Ground Improvement Techniques

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Techniques that can be employed to improve ground conditions range from jet grouting, dynamic compaction and lime stabilisation, to vibro-compaction, vibro-replacement (stone columns) and vibro-concrete columns to consolidation by pre-loading and deep soil mixing. 
geotechnics team have the specialist expertise needed to undertake these processes and can provide clients with support and advice.

Ground Improvement Technologies like Dynamic Compaction and In-Situ Soil Mixing among others are used to change the characteristics of soil or rock. Ground Improvement techniques have several applications such as

 Providing foundation support for structures

 Protection from earthquake-induced soil liquefaction

 Subsidence Remediation

 Site improvementThe experts at Geo Solutions can help you decide what Soil Improvement Technology would benefit your project.

Ground improvement techniques have developed greatly in recent years and have wide application in areas of construction such as:

• Tunneling
• Deep excavations
• Foundations
• Earthworks

Soil and rock grouting:

Soil and Rock Grouting is the injection of a slurry or grout into the subsurface profile. The grout fills cracks and voids and is used to strengthen the ground or to make it more water resistant. There are many kinds of soil grouting and rock grouting, which are specialized for different soil types and different project requirements. Grouting work can be simple or complex, highly laborious or highly mechanized. Often the most important decision is the decision as to which grouting technique will be successful at the lowest overall cost.

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Grouting to Stabilize a Retaining Wall

 

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Jet Grouting and Jet Mixing Techniques:

Jet grouting, also sometimes referred to as jet mixing, is a method of grouting that uses very high pressure streams (6,000 psi or 40 MPa) of grout to erode, replace, mix, and cement soils. Jet grout construction uses a rotating and rising drill rod with small nozzles that direct the grout horizontally to form columns of soilcrete or soil-cement. Typical column diameters are 2 to 6 ft. Jet grouting is the only type of grouting that is capable of treating all types of soils from clays to gravel. Jet grouting is also useful in grouting isolated zones of soil and for grouting around and below buried utilities.

Creating Soil-Concrete Columns Using Jet Grouting Technology:

There are at least three of types of jet grouting, some of which use air and / or water with the high pressure grout stream to improve soil penetration and column diameters. The procedure that is common to all jet grouting types (including double fluid jet grouting and triple fluid jet grouting) involves first drilling to the plan depth using small diameter drill rods. Next, a large and powerful pump is connected to the drill rod, which pumps the high pressure jet grout through the drill rods and horizontally into the soil. The drill rods are slowly rotated and raised creating columns of soil-cement. The shape of the grouted zone can be changed by directing the grout in ways that create panels, floors, or other shapes.

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Uses of jet grouting or jet mixing:

jet grouting is used to stabilize contaminated soils, create groundwater barriers and to underpin distressed foundations. Probably our most frequent application is the use of a jet grout with another technique, e.g. slurry walls or soil mixing, to extend the work into areas with limited access or into areas with concentrated utilities. Jet grouting uses smaller equipment and a small drill hole so it is well suited for work in tight quarters.

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From Ground and Sludge Stabilization to Hazardous Waste Treatment:

In Situ Soil Mixing is a technology that was reintroduced into the U.S in the late 1980's by the principals of Geo-Solutions. It is also referred to as auger mixing, In Situ Stabilization / Solidification, deep mixing method, soil cement columns / piles, SMW, cement soil mixing, rotary mixing, and, simply, soil mixing. Three specific types of In Situ Soil Mixing include Deep Soil Mixing (DSM), Shallow Soil Mixing (SSM), Backhoe Stabilization (BOSS). With In Situ Soil Mixing, a large diameter (typically 3 to 12 ft diameter) auger with mixing paddles and grout ports is drilled into the ground as a fluid grout is pumped through the shaft. The fluid acts as an aid to drilling and is mixed into the drilled soil column, creating a soil-cement mass.

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Soil Mixing Equipment

 

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The Uses of In Situ Soil Mixing:

In Situ Soil Mixing is used to create structural elements for foundations and retaining walls, soil improvement, and in situ treatments of buried contaminates. It is also used with specialized cementing and chemical reagents for hazardous waste treatment, sludge stabilization / solidification, lagoon stabilization, chemical oxidation, and for constructing underground vertical barriers for groundwater containment.

New Applications of In Situ Soil Mixing:

The in situ treatment of contaminated soils and groundwater with reactive media is a new and growing application for In Situ Soil Mixing. Regents such as zero valent iron, certain clays, carbon, oxidants, and reactive media can be economically introduced and mixed to treat chemical hot spots using Deep Soil Mixing and Shallow Soil Mixing. Geo-Solutions has been at the forefront of this type of application. We help formulate workable and practical soil / grout mixtures that can be used for sludge stabilization and the successful treatment of certain other toxic contaminants.

 

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Bio-Polymer Drains: 

Bio-Polymer (BP) Slurry Trenches are trenches or French drains constructed for draining, diverting or collecting groundwater or leachate. Bio-Polymer drains are typically used when in-the-dry installation methods are not feasible or unnecessarily expensive. The Bio-Polymer method is a modified slurry trench technique that temporarily supports deep and narrow trench walls below the groundwater table using a degradable polymer instead of bentonite slurry. Usually, a hydraulic excavator digs the drainage trench while the polymer slurry supports the trench walls. After the trench is backfilled, the slurry is degraded or reversed back to water and a minute amount of non-toxic residue leaving a fully functional drainage trench.

Groundwater and Leachate Collection, Reactive Barriers, Air Sparging, and Toe Drains:

Since their introduction into the USA in the 1980’s, Bio-Polymer trenches have been used on a variety of projects where steel sheet piling, trench boxes, mass excavation and/or dewatering have traditionally been used. The Bio-Polymer drainage trench method is much faster, safer, and less expensive than traditional methods and has been used in applications up to 80 ft deep. Typical applications include: 

 Landfill leachate collection

 Reactive barriers

 Toe drains for earthen dams

 Air sparging

 Groundwater collection for pump and treat systems.

Often Bio-Polymer trenches are combined with slurry walls for groundwater collection and containment using the same basic construction technique to create the barrier and the drain.

The Bio-Polymer method creates a narrow, open slot in the earth that permits the installation of most construction materials. Unlike bentonite slurry trenches, the polymer used in the slurry does not plug the formation, so groundwater can be collected in the drainage trench after the polymer is degraded. Because the polymer can degrade naturally, speed and expertise are required on every project, including groundwater collection and leachate collection. Plastic pipes and geo-fabrics float in the Bio-Polymer slurry.

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Permeable Reactive Barrier Wall Technologies:

A permeable reactive barrier wall or Insitu Chemical Reduction (ISCR) are technologies that remediate contaminated groundwater and soil without mass excavation, disposal or conventional "pump and treat" methods. Usually, a treatment media, or reactive barrier, is buried in a narrow trench beneath the ground surface so that contaminated groundwater passes through the media, and it emerges 'clean' because contaminates are treated and/or removed by the reactive barrier. Typical treatment media used as a permeable reactive barrier wall include granular iron, activated carbon, engineered bacteria, chemicals, and special clays.

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Permeable Reactive Barrier Wall Illustration

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Remediate and treat contaminated groundwater with a Permeable Reactive Barrier Wall (PRB):

Often, slurry walls are used to funnel the groundwater toward a reactive media gate; this type of installation is called a "funnel and gate". Special construction considerations are needed for installing reactive barrier walls to ensure the design life of the media and to be cost-effective. Since any permeable reactive barrier wall must be buried deep underground and below the groundwater table, geotechnical methods are quite useful in minimizing excavation volumes, eliminating dewatering, and reducing costs.

On some sites, the reactive media can be applied directly to the contamination instead of through a funnel and gate. Usually, these sites have lower groundwater flows and the contamination is less mobile. For these sites, In Situ Soil Mixing with ISCR provides an ideal method for applying the reactive materials directly without excavation or dewatering. In-situ treatment using soil mixing is usually much less expensive than off-site disposal and completely avoids excavation and transportation costs.