Numerical Analysis of Shallow Foundations Considering Hydraulic Hysteresis and Deformation Dependent Soil-Water Retention

Abstract

Shallow foundations are one of the most common methods for transmitting loads of structures to the underlying ground. Design standards are often based on the bearing capacity of shallow foundations in saturated soils or dry soils. However, many shallow foundations are located within unsaturated soil above the groundwater table. Although experimental studies show that the bearing capacity is significantly increased by the presence of suction in unsaturated soils, the foundation settlement caused by infiltration, e.g., due to rainfall and pipe leaking, may develop further problems for structures, such as wall cracks, sticking windows and doors and the presence of water in basements. This kind of damage is happening more often now, with more extreme weather conditions as a result of climate change. A finite element model has been developed in this paper to analyse shallow foundation behaviour under infiltration conditions. An advanced unsaturated soil model has been implemented in the finite element code that considers the soil-water retention with hysteresis and deformation dependency. Numerical analysis results indicate that the foundation settlement is significantly influenced by the hydraulic history (seasonal changes with drying-wetting cycles), and hydraulic hysteresis should be included in the numerical analysis of the mechanical response of shallow foundations in unsaturated soils.