不同节理粗糙度系数单裂隙渗流特性试验研究

EXPERIMENTAL RESEARCH ON HYDRAULIC BEHAVIORS IN A SINGLE JOINT WITH VARIOUS VALUES OF JRC

实际岩石裂隙的裂隙面具有不同的粗糙度,难以满足立方定律的使用条件。根据N.Barton和V.Choubey(1977年)提出的10条节理粗糙度(JRC)标准剖面轮廓曲线,本试验运用数控电火花线切割技术,加工出具有不同节理粗糙度系数(JRC=0～20)的10个钢模板,制作出10个包含不同JRC值单裂隙的圆柱形水泥试样(直径φ50mm,高度100mm),采用RCCP联测系统测试不同JRC值单裂隙在不同应力水平下的渗透性。试验结果表明:(1)在低应力水平下,JRC值对单裂隙的渗流特性有较大影响;随应力水平的增大,JRC值对单裂隙渗流特性的影响迅速减小;(2)不同JRC值单裂隙的渗透率与有效应力之间的关系可用负指数函数描述,并表现出明显的非线性特征,低有效应力阶段试样渗透率随有效应力的变化速度大于中高有效应力阶段的变化速度。

Fluid flow through rock joints is commonly described by the smooth parallel plate model, which includes cubic law. However, the real rock joint surfaces are rough, and the fluid flow through a single fracture is not always consistent with the cubic law. Based on the typical joint roughness profiles proposed by N. Barton and V. Choubey（1977）, the templates with different joint roughness coefficients（JRCs） are manufactured by using numerical control wire cut electron discharge machining, and then, ten single-fracture column concrete samples with various JRCs from 0 to 20 are produced（50 mm in diameter and 100 mm in height）. The single fracture＇s permeability tests were conducted at various effective stresses using RCCP test system. The test results show that： （1） The JRC has significant effect on the permeability of a single joint under low effective stress, and the effect of JRC on the permeability of a single joint decreases rapidly with the increasing effective stress. （2） The relationship between the permeability and the effective stress of a single joint follows the law of negative exponent, showing an obvious nonlinear behavior. For a single joint, the rate of change in the permeability versus the effective stress under low stress level is greater than that under middle-high stress level. Moreover, under the low stress level, the permeability of a single joint has a trend of decreasing with the increase of JRC at the same effective stress conditions.