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Abstract According to the available expressions about anisotropy of soil strength，the simple elasto-perfectly plastic Tresca model is modified to allow for the strength anisotropy of soft soil under undrained condition based on the general purpose finite element software ABAQUS. Combining swipe loading method with fixed displacement ratio loading method，the bearing capacity of shallow strip foundations under combined loading is simulated through finite element numerical studies. The effect of soil strength anisotropy and vertical load level on the failure envelope of shallow strip foundations is studied. The undrained bearing capacity of shallow strip foundations under uniaxial vertical(V)，moment(M) and horizontal(H) loads is predicted and compared with available solutions. Then the VMH capacity of shallow foundations under combined loading is reported in the form of slices through the three-dimensional VMH failure envelope as planes in H-M at various levels of vertical loads. The results show that the swipe path can considerably undercut the true failure envelope for shallow foundation with the ratio of buried depth to width larger than 0.5 or subjected to three degrees of freedom combined loading. For shallow foundation with given buried ratio，the size of the failure envelope is both dependent on soil strength anisotropy and the level of vertical load，however the shape of failure envelope is only dependent on the level of vertical load but almost independent on soil strength anisotropy.
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Received: 01 January 2010
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2010, Vol. 29 
