An analytical solution for the settlement of stone columns beneath rigid footings

This paper presents a new approximate solution to study the settlement of rigid footings resting on a soft soil improved with groups of stone columns. The solution development is fully analytical, but finite element analyses are used to verify the validity of some assumptions, such as a simplified geometric model, load distribution with depth and boundary conditions. Groups of stone columns are converted to equivalent single columns with the same cross-sectional area. So, the problem becomes axially symmetric. Soft soil is assumed as linear elastic but plastic strains are considered in the column using the Mohr-Coulomb yield criterion and a non-associated flow rule, with a constant dilatancy angle. Soil profile is divided into independent horizontal slices and equilibrium of stresses and compatibility of deformations are imposed in the vertical and horizontal directions. The solution is presented in a closed form and may be easily implemented in a spreadsheet. Comparisons of the proposed solution with numerical analyses show a good agreement for the whole range of common values, which confirms the validity of the solution and its hypotheses. The solution also compares well with a small scale laboratory test available in literature

Engineering of Ground for Liquefaction Mitigation

Liquefaction is considered as a major crucial hazard among different seismic risks. Ground improvement methods commonly employed, to improve the natural site conditions under such situations, lead to better performance of various engineering structures built up on. The paper presents various aspects of liquefaction hazard mitigation of loose saturated sands with a spectrum of ground engineering methods. A short discussion on liquefaction hazard associated with loose sand deposits and its evaluation followed by outlines of the ground engineering applications with the main focus on stone columns/granular piles, sand compaction piles, deep soil mixing, and dynamic compaction as liquefaction hazard mitigation measures are presented