Field Installation Effects of Stone Columns on Load Settlement Characteristics of Reinforced Soft Ground

Abstract

Soft-soil reinforcement with stone columns is a popular ground improvement method. Installation of columns modifies the surrounding soft soil properties; this phenomenon is termed “smear.” Although several previous investigations were carried out on smear zone characterization, appropriate field-based studies are limited. The authors performed field-based investigations to quantify the installation effects by collecting a series of undisturbed soil samples from a reinforced soft ground site with newly installed stone columns and conducting laboratory testing followed by nonlinear regression analysis. It is observed that the stone column installation induced significant alteration in the soft soil properties when the columns are closely spaced. An explicit fast Lagrange finite-difference modeling is carried out employing unit cell analogy, where the nonlinear variation in soft clay permeability and compressibility is simulated. The disturbed soft-soil parameters obtained are successfully utilized to conduct numerical modeling. To cross-check, a 2D finite-element modeling by PLAXIS has been carried out as well. It is observed that the results obtained from finite-difference model were in sufficient agreement with the measured field data, compared with the finite-element results. Brief descriptions of the investigation and relevant conclusions drawn are presented in the paper.