多形态贯通型岩体结构面宏细观剪切力学行为研究

采用室内直剪试验和PFC^2D离散元程序,系统地研究了考虑一阶(二阶)起伏体影响的贯通型锯齿状(波浪状)岩体结构面宏细观剪切力学行为。研究表明:(1)相同法向压力下,结构面宏观损伤质量、峰值剪应力(位移)及应力降随一阶起伏角变大而分别增大、近似线性增大(减小)及先增大后减小;相同一阶起伏角下,其则随法向压力变大而分别增大、均近似线性增大及增大(锯齿状)或先增大后减小(波浪状)。(2)结构面宏细观损伤演化过程经历初始压密非线性变形(压密效应)、近似线弹性压剪变形(爬坡效应)、缓慢压剪断裂非线性变形(爬坡-啃断效应)、应力脆性跌落塑性变形(啃断效应)及理想塑性流动变形(滑移效应)5个发展阶段。(3)结构面宏细观剪切破坏模式可概化为压密-爬坡破坏、爬坡-啃断破坏及啃断-滑移破坏3种基本类型;结构面细观损伤裂纹数量(能量)演化曲线均呈初期微增、中期陡增及后期缓增的阶段性变化特征,且细观损伤颗粒近似呈"梯形面状"分布于结构面附近。(4)根据极限平衡法和强度折减法,通过岩质边坡算例稳定性分析验证了结构面剪切强度估算公式的合理性。

Macro-meso shear mechanical behaviors of coalescent rock joints with different morphologies

To investigate the macro-meso shear mechanical behaviors of coalescent saw-tooth(wavy) rock joints considering the impact of the first-order(second-order) asperities, the laboratory direct shear tests and PFC^2D numerical simulations are conducted. The results indicate that:(1) The macro-damage mass increases, the peak shear stress(displacement) approximately linearly increases(decreases) and the stress drop increases first then decreases as the first-order undulant angle increases under the same normal stress. The macro-damage increases, the peak shear stress(displacement) approximately linearly increases, and the stress drop increases(saw-tooth) or increases first then decreases(wavy) as the normal stress increases under the same first-order undulant angle.(2) There are five stages in the macro-meso damage evolution process, i.e., initial nonlinear deformation(compacting effect), approximately linear-elastic deformation(climbing effect), nonlinear deformation due to compression-shear fracture(climbing-gnawing effect), plastic deformation due to a drop in the brittle stress(gnawing effect) and ideal plastic flow deformation(sliding effect).(3) The macro-meso shear failure modes include compacting-climbing failure, climbing-gnawing failure and gnawing-sliding failure. The curves of the meso-damage crack quantity(energy) include three stages, i.e., a slight, steep and slow increase in the initial, middle and later stages, respectively, and the meso-damage particles are distributed near the rock joints in an approximately "trapezoidal-shape".(4) According to the limit equilibrium and strength reduction methods, the rationality of shear strength estimation formulas for the rock joints is verified through the stability analysis of rock slope examples.