求助各位大侠，此命令流问题出在哪？模型计算为何无法收敛？

mk05230723

本人初学者，在建立复合地基模型时发现问题，想求教在计算初始应力场时，什么情况下应该设置边界初始应力？初始应力大小怎么确定？附模型计算命令流（只建立了垫层跟地基土）：
new
gen zone brick p0 (0,0,0) p1 (36,0,0) p2 (0,36,0) p3 (0,0,20) & size 36 36 20
group soil
model mohr
prop bulk 2e7 shear 7e6 coh 34e3 fri 19 dens 1900
fix z ran z -0.1 0.1
fix x ran x -0.1 0.1
fix x ran x 35.9 36.1
fix y ran y -0.1 0.1
fix y ran y 35.9 36.1
set grav 0 0 -10
solve
gen zone brick p0(0,0,0) p1 (36,0,0) p2 (0,36,0) p3 (0,0,20.3) & size 120 120 1
group cushion
model mohr
prop bulk 4e7 shear 2e7 coh 3e4 fri 30 dens 1800
fix z ran z -0.1 0.1
fix x ran x -0.1 0.1
fix x ran x 119.9 120.1
fix y ran y -0.1 0.1
fix y ran y 119.9 120.1
set grav 0 0 -10
solve
gen separate soil
Create interface elements on the cushion surface of the soil
interface 1 wrap soil cushion
plot create view_int
plot add surface
plot add interface red
plot show
save int.sav
求高手指教！