On the use of spatially averaged shear strength for the bearing capacity of a shallow foundation Ching, Jianye; Hu, Yu-Gang; Phoon, Kok-Kwang
This study examines the validity for representing the mobilized shear strength as the spatial average over a prescribed soil volume. A shallow foundation problem is adopted to demonstrate this. The approach is simple. Two sets of field finite element (FEM) analyses are taken. The first set considers a spatially variable soil mass whose shear strength is simulated by a random field. The bearing capacity simulated by this first set of FEM is the actual (reference) capacity. The same random field is averaged over a prescribed volume of interest to obtain the mobilized value. The second set of FEM then considers a homogeneous soil mass whose shear strength is equal to this mobilized value. The bearing capacity simulated by this second set of FEM is then compared to the reference value. The comparison will be made on two levels. Level I compares the statistics of the two sets of capacities, whereas Level II compares the two sets of capacities on the 1:1 line. Based on these numerical studies, it is observed that the two sets of capacities are at most equal in “distribution”, but not “almost everywhere”.
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