矩形基坑降水计算的列井法

Application of line-well method in rectangular excavation pit dewatering calculation

根据干扰井群稳定流叠加原理,导出了矩形基坑传统等效圆半径就是外接圆半径。根据汇线稳定流原理,导出了矩形、狭长条形基坑涌水量计算的新方法——"列井法",并分别与传统等效圆半径及"大井法"对比。"列井法"也定义了等效圆半径——称为"相对等效圆半径",即相对于基坑边界的等效圆半径,形式简单易记。通过对比,外接圆半径总大于传统等效圆半径。对于狭长条形基坑,两种方法基坑涌水量的计算结果随基坑宽长比呈平稳一致的变化趋势,数值相差不大,"列井法"稍大于"大井法",而潜水含水层,两者几乎一致;矩形基坑两种方法基坑涌水量的计算结果随基坑宽长比相差较大,且"列井法"大于"大井法",但变化特征一致。由于"列井法"是针对整个基坑边界的积分,其计算结果更能代表基坑的渗流特征。

The circumradius of rectangular foundation pit is its equivalent circle radius which is deduced based on steady flow superposition principle. According to the sink-line steady flow theory,a new method named line-well method is proposed to calculate water-inflow of long and narrow rectangular excavation pit,and the comparison with traditional equivalent circle radius and large-diameter well method are carried out.The equivalent circle radius of line-well method is defined named relative equivalent circle radius relative to the excavation pit boundary. The circumradius is always larger than the equivalent circle radius after comparison. For a strip-shaped excavation foundation pit,there is a smaller difference in the calculation results between these two methods. The calculated water inflow by the two methods is similar and varies with the width-long ratio of the pit. The results of the line-well method are a little greater than that of the large-diameter well method,while the results are almost the same for unconfined aquifer. For rectangular pit,the result of these two methods is quite different with the width-long ratio. The result of line-well method is greater than the large-diameter well method,but the trend of their changes is consistent. The calculation result of the line-well method could represent the seepage characteristics of the excavation pit better because the method employing integrals on the whole pit boundary.