做了一个路基沉降模型，想研究分层填土引起的沉降问题，但是计算一直收敛不了，怎么办！命令流如下，请高人指点！
new
gen zone brick p0 0 0 0 p1 150 0 0 p2 0 5 0 p3 0 0 5 size 10 1 5 group soil1
gen zone brick p0 0 0 5 p1 150 0 5 p2 0 5 5 p3 0 0 10 size 10 1 5 group soil2
gen zone brick p0 0 0 10 p1 150 0 10 p2 0 5 10 p3 0 0 20 size 10 1 10 group soil3
gen zone brick p0 42.5 0 20 p1 107.5 0 20 p2 42.5 5 20 p3 47 0 23 p4 107.5 5 20 &
p5 47 5 23 p6 103 0 23 p7 103 5 23 size 8 1 5 group soil4
fix x y z ran z -0.1 0.1
fix x ran x -0.1 0.1
fix x ran x 149.9 150.1
fix y ran y 4.9 5.1
fix y ran y -0.1 0.1
model mohr ran z 0 20
model null ran z 20 23
prop bulk 1.3e7 shear 8.0e6 coh 10e10 tension 1e10 ran group soil1
ini dens 1700 ran group soil1
prop bulk 2e7 shear 9e6 coh 10e10 tension 1e10 ran group soil2
ini dens 1800 ran group soil2
prop bulk 1.2e7 shear 6e6 coh 10e10 tension 1e10 ran group soil3
ini dens 1900 ran group soil3
set grav 0 0 -9.8
hist id=1 unbal
solve
prop bulk 1.3e7 shear 8.0e6 coh 7e3 fric 28 ran group soil1
prop bulk 2e7 shear 9e6 coh 1.8e4 fric 32 ran group soil2
prop bulk 1.2e7 shear 6e6 coh 2.2e4 fric 23 ran group soil3
solve
ini xdis 0 ydis 0 zdis 0
ini xvel 0 yvel 0 zvel 0
model elastic ran z 20 23
prop bulk 1.17e8 shear 4e7 ran z 20 23
ini dens 1900 ran z 20 23
solve
