Triaxial response of natural clay reinforced with sand columns under partially drained conditions -

Abstract

Engineers in the field of soil improvement have long referred to the method of constructing sand columns to improve soft clays. This method of soil improvement is relatively more environmentally friendly, economical, faster and practical than other applied techniques. Sand columnar inclusions help accelerate the rate of consolidation, increase the loading-bearing capacity and reduce settlements. Various experimental studies have been conducted to investigate the main characteristics of this composite system. Recently the experimental studies shifted towards reliance on triaxial testing, where the confining pressure, drainage conditions and loading rates could be controlled and varied. A comprehensive assessment of published triaxial tests indicates that almost all tests are conducted using Kaolin clay with no data being gathered for natural clays. In addition, most studies were performed on fully drained or undrained conditions, in contrast to field conditions where the composite system is expected to exhibit partial drainage. The objectives of this study are to (1) conduct conventional drained and undrained triaxial tests to study the performance of natural clay specimens that are reinforced at intermediate and high area replacement ratios (about 18percent and 31percent respectively) under different confining pressures, (2) compare the results obtained with the results of previous tests performed under same conditions but on Kaolin samples, (3) conduct partially drained triaxial tests on natural clay specimens that are reinforced with sand columns and sheared at different rates of loading under a confining pressure of 100kPa, and (4) compare the results obtained from the partially drained tests with those from conventional drained and undrained tests. The series of triaxial tests will be performed on back-pressure saturated, normally consolidated, natural clay specimens from Achrafieh, Beirut, that are prepared from slurry. The parameters that are varied in the study are the confining pressures, drainage conditions, diame