Failure Mechanism and Bearing Capacity of Footings Buried at Various Depths in Spatially Random Soil

The objective of this paper is to demonstrate how the spatial variability of random soil affects the failure mechanism and the ultimate bearing capacity of foundations buried at various depths. Anonlinear finite-element analysis combined with random field theory is employed to explore the vertical capacity of foundations embedded at different depths in random soil. Different possibilities of shear failures resulting from spatial patterns of soil are demonstrated and are used to explain the significant discrepancy between the bearing capacity of the random soil and that of uniform soil. The effect of the spatial pattern of the soil on the development of shear planes is also investigated, with the coefficients of variation for the bearing capacity demonstrated to be closely related to the shear plane length. The results of the statistical variation in the bearing capacity are provided for different embedment depths, and these are also reported as the failure probability of the footing compared with the established uniform soil bearing capacity. Safety factors are proposed for foundations at different levels of failure probability. This study provides a thorough understanding of the failure mechanisms of footings in random soil, especially where structures can penetrate deeply into soil. (C) 2014 American Society of Civil Engineers.