基于有限元法的岩质边坡地震稳定性数值分析

Numerical Analysis of Seismic Stability of Rock Slopes Using Finite Element Method

基于有限元法,采用三维非线性时程分析,运用强度折减理论,通过位移突变性判据和塑性区贯通判据综合分析岩质边坡在地震工况下的稳定性。在三维有限元模型中,通过设置黏弹性人工边界来吸收地基的辐射阻尼效应,充分考虑由岩体自重产生的地应力场和岩脉及断裂破碎带对稳定性的影响。分析结果表明:以位移突变为稳定安全系数的一项判据,沿边坡高程分布的特征点位移突变对应的动力稳定安全系数均大于1.35;以塑性区贯通为稳定安全系数的一项判据,随着安全系数的增大屈服区逐渐增大,安全系数较小时塑性屈服区小;当安全系数达到1.35时坡脚位置局部出现大量的屈服塑性区;当安全系数继续增大时,开挖边坡位置屈服塑性区出现贯通;安全系数超过1.5时边坡出现破坏。联合考虑位移突变和塑性区贯通进行安全系数判定得到动力稳定安全系数为1.35,满足要求。

This paper presents the three-dimensional numerical analysis results using elastoplastic constitutive model on the stress-deformation in a rock slope under seismic conditions.In the analysis,the Mohr Coulomb failure criterion,the nonlinear time history analytical method as well as the strength reduction theory were used and the stability of the rock slope is evaluated by the sudden displacement as well as the development of a throughout plastic zone in the model.The viscoelastic artificial boundaries were established in the model to absorb the radiational damping effect from the foundations and the effect of the gravitational field of the rock slope and the fracture zone or rock vein on the seismic stability of the rock slope were also considered.The results show that:under the sudden displacement criterion,the dynamic stability factor of safety corresponding to a sudden change in the displacement of the characteristic points along the slope elevation is greater than 1.35;when plastic zone penetration criterion used,the factor of safety increases with the gradual increase of the plastic yield zone.When the factor of safety is low,the plastic yield zone is relatively small;When the safety factor reaches 1.35,a large number of yielded plastic zones appear locally at the toe of slope.With the further development of the locally isolated yielded plastic zones at the excavation slope position gradually grow connected;Slope failure will occur when the factor of safety exceeds 1.5.Combined consideration of sudden change in displacement and the development of a throughout plastic zone in the slope failure consideration,a satisfactory dynamic stability factor of safety should be 1.35.