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天津市平原区地面沉降主要由地下水大量开采引起,影响范围广、危害大,已成为天津市主要的环境地质问题。分析了研究区的水文地质条件,结合地下水开发利用状况,将研究区概化为6个含水层组,地下水流考虑三维非稳定流,地面沉降选用一维固结压缩模型,运用地下水流模型Modflow 2005和地面沉降模拟模块Sub,建立了天津市平原区地下水流-地面沉降数值耦合模型,模型面积为1.1×104 km2,利用1998—2008年地下水位等值线、过程线、地面沉降过程线等资料对模型进行了识别。模拟期的地下水均衡分析表明,在多年开采条件下,越流补给、压缩释水、侧向边界流入分别占深层含水层补给量的41.84%、32.15%和24.17%。将调试后的模型应用于南水北调实施后地下水控采条件下的地面沉降趋势预测,显示出停采或减少地下水的开采,有利于减缓地面沉降下降速度,且表现出开采层位越往下,地面沉降恢复难度越大的变化趋势。
The land subsidence in the plain area of Tianjin Municipality is mainly caused by a large amount of groundwater exploitation, affecting a wide range of areas and causing great damage. It has become a major environmental and geological problem in Tianjin. The hydrogeological conditions of the study area are analyzed. According to the development and utilization of groundwater, the study area is generalized into six aquifer groups. Three-dimensional unsteady flow is considered for groundwater flow and one-dimensional consolidation compression model for ground subsidence. The groundwater flow model Modflow 2005 and ground subsidence simulation module Sub, a numerical coupled model of groundwater flow-land subsidence in the plain area of Tianjin was established. The model area is 1.1 × 104 km2. Using the contours of groundwater level, the process line and the land subsidence process line from 1998 to 2008 The data identifies the model. The analysis of groundwater balance during the simulation period shows that under multi-year mining conditions, the inflow, compression and discharge, and lateral boundary inflow respectively account for 41.84%, 32.15% and 24.17% of the deep aquifer recharge. The model after commissioning is applied to forecast the tendency of land subsidence under groundwater controlled mining conditions after the implementation of South-to-North Water Diversion Project. It shows that stopping or reducing the exploitation of groundwater is beneficial to slow down the rate of land subsidence and shows that the more strata of mining area go down and the ground Subsidence recovery more difficult changes in the trend.