开挖未支护条件下，监测的顶底板位移变量很小，只有几毫米，是怎么回事?

chengshaobei

是开挖范围太小？参数取值太大？还是实际情况就很小？
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plot block group
gen zone cshell size 1 30 10 p0 0 0 0 p1 2.8 0 0 p2 0 30 0 p3 0 0 2.8 dim 2.75 2.75 2.75 2.75 ratio 1 1 1

group 喷层
gen zone brick  size 5 30 1 p0 2.75 0 0 p1 2.75 0 -1.8 p2 2.75 30 0  p3 2.8 0 0 group 喷层
gen zone cshell size 4 30 10 p0 0 0 0 p1 4.3 0 0 p2 0 30 0 p3 0 0 4.3 dim 2.8 2.8 2.8 2.8 ratio 1.1 1 1

group 等效层1.5m
gen zone radtunnel p0 0 0 0 p1 0 0 -3.3  p2 0 30 0  p3 4.3 0 0 size 5 30 5 4  dim 1.8 2.8 1.8 2.8  ratio 1 1

1 1.1 group 等效层1.5m  
gen zone radc p0 0 0 0 p1 10 0 0 p2 0 30 0 p3 0 0 10 dim 4.3 4.3 4.3 4.3 size 10 30 10 9 ratio 1 1 1 1.1

group 围煤
gen zone radtunnel p0 0 0 0 p1 0 0 -10 p2 0 30 0  p3 10 0 0 size 5 30 5 9  dim  3.3 4.3 3.3 4.3  ratio 1 1 1

1.1 group 围煤
gen zone brick p0 0 0 10 p1 20 0 10 p2 0 30 10 p3 0 0 20 size 10 30 10 group 顶底部煤岩体
gen zone brick p0 0 0 -20 p1 20 0 -20 p2 0 30 -20 p3 0 0 -10 size 10 30 10 group 顶底部煤岩体
gen zone brick p0 10 0 -10 p1 20 0 -10 p2 10 30 -10 p3 10 0 10 size 5 30 10 group 两帮煤岩体
gen zone cylinder p0 0 0 0 p1 2.75 0 0 p2 0 30 0 p3 0 0 2.75 size 5 30 10 group 内部煤岩
gen zone brick p0 0 0 -1.8 p1 0 0 -1.8 p1 2.75 0 -1.8 p2 0 30 -1.8 p3 0 0 0 size 5 30 5 group 内部煤岩
gen zone reflect ori 0 0 0 norm -1 0 0
mo mohr
def derive
s_mod=E_mod/(2.0*(1.0+p_ratio))
b_mod=E_mod/(3.0*(1.0-2.0*p_ratio))
end
set E_mod=6.5e9 p_ratio=0.27
derive
prop bu b_mod sh s_mod c 3e6 f 16
ini dens 1500
fix x ran x 19.9 20.1
fix x ran x -19.9 -20.1
fix y ran y -0.1 0.1
fix y ran y 29.9 30.1
fix z ran z -19.9 -20.1
ini szz -1e8 grad 0 0 1.538461538e5 ran z -20 20
ini sxx -7.5e8 grad 0 0 1.15384613e6 ran x -19.9 -20.1
ini sxx -7.5e8 grad 0 0 1.15384613e6 ran x 19.9 20.1
ini syy -7.5e8 grad 0 0 1.15384613e6 ran y -0.1 0.1
ini syy -7.5e8 grad 0 0 1.15384613e6 ran y 29.9 30.1
set grav 0 0 -10
solve
ini xdisp 0 ydisp 0 zdisp 0
ini xvel 0 yvel 0 zvel 0
ini state 0
plot con szz shade on
hist unbal
hist gp zdisp 0 3 2.8
hist gp zdisp 0 5 -1.8
hist gp xdisp 2.8 3 0
hist gp xdisp 2.8 3 -1
hist gp zdisp 0 15 2.8
hist gp xdisp 0 15 -1.8
plot con szz shade on