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Abstract

In this study, the bearing capacity of a surface foundation resting on a double-layered cohesive soil profile was investigated by applying a rotational mechanism and finite-difference numerical simulations. The bearing capacity factor behaviors of a surface footing on double-layered cohesive soils can be classified and illustrated using a characteristic chart. Depending on the soil strata strength ratio and normalized layer thickness, the soil-foundation system can be in the squeezing, factor-increasing, factor-decreasing, or constant factor zones. The results indicated that the trend of the curves in the characteristic chart computed from the asymmetric failure mechanism was in accordance with that of the symmetric failure mechanism of the numerical simulation. Based on the strength conditions of the upper and lower soil layers, the soil plastic flow zone may enlarge, shrink, or even become constrained. For the analysis of the critical soil strength ratio that causes punching shear failure, the results from the SNAME method were less conservative. Moreover, the footing roughness effect was significant in the weaker upper soil case and may have contributed to a 25% higher bearing capacity.

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