巨厚非均质潜水含水层抽水试验及参数计算

Pumping Test and Calculation of Hydrogeological Parameters for Massive Anisotropic Phreatic Aquifers

摘要:

渗透系数决定了深基坑工程涌水量的估算及止水帷幕的型式，影响工程安全及造价，对富水地区深基坑工程建设具有重大的意义。对于非均质含水层组，现有的解析公式中，很难找到合适的方法计算水文地质参数，特别是垂直方向的渗透系数。通过在现场施作临时止水帷幕，利用帷幕的绕流阻水作用进行抽水试验，模拟基坑开挖过程中的降水问题，再建立水文地质概念模型和地下水流数学模型，并利用三维有限差分数值模拟软件反演出各层渗透系数，最后通过验证性抽水资料对模型进行了验证，为福州一临江巨厚砂卵石地层地铁车站的围护结构设计中地下水控制提供了设计参数。该试验和数值模拟结果可为类似工程参考。

关键词:渗透系数;抽水试验;非均质含水层;临时止水帷幕;深基坑工程

Abstract:

The permeability coefficient determines the estimation of water inflow at deep foundation pits and the type of the water cutting-off curtain, and affects the safety and cost of the project; thus, it is of great significance to the construction of deep foundation pits in water-rich areas. For anisotropic aquifers, it is difficult to find a suitable method to calculate the hydrogeological parameters from the existing analytical formula, especially for the vertical permeability coefficient. A pumping test was carried out on the flow resistance by using the temporary water cutting-off curtain in the field to simulate the dewatering of foundation pits; then, the hydrogeological conceptual model and the groundwater flow mathematical model were established to invert the permeability coefficient of each layer by using a 3D finite difference numerical simulation software; finally, the model was validated by the data of verification pumping; which provided a guiding basis for the design of the envelope of a subway station in the super-thick sand and gravel stratum near the river in Fuzhou. The results of the test and the numerical simulation can be used for reference for similar projects.

Key words:permeability coefficient; pumping test; anisotropic aquifer; temporary water cutting-off curtain; deep foundation pit