基于改进动剪切模量模型的堆石坝动力响应分析

Dynamic response analysis of rockfill dam based on modified dynamic shear modulus model

堆石料的动剪切模量与围压和应力比有关,在堆石料的动力本构模型中计入围压与应力比的影响十分必要。简要介绍了已有的考虑围压及应力比的动剪切模量计算公式,并提出一个改进的动剪切模量计算公式。通过与猴子岩灰岩堆石料、流纹岩堆石料、覆盖层砂砾石、过渡料-垫层料动力特性试验结果对比,认为该模型能较好地拟合不同围压和应力比组合下归一化的动剪切模量与动剪应变的试验数据,表明该模型具有较好的适用性和预测精度。采用Hardin-Drnevich双曲线本构模型进行猴子岩堆石坝的动力响应有限元分析,动剪切模量分别采用常规公式和文中提出的改进公式计算。对比了大坝的整体动力响应,采用考虑围压和应力比的改进动剪切模量计算公式,坝顶各方向的最大加速度响应均会有所增大,增大值为20%~35%,最大动位移在顺河向降低14%,竖直向与横河向均增大10%左右。

Experimental studies indicate that the dynamic shear modulus of rockfill is related to confining pressure and stress ratio;therefore, it is necessary to include the influence of confining pressure and stress ratio in the dynamic constitutive model of rockfill materials. This paper briefly introduce the existing dynamic shear modulus calculation formula considering the confining pressure and stress ratio, and proposes an improved dynamic shear modulus calculation formula. Comparing with the experimental results of dynamic characteristics of Houziyan limestone rockfill, rhyolite rockfill, overburden gravel, transition material and cushion material, the model can better fit the combination of different confining pressure and stress ratios. The experimental data of dynamic shear modulus and dynamic shear strain show that the model has good applicability and prediction accuracy. The Hardin-Drnevich hyperbolic constitutive model is used to the finite element analysis of the dynamic response of Houziyan rockfill dams. The dynamic shear modulus is calculated using the conventional formula and the improved formula presented in this paper. The overall dynamic response of the dam is compared. Using the formula for calculating the modified dynamic shear modulus considering the confining pressure and stress ratio, the maximum acceleration response in all directions of the crest will increase;and the increase value will be about 20%-35%.The maximum dynamic displacement decreases by 14% in the river direction and increases by about 10% in both the vertical and horizontal rivers.