岩石结构面粗糙度系数尺寸效应的推拉试验研究

An experimental study of size effect of roughness coefficient on rock joint using push-pull apparatus

粗糙度系数是结构面抗剪强度的主要影响因素,然而由于结构面表面形态的复杂性,粗糙度系数尺寸效应研究并未获得较大进展。总结了结构面粗糙度系数的3种获取手段:标准剖面对比法、理论公式法、试验反分析法。在此基础上分析了3种方法在研究粗糙度系数尺寸效应方面存在的问题和困难。为了研究结构面粗糙度系数与试样尺寸的相关度,对中砂、硅粉、水泥、非引气型萘系减水剂等原材料的配比进行了研究,获得了与天然钙质板岩物理力学特性相类似的岩石模型材料,然后采用研发的结构面制作模具及其制备工艺制作了8组共176对具有不同尺寸和表面起伏粗糙程度的结构面,并利用改进的高精度岩石结构面推拉仪对结构面粗糙度系数进行了推拉试验研究和数据统计分析,结果表明:模型结构面粗糙度系数的统计均值随试样尺寸的增加而降低,但特定结构面粗糙度系数的尺寸效应规律需要根据结构面的具体表面形貌进行测试;Barton理论公式计算的结构面粗糙度系数尺寸效应变化规律与推拉试验测试规律总体上一致,但试验值与理论值有差异,且结构面试样尺寸越小,二者的差异就越大;具有特定表面形貌的模型结构面粗糙度系数也有差异,工程大尺寸岩体结构面粗糙度系数需要根据表面形貌和分布特征进行综合判定。

The roughness coefficient is an important influencing factor of the joint shear strength. However, the research of size effect on joint roughness coefficient has not gained great progress due to surface morphology complexity of rock joint. This paper summarizes three methods to obtain joint roughness coefficient, i.e. standard profile comparison method, theoretical equation method and inverse analysis method, and then analyzes some existing problems and difficulties on studying size effect on joint roughness coefficient. In order to achieve the relationship between joint roughness coefficient and sample size, the ratios of raw materials such as medium sand, silica fume, cement, non-air entraining naphthalene super-plasticizer, are firstly investigated. Then rock materials for simulation are obtained, in which physico-mechanical properties are similar to calcareous slate. Finally, eight groups of rock joints with 176 pairs of different sizes and roughness are made through molds in preparation process. In addition, the roughness coefficients of rock joints are tested by homemade push-pull shear apparatus and experimental data are further analyzed. The results show that statistical mean values of joint roughness coefficient generally decrease with the increase of sample size. However, the size effect tests on the specific rock joints need to be performed through push-pull shear strength testing method. It is found that size effect variations calculated by Barton formula are in good agreement with experimental results, whereas the theoretical and experimental values are different. In particular, when the size of sample is smaller, the differences are greater. Furthermore, rock roughness coefficients even with specific joint surfaces are various and the roughness coefficients of large size rock joint should be comprehensively judged according to the surface morphology and distribution.