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Custom Designed Rigid Inclusions Transfer Loads to Stable Layers for Greater Strength, Lower Cost, and Shorter Construction Time
Rigid inclusions are used for ground stabilization when a load must be transferred through very soft soils to stiffer soil or rock. They create a system structure that has potential for extensive soil stabilization. The technique itself dates from ancient times, but its use has expanded greatly since the 1990s. This recent attention has produced new and improved equipment that achieves better production at greater depths with increased loadbearing capacity. Excellent quality control is now possible, so that technical requirements, settlement factors, and load bearing parameters can be satisfied at lower cost with shorter lead times.
As with any geotechnical construction project, vertical rigid inclusions must be tailored to the subsurface conditions, including the types, depths, and compaction of various geologic strata—soil, organic matter, clay, rock, etc. Obviously, your geotechnical solution must also reflect the nature of the load on the site, whether it is a building, embankment, tank, or other type of project. Any ground slope and potential seismic activity requires consideration of lateral forces impacting the inclusion design as well. Earth Tech geotechnical engineers take all these factors into account and offer you effective and efficient approaches to ground stabilization for your specific project. The quality and affordability of your project is enhanced by our extensive rigid inclusion experience across the country.
Vertical rigid inclusions always involve creating high modulus columns of material whose stiffness is carefully controlled to make sure that the load ultimately rests on stable strata. The technique is most often used when substrata have poor mechanical properties and also in areas where the disposal of excavation debris creates issues of cost, logistics, or compliance. Fortunately, rigid inclusions can achieve massive soil improvement. Concrete contamination is prevented by continuous placement.
The difference between piles and rigid inclusions is that inclusions normally include a distribution layer or relieving platform known as an LTP (Load Transfer Platform). This distribution layer is placed at the top of the inclusions and under the load. Therefore, there is not a direct mechanical link between the inclusion and the structure. This layer spreads out the load toward the rigid inclusion system. Footings can be used to transfer concentrated loads to the inclusion structure, and a continuous LTP may not be required across the entire system.
Rigid inclusions may be used to support a landfill or embankment over compressible soils supported ultimately by a hard layer.
To accomplish rigid inclusions, a mandrel or hollow augur is used to penetrate the ground and displace weak soils laterally at the moment of drilling. This increases the compactness of soils with significant friction between particles. Forces applied may include vibration, rotor torque, and/or downward vertical force. This downward penetration continues until the design depth is reached. Concrete must be forced into the mandrel or hollow augur under pressure to begin filling the column.
As the mandrel or augur is lifted slightly, a cover at the bottom opens, allowing concrete under pressure to begin filling the hole. The mandrel or augur may be lowered and lifted multiple times to expand the column into surrounding soils as required by the design.
The operator who implements the process monitors various executional parameters to maintain quality. These factors include the drilling depth, the torque of the rotation, the pressure on the concrete, the volume of concrete inserted, and the rate of vertical motion. These variables may be recorded digitally across the entire rigid inclusion system and analyzed later for quality control verification. Strength tests on samples of the concrete used further enhances quality control and may be required by local regulations.
The load of a new building or structure produces an immediate shock to the soil on which it rests. It also generates settlement over time that can harm long term stability. Both load and settlement factors must be considered in designing an appropriate stabilization solution. Tailored geotechnical construction designs have varied impacts on project cost, time of construction, and environmental impact.
Earth Tech’s geotechnical experts have the experience to appropriately utilize the advantages of rigid inclusions as needed for your soil stabilization challenges.