Abstract

Collapsible soils are problematic soils that cover large parts of North and South America, Eastern Canada, Eastern Europe, China, Northern and Southern Africa, Russia and Egypt. Collapsible soils are identified as unsaturated soils that exhibit high strength when dry, but experience a drastic volume reduction when subjected to inundation. Due to today’s constant growth in construction and urban development, being exposed to these types of soils has become unavoidable. Collapsible soils are mainly challenging when exposed to water, which is usually the case in excavations where retaining walls are used. Therefore, this thesis focuses on analyzing the earth pressure acting on walls retaining collapsible soils subjected to partial inundation. The thesis will analyze the behavior of at-rest and passive earth pressure on walls retaining collapsible soils, with respect to the change in the degree of saturation, at variable values of over-consolidation ratio.
A 2-D finite element model was developed using the software “ABAQUS”, that incorporates the change in collapsible soils strength parameters when subjected to inundation. It employs the theory of unsaturated soil mechanics: including the soil water characteristic curve (SWCC) and the variation in the soil’s strength parameters (angle of friction, cohesion and modulus of elasticity) with respect to matric suction. The thesis presents empirical formulae that can be used to estimate both the coefficient of at-rest and passive earth pressure of walls retaining collapsible soils, for a given collapse potential, over-consolidation ratio, and degree of saturation.