裂隙水流运动的入渗试验及数值模拟研究

Fracture infiltration experiment and numerical simulation

裂隙对喀斯特水流起着重要控制作用。选取具有垂向与水平向交叉裂隙的岩石剖面,做单环注水入渗试验,基于Navier-Stokes(N-S)方程组建立入渗水流数值模型,运用试错法,以实测单环水位变化为目标推求裂隙水力隙宽,计算入渗水量在不同裂隙中的比例;利用立方定律,估计出裂隙饱和渗透系数,基于地下水流连续性方程构建裂隙水流数值模型;比较两种数值模型计算结果。模拟结果表明:N-S方法推求的裂隙等效水力宽度远小于实测裂隙宽度;裂隙水流大部分沿垂向裂隙下渗,但也有部分水流沿横向裂隙渗流;立方定律与N-S方法数值模拟结果差异不大,前者估计的裂隙下渗率稍小于后者,相对而言,N-S方法能更精确地描述裂隙水流运动过程。

Rock fractures are very important for water storage and movement in Karst regions.We select a typical limestone profile which has vertical and horizontal cross fractures,and conduct an infiltration experiment by a single ring permeameter on the fracture.Firstly,we build a numerical model for the experiment based on Navier-Stokes(N-S)equations.Then use the try-and-error method based on the objective of measured water levels in the single ring to estimate the fracture hydraulic aperture and calculate the proportion of infiltration water in different fractures.We estimate the hydraulic conductivity based on the cubic law,and build another numerical model based on the continuity equation.Finally we compare with the simulation results of two numerical models.The results show that the estimated fracture hydraulic aperture with the N-S method is much less than the measured value;most of water infiltrates along the vertical fracture,but part flows along the lateral fracture;the difference of simulated results between the N-S and cubic law method is not significant,but the fracture infiltration rate estimated with cubic law method is less than that with the N-S method,and N-S method can more accurately describe the process of water movement in fractures.