Creating deep and Impermeable barriers in the Earth
Patented method for Levee wall and Earthen Dam Keywall Construction
The Slim Wall Jet Grouting technique allows continuous cutoff walls to be constructed much deeper in the Earth and more economically than traditional methods. This technique may be useful in repair of earthen dams and levees.
It starts with pre-drilling a series of vertical holes in the ground along the desired path of the barrier. The holes are nominally 6 inches in diameter and 4 to 8 feet apart depending of soil conditions. Two jetting pipes are tethered together by a length of steel wire rope cable and inserted into adjacent holes. Each pipe has a jet orifice near its end that is pointed at the adjacent pipe. A liquid grout mixture is expelled from the jet orifices at sufficient energy to cut and form a connected pathway of grout/soil mixture between the two pipes as they are lowered into the adjacent holes. The tether cable extends between the two pipes and slices through the grout soil mixture as the pipes are lowered. The passage of the cable assures a continuous pathway has been formed between the adjacent pipes before allowing further downward progress. The cable is positioned relative to the jet orifices such that obstructions or rocks in the pathway between the pipes will stop the continued descent of the pipes and allow the energy of the jets to erode and cut through the obstruction. Downward progress then resumes automatically.
Upon reaching the bottom of the pre-drilled holes the pipes are lifted out of the holes and indexed one hole along the desired path and inserted to begin the next segment of the barrier. This allows the Barrier to be continuous from hole to hole. The tether cable forms a catenary arc as it is pulled down through the ground allowing it to adjust to variable spacing between adjacent bore holes.
Conventional jet grouted barriers have difficulty in maintaining continuity as depth increases. The drilled holes tend to diverge and do not remain close enough to assure continuity of the barrier. This is true of both connected column and X-panel type approaches. With the new technique barrier depth is limited only by the depth capability of the drilling machine.
The method may use many types of grout material from cement-bentonite to molten wax grout.
Carter Technologies offers a specialized molten wax that permeates through damp or wet soil to form a barrier beyond the actual disrupted soil. This helps ensure barrier continuity even in soft or wet soils that might tend to pinch out a grout due to lateral earth pressure.
The method may be practiced using two individual drilling machines or by custom-made drilling machine able to lower two pipes at once. The drilling machines may utilize the weight of the pipe to fall through the soil or they may utilize a hydraulic hammer to advanced the pipe through the soil.
Another variation of the technique is to use no jet grouting at all but simply allow gravity flow of a dense barrier grout such as Carter Technologies TECT B into the pathway created by the passage of the tether cable. Grout denser than the surrounding formation will fill the gap created by the passage of the tether cable and slightly expand it creating additional thickness of the barrier as opposed to allowing the barrier to be pinched out as is often the case with common cement bentonite grouts.
Variations on this process are available to construct barriers in horizontal orientation or even a basin shape such as under and existing landfill.
The process has issued current patents united States Canada and Japan available for license either exclusively or not exclusively or even assignment.
Construction of Flexible Subterranean Hydraulic Barriers in Soil and Rock-8281
WM2008 Conference, February 24 -28, 2008, Phoenix, AZ
E. E. Carter, P.E.
Carter Technologies Co, Sugar Land, Texas 77478
D.C. Cooper, Ph.D. Idaho National Laboratory
Idaho Falls, ID 83415
In the management of radioactive waste sites, there is sometimes a need to divert infiltration water; or contain or divert contaminated groundwater. This paper discusses several experimental techniques based on super permeating molten wax. Many of the methods are suited to form both vertical or horizontal barriers in-situ in the ground. The first method is based on thermally controlled permeation grouting between drilled holes that produces a very thick barrier in soil, rock, or even fractured rock up to 600 meters deep. The second method is a variation on jet grouting for producing a thin low cost barrier in soil. Also discussed is a technique for forming an infiltration barrier within the surface soil over an underground tank farm and a method for encapsulating a buried waste without excavation.
These new methods can produce durable subterranean barriers of high integrity. These barriers are made with a special malleable wax that soaks into the soil or rock matrix. The wax is far more impermeable than clay or cement and can flex and stretch in response to soil movements. The wax contains no water and is not prone to damage from soil moisture changes.
Technology available for license.
Carter Technologies Co.
9702 Garden Row Drive
Sugar Land, TX 77498
Phone (281) 495-2603