Numerical analyses of the optimum length of stone columns and their encasements
Numerical analyses of the optimum length of stone columns and their encasements
Stone columns are vertical inclusions in soft soils formed by gravel. In very soft soils, they may be wrapped typically with a geotextile to increase its lateral capacity. In the latter case, they are usually named encased stone columns. Their critical or optimum length may be defined as the one where further lengthening of the column provides a negligible improvement and it is therefore not cost-effective to build columns longer than it. Besides, for encased stone columns, the optimum length of the encasement is also relevant. In previous finite element analyses, the authors have studied the column and encasement critical length considering a uniform soft soil layer with a linear elastic perfectly plastic behaviour for simplicity. For those cases, the optimum column length is around 1.5-2.0 times the footing diameter for encased stone columns, and slightly lower for ordinary stone columns, namely around 1.5. These critical lengths should be related to the loaded area and not to the column diameter. Here, the authors extend those previous analyses using a constitutive model that considers a stress-dependent soil stiffness, namely the Hardening Soil model. The results are very similar, but columns are slightly more effective when considering stress-dependent stiffness and the optimum column length is slightly lower. Finally, the critical length of the encasement is found to be slightly lower than the critical column length.
Jorge Castro; Marina Miranda; A. Marquez; Jesus Fernandez-Ruiz; Svetlana Melentijevic
18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)
D - Current and new construction methods
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