承压含水层非达西变速抽水井流模型研究

Model investigation of non-Darcian flow by variable-ratepumping tests in confined aquifers

为了精确预测地下水流动中由变速抽水引起非达西流的情况,提出了一个考虑了井储效应和表皮效应的新数值模型。该数值解是利用有限差分法和叠加原理推导得出的,并使用了Izbash方程去描述非达西流的非线性特征。进一步研究中,得到了表皮效应对承压含水层抽水降深的影响。结果表明,表皮区域内的降深曲线会明显受到表皮效应的影响。表皮区域的准渗透率和非达西系数与对应降深呈现负相关关系,并且当表皮区域的径向距离增加时,表皮效应也随之增强。在重点考虑大口径抽水井附近工况时,表皮效应的影响是不可忽略的。

In order to obtain a precise prediction for groundwater in non-Darcian flow induced by variable-rate pumping tests,this study develops a numerical model considered skin effect and wellbore storage effect.The finite difference and superposition principle are used to propose numerical solution and the nonlinear characters of the non-Darcian flow has been depicted by the Izbash equation.The skin effect for pumping drawdown in a confined aquifer has been obtained by further investigation.The results suggest that the drawdown in the skin region is distinctly changed by the skin effect.There are negative relationships between quasi-hydraulic conductivity and non-Darcian index of skin region and the drawdown simulation.It is worth mentioning that as the radial distances of skin region is larger,skin effect is stronger.The influence of skin effect should not be ignored in practice in case of considering the use of large diameter well.