岩石裂隙面粗糙度参数关系分析

Relationship Among Sevral Roughness Parameters of Rock Fracture Surfaces

粗糙度是解释岩石裂隙力学及渗流特性的重要参数.采用自制模具,在轴向中部劈裂岩样,形成垂直于岩样轴向的新鲜裂隙.通过测取7组47个圆柱形岩样裂隙面188条轮廓曲线,分析了粗糙度系数JRC、粗糙轮廓指数Rp、粗糙角i、分维D和截距A等参数的相互关系.结果表明:JRC与岩样组成矿物颗粒大小关系密切,粒径越大,JRC越大.JRC与Rp-1呈明显的对数关系,而不是直线关系;JRC与粗糙角i为正相关关系,由Z2和Rp得到的粗糙角i相差不大,当i大于7.2时,后者大于前者,否则,前者大于后者.JRC与截距A近似满足公式JRC=37.087+16.235A,因此,截距A可以用于描述粗糙度大小.对于同组岩样来说,JRC与分维D负相关,但相关性很低;在除砂岩外的5组岩样之间,粗糙度平均值JRCave与分维平均值Dave有较好的正相关关系.总体上,JRC随尺度增加而增加,而分维D随之增加而降低.

Roughness is a key factor to explain mechanical and hydraulic feature of rock fracture.Using the self-made mold,we split the rock sample through the middle to produce fresh fractures which are perpendicular to the axial direction.188 fracture profiles from 47 cylindrical specimens of seven rocks were measured.Relationship among joint roughness coefficient JRC,asperity profile index Rp,asperity angle i,fractal dimensions D,and intercept A were analyzed.The results show that the JRC has a close relation with the sizes of grains of rocks,the bigger the grain size is,the bigger the JRC is.JRC has a logarithmic relationship with Rp-1,but not a linear relationship;the JRC is positively related to i and the two roughness angles i derived from Z2 and Rp respectively are close to each other,the latter one is a little larger while i is larger than 7.2,otherwise,the former one is larger.The JRC and intercept A meet approximately the equation JRC=37.087＋16.235A,so that the intercept A can be used to represent fracture roughness.The JRC has the lowest negative correlation with fractal dimension D for every group of rock specimen fractures.However,for the average values of a group of specimen,the JRCave and fractal dimension Dave have a good positive correlation among five groups of rock specimen fractures except for two groups of sandstone.As a whole,the JRC increases while the fractal dimension D decreases with increase of profile size.