岩体非连续裂隙网络三维面状渗流模型

THREE-DIMENSIONAL PLANAR MODEL FOR FLUID FLOW IN DISCRETE FRACTURE NETWORK OF ROCK MASSES

模拟了一个野外实际入渗试验的岩体裂隙网络及其中的渗流。通过逆方法建立岩体三维裂隙网络模型,其指导原则是使模型能够再现野外通过露头和钻孔所观察到的裂隙现象。逆方法由于可以对模拟和实测裂隙进行相同条件统计抽样,因此避免了实测数据统计分析中复杂的误差矫正。裂隙面状渗流分析采用了任意多边形有限差分法。讨论了通过模型校正确定裂隙导水系数的方法,进行了随机模型重复实现,验证了模型的稳定性。

The discrete fracture network and fluid flow of an actual infiltration experiment performed in fractured rock masses are simulated with planar flow model. The fractures in the rock masses of the experiment are characterized through a mapped vertical shaft about 160 m2 and 7 television borehole of 8 m long. In the construction of the discrete fracture network model, an inverse method is used with the guiding principle that the observed fractures through outcrops and boreholes can be reproduced. With the inverse method, the complex error corrections associated with previous approaches in the statistics of observed fractures can be avoided. This is achieved by sampling simulated and measured fractures in the same way, and by fitting the simulated fractures to the observed ones. The mean and standard deviation of trace lengths, area density, and fracture frequency on boreholes of each fracture set are taken into account in fitting observed fractures. In the flow model, fractures are disc-shaped with a small thickness, and fluid flow takes place over whole the disc plane. The finite difference method is used in solving fluid flow problem, in which each fracture disc is automatically meshed into planar triangular elements, and 2D triangular grid in 3D space covering the entire fracture network is constructed. The transmissivity and hydraulic aperture of fractures of the test rock are estimated by fitting the observed discharge data. 30 fracture networks are generated, and the flow in each of them is analyzed to demonstrate the stability of the stochastic models of fracture networks and the flow. The mean discharge of the 30 fracture networks is very close to the observed.