基于改进阻力系数法的悬挂式帷幕基坑渗流计算

帷幕结合基坑内降水的方案是深基坑工程中地下水控制的主要趋势，由于基坑渗流场的复杂性和尺度效应，业内尚无成熟且精确的解析计算方法。在分析悬挂式帷幕基坑与闸坝渗流场特点异同的基础上，对闸坝改进阻力系数法进行修正，提出了承压水条件下悬挂式帷幕基坑渗流段的分段方式，推导了新的考虑基坑特殊段"水平汇流段"的等效阻力系数计算公式，并将之拓展至含水层各向异性条件下，实现了悬挂式帷幕基坑涌水量和坑外水位降深的定量计算；最后，结合典型基坑案例，通过数值模拟验证了该方法的精确性。研究表明:经过合理分段、等效和修正处理后，改进阻力系数法在悬挂式帷幕基坑承压水渗流计算中，与数值法计算结果的相对误差能控制在5%以内，精度较高，且具有分段灵活、计算简单的优点，能适用于不同场地条件下基坑降水设计的计算。 

Seepage calculation of foundation with suspended curtain based on improved resistance coefficient method

The combination of the curtain and pit dewatering is the main trend of groundwater control in the deep foundation pit project.Due to the complexity and scale effect of the seepage field around the deep foundation pit, there is still no mature and accurate analytical calculation method for dewatering design.Based on the comparison of the characteristics of the seepage field between the suspended curtain and the gate dam, a new subsection mode of seepage section of suspended curtain foundation pit under confined aquifer is proposed.Modified from the improved resistance coefficient method of the gate dam, a new formula for calculating equivalent resistance coefficient of "horizontal confluence section"within special zone of foundation pit is derived, which is extended to the anisotropic condition of aquifer and can be used in the quantitative calculation of the water outflow and drawdown in the suspended curtain foundation pit.Finally, the accuracy of the method is verified by numerical simulation combined with a typical foundation pit case.The studies show that, after reasonable segmentation, equivalence and correction, the relative error between the improved resistance coefficient method and the numerical modeling can be controlled within 5%, with high accuracy.Besides, it has the advantages of flexible segmentation and simple calculation, and can be applied to the calculation of foundation pit dewatering design under different site conditions.