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.

Description

RELATED APPLICATIONS

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

This invention relates to geophysics and, more particularly, to a process and system for earth stabilization.

BACKGROUND

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

FIGS. 1A-C are line drawings illustrating one implementation of a system for earth stabilization.

FIG. 2 is a conceptual drawing illustrating one example of an injection pattern for earth stabilization.

FIGS. 3A-B are line drawings illustrating another implementation of a system for earth stabilization.

FIG. 4 is a flow chart illustrating one implementation of a process for earth stabilization.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

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.

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.

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.

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.

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° 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.