Analytical Studies on the Use of Stiffer Drains for Soft Soil Improvement

Abstract

AbstractThe objective of the present study is to examine the use of stiffer drains for accelerating consolidation and soft soil improvement. Higher drained elastic modulus of stiff drains when compared to soft clay is assumed in the study. Soft soil and stiffer drains are considered to deform one dimensionally during the consolidation process. The analytical solutions presented in the study are based on the vertical and radial consolidation after Terzaghi 1D and Barron solutions for free draining wells, respectively. The study was carried out in the framework of a unit cell. Equal strain between the stiffer drain and the surrounding soil at any depth is assumed in the solution. The solution also accounts for the changes in stress on stiffer drain and the soft soil which is also presented in terms of stress concentration ratio, and improvement in the dissipation of excess pore water pressure with the installation of stiffer drains is illustrated. The study demonstrates dissipation of excess pore water pressure by two factors, drainage and reduction of vertical stress on soft soil during consolidation. However, influence of any lateral deformation of the drain is not considered. Modified coefficients of consolidation which account for the effects of modular ratio are adopted. The acceleration in rate of consolidation by changing modular ratio (ratio of elastic moduli of drain to soft soil) and diameter ratio (ratio of influence diameter to drain diameter) is also presented.KeywordsSoft soil improvementSoft clayStiffer drainsConsolidationModular ratio