接触的应用

用恒力拉一个砖块，施加了重力加速度，结果砖块飞起来了，求解释？附图和命令流，在线等，急！
finish
/clear
/UNITS,SI
/prep7
et,1,solid164
r,1
mp,dens,1,2200
mp,ex,1,3.552e9
mp,nuxy,1,0.15
block,0,0.24,0.053,0.106,0,0.115
mat,1
r,1
type,1
esize,0.12
vmesh,1
cm,kuai1,node
block,0,5,0,0.053,-0.5,0.5
mat,1
r,1
type,1
esize,0.12
vmesh,2
NSEL,S,NODE,,13,872
cm,kuai2,node
EDCGEN,ASTS,kuai1,kuai2,0.8,0.8,,,,,,,,,
*dim,time,array,2
*dim,f,array,2
*dim,gy,array,2
time(1)=0,1
f(1)=8.0454,8.0454
gy(1)=9.8,9.8
edcurve,add,1,time,f
edcurve,add,2,time,gy
nsel,s,loc,y,0
d,all,all
edload,add,fx,,kuai1,,,,1,1
edload,add,acly,,kuai1,,,,2,1
allsel,all
/solu
time,2
edopt,add,,lsdyna
edrst,10
edhtime,10
eddump,1
edwrite,lsdyna,1,k