基于深基坑开挖降水对泥岩层含水特性的再认识

Water-bearing features of mudstone based on deep excavation and dewatering

针对泥岩层的含水特性问题,结合区域构造情况,通过基坑开挖、钻孔及降排水揭露了泥岩的地质和水文特征;引入巨厚含水层有效厚度的概念,利用单井和基坑简化大井抽水数据,采用承压水完整井和承压水—潜水非完整井模型分别估算泥岩的渗透性。分析结果表明:泥岩层具有成层性、渗流各向异性、兼具承压水与潜水等含水特性。在分析了基坑泥岩层补迳排条件和含水特性对工程影响的基础上,提出了水文地质勘察分层止水测量、采用等效渗透系数综合评估基坑涌水量以及采用多种降排水措施等建议。

In order to study the water-bearing features of mudstone,excavation,drilling and dewatering were used to investigate the stratum and hydrological characteristics,combined with the geological background.Based on the data of single well and simplified large well of the pit,the concept of extremely thick aquifer and the model of fully penetrating well in confined groundwater and confined groundwater-diving partially penetrating well were introduced to estimate the permeability of mudstone.The results show that mudstone layer has the water-bearing features of stratification,anisotropic seepage and dual characteristics of confined and phreatic groundwater.According to the analysis of supplying,flowing and discharging condition and aquifer character,some measures are suggested,including water table monitoring with different aquifer cut-off measures in the investigation,using equivalent permeability coefficient to evaluate the water inflow,and multiple measures should be taken in the dewatering and discharging to insure the safety of excavation.