Numerical simulations of stone column installation

Abstract

This paper describes the results of numerical simulations investigating the installation effects of stone columns in a natural soft clay. The geometry of the problem is simplified to axial symmetry, considering the installation of one column only. Stone column installation is modelled as an undrained expansion of a cylindrical cavity. The excess pore pressures generated in this process are subsequently assumed to dissipate towards the permeable column. The process is simulated using a finite element code that allows for large displacements. The properties of the soft clay correspond to Bothkennar clay, modelled using S-CLAY1 and S-CLAY1S, which are Cam clay–type models that account for anisotropy and destructuration. Stone column installation alters the surrounding soil. The expansion of the cavity generates excess pore pressures, increases the horizontal stresses of the soil, and most importantly modifies the soil structure. The numerical simulations performed allow quantitative assessment of the post-installation value of the lateral earth pressure coefficient and the changes in soil structure caused by column installation. These effects and their influence on stone column design are discussed.