Evaluation of Hydro-Mechanical Behavior of Collapsible Soil

Abstract

Collapsible soils are generally found in arid and semi-arid regions of the world, which undergo large deformation upon loading and wetting, showing significant decrease in void ratio. These soils are quite spread in Pakistan, in addition to other regions of the world. Research shows that cracks are generally developed in the structure, built on such types of soils during or after certain period of construction work which ultimately results in the structure failure, leading to human and financial losses. These changes in the performance of these soils are associated with changes in their hydraulic and mechanical properties due to moisture content variations over time. So, in this study, the hydraulic and mechanical properties of untreated and treated collapsible soils were investigated for various moisture contents of the compaction curve. The grain size distribution, Atterberg limits, standard Proctor, direct shear, oedometer and hydraulic conductivity were performed in this regard. The additives, such as ground granulated blast furnace slag (GGBS) and bagasse ash (BA) were used to improve the engineering behavior of collapsible soil in this study. GGBS and BA are the by-products of iron and sugarcane. The test results show that the Kallar Kahar soil falls in the category of low plastic clay (CL) and the collapsible potential of treated soil is about 50-60%less than untreated soil. The dry unit weight decreases and optimum moisture content increases up to a certain threshold of BA and GGBS, showing that there is no efficacy to use additives beyond a certain threshold. The cohesion and angle of internal friction are relatively higher for dry of optimum than wet of optimum side. Furthermore, the treated soil shows lower hydraulic conductivity than untreated soil due to their lower void ratios and higher consolidation potential.