砂岩-泥岩沉积互层面剪切特性数值模拟研究

Numerical Simulation of Shear Characteristics of Sedimentary Layer in Sand-Mudstone Stratum

沉积层面力学特性是探究砂岩泥岩互层岩质边坡变形及稳定的重要因素。以室内试验结果为依据,采用接触面与薄层单元模拟层面剪切特性,对比了两者应力应变曲线特点,分析了开挖条件下软硬互层岩质边坡层间应力分布。结果表明,接触面模拟砂岩泥岩界面特性时,其剪切应力应变曲线符合双曲线特征,呈应变软化现象,存在明显残余强度。薄层单元模拟层面剪切力学特性时存在初期应力剧增现象,模拟结果与试验值存在一定程度离散性。接触面与薄层单元均能模拟砂岩泥岩界面剪切应力应变特性。顺层岩质边坡开挖时难以控制接触面法开挖过程模型计算收敛程度,薄层单元方式更能有利于模拟开挖作用下其层面剪应力分布(即剪切错动效应)。

Mechanical property of sedimentary layer is an important factor to study the deformation and stability of sandmudstone interbedded rock slope. Based on laboratory test results,the simulative methods both contacting surface and thin layer element were adopted to simulate the shear behavior of sedimentary layer and compare the characteristics of stressstrain curves. The interlayer stress distribution of soft-hard interbedded rock slope under excavation condition was analyzed. The results show that when the contacting surface simulates the interfacial characteristics of sandstone and mudstone,the shear stress-strain curve conforms to the hyperbolic characteristics,showing the phenomenon of strain softening and obvious residual strength.The initial stress increases sharply when the thin layer element simulates the shear mechanical properties of the layer,and the simulation results are discrete to some extent compared with the experimental values. Both contacting surface and thin layer elements can simulate the shear stress-strain characteristics of sandstonemudstone interface.It is difficult to control the convergence degree of the model calculation in the excavation process of bedding rock slope by the contacting surface method. The thin-layer element method is more conducive to simulate the shear stress distribution( i.e. shear dislocation effect) of the bedding rock slope under excavation.