Bearing Capacity and Liquefaction Assessment of Shallow Foundations Resting on Vibro-Stone Column Densified Soil in Vallur Oil Terminal, India

This article includes bearing capacity and liquefaction potential analysis of shallow foundations in Vibro-stone column densified soil using Indian Standard (IS) codes and finite element methods. The efficacy of stone columns was demonstrated through a real field project in Vallur oil terminal, Chennai, India. The subsoil at the project site was majorly non-plastic silty liquefiable soil having a very soft silty clay layer at the top 2 to 3 m. The codal analysis showed the presence of a liquefiable layer at a depth of 3 to 5 m. However, the ultimate bearing capacity effectively increased by 3 to 4.5 times, and settlement reduced to 84-92% after Vibro-stone column installation. The finite element-based computer program PLAXIS 2D was used to perform numerical analyses with plane strain idealization. Primarily, all the soil layers were modeled as Mohr-Coulomb material in numerical analysis to compute bearing capacity and settlement before and after ground improvement. Then after an effective stress-based elastoplastic UBC3D-PLM material was used to model the liquefiable layer for liquefaction potential analysis in PLAXIS 2D. The numerical analyses exhibited that the stone columns improved the bearing capacity by 43%, and consequently, the settlement was reduced by 2 times. Also, it was observed that introducing stone columns resulted in a considerable reduction in excess pore water pressure. The bearing capacity and settlement values obtained from codal and numerical analyses were compared and found to be in good agreement. The calculated settlements were within the desired limit, and the estimated bearing capacity values were greater than the allowable load intensity. Hence, the installation of Vibro-stone columns can be an effective solution to improve the strength of liquefiable soil.