悬挂式止水帷幕条件下基坑涌水量计算研究

Water Inflow Calculation of Foundation Pit under the Condition of Suspended Waterproof Curtain

在基坑工程中,悬挂式止水帷幕在工程中的应用越来越广泛,但现行《建筑基坑支护技术规程》(JGJ 120—2012)中只给出了开放式场地下基坑涌水量的计算公式,业内对悬挂式止水帷幕条件下基坑涌水量尚无统一的计算方法。基于裘布依理论,对承压含水层、悬挂式止水帷幕条件下基坑涌水量的理论计算公式进行推导,通过收集相关基坑工程案例水位降深资料验证理论计算公式的可行性,并以汉口客运中心基坑为工程实例,对该基坑涌水量数值模拟结果与理论公式计算结果进行对比,最后对理论计算公式中参数对基坑涌水量的影响进行分析。结果表明:考虑悬挂式止水帷幕后的基坑涌水量理论计算公式符合工程实际,提出的考虑止水帷幕影响下基坑涌水量的理论计算公式是合理、可用的,其计算结果精确度较高;理论计算公式参数影响分析显示,当r_(0)/M≤0.4时,基坑面积对基坑外水位降深s的影响较大,当L/M≥0.6时,止水帷幕深度的增加对基坑涌水量的减小效果显著,基坑涌水量与基坑面积和基坑设计水位降深呈线性正相关关系。该研究结果可为悬挂式止水帷幕条件下基坑内降水井的布置数量和方式优化提供依据,可应用于指导基坑工程的降水设计,具有一定的工程实际应用价值。

In the foundation pit project, the application of suspended waterproof curtain is becoming more and more extensive.Technical Specification for Buidling Foundation Pit Support(JGJ 120-2012) only gives the calculation formula of foundation pit water inflow under the open site, and there is no uniform calculation method for water inflow in foundation pit under suspended curtain condition in the industry.Based on Dupuit theory, the theoretical calculation formula of foundation pit water inflow under the condition of confined aquifer and suspended waterproof curtain is derived.The data of water level drawdown foundation pit engineering cases are collected to verify the feasibility of theoretical calculation formula.Taking foundation pit of Hankou Passenger Transport Center as an example, the numerical simulation results of the water inflow of the foundation pit are compared with the theoretical calculation results.Finally, the parameters of theoretical calculation formula are analyzed.The results show that the theoretical formulas of the water inflow of the foundation pit considering the waterproof curtain are in accordance with the engineering practice, and the theoretical formulas for calculating the foundation pit water inflow under the influence of curtain are reasonable and available with high accuracy.Theoretical calculation formula parameter impact ana-lysis shows that when r_(0)/M≤0.4,the foundation pit area has a greater influence on the water level drop s outside the pit.When L/M≥0.6,the increase of curtain depth has a significant effect on the reduction of foundation pit water inflow.The water inflow of foundation pit is in positive correlation to the area and design water level drop of foundation pit.The research results can provide a basis for the quantity and layout of the dewatering wells in the foundation pit under the condition of suspended waterproof curtain, and can be used to guide the design of foundation pit dewatering, which has certain practical application value in engineering.