COEFFICIENT OF LATERAL EARTH PRESSURE FOR UNSATURATED SOILS

摘要

Based on Fredlund's two stress state variables for unsaturated soils, constitutive equations for continuous material and relation between matric suction and saturation degree are employed to establish formulas considering change both in matric suction and in bulk weight along depth to evaluate coefficients of three types of lateral earth pressure i. e. lateral earth pressure at rest and active and passive lateral earth pressure. After this, coefficients of an example are calculated in numerical integration method with aforementioned factors taken into account and some constructive results are obtained. Firstly, there are additional parameters in formulas for unsaturated soils comparing with saturated situation, for example strata depth and matric suction distribution. Secondly, coefficients of lateral earth pressure will increase with depth and may be zero near ground, that is to say cracks will take place. And when the soil is in active situation the cracks will be deeper than those in other two situations. Thirdly, the magnitudes of coefficient are closest to those of saturated soils when matric suction is linear decrease along depth. And especially, the larger the decrease rate is, the comparable the coefficients of unsaturated soils are to those of saturated soils.