At-Rest Earth Pressure of Overconsolidated Collapsible Soil Subjected to Full Inundation

Collapsible soil can be found in several parts of the world. Collapsible soil is categorized as problematic soil, which displays high shear strength when it is in dry or at low degree of saturation condition, and experiences radical particles rearrangement and sudden deformation when inundated. In the field, collapsible soil can be inundated from the bottom due to rising the groundwater table or from the top due to rainfall, excessive irrigation, leakage of underground water/sewer pipe lines. This paper presents the results of an experimental investigation on walls retaining collapsible soil at the dry and at full saturation conditions. A prototype model of a vertical wall retaining horizontal backfill of collapsible soil was developed in the laboratory. The model was instrumented to measure the at-rest earth pressure at strategic points on the wall and in the soil mass, the total earth pressure acting on the wall, the overconsolidation ratio (OCR) and the collapse potential (Cp) of the soil. Test results showed that for collapsible soil at the dry condition, the coefficient of earth pressure at-rest increased with the increase of the overconsolidation ratio (OCR) and agreed well with the theories available in the literature. After full inundation, the coefficient of earth pressure at-rest decreased with the increase of the collapse potential (Cp), while the particles interlocking due to overconsolidation is dismantled. Empirical formulae are presented to predict the coefficient of at-rest earth pressure of overconsolidated collapsible soil for the dry and saturated states.