Based on the nonlinear Mohr-Coulomb failure criterion and an associated flow rule, a kinematic admissible velocity field of failure mechanism of the 2-layer soil above a shallow horizontal strip anchor plate is constructed. The ultimate pull-out force and its corresponding failure mechanism through the upper bound limit analysis according to a variation principle are deduced. When the 2-layer overlying soil is degraded into single-layer soil, the model of ultimate pullout force could also be degraded into the model of single-layer soil. And the comparison between results of single-layer soil variation method and those calculated by rigid limit analysis method proves the correctness of our method. Based on that, the influence of changes of geotechnical parameters on ultimate pullout forces and failure mechanism of a shallow horizontal strip anchor with the 2-layer soil above are analyzed. The results show that the ultimate pull-out force and failure mechanism of a shallow horizontal strip anchor with the 2-layer soil above are affected by the nonlinear geotechnical parameters greatly. Thus, it is very important to obtain the accurate geotechnical parameters of 2-layer soil for the evaluation of the ultimate pullout capacity of the anchor plate.%基于非线性Mohr-Coulomb强度准则及相关联的流动法则,构造出水平浅埋条形锚板上覆双层土体破坏的机动许可场;利用极限分析上限法,结合变分原理,推导出了水平浅埋条形锚板上覆双层土体的极限抗拔力表达式及其对应破裂机制;当上覆土层退化为单层土体时,极限抗拔力计算模型可以退化为既有单层土体计算模型;通过单层土体变分法计算结果与刚体极限分析法计算结果的对比,进一步证明了本文方法的正确性;在此基础上,分析了岩土物理力学参数变化对上覆双层土体锚板极限抗拔力与土体破裂机制的影响.计算表明:水平浅埋条形锚板上覆双层土体极限抗拔力和破坏模式受岩土体非线性物理力学特性参数的影响非常显著,工程实际中准确获取双层土体的岩土体物理力学特性参数对于正确评估锚板极限抗拔特性非常重要.
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