Based On The Nonlinear Failure Criterion, The Maximum Circular Foundation Bearing Capacity Analysis

Conventional calculations of bearing capacity of circular foundation soil were formulated in terms of a linear Mohr-Coulomb failure criterion. However, soil is non-linear, and linear failure criterions of soil is a special example of non-linear failure criterions, so it is necessary to analyze bearing capacity of circular foundation soil. Some scholars employed non-linear failure criterions and obtained the strength parameters by single-tangential method when calculating the bearing capacity. Actually, the tangential method, which is just a way to linearize the non-linear curve, cannot be equal to the non-linear failure criterions. In this article, the mufti-tangential method is introduced by dividing the base into circular units and combining with the non-linear failure criterion, then minimum upper bound solutions are obtained after optimized,main work of this essay as as follows:Firstly, based on the nonlinear failure criterion ,a multi-tangent method and a multi-blocks method are adopted when sloving bearing capacity of circular foundation soil by using limit analysis upper bound theory. The optimal upper bound solution is obtained after optimizing the divisions of the filling elements and the volocity field by using sequential quadratic programming method.Secondly, both multi-tangent method and singal tangential method are used for calculating bearing capacity of circular foundation soil. It is found that The results of multi -tangent method is closer to the real value. From the results, the results of single-tangent method are obviously bigger than the results of multi -tangent method, the biggest difference can be reached 13.44%.Thirdly, The impact of GSI,m_i,unit weight of soil,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 can be neglectable.