异性结构面剪切特性及抗剪强度计算方法

Shear Properties of Anisotropic Structural Surfaces and Shear Strength Calculation Method

天然结构面常存在两侧岩体岩性不一致的情况,对该类异性结构面抗剪特性进行研究有利于更全面地分析复杂地层中岩石的稳定性。首先,通过光学扫描技术获取天然结构面形貌点云数据并构建结构面网格模型;其次,将模型进行3维实体重构以浇筑多组含不同异性结构面的人工试样;然后,开展不同法向应力及剪切方向条件下的直剪试验;最后,通过有限差分仿真模拟软件FLAC3D进行数值模拟。基于JRC–JCS(joint roughness coefficient–joint wall compressive strength)结构面剪切模型,采用2维剖面法量化处理结构面粗糙度系数JRC,引入结构面组合壁面强度CJCS(combined joint wall compressive strength)及壁面强度系数比λ的概念以体现不同强度组合情况下的结构面抗剪特性差异。结果表明:数值模拟与直剪试验结果的规律性表征情况较为一致;在结构面单轴抗压强度较高或者较低一侧被确定时,强度较低侧对结构面峰值抗剪强度起主要的控制作用,强度较高侧则起到一定的增强作用,且壁面强度系数比λ对峰值抗剪强度的影响与法向应力的数值成正比。基于上述现象,利用相关函数对试验结果进行非线性曲面拟合,推导出一种表征不同岩石强度组合情况下的结构面峰值抗剪强度计算公式,并得出有效影响岩石结构面强度的强度比区间。该公式是对JRC–JCS模型的扩展且可在工程实践中广泛应用。

Natural structural faces often exhibit inconsistent lithology on either side of the rock mass.The study of the shear strength of such heterogeneous structural surfaces facilitates the analysis of rock stability in complex stratigraphy.Initially,an optical scanning technique is utilized to obtain the point cloud data of natural structural surface morphology and to construct the structural surface mesh model.Subsequently,the model is reconstructed in three dimensions to cast multiple artificial specimens with varying heterogeneous structural surfaces.Direct shear tests are then conducted under different conditions of normal stress and shear direction.Finally,numerical simulations are performed using the simulation software FLAC3D.Based on the JRC–JCS(joint roughness coefficient–joint wall compressive strength)model,the two-dimensional profile method is employed to quantify the structural surface roughness coefficient JRC,and the combined wall strength CJCS(combined joint wall compressive strength)and wall strength coefficient ratio are introduced to reflect different strength combination cases.The results demonstrate that the numerical simulations align more closely with the shear experimental results.When the compressive strength of either the higher or lower side of the structural face is determined,the lower strength side mainly controls the peak shear strength,while the higher strength side enhances it.The effect of on the peak shear strength is proportional to the normal stress.A nonlinear fitting of the experimental results is conducted to derive a formula for calculating the peak shear strength of the structural face,characterizing the case of different rock strength combinations.The derived strength ratio interval effectively influences the strength of the rock’s structural face.This novel formula extends the JRC–JCS model and can be applied in a wide range of applications.