地震作用下反倾向层状岩质边坡弯曲倾倒稳定性分析

Stability Analysis for Anaclinal Layered Rock Slopes Subjected to Flexural Toppling under Earthquake Load

当前关于弯曲倾倒破坏的研究鲜有涉及到地震荷载,地震荷载对反倾向边坡弯曲倾倒稳定性的影响规律尚不清楚。为了解决上述问题,提出一种分析地震作用下反倾向层状边坡弯曲倾倒稳定性的极限平衡方法,该方法认为边坡发生破坏时,坡体内部应力达到极限平衡状态,即基于边坡破坏面计算得到的坡脚岩层剩余下滑力(倾倒力)为0。基于静力等效替代思想推导了推力线高度的计算公式;通过严格的力学推导确定岩层的稳定区域、破坏区域及破坏区岩层的破坏模式,并通过逐步迭代的方式计算坡脚剩余下滑力(倾倒力)。选用皖南板岩边坡作为工程实例,计算结果表明采用本文方法得到的边坡破坏面和稳定系数是合理可信的。通过地震影响系数的敏感性分析发现,随着地震影响系数的增大,坡脚剩余下滑力(倾倒力)增大,而边坡稳定系数减小,边坡更容易发生浅层破坏,变得愈发不稳定。

Current studies of flexural toppling failure rarely involve earthquake loading,and the influence laws of earthquake load on the stability of anaclinal layered rock slopes subjected to flexural toppling is unclear.In order to solve the above problems,we present a limit equilibrium method to evaluate the stability of anaclinal layered rock slopes subjected to flexural toppling under earthquake load.We consider that once the overall failure of a slope occurred,the stress of the slope reached the limit equilibrium state,i.e.,the residual sliding force(toppling force)of slope toe calculated along the failure surface was zero.Based on the idea of static equivalent substitution,the calculation formula of the non-dimensional height of the point of application of normal force was derived.The stable zone,potential failure zone and the failure modes of potential failed strata were determined via strict mechanical derivation,and the residual sliding force(toppling force)of slope toe was obtained with step by step analysis method.The calculation results for a slate slope in South Anhui as an engineering example demonstrate that the slope failure plane and the safety factor of the stability of the slope are credible.Through the sensitivity analysis of seismic coefficient,we found that with the increase of seismic coefficient,the residual sliding force of slope toe increase while the safety factor of the stability of the slope decrease,and consequently,the slope is subjected to shallow damage and becomes more unstable.