涵洞与路线的直角交角为120(α= 90°-120 =-30°)，路基边坡m0=1.5(即1:1.5)，河北墙正线段背坡比n0=4。相关计算如下:1。墙体考虑流水坡度I计算:m = m0/(1 m0i/cos α)，上游为正，下游为负，m = 1.5/(1+1.5 * 2。2.涵洞轴线长度:l =(h-h)m/cosα=(4.79-0.7)* 1.4498/cos 30 = 6.847m；3.洞口段墙顶宽度:c = c0/cos(β-α)= 0.40/cos(-20+30)= 0.406m；4.传送门横断面墙背面的坡率:n=[n0+signβsin(β-α)/m]cos(β-α)，其中sign为符号函数sign β = sign (-20) =-1，n = [4-sin (-20+30)。n ' =[4-SIN(-20+30)/1.5]COS(-20+30)= 3.82525。孔截面底部宽度:a = c+h/n = 0.406+4.79/3.8259.1000000000605 6。河北尾部断面宽度:b = c+h/n = 0.406+0.70/3.8213 = 0.589m，(n '→0.588m)；7.墙体体积的计算(取一个与洞口横截面平行的超薄dz截面进行分析，如立面阴影部分)，其体积为dV≈[(c+x) y /2]dz，其中x=c+y/n，dz =mdy代入:dV≈ [y2/2/n+ cy]mdy。y从H ~ H积分整理如下:V = 0.5[(H3-H3)/3/N+C(H2-H2)]MV = 0.5 *[(4.793-0.73)/3/3.8213+0.406 *(4.792)。1.4498 = 13.536 m3(N '→V = 13.529 m3)替换为(H-H)m = lcosα:V = 0.5[(H2+HH+H2)/3/N+C(H