多级加载下岩石裂隙渗流分段特性试验研究

TEST RESEARCH ON PIECEWISE SEEPAGE CHARACTERISTICS OF ROCK FRACTURE UNDER MULTISTAGE LOADINGS

利用自行研制的岩石裂隙辐射型渗流系统,试验研究室温下粗晶大理岩、中砂岩、灰岩和细晶大理岩4个岩石张裂隙在法向闭合过程中的渗流分段特性及加载历史的影响。根据闭合裂隙的接触状态及流域分布特征,裂隙渗流可分为群岛流、过渡流、沟槽流3个阶段;单位水头流量与法向应力呈指数函数关系,随法向应力增加而降低,后次加载中相同法向应力下单位水头流量明显较低;单位水头流量与力学隙宽呈幂函数关系,幂指数范围为1.93～2.60,可认为接触型粗糙岩石裂隙渗流量与力学隙宽呈次立方关系;后次加载时,相同力学隙宽下单位水头流量也明显较低;水力等效隙宽与力学隙宽呈分段的线性关系,修正的立方定律在相应分段内成立。研究结果对岩体裂隙渗流计算有一定的理论意义。

The piecewise seepage characteristics of closed tensile fracture and loading history effect were investigated at room temperature using cylindrical rock samples of coarse-grained marble,sandstone,limestone and fine-grained marble with self-developed radial flow system.The results show that fracture seepage can be divided into three phases of islands flow,transitional flow,and groove flow according to different contact states and watershed distributions.Flowrate per head follows an exponential function with the normal stress,and it will be significantly lower in the subsequent loading process at the same normal stress.The relationship between flowrate per head and mechanical aperture was well simulated by the power function,in which the range of index is 1.93–2.60,so that sub-cubic law could be used to describe seepage in contacted rough rock fracture;flowrate per head is significantly lower at same mechanical aperture in subsequent loading process.Moreover,there is a piecewise linear relationship between equivalent hydraulic aperture and mechanical aperture,therefore,the modified cubic law can be established in each appropriate phase.The results have some theoretical significance for calculation of rock fracture seepage.