基于多尺寸结构面的循环剪切力学特性及其抗剪强度研究

Cyclic shear mechanical characteristics and shear strength of multi-scale joints

岩石结构面的抗剪强度具有强烈的尺寸依赖性,开展结构面多尺寸试验对于研究大尺寸结构面力学特性具有重要的理论价值和实践意义。针对过往研究较少的循环作用下结构面力学特性尺寸效应问题,首先基于立方体劈裂试验获得不同粗糙度的近天然岩石结构面,然后运用三维扫描技术获得结构面点云数据,进而采用三维打印技术制作不同尺寸结构面树脂模型,最后,通过倒模法制作试样并进行室内试验,研究不同法向应力下结构面尺寸效应的规律以及不同粗糙度和不同法向应力对结构面抗剪强度的影响。基于黏着摩擦理论-Barton经验公式,提出了一个可以考虑结构面尺寸效应的峰值抗剪强度公式。研究结果表明:岩石结构面的峰值抗剪强度具有明显的负尺寸效应,且峰值抗剪强度的改变对小尺寸大法向应力和大尺寸小法向应力下的结构面更为敏感;低法向应力下的残余剪切强度具有明显的负尺寸效应,而高法向应力下的残余剪切强度随着结构面尺寸的增大,从正尺寸效应变为负尺寸效应。

The shear strength of rock joints exhibits strong size dependency.Conducting multi-scale experiments on joints is of great theoretical value and practical significance for studying the mechanical properties of large-scale joints.This study focuses on the less explored issue of size effect on the mechanical properties of joints under cyclic loading,near-natural rock joints with varying roughness were obtained through cubic splitting tests.Three-dimensional scanning technology was then utilized to capture point cloud data of the joints,followed by the production of resin models of different sizes using three-dimensional printing technology.Finally,model replicas were made through mold casting.Experiments were conducted to investigate the size effect of the structural joints under different normal stresses,as well as the influence of roughness and normal stress on the shear strength of the joints.A peak shear strength formula was developed considering the size effect of the joints,utilizing the adhesive friction theory and Barton’s empirical formula.The results show that the peak shear strength of rock joints exhibits a noticeable negative size effect.Variations in peak shear strength are more sensitive in smaller-sized surfaces subjected to high normal stresses and larger-sized surfaces under low normal stresses.Moreover,the residual shear strength at low normal stresses demonstrates a distinct negative size effect.Conversely,under high normal stresses,the residual shear strength transitions from a positive size effect to a negative size effect as the joint size increases.