Large-Scale Instrumented Triaxial Setup for Investigating the Response of Soft Clay Reinforced with Sand Column Groups

Abstract

Granular columns are widely used as a soil improvement solution adopted in the case of soft clays in an effort to increase their bearing capacity and stiffness. Granular columns, whether sand drains or gravel columns, are designed and constructed in groups and not as individual elements, given that there is a clear need to study the group effects and load sharing under various drainage conditions. Toward this need, a new fully instrumented triaxial test setup was developed and utilized to investigate the overall response of the composite. Particular emphasis was placed on monitoring pore-water pressures and contact stresses over the sand columns and the surrounding clay. The results from clay specimens that were reinforced at area replacement ratios of 17.1% and 30.4% indicate that the test setup is capable of quantifying the distribution of the stresses in the columns and the surrounding clay at different levels of axial strain. As such, previous information about the dependency of the stress concentration ratio on the area replacement ratio, axial strain, rate of loading, and drainage conditions could be inferred. It is anticipated that the insights gained and reported in this paper will facilitate the development of design methodologies for soft clays reinforced with sand column groups. © 2021 American Society of Civil Engineers.