[求助]急啊，有没有做隧道开挖的高手啊

tunshitiandi

我是个菜鸟，仿照参考书做的隧道开挖，怎么不行啊，每次都会出现：
*** ERROR ***                           CP=   1403.766   TIME= 15:18:44
One or more elements have become highly distorted.  Excessive           
distortion of elements is usually a symptom indicating the need for     
corrective action elsewhere.  Try incrementing the load more slowly     
(increase the number of substeps or decrease the time step size).  You  
may need to improve your mesh to obtain elements with better aspect     
ratios.  Also consider the behavior of materials, contact pairs,        
and/or constraint equations.  If this message appears in the first      
iteration of first substep, be sure to perform element shape checking.
为什么会这样啊，怎么改啊？