岩石结构面形貌分级方法及两级粗糙特性研究

Study on morphological classification method and two-order roughness of rock joints

岩石结构面三维形貌是影响剪切力学特性的主要因素,针对不同采样间距下结构面形貌的变化特征,提出基于界限采样间距的形貌分级方法,获取表面宏观起伏分量和微凸体的两级粗糙参数,进一步研究4种天然岩石结构面两级粗糙参数的尺寸效应和间距效应特性。结果表明:小采样间距下结构面总粗糙参数与二级粗糙参数相近,大采样间距下结构面总粗糙参数与一级粗糙参数相近,验证了利用采样间距进行结构面形貌分级的可行性;一级粗糙参数存在较明显的负尺寸效应,二级粗糙参数尺寸效应不明显,体现了结构面粗糙度尺寸效应主要由一级粗糙参数反映。通过两级粗糙参数的几何机制分析表明,宏观起伏分量较微凸体具有的大起伏波长是造成两级粗糙参数存在尺寸效应与间距效应的关键因素;通过模型剪切试验的力学分析发现,两级形貌在剪切过程中的不同阶段粗糙值贡献不同,结构面抗剪强度研究应综合考虑不同尺度下的两级粗糙特征。

Three-dimensional morphology of rock joints is the main factor affecting the shear mechanical properties.Aiming at the change of the morphological characteristics of rock joints with different sampling intervals,a morphological classification method based on the limit sampling interval is proposed,the two-order roughness of the macroscopic undulation component and asperities of joint surfaces is obtained,and further the size and interval effects of the two-order roughness of four types of natural joints are studied.The results show that the total roughness of joints is close to the second-order roughness at a small sampling interval while close to the first-order roughness at a large sampling interval,which verifies the feasibility of morphology classification using the sampling interval.The first-order roughness has obvious negative size effect while the size effect of the second-order roughness is not obvious,indicating the size effect of the joint roughness is mainly reflected by the first-order roughness.The analysis of the geometric mechanism of two-order roughness shows that the larger undulation wavelength of the macroscopic undulation component compared to asperities is the key factor that causes the size and interval effects of the two-order roughness.Through the mechanical analysis of the shear model test,it is found that the two-order roughness contributes differently at different shearing stages.The study of the joint shear strength should comprehensively consider the two-order roughness characteristics at different scales.