求助：边坡稳定分析计算几步就退出了，未出现滑弧，附...

swpf

建了个多土层的边坡稳定分析模型，重力增加法求安全系数，但程序只计算了几步就退出了，查看结果文件，边坡并未出现滑弧，不知什么原因，请高手帮忙看一下。谢谢！


                  *** STIFFNESS MATRIX NOT POSITIVE DEFINITE ***

NODE=      4150 EQUATION=      8245  DOF= Y-TRANSLATION  PIVOT= -4.27414311E+06

*** CHECK THE FOLLOWING ***

(A) STRUCTURE COLLAPSE:
        - COLLAPSE LOAD OF THE STRUCTURE MAY HAVE BEEN REACHED

(B) LOCAL COLLAPSE:
        - ALL MATERIAL POINTS CONTRIBUTING TO A NODE MAY HAVE RUPTURED OR LOST STIFFNESS

(C) ELEMENT DISTORTION:
        - ELEMENTS MAY HAVE OVERDISTORTED DUE TO LARGE DISPLACEMENTS OR POOR INITIAL MESH QUALITY


Stiff.matrix not positive definite,wrong boundary conditions or model collapsed
*** ERROR NO. A1002 ***