阶梯地形下坝-库水-地基非线性相互作用的动力模型与多因素耦合模拟

为了更精细模拟阶梯地形坝址的混凝土坝在考虑材料非线性、库底吸收等多因素耦合下的地震响应,需要发展适用的坝-库水-地基非线性相互作用动力模型,其中合理的地震动输入是面临的首要问题之一。本文根据波场分离原理和坡面应力自由条件,提出了求解阶梯地形地基自由场的计算方法和该场地条件下坝-基体系的地震动输入方法,可较为准确地反映阶梯地形对坝体动力响应的影响。通过构建坝-库水-阶梯地形地基全域分析模型,可全面考虑坝-库水、坝-复杂场址动力相互作用以及坝体混凝土、近场基岩的非线性力学特性,从而提高了重力坝整体抗震安全评价的合理性。通过场地反应分析和波动散射分析的数值算例,验证了输入方法的有效性。并以阶梯地形下某重力坝挡水坝段为例,研究了场址条件对静-动力组合作用下坝体损伤演化的影响规律,结果表明:距坝踵约一倍坝高以外淤泥覆盖层的吸能作用对坝体损伤影响轻微;岩基的塑性主要从坝踵开始,导致坝踵损伤减轻,坝体位移响应改变,对水平方向的影响更大。

Dynamic model and multi-factor coupling simulation of nonlinear interaction among dam-reservoir water-foundation under stepped terrain

In order to more finely simulate the seismic response of concrete dams at stepped terrain dam sites under consideration of multiple factors such as material nonlinearity and reservoir bottom absorption coupling,it is necessary to develop applicable dynamic models for dam-reservoir water-foundation nonlinear interactions,of which reasonable ground vibration input is one of the primary problems faced.Based on the wave field separation principle and the stress free condition on the slope surface,this paper proposes a computational method for solving the free field of stepped foundation and an earthquake input method for the dam-foundation system under this site condition,which can reflect the effect of stepped terrain on the dynamic response of the dam more accurately.The dam-reservoir-stepped foundation full-domain model is established,which can comprehensively consider the dam-reservoir and the dam-complex site dynamic interactions as well as the nonlinear mechanical properties of dam concrete and near-field bedrock,thus improving the rationality of the overall seismic safety evaluation of the gravity dam.The validity of the input method is verified by numerical examples of the site response analysis and the scattering analysis.Then,taking a gravity dam as an example,the influence laws of site conditions on the damage evolution of the dam under combined static load-earthquake are studied.The results show that the energy dissipation effect of the silt cover layer located outside around one times the height of the dam away from the dam heel has a minimal impact on the seismic damage of the dam;the plasticity of the rock foundation mainly starts from the heel of the dam,leading to a reduction of damage at the heel and a change in the displacement response of the dam,which has a greater effect in the horizontal direction.