Abstract
The ultimate bearing capacity of shallow foundation supported by unsaturated soil depends on the degree of saturation of the soil within the influence zone because the strength and deformation parameters of soil are affected by the degree of saturation. As the degree of saturation varies with rainfall, surface runoff, evapotranspiration and other climatic and geotechnical parameters, these parameters must be systematically incorporated for accurately computing the ultimate bearing capacity. In this study, a framework is proposed to compute the ultimate bearing capacity of a shallow footing in unsaturated soil considering site specific rainfall and water table depth distributions. The randomness in rainfall and water table depth is systematically considered using Monte Carlo method. The infiltration of water through the unsaturated zone is modelled using Richards equation considering infiltration and water table location as the top and bottom boundary conditions, respectively. The results show that the bearing capacity calculated using the proposed method is approximately 2.7 times higher than that calculated using the deterministic approach with fully saturated soil parameters.
Highlights
Shallow foundations are typically considered as the simplest and most economical foundation for supporting small to medium size structures
The mean is the location parameter and the coefficient of variation takes into account the shape. With both of these measurements of the distribution, it can be understood that the empirical cumulative distribution function (CDF) created from the Monte Carlo simulations accurately represents the bearing capacity for the footings considered in Victorville, CA
To determine if considering the unsaturated soil mechanic principles is advantages for computing the ultimate bearing capacity over the conventional method based on fully saturated soil mechanics principles, the Meyerhof’s equation was used to calculate the bearing capacity of the footing assuming the soil to be fully saturated (Table 1) and compared with
Summary
Shallow foundations are typically considered as the simplest and most economical foundation for supporting small to medium size structures. They transfer the structural loads to the near surface soil that is mostly unsaturated and fluctuates. Recent studies show that the strength and deformation parameters of soil are influenced by the degree of saturation of the soil. Since the degree of saturation of the near surface soil varies with climatic and geotechnical parameters such as rainfall, water table depth, evapotranspiration, hydraulic conductivity, there can be variation in the strength and deformation parameters of the near surface soil. This paper focuses on systematically incorporating the site specific climatic and geotechnical parameters in computing ultimate bearing capacity of soil
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