刚体离散元动力方法在基于位移的岩坡地震响应分析中的应用

当前岩坡地震动力响应分析中,多采用极限平衡方法分析拟静力安全系数,采用Newmark滑块分析动力永久位移,假设较多,工程实用性受限。将刚体离散元方法引入岩坡地震动力稳定性评价工作中。通过与强度折减法、Newmark法中的永久位移评价相结合,提出一种复杂岩坡静动力稳定性分析方法。初步认识表明:(1)采用极大节理刚度可以减少节理刚度带来的弹性接触位移,使得刚体离散元用于求解岩坡楔形块体的静/动力稳定性问题。(2)刚体离散元强度折减法可以无需假设块体运动方向或假定滑动形式,直接求解获取安全系数、下滑力等结果,可以考虑复杂形状块体,相比传统方法更具优势和实用性。(3)与4个经典静力算例与3个动力算例的对比验证,表明提出的刚体离散元方法及程序实现的正确性。(4)采用提出的方法,研究幅值、节理面交线倾角等参数对岩坡地震响应永久位移的影响规律研究,表明刚体离散元方法可以根据参数变化得到正确的得到相应的结果变化规律。且对比发现在某些特定条件下拟静力安全系数不能正确反映岩坡地震响应的陡增程度。(5)在工程实例中,采用刚体离散元方法进行K1块体基于位移的地震稳定性评价,给出基于超越概率的支护设计方案。相比拟静力安全系数设计方案,在满足使用条件的前提下优化程度更高。研究可为岩坡静动力稳定性分析提供一种新的思路。

Application of rigid discrete element method in the displacement-based seismic stability analysis of rock slopes

In the present seismic response analysis of rock slopes，the limit equilibrium method is used to analyze the static safety factor and the Newmark dynamic analysis is used to analyze the dynamic permanent displacement. Their use in engineering practice was limited due to the complexity. In this paper，the rigid body discrete element method is introduced into the evaluation of seismic stability of rock slopes. Combining the rigid body discrete element method with the strength reduction method and Newmark method，a static and dynamic stability analysis method for complex rock slopes is presented. Assuming the large stiffness for joints，the contact displacement caused by the elastic deformation of joints was limited so that the rigid discrete element method can be used to solve the static/dynamic stability of rock wedges. The rigid discrete element method does not need to assume the sliding direction and sliding mode in calculating the safety factor of the rock slope and is therefore very useful in engineering practice with the complex rock wedges. The correctness of the proposed method and the programming in the 3DEC code is demonstrated through comparisons with 4 classical static examples and 3 dynamic examples. Parameter studies confirmed that the proposed rigid discrete element method is capable of obtaining the correct trend of variation according to the changing parameters. It was found that under certain conditions the pseudo static safety factor cannot reflect correctly the extent of the earthquake response of the rock slope. In the case study，the seismic stability evaluation of K1 block based on the displacement was carried out with the rigid discrete element method. The results with the rigid discrete element method were better than those from the method of pseudo static safety factor.