Improvement of Penetration Resistance and Undrained Shear Strength Due to the Installation of Floating Stone Compaction Columns in Clay

Abstract

This paper presents a detailed investigation on quantifying the changes in the penetration resistance and undrained shear strength of clayey soil due to the installation of floating stone compaction columns. The columns were of 100-mm diameter, provided at 300-mm center-to-center spacing up to a depth of 5.0 m, and constructed using 6-mm broken stones. A total number of 12 locations were selected for the study considering various aspects. Standard Penetration Test and Static Cone Penetration Tests were conducted in the field and the penetration resistance of virgin soil and soil after stone column installation was investigated. The study was extended up to 2 years after installation to understand the behavior due to dissipation of pore water and consolidation settlement. A considerable increase in penetration resistance and hence an improvement in shear strength was observed due to the installation of floating stone compaction columns/piles (FSCPs). Empirical relations are proposed for predicting SPT N value after installation, and effective angle of internal friction for granular material and soil after installation.