为了探究孔隙含水层的非均质性对注水井附近溶质运移的控制机理以及溶质羽的空间分布特征,基于美国MADE场地含水层地质统计学数据,利用T-PROGS(transition probability geostatistical software)构建了三维径向非均质随机模型;并结合MODFLOW和MT3DMS模块模拟了注水井附近的溶质运移过程,研究了沉积相不同空间结构对溶质运移过程的影响.结果表明:在非均质含水层注水井附近普遍存在双峰反常运移现象;径向溶质运移受高渗透性沉积相的沉积长度和厚度影响较大,沉积长度越大溶质质量空间分布曲线双峰现象越明显,尤其当沉积长度扩大到1.75倍时,双峰现象最明显;通过模拟结果可以得出高渗透性沉积相所在位置与高流速优先流所处位置呈一定的正相关性.总体而言,高渗透性的含水介质在冲洪积孔隙含水层中具有很强的连通性,易形成优先水流通道,导致溶质沿快速和慢速两种通道运移,从而使得穿透曲线出现双峰现象.
Numerical simulation study on bimodal migration of heterogeneous radial solute anomaly in porous media
To investigate the control mechanism of the heterogeneity of the porous aquifer on the solute transport near the injection well and the spatial distribution characteristics of solute plume,a three-dimen-sional radial heterogeneous stochastic model was developed by using T-PROGS(transition probability geostatistical software)based on the geostatistical data observed at the MADE site in USA.MODFLOW and MT3DMS were used to simulate solute transport in the vicinity of water injection wells,and the effects of different hydrofacies architecture on the solute transport were investigated.The results show that the phenomenon of bimodal anomalous transport can be universally observed in heterogeneous aquifers;the ra-dial solute transport is greatly affected by the deposition length and thickness of high permeability,the lar-ger the deposition length,the more obvious the bimodal phenomenon of the spatial distribution curve of solute mass,and the bimodal phenomenon is the most obvious,especially when the deposition length increa-ses to 1.75 times;there is a positive correlation between the zone of high permeability hydroface and that of the preferential flow path with high velocity.In general,the highly permeable media have strong inter-con-nectivity in the alluvial porous aquifer,leading to a preferential flow channel,which results in the formation of double peaks for the breakthrough curve due to the fast-flow and the slow-flow domains.
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