Investigating the behavior of soil improved with a granular column before and after experiencing cyclic load considering the clogging in the column

Document Type : Research Article

Authors

1 Department of Civil Engineering, University of Qom, Qom, IRAN

2 Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, IRAN

Abstract

An attempt was made in the present study to evaluate the pre-and post-liquefaction behavior of the soft ground improved by granular columns (with and without a geogrid encasement) by simulating a loose soil mass reinforced with a granular column in a triaxial cell. For this purpose, a series of large-scale monotonic compressive tests and also stress-controlled cyclic triaxial tests followed by drained and undrained monotonic compression tests were carried out on the loose sand specimens including the granular column with and without geogrid encasement. The pre-cyclic behavior of specimens showed that the deformation modulus improvement due to the use of a stiffer encasement would be less noticeable in case of clogged granular columns. It was found that during a cyclic loading, the use of geogrid encasement will be effective in reducing cumulative settlements and mitigating the liquefaction potential when its tensile stiffness is large enough. Moreover, the post-cyclic behavior of specimens showed that the use of granular columns (whether encased or non-encased) decreased the dependence of the ground deformation modulus on the CSR changes so that the evaluation of the cyclic-induced ground deformation can be done completely independent of the cyclic loading magnitude. It was also found that the use of an encasement with appropriate stiffness played an important role in minimizing the loss of the strength of the ground stabilized by granular columns after experiencing cyclic loads, especially under large earthquakes and after the occurrence of possible liquefaction.

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