临江砂卵石地层井群降水试验及数值反演研究

Test and numerical inversion of well group dewatering in sandy and pebble strata around river

汉江中游地区深厚的砂卵石强透水地层与周边地表水系的联系性较强,地下水埋深浅,基坑开挖时降水难度大。针对临江富水砂卵石这一特殊地层,以襄阳市东西轴线沉管隧道工程轴线法管节预制干坞的基坑为例,进行了井群降水试验与数值模拟计算。通过现场降水试验确定了降水影响半径、单井出水量、水位恢复速率等参数,在此基础上利用非稳定流分析法与三维渗流数值模型分别计算出地层的综合渗透系数为64.5 m/d,各分层渗透系数分别为上部砂层12 m/d、中间卵石混圆砾102.5 m/d、下部圆砾25.4 m/d,为轴线干坞基坑降水设计方案提供参考。

The deep permeable sandy and pebble strata are closely related to the surrounding surface water in the middle reaches of the Hanjiang River, and the depth of the ground water is shallow so that it caused great difficulty to dewater of the strata during the foundation pit excavation. Considering the specific characteristics of the permeable sandy and pebble strata around Hanjiang River, we take the foundation pit of pipe joint prefabrication dry dock with axis method in Xiangyang EastWest Axis Road Project as an example to carry out well group dewatering test and numerical simulation calculation. The influence radius of dewatering, water output of single well, water level recovery rate and other parameters are determined by field dewatering test. On this basis, using the unsteady flow analysis method and three-dimensional seepage numerical model,the comprehensive permeability coefficient of the formation is 64.5 m/d, and the permeability coefficient of each layer is 12 m/d for the upper sand layer, 102.5 m/d for the middle pebble mixed with round gravel, and 25.4 m/d for the lower pebble, which can provide reference for the design scheme of axis dry dock foundation pit dewatering.