复合加载情况下非均质地基上条形基础的极限承载力研究

Ultimate bearing capacity of strip footings on inhomogeneous soil foundation under combined loading

复合加载情况下精确求解非均质地基上条形基础的极限承载力以及评价影响极限承载力的相关因素,具有很强的工程实用与理论参考价值。基于极限平衡原理,在Mohr-Coulomb破坏准则的基础上,将非均质地基上条形基础极限承载力问题等价为一个边界待定的泛函极值问题。利用变分原理得到与平衡方程相等价的积分约束条件以及相应的欧拉方程与横截条件。引入问题边界条件,利用VC++6.0编制了数值计算程序,求得了复合加载情况下非均质地基破坏时的滑裂面函数与破坏包络曲线。从理论上研究了土体内摩擦角、土体黏聚力、土层强度比与地下水位变化等因素对地基破坏包络曲线的影响。研究结果表明,其解答是地基极限承载力真实解的某一最小上限。

To evaluate the ultimate bearing capacity of strip footings on inhomogeneous soil foundations under combined loading accurately and to estimate the relevant factors which affect the ultimate bearing capacity are very valuable in engineering practice and significant in theory. Based on limit equilibrium theory and yielding criterion of Mohr-Coulomb, the application of the variational principle transforms the problem from its equilibrium equation format to a format of functional extremization equivalently which boundary value is undetermined. A nonlinear program, which is generated using VC＋＋6.0, is used to achieve the function of the 2-D sliding surface and the failure envelope of strip footings on inhomogeneous soil foundation under combined loading. The friction angle of soil, the cohesive force, the shear strength ratio ci/ci＋1 and the fluctuation of groundwater level, which affect the ultimate bearing capacity of strip footings on inhomogeneous soil foundation and the failure envelope, are studied theoretically. The results show that it is a certain upper bound minimum solution of the bearing capacity of soil foundation.