model null range group excavation1
sel cable id=1 begin=(11 0.8 38.5) end=(16.91 0.8 37.46) nseg=6
sel cable id=1 prop emod=210e9 density =7.8e3 gr_coh=100 gr_fri=25 gr_k=24e6 gr_per=0.345 slide=on &
slide_tol=1e-6 ycomp=0.103e9 xcarea=3.8e-4 ytens=1.414e5
sel shell id=100 range x 10.8 11.6 y 0 1.6 z 38 40 group bianpo
sel shell prop iso=(10e9,0.2) density =2.5e3 thick=0.1 range id=100
sel delete link range id 1；1 为节点1的link号
sel delete link range id 9；9 为节点10的link号
sel link 1 target node tgt_num 10
sel link attach xdir=rigid ydir=rigid zdir=rigid xrdir=rigid &
yrdir=rigid zrdir=rigid（到此为止，运算没有问题）
model null range group excavation2
sel cable id=2 begin=(10.4 0.8 37) end=(16.31 0.8 35.96) nseg=6
sel cable id=2 prop emod=210e9 density =7.8e3 gr_coh=100 gr_fri=25 gr_k=24e6 gr_per=0.345 slide=on &
slide_tol=1e-6 ycomp=0.103e9 xcarea=3.8e-4 ytens=1.414e5
sel shell id=100 range x 10 10.8 y 0 1.6 z 36 38 group bianpo
sel shell prop iso=(10e9,0.2) density =2.5e3 thick=0.1 range id=100
sel delete link range id 45 ；45 为节点23的link号
sel delete link range id 39 ；39 为节点36的link号
sel link 23 target node tgt_num 36
sel link attach xdir=rigid ydir=rigid zdir=rigid xrdir=rigid &
yrdir=rigid zrdir=rigid 到这一步时，出现source node 23 already has a link。
请问这是怎么回事？谢谢
