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SHALLOW SOIL MIXING
TECHNOLOGY OVERVIEW |
TABLE OF CONTENTS
- INTRODUCTION
- HISTORY
- METHODS
- APPLICATIONS
- CONCLUSION
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INTRODUCTION
Soil mixing is a technique that utilizes the introduction of an engineered grout or reagent to modify the physical or chemical characteristics of soil without excavating. The technique has numerous civil and environmental applications and can use a wide range of mixing equipment. |
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HISTORY
The practice of mixing soil with various reagents, such as cement, lime, bentonite, etc., has been used in the United States since the mid 1930s. Early applications were primarily for improving the engineering properties of soil for civil construction projects, including road and dam construction. Common equipment such as plows, discs and tillers were used to mix reagents with the soil at relatively shallow depths.
Modern soil mixing techniques in the United States can be traced back to the 1950s and the Mixed-In-Place Method. This method was used to construct piles by injecting cementitious grout from the tip of a drill rig's auger into the soil. In addition, major research and development of soil mixing techniques and equipment began in Japan about the same time.
With the adaptation, introduction, and development of speciality foundation construction equipment by the 1980s, advancement in soil mixing technologies became prevalent. These advances include increased depth capabilities, more homogeneous mixing, and the ability to capture harmful vapors common on environmental projects. |
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METHODS
The specific soil mixing method discussed below is known by several names, including Single Axis Mixing and Shallow Soil Mixing. Additional information on other soil mixing methods can be found at DEEPSOILMIXING.COM and JET-GROUTING.COM.
Single Axis Mixing uses a crane-mounted turntable or a self-contained hydraulic or electric drill rig to rotate and advance a specially designed mixing tool into the soil. The type of mixing tool is selected based on site requirements and will usually vary from six to twelve feet in diameter. The technique is generally used for depths up to 45 feet.
As the mixing tool advances, cement, grout or other reagents are injected into the soil through the tool. Reagents usually are mixed with water to produce a grout or slurry. Gases, such as hot air or steam, can be used with the process, particularly for environmental applications. The advancement and injection rates are phased to create treated soil columns.
Because soil mixing is an in-situ process, off-gassing is reduced in environmental applications. However, if required, a hood can be used to cover the point of mixing to further reduce emissions. In addition, a vacuum can be used to draw collected gasses through an emission treatment system. Soil mixing creates columns of uniformly treated soil. The columns can be used as individual elements, overlapped to form walls, or to treat soil masses for a variety of applications. |
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APPLICATIONS
Typical applications for soil mixing include:
- Groundwater barriers
- Retaining walls
- Foundations
- Mass treatment of subsurface contaminants using solidification, stabilization, and chemical oxidations.
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CONCLUSION
Whether the goal is to improve the bearing capacity of soft soils, provide structural support, reduce permeability, or to improve other soil characteristics, soil mixing is a valuable technique. |
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