Ground Improvement Using Sand Columns to Mitigate Liquefaction—A Case Study

Abstract

Soil strata is highly varying in nature and it is a challenging task for Geotechnical engineers to come up with the most suitable foundation system that is safe during static and dynamic loadings. In this paper, a case study on ground improvement using sand columns at Puri in Odisha is discussed. The strata at site comprised mostly fine sands of low SPT-N values with some intermittent clay seams at intermediate depths. The water table was also encountered at very shallow depths at the location. The geotechnical profile of the boreholes was analyzed on the guidelines of Seeds and Idris and it was observed that the liquefaction potential of the soil layers is prominent and ground improvement is inevitable up to a depth of 10.5 m below existing ground level in view of stability of structures. The selective methods like vibro compaction, dynamic compaction were considered to be the suitable methods for the ground improvement. However, as the liquefiable layer is 10–11 m deep from ground level, provision of sand column is found to be the best alternative to reach those depths. In this method, the natural sand is densified with displacement method so that the relative density of the sand will be enhanced to avert the liquefaction risk. It was proposed to use Raft foundation with supporting ground improvement. Field tests such as sand column test, Pre and post DPTs, SPTs tests were carried out at site for assessing the extent of improvement and the results for the same are briefed in this paper.