基于三维形貌分析的结构面剪切试验研究

为研究结构面表面形貌、正应力及剪切历史对岩石结构面剪切特性及强度的影响规律,利用近景摄影测量技术测量试验前后结构面三维形貌数据,对影响结构面剪切特性的因素开展定性与半定量的分析。分析结果表明:(1)结构面形貌对剪切特性的影响具有方向性,视倾角0°的凸起体才可能在剪切过程中起抵触作用;(2)起伏粗糙对剪切特性的影响随正压力增大而降低,相应的剪胀效应也随正压力增大而减小;(3)在低正压力条件下,结构面表面的起伏凸起体即可被磨损剪断,首先出现磨损剪断的是视倾角较大的凸起,在经历1次正应力条件下剪切变形后,剪切曲线便不再出现峰值现象;(4)摩擦角随正压力增大而减小,而黏聚力随正压力增大而增大;(5)单块试样反复剪切试验中,取第1次残余值与后续剪切强度值拟合得到的剪切强度参数可代表具有剪切运动历史的结构面剪切强度。

Shear Test of Rock Discontinuity Based on 3-D Morphologic Analysis

The shear failure characteristics of rock mass discontinuities are influenced by surface morphology, normal stress and shear history.Close range photogrammetry is a quick and accurate approach to obtain the 3-D morphology of surface features.In this paper, the 3-D surface morphology of the discontinuities is analyzed before and after the multiple normal pressure repeated shear test, and the factors that affect the shear characteristics are analyzed in qualitative and semi-quantitative sense.Results reveal that 1) the influence of morphology on the shear behavior is directional, and only the asperity with the apparent inclination greater than 0 degree could resist each other in the shearing process, but the actual contact surface is quite smaller than potential resistant surface;2) the effect of roughness on the shear behavior decreases with the increase of normal pressure, and so does shear dilation behavior;3) the asperity is easily worn and cut even under low normal stress, in particular, asperity with large apparent inclination will be primarily damaged, and peak value of the shear curve does not occur in subsequent shear after the first shear;4) friction angle increases with the decrease of positive pressure, while cohesion displays an opposite trend;5) the shear strength parameters fitted from the first residual value and the subsequent shear strength value can be used to represent the shear strength of the discontinuities with the shear movement history.