自由渗流面及渗流量推求的数值计算方法探讨

Estimation free seepage surface and seepage flow based on numerical method

自由渗流面具有复杂的非线性,较难确定。本文采用开源地下水数值模拟程序MODFLOW及SUTRA,分别运用MODFLOW模型中干湿单元转化技术、SUTRA模型中单元渗透矩阵调整法以及本文建立的缓变渗透系数矩阵法推求自由渗流面。对比其求解结果表明,采用MODFLOW运用干湿转化技术求解自由渗透面的方法稳定性最好、精度最高,而采用缓变渗透系数矩阵法的SUTRA程序,改善了传统单元渗透矩阵调整法的不稳定性,提高了数值计算精度,避免了MODFLOW必须矩形网格的局限性,是一种实用的计算自由渗流面及估算地下水与河流水量交换量的方法。

Free seepage surface is difficult to be determined because of nonlinear processes. Based on open - sources of groundwater modeling programs of MODFLOW and SUTRA, the seepage face was simulated using the dry - wet cell transfer technique in MODFLOW, adjustment of hydraulic conductivity and smooth variation of hydraulic conductivity in SUTRA. Sim- ulated results of these three methods shows that the dry - wet cell transfer technique in MODFLOW offers a steady and highest precision of the equation solution which describes free seepage surface; the method of smooth variation of hydraulic conductivi- ty we developed in this study improves steady of the equation solution because this solution using the original method of adjust- ment of hydraulic conductivity in SULTRA is often unsteady. The proposed method also avoids limitations in MODFLOW that grid must be rectangular, it offers a practical method for calculating the free seepage face and estimating water exchange be- tween groundwater and river.