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UBC Theses and Dissertations

Evaluation and control of collapsible soils in Okanagan-Thompson region Bigdeli, Amin


An increase in population levels has led to extensive land development and increased construction on problematic soils. Problematic soils such as collapsible soils are the main reason for many geological hazards that lead to significant maintenance costs. The existing gaps in knowledge regarding the characterization and remediation of collapsible soil have resulted in the amplification of these collapse-associated hazards. Although many studies have investigated collapsible soil, its behavior is not yet fully understood. Few studies have focused on the micro-mechanism of the soil structure during the collapse; consequently, the current methods used to characterize collapsible soil are not entirely reliable. It is essential to bridge this gap to understand collapsible soils better in order to reduce maintenance costs and save lives. With these research gaps in mind, this dissertation focused on characterizing collapsible soil by understanding the micro-mechanism of collapse, analyzing the pore-size distribution, and studying the relationship between the Soil Water Characteristic Curve (SWCC) and the micro-mechanics of collapse. Further, the outcomes of the study have been used to identify the influence of the pore water pH level on soil collapse. The results also aid in determining the feasibility of using a green stabilizer to control soil collapsibility. The results showed that the initial moisture content and therefore suction has the highest influence on the collapsibility of the soil. A transformation technique was proposed to constantly update the SWCC. This method showed a satisfactory correlation between total applied pressure and suction of the soil during consolidation of the soil. Further studies showed that infiltration of acidic pore water into the soil results in destruction of the micro/macro pores of the soil which leads to the collapsibility of the soil without any additional load. Finally, the results proved that the acidic environment developed in the soil due to the high solubility of MgCl2 in the water, force the soil to go under more settlement. It is shown that 7% MgCl2 solution causes the soil to experience 50% of its collapsibility prior to any loading after 28 days of curing.

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