断裂岩石双翼表面细观接触特征与剪切强度关系

RELATIONSHIP BETWEEN MICRO-CONTACT CHARACTERISTICS OF TWO ROUGH SURFACES AND SHEAR STRENGTH OF FRACTURED ROCKS

断裂岩石抗剪强度对岩体稳定性预测至关重要,为从细观层面探究断裂岩体双翼粗糙面接触与抗剪强度关系,采用蠕剪试验的方法对压剪和间接拉伸两类断裂岩石的力学行为进行研究。通过对断裂岩石双翼粗糙面的激光扫描图像处理和几何重构,采用新提出的"切层法"对双翼啮合时断裂岩石两翼粗糙面的接触状态和接触面积进行分析。结果表明:压剪形成的断裂岩石在蠕剪过程中双翼粗糙面呈不规则"海岸线式"接触;拉断裂岩石双翼表面呈离散"群岛式"接触。拉破裂岩石双翼接触面积明显大于压剪破裂岩石接触面积。尽管岩石断裂生成机制乃至施加的法向荷载不同,断裂岩石的蠕剪强度与接触面积成正比关系,喻示断裂岩石的双翼表面接触面积是考量断裂岩石表面粗糙性对抗剪强度影响的重要指标。此研究对建立岩石节理的接触力学本构模型和构建抗剪强度准则有所借鉴。

The shear strength of fractured rocks is of great importance for predicting the stability of rock mass. In order to investigate microscopically the relationship between the contact configuration of two rough surfaces and the shear strength of fractured rocks,the shear creep tests were carried out for fractured rocks induced by compressive shear and indirect tension respectively. After the process of the laser scanning images and the geometric reconstruction of the two rough surfaces in contact,the'slice-cutting method'was proposed to analyze the contact configuration and contact area. The contact shape was found to display an irregular'coastline'style for compressive shear fractures and an'islands'style for tensile fractures in rocks. The contact area of tensile fractured rocks was significantly greater than that of compressive shear fractured rocks. Although the mechanism of the rock fracture formation was different,or even the fractured rocks were subject to the different normal forces,the shear strength was directly proportional to the contact area,which implied that the contact area was a candidate index in evaluating the influence of surface roughness on the shear strength of fractured rocks.