模型中出现零刚度是什么问题？

whlxpp521

下面是我建的一个模型的部分命令，运行到这里就出现零刚度问题，请各位高手帮忙看下是哪里出问题了。
  new
;确定各单元组
gen zone brick p0 0 0 0 p1 7.5 0 0 p2 0 6 0 p3 0 0 0.6 &
               p4 7.5 6 0 p5 0 6 0.6 p6 6.6 0 0.6 p7 6.6 6 0.6 size 20 20 1 group geogrid
gen zone brick p0 0 0 0.6 p1 6.6 0 0.6 p2 0 6 0.6 p3 0 0 3 &
               p4 6.6 6 0.6 p5 0 6 3 p6 3 0 3 p7 3 6 3 size 20 20 4 group AB组料
gen zone brick p0 0 0 -5 p1 7.5 0 -5 p2 0 6 -5 p3 0 0 0 size 20 20 8
group soil ran z -1 0
group clay ran z -5 -1
;预留桩帽和桩
m null ran x 0   0.6 y 0.4 1.6 z -0.5 0
m null ran x 0   0.6 y 2.4 3.6 z -0.5 0
m null ran x 0   0.6 y 4.4 5.6 z -0.5 0
m null ran x 1.4 2.6 y 0.4 1.6 z -0.5 0
m null ran x 1.4 2.6 y 2.4 3.6 z -0.5 0
m null ran x 1.4 2.6 y 4.4 5.6 z -0.5 0
m null ran x 0   0.3 y 0.7 1.3 z -4.5 -0.5  
m null ran x 0   0.3 y 2.7 3.3 z -4.5 -0.5
m null ran x 0   0.3 y 4.7 5.3 z -4.5 -0.5
m null ran x 1.7 2.3 y 0.7 1.3 z -4.5 -0.5
m null ran x 1.7 2.3 y 2.7 3.3 z -4.5 -0.5
m null ran x 1.7 2.3 y 4.7 5.3 z -4.5 -0.5
;建立桩帽和桩
gen z b p0 0 0.4 -0.5 p1 0.6 0.4 -0.5 p2 0 1.6 -0.5 p3 0 0.4 0 size 6 12 10
gen z b p0 0 2.4 -0.5 p1 0.6 2.4 -0.5 p2 0 3.6 -0.5 p3 0 2.4 0 size 6 12 10
gen z b p0 0 4.4 -0.5 p1 0.6 4.4 -0.5 p2 0 5.6 -0.5 p3 0 4.4 0 size 6 12 10
gen z b p0 1.4 0.4 -0.5 p1 2.6 0.4 -0.5 p2 1.4 1.6 -0.5 p3 1.4 0.4 0 size 6 12 10
gen z b p0 1.4 2.4 -0.5 p1 2.6 2.4 -0.5 p2 1.4 3.6 -0.5 p3 1.4 2.4 0 size 6 12 10
gen z b p0 1.4 4.4 -0.5 p1 2.6 4.4 -0.5 p2 1.4 5.6 -0.5 p3 1.4 4.4 0 size 6 12 10
gen z b p0 0 0.7 -4.5 p1 0.3 0.7 -4.5 p2 0 1.3 -4.5 p3 0 0.7 -0.5 size 6 6 20 gro pile1
gen z b p0 0 2.7 -4.5 p1 0.3 2.7 -4.5 p2 0 3.3 -4.5 p3 0 2.7 -0.5 size 6 6 20 gro pile2
gen z b p0 0 4.7 -4.5 p1 0.3 4.7 -4.5 p2 0 5.3 -4.5 p3 0 4.7 -0.5 size 6 6 20 gro pile3
gen z b p0 1.7 0.7 -4.5 p1 2.3 0.7 -4.5 p2 1.7 1.3 -4.5 p3 1.7 0.7 -0.5 size 6 6 20 gro pile4
gen z b p0 1.7 2.7 -4.5 p1 2.3 2.7 -4.5 p2 1.7 3.3 -4.5 p3 1.7 2.7 -0.5 size 6 6 20 gro pile5
gen z b p0 1.7 4.7 -4.5 p1 2.3 4.7 -4.5 p2 1.7 5.3 -4.5 p3 1.7 4.7 -0.5 size 6 6 20 gro pile6
save 各单元组.sav
plot blo gro
pause
;边界条件
fix x y z ran z -4.9 -5.1
fix x ran x -.1 .1
fix x ran x 7.4 7.6
fix y ran y -0.1 0.1
fix y ran y 5.9 6.1
;参数
model mohr ran z -5 0
model null ran z 0 3
prop bulk 2.8e7 shear 1.68e7 coh 10e10 tension 1e10 ran group soil
ini dens 2230 ran group soil
prop bulk 6.73e6 shear 2.24e6 coh 10e10 tension 1e10 ran group clay
ini dens 2040 ran group clay
set grav 0 0 -9.8
prop bulk 29.2e9 sh 13.46e9 coh 10e3 fric 15 ran gro pile1 any pile2 any pile3 any pile4 any pile5 any
pile6 any
ini dens 2000 ran gro pile1 any pile2 any pile3 any pile4 any pile5 any pile6 any
hist id=1 unbal
solve
prop bulk 2.8e7 shear 1.68e7  coh 10e3 fric 20 ran group soil
prop bulk 6.73e6 shear 2.24e6   coh 32.07e3 fric 11.05 ran group clay
prop bulk 29.2e9 sh 13.46e9 coh 10e3 fric 15  ran gro pile1 any pile2 any pile3 any pile4 any pile5
any pile6 any
ini dens 2000 ran gro pile1 any pile2 any pile3 any pile4 any pile5 any pile6 any
solve