青川县东山斜坡地震动力响应数值验证

Numerical verification of seismic dynamic response of Dongshan Slope in Qingchuan County

岩质边坡地震动力响应分析对于防灾减灾极为重要,但是以往研究大多仅考虑地形因素影响,鲜有成功定量分析边坡动力响应分析的报道。为此,在充分考虑地形效应的基础上,试图探索以数值方法在考虑结构面因素的情况下,定量分析岩质边坡动力响应的可行性。选取一种离散方法——非连续变形分析(DDA)作为数值分析方法,结构面效应通过改变结构面处DDA罚弹簧值实现,将水平向和竖直向地震荷载同时输入至模型中。计算结果表明,在阻尼选择合理的情况下,DDA能够准确反应水平向放大系数,而竖向只能定性吻合;广泛分布的结构面会由于降低岩层的等效阻抗,增加与周围岩层的阻抗差进而影响边坡动力响应结果,影响程度在40%~70%。另外,结构面产状会使边坡动力响应出现较强的各向异性,而这也是传统基于连续介质力学的数值方法难以反映的现象。本研究结果验证了结构面效应,同时证实了DDA能够准确地反映和验证边坡水平向地震动力响应关系,对岩质边坡抗震设计具有重要意义。

The analysis on the seismic dynamic response of rocky slope is quite important for disaster prevention and mitigation.However,there are few reports on successful quantitative analysis of the slope dynamic response due to most of the relevant previous studies being carried only under the consideration of the impact from the topographic factors.On the basis of fully considering the topographic effects,it is tried to explore the feasibility of quantitatively analyzing the dynamic response of rocky slope by means of numerical method under the consideration of the factors of structural plane herein.Therefore,a dynamic discrete element method-discontinuous deformation analysis(DDA)is selected as the analysis method.By which,the effects of structural plane are realized through changing the DDA penalty spring value at the structural plane,and then the horizontal and vertical seismic loads are simultaneously put into the model.The calculation result shows that under the condition of reasonable damping selection,the horizontal amplification factor can be accurately reflected,but the vertical one can only be qualitatively fitted.Due to decreasing the equivalent impedance of rock stratum,the widely distributed structural plane can increase the impedance difference with the surrounding rock strata and then impact the slope dynamic response result with the impacting degree of 40%-70%.Additionally,the occurrence of structural plane can make the slope dynamic response present strong anisotropy,and that is just the phenomenon which is difficult to be reflected through the conventional continuum mechanics-based numerical method.The study result verifies the effects of structural plane and simultaneously demonstrates that the verification of the the horizontal seismic dynamic response relationship can be accurately reflected by DDA,thus has an important significance for the seismic design of rocky slope.