Effect of Unsaturated Soil Hydraulic Characteristics on Foundation Bearing Capacity in Mountainous Regions Using Slip-Line Theory

Abstract

Infrastructure development in mountainous regions is vital due to rapid population growth and increased tourism. Most of these regions are vulnerable to landslides under rainfall events due to changes in the shear strength of the soil slopes under wetting cycles. Thus, the stability of foundations on slopes must be evaluated under variably saturated conditions. Models for evaluating the bearing capacity of foundations on slopes by accounting for variably saturated and transient conditions are scarce. A comprehensive semi-analytical model in the slip-line framework was developed in this study to investigate the bearing capacity of foundations on slopes under various controlling factors. The proposed model integrated the slip-line theory using a one-dimensional unsaturated transient-flow equation––the Richards equation––to evaluate the stability of foundations on soil slopes under unsaturated transient-flow conditions. Suction stress profiles were estimated using different soil hydraulic models for partly saturated soils to incorporate into the slip-line theory for estimating the bearing capacity of foundations under different field conditions. The developed framework was successfully validated using the existing limited cases under unsaturated steady-state and transient conditions. A parametric study was undertaken to study the influence of soil type, slope angle, rainfall infiltration, and depth of water table. The influence of different unsaturated hydraulic characteristics on the bearing capacity was clearly brought out, for the first time, using the measured soil hydraulic characteristics data. The model performance was satisfactory and is useful for evaluating the bearing capacity of footings resting on slopes under different natural conditions.