有限元强度折减法计算边坡稳定的对比分析

Comparative analysis of slope stability by strength reduction method

采用目前边坡稳定性分析比较流行的强度折减法,对比研究了MIDAS/GTS、FLAC、ANSYS配合Drucker-Prager(简称D-P)屈服准则和Mohr-Coulomb(简称M-C)屈服准则时软黏土、硬黏土、弱膨胀土3种工况下计算结果的偏差。软黏土工况下D-P准则和M-C准则计算结果的偏差相对较小,当边坡土体为硬黏土时,采用D-P准则与采用M-C准则计算结果的偏差明显增加。3种软件2种屈服准则下的计算结果都反映出,硬黏土的滑动面比弱膨胀土和软黏土的滑动面浅,而且同等情况下MIDAS计算得到的滑动面比ANSYS计算得到的滑动面浅;坡度较小时FLAC(M-C)计算的安全系数比MIDAS(M-C)计算得到的大,坡度较大时则相反;坡度较小时计算过程中先出现塑性区贯通,后出现计算不收敛;坡度较大时计算过程中先出现计算不收敛,后出现塑性区贯通。坡度较小时计算不收敛时的折减系数与出现塑性区贯通时的折减系数差别较大;坡度较大时这一差别较小,甚至计算到不收敛时塑性区仍未贯通,在用MIDAS计算时这一现象反映得更加明显。

The strength reduction method,which is popular at present in the slope stability analysis,is used to analyze the relative error of calculation results by using software MIDAS/GTS,FLAC,ANSYS with D-P and M-C yield criteria in three cases（soft clay,hard clay,weak expansive soil）.In the case of soft clay the relative error of calculation results by using D-P criterion and M-C criterion is relatively small.For hard clay slope,the relative error of calculation results by using D-P criterion and M-C criterion increases significantly.The calculation results by using three kinds of software with two yield criteria all indicate that sliding surface in hard clay is shallower than the sliding surface in weak expansive soil and soft clay.Under the same circumstances,sliding surface determined by MIDAS is shallower than the result by ANSYS.When the slope is small the safety factor of the calculation by MIDAS is smaller than that by FLAC（M-C）;when slope is large the result is opposite.When slope is small the calculation convergence is realized after the breakthrough of plastic zone,but for large slope calculation divergence occurs before the breakthrough of plastic zone.In the case of small slope the difference between reduction factors upon appearance of calculation divergence and upon breakthrough of plastic zone is significant.But the difference between reduction factors is relative small in the case of large slope,even breakthrough of plastic zone does not occur upon the calculation divergence,which is more remarkable when using MIDAS software.