重算了一下, 第一题答案 是 1.08, 第二题答案是1.21
第一题: Ea=1/2*(19-10)*10^2*0.27=121.5
Ew=1/2*10*10^2=500
墙前三角形卵石和挡墙一起考虑重量: G=2*10*20+1/2*10*15*17=1675
Ks=1675*0.4/621.5=1.08
It is a bit tedious to compute the second
The force P2 should be decomposed in to x and y direction first, and then be considered together with W2, as follows:
P1x=P1*cosa2, P1y=P1* sina2
Ks=[(W2+P1 SINa2)cos a1 - P1 cosa2 sina1]*tanphi / [(W2+P1 SINa2)sina1 + P1 cosa2 cosa1] = 1.21