基于压敏胶片的法向应力作用下砂岩节理的接触特征研究  

Investigation of contact characteristics of sandstone joint under normal stress using pressure-sensitive film

作　　者：龚耕 潘佳 赵立春 熊峰 张国华 唐志成 GONG Geng;PAN Jia;ZHAO Li-chun;XIONG Feng;ZHANG Guo-hua;TANG Zhi-cheng(Faculty of Engineering,China University of Geosciences,Wuhan,Hubei 430074,China;Jarud Banner Zhahanaoer Coal Industry Co.,Ltd.,Tongliao,Inner Mongolia,028000,China;Key Laboratory of Geological Survey and Evaluation of Ministry of Education,China University of Geosciences,Wuhan,Hubei 430074,China)

机构地区：[1]中国地质大学(武汉)工程学院,湖北武汉430074 [2]扎鲁特旗扎哈淖尔煤业有限公司,内蒙古通辽028000 [3]中国地质大学(武汉)地质探测与评估教育部重点实验室,湖北武汉430074

出　　处：《岩土力学》2024年第10期2907-2918,2928,共13页Rock and Soil Mechanics

基　　金：国家自然科学基金面上项目(No.42177165,No.42277173);地质探测与评估教育部重点实验室主任基金(No.GLAB2023ZR03)。

摘　　要：定量测量岩石节理的接触特征是开展节理岩体的水-力特性研究的基础,然而其接触特征难以直接在室内试验中测量。采用闭合变形试验研究了法向加载下岩石节理的接触特征变化规律。首先利用岩石雕刻系统构建系列粗糙砂岩节理,然后在节理两个面壁间重复置入多种型号(MS、HS和HHS)的压敏胶片进行闭合变形试验,再引入自适应阈值分割方法识别压敏胶片图像信息并定量分析其接触特征变化规律。岩石节理的力学特性主要受接触区域演化过程的影响,主要包括新接触点产生、接触区域扩展和融合。接触面积比随法向应力增加从线性增加逐渐变为非线性增加趋势,双曲线经验模型可较好地表征接触面积的变化趋势;模型中初始接触面积增长速率与节理粗糙度系数JRC呈正相关关系。接触点数量随法向应力增加呈波动性增加,增长速率与表面分形维数呈负相关关系。低法向应力(0.5 MPa)下岩石节理的局部真实接触应力最大可达名义法向应力的600倍,导致微凸体崩解破坏;随着法向应力和节理粗糙度的增加,其接触应力分布越不均匀;高法向应力条件下粗糙度对其接触面积的影响程度是低法向应力条件下的20倍。该试验结果可为相关力学模型构建提供参考,所提出的测量方法亦可为数值模拟结果的验证提供途径。Measuring the real contact characteristics between joint surface walls is challenging due to their inherent characteristics,which closely relate to the hydro-mechanical behaviors of rock mass.To quantitatively investigate the real contact area of rock joints under normal stress,rock engraving systems were used to manufacture a series of rough rock joints.The real contact area of rock joints was investigated using a multi-type pressure-sensitive film(MS,HS,and HHS),and an adaptive threshold method was utilized to recognize the scanning image of the film.Simultaneously,the contact stress transformed by the scanned film was also quantified.The evolution of the real contact area affects the mechanical characteristics of rock joints,characterized by the emergence,expansion,and coalescence of contact patches.The real contact area ratio increases hyperbolically with normal stress,and an empirical model can effectively predict the evolution characteristics.Joint roughness coefficient JRC has a positive correlation with initial growth rate of contact area.The contact points oscillate with increasing normal stress,and their growth rate has a negative correlation with the fractal dimension.Even at low normal stress(0.5 MPa),the highest contact stress can exceed 600 times the nominal normal stress.Distribution of the contact stress becomes more inhomogeneous with the increase of normal stress and roughness.The impact extent of roughness at high normal stress is approximately 20 times greater than at low normal stress.The experimental results can provide a reference for the constructive of the constitutive model and validation for numerical simulations.

关 键 词：岩石节理 接触面积 闭合变形 压敏胶片 

分 类 号：TU451[建筑科学—岩土工程]