tight joint |
| DE4343851C1 (en) * | 1993-12-22 | 1995-06-29 | Bauer Spezialtiefbau | Reinforced concrete underground curtain |
-
1978
- 1978-09-02 DE DE19782838363 patent/DE2838363A1/en not_active Withdrawn
- 1978-09-07 CA CA310,813A patent/CA1112466A/en not_active Expired
- 1978-09-08 GB GB7836113A patent/GB2003965B/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4784522A (en) * | 1986-11-14 | 1988-11-15 | Dennis Mraz | Method and apparatus for effecting high pressure isolation of liquids |
| US4818144A (en) * | 1986-11-14 | 1989-04-04 | Dennis Mraz | Flood isolation dam |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2838363A1 (en) | 1979-03-29 |
| GB2003965A (en) | 1979-03-21 |
| GB2003965B (en) | 1982-02-03 |
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