Based On The Rock Foundation Bearing Capacity Limit In The Nonlinear Failure Criterion

Conventional calculations of bearing capacity were formulated in terms of a linear Mohr-Coulomb failure criterion. Some authors employed nonlinear failure criterions and obtained the strength parameters by single tangential technique when calculating bearing capacity. Actually, the tangential technique, which is just a method to linearize the non-linear curve, cannot completely simulate the non-linear failure process. In this article, the multi-tangential technique is introduced, combining with the multi-wedge translation failure mechanism and the upper bound theorem of classical plasticity, minimum upper bound solutions are obtained.As the results show, there is little difference between the results in this article and that presented in other articles by using finite elements in conjunction with the lower and upper bound theorems of classical plasticity, but the former method is more convenient and efficient. However, huge difference is observed when compares with the results by using single tangential technique. It would overestimate the bearing capacity by 179.3% at most, thus run a great risk on practical applications when using single tangential technique. It was suggested by Hoek that the strength parameters should be factored by at least 25% when using single tangential technique.The impact of GSI,m_i,unit weight of rock,surcharge and disturbance coefficeent on bearing capacity is also discussed. As the results shows, bearing capacity increases with the increasing of GSI and m_i, which indicates that the bearing capacity is mainly depended on the integrity and property of the rock mass. Bearing capacity also increases as the unit weight and surcharge increase. Especially when GSI and m_i are small, these two factors show an obvious effect on bearing capacity, but the same effect is not observed when GSI and m_i are great. The disturbance coefficient has a negative effect on bearing capacity, when GSI and m_i are small the effect is obvious, while GSI and m_i are great the effect turns to be neglectable.