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武汉地区长江Ⅰ级阶地含水层在水流等沉积动力的分选作用和上覆土层压力的固结作用下,其渗透系数必然存在各向异性。因此,基于含水层渗透系数的各向同性和以单井稳定流抽水试验得到的含水层水文地质参数所完成的基坑降水设计亦必然与工程实际存在差异。通过现场分层抽水试验、群井抽水试验,结合三维数值模拟反演计算,得出了武汉长江Ⅰ级阶地各含水层水文地质参数的基本规律和特性,即:各含水层渗透系数自上而下逐渐增加且表现为各向异性,其水平渗透系数大于垂直渗透系数,其比值介于1.6~2.6之间。工程实例表明,采用各向异性的水文地质参数和三维渗流分析进行的超深基坑降水设计,结果更接近于实际,且有利于降低工程造价和基坑周边环境损伤,亦有利于节约宝贵的地下水资源。
The anisotropy of anisotropy exists in the permeability coefficient of the first-order terrestrial aquifers of the Yangtze River in Wuhan, under the action of sedimentation power such as water flow and consolidation of overlying soil pressure. Therefore, the design of foundation pit dewatering based on the isotropy of aquifer permeability coefficient and the aquifer hydrogeological parameters obtained from the single well steady flow pumping test will inevitably have differences from the engineering practice. Through the stratified pumping test in the field, the well pumping test and the 3D numerical inversion calculation, the basic laws and characteristics of the hydrogeological parameters of each aquifer in the terraces of Grade I terrains of Wuhan Yangtze River were obtained, that is, the permeability coefficient of each aquifer from top to bottom Under the gradual increase and the performance of anisotropy, the horizontal permeability coefficient is greater than the vertical permeability coefficient, the ratio between 1.6 to 2.6. The engineering examples show that the design of ultra-deep foundation pit dewatering using anisotropic hydrogeological parameters and three-dimensional seepage analysis is closer to the actual result and is conducive to reducing the project cost and damage to the surrounding environment of the foundation pit, as well as saving valuable Groundwater resources.