平面应变条件下土的强度准则在黄土工程问题中的应用研究

Application research of soil strength criterion under plane-strain condition for loess problems

文章依据Mohr-Coulomb、Matsuoka-Nakai、■空间滑动面、Lade-Duncan、AC-SMP强度准则所建立的平面应变条件下的中主应力公式和土的平面应变强度准则,对黄土工程中常见的平面应变问题进行分析和计算,包括黄土基坑直立开挖平面应变问题、挡土结构土压力问题和条形基础地基承载力问题。研究结果表明,平面应变条件下Lade-Duncan准则和■空间滑动面强度准则对于各种黄土工程的计算结果是基本相同的,进一步说明Lade-Duncan强度准则描述土单元剪切破坏时的空间滑动面近似为■空间滑动面;平面应变条件下所推导的各个强度准则在进行黄土工程具体问题分析时与常用的Mohr-Coulomb准则有较大的差异,Mohr-Coulomb准则趋于保守,未能充分发挥黄土的强度。在进行平面应变问题的黄土工程设计时,可选择适合黄土的强度准则,考虑平面应变条件下中主应力对土强度的贡献,充分的发挥黄土的原生结构特性,在工程建设中提高经济性。

In terms of the intermediate principal stress formula and the plane-strain strength criterion established from the strength criteria of Mohr-Coulomb, Matsuoka-Nakai, the 3√σ spatially mobilized plane, Lade-Duncan and AC-SMP, the commonly encountered plane-strain loess problems, including the plane-strain upright excavation pit of loess, the earth pressure of retaining structure and the bearing capacity of strip footing, were analyzed and calculated. The results show that the spatial failure plane of the infinitesimal soil element described by the Lade-Duncan criterion is close to the 3√σ spatially mobilized plane strength criterion; when applied to some specific loess problems, various strength criteria derived from the plane-strain condition may lead to big difference compared to the commonly used Mohr-Coulomb strength criterion, and the Mohr-Coulomb criterion is more conservative so that the loess strength is not fully exploited. In design of plane-strain loess works, the strength criterion suitable for loess shall be selected. Considering the contribution of intermediate principal stress to soil strength under the plane-strain condition, the original structural characteristics of loess shall be fully exploited, so that the economy in construction of works can be improved.