基于黏聚力裂缝模型的反倾层状岩质边坡倾倒破坏模拟

A numerical study of the toppling failure of an anti-dip layered rock slope based on a cohesive crack model

反倾层状岩质边坡的倾倒破坏是一种常见的地质灾害。为探究开挖条件下反倾层状岩质边坡的倾倒破坏机制以及层间剪切强度、岩层厚度因素对破坏特征的影响,利用ABAQUS有限元软件,建立黏聚力裂缝模型(Cohesive Crack Model,CCM),基于连续-离散方法,经参数标定和对比,建立反倾层状岩质边坡CCM,采用开挖并增重的方式诱发边坡倾倒破坏。数值模拟结果与古水水电站坝前倾倒变形体离心模型试验结果基本一致,验证了CCM的正确性。进一步,基于以上参数及模型,研究了反倾层状岩质边坡的破坏演化过程和应力分布特征,并探讨层间剪切强度对边坡倾倒破坏特征的影响。结果表明:坡体前缘首先发生局部折断,后缘出现明显拉裂缝,反倾岩层由下往上依次折断直至倾倒体中部(一级破裂面)。随后,坡体前缘的表层岩层被挤出,形成二级破裂面,最后一级破裂面扩展至坡体后缘,形成连通宏观的破裂面。最后,二级破裂面扩展至坡体中部,边坡完全倾倒破坏;破裂面基本沿层间法向应力峰值位置连线发育;层间剪切强度对边坡倾倒破坏特征具有显著的影响,随着层间剪切强度的增大,岩层初始折断位置逐渐降低,垮塌范围逐渐减小,破裂面倾角增大;坡体层厚越大,一级破裂面分布越深,垮塌区范围越大,坡体滑动的整体性越强。研究成果可为反倾层状岩质边坡倾倒破坏的分析和监测提供有效计算方法及依据,为此类滑坡灾害的防治提供一定参考。

The toppling failure mechanism of an anti-dip layered rock slope is a kind of common geological hazard.In order to explore the toppling failure mechanism of an anti-dip layered rock slope and the influence of interlayer shear strength and rock thickness on the failure characteristics under the condition of excavation,based on the continuous-discrete method,the finite element cohesive crack model(Cohesive Crack Model,CCM)is established by ABAQUS.Through parameter calibration and comparison,the CCM of an anti-dip layered rock slope is established,and the slope toppling failure is induced by excavation and weight increase.The numerical results are basically consistent with the centrifugal model test results that are based on the toppling deformable body in front of the dam of Gushui Hydropower Station,which verifies the correctness of the CCM.Furthermore,the failure evolution process and stress distribution characteristics of the anti-dip layered rock slope are studied,and the influence of inter laminar shear strength on the toppling failure characteristics of the slope is discussed.The results show that the front edge of the slope is partially broken at first,and obvious tensile cracks appear at the back edge,and the anti-dip rock layer breaks from bottom to top until the middle of the dumping body(first-order fracture surface),and then the surface layer of the front edge of the slope is extruded to form a second-order fracture surface.The last first-order fracture surface extends to the back edge of the slope to form a connected macroscopic fracture surface,the second-order fracture surface extends to the middle of the slope,and the slope is completely toppled and destroyed.The fracture surface basically develops along the position of the peak value of the interlayer normal stress and the inter laminar shear strength has a significant influence on the toppling failure characteristics of the slope.With the increase of the inter laminar shear strength,the initial breaking position of the rock layer become lower,the collapse range decreases gradually,and the angle of the fracture surface increases.With the increase of the layer thickness of the slope,the distribution of the first-order fracture surface deepens,the range of the collapse area increases,and the integrity of the slope slip is enhanced.The research results provide an effective calculation method and basis for the analysis and monitoring of the toppling failure of reverse-dip layered rock slopes and provide some references for the prevention and control of such landslide disasters.