强透水地层半封闭基坑降水特性及排水量预测

Dewatering characteristics and inflow prediction of deep foundation pits with partial penetrating curtains under deep and highly permeable strata

采用有限差分法分析了半封闭基坑的降水渗流特征,发现地层渗透性仅改变地下水流速,而帷幕嵌入深度、含水层厚度、降水井滤管长度均会导致流网形态变化,与帷幕阻隔效应耦合,进而影响排水需求.基于等效井假设,建立了标准状态下排水量随帷幕变化的特征曲线,提出了阻隔效应的量化公式;并针对非标准降水条件提出了对应的特征曲线修正方法,进而可对需求排水量进行初步预测.数值模拟和现场测试对比验证表明所提出的量化预测方法具备可靠性,且保留了一定程度的安全冗余度.

Deep foundation pits dewatering construction in highly permeable geology requires waterproofing methods to relieve groundwater flow.However,no effective prediction formula is yet available for determining water inflow.In this study,dewatering characteristics with partial penetrating curtains were analyzed via the finite difference method.Results show that the permeability only changes the seepage velocity,while the curtain inserts depth,the formation thickness,and the filter pipe length affects the seepage field morphology and is coupled with the blocking effect,thus change the dewatering requirement.Furthermore,by assuming an equivalent well,the characteristic curve of the inflow versus the insertion depth of curtain under the standard condition was established,and formulas of the quantified blocking effect were proposed.Then,the variation curve correction method could preliminarily predict the required inflow aiming at different dewatering conditions.Numerical simulation and field tests validate the reliability of the proposed method and the safety redundancy.