小断面排水减压沟的渗流计算

Calculation of seepage from small-section drain and relief ditches

应用正、反对称流叠加法计算减压沟渗流 ,需先求出相应于正、反对称流减压沟的附加渗径长度dp 和dn.先用数值积分法求出其理论解 ,然后从此理论解整理出关于小断面沟dp 和dn 的经验计算式 .该经验公式适用于沟深和半沟顶宽分别小于 0 .3倍砂层厚度的常见沟型 (这类沟型通常已能满足排水减压工程的要求 ) .算例表明 ,用本文公式计算的dp 的相对误差平均为± 2 % ,最大为± 7% ;dn 的相对误为± 2 % ,最大为± 9% .

Before calculation of seepage from relief ditches by the symmetric and anti symmetric flow superposition method, the additional seepage paths d p and d n of ditches corresponding to symmetric and anti symmetric flows must be given. In this study, the theoretical solution of d p and d n is obtained first by the numerical integration method, and then, an empirical formula for calculation of d p and d n is deduced based on the theoretical solution. The empirical formula is applicable if the depth and half top breadth of ditches are smaller than 0.3 of the sand layer thickness respectively (usually, the ditches of this type meet the requirements of drainage). Examples calculated by the formula show that the average relative error of d p is ± 2%, the maximum relative error of d p is ±7%, the average relative error of d n is ± 2%, and the maximum relative error of d n is ±9%.