【摘要】 土石坝覆盖层中混凝土防渗墙的性能对大坝设计及安全评价至关重要,由于传统数值方法局限于非线性弹性,难以开展深入研究。本文首先通过系统的三维非线性有限元数值模拟,聚焦墙体变形模式及应力分布空间特征,研究三维河谷效应机制;然后针对墙体计算应力超过材料强度的现象,开发了混凝土三维塑性损伤模型和堆石体本构模型协同分析的自适应增量迭代算法,揭示了防渗墙的损伤-应力特性;最后讨论了防渗墙性能评价分析的思路。结果表明:在墙体弯曲变形及覆盖层负摩阻力的联合作用下,防渗墙的三维河谷效应表现突出:墙体拉应力的方向偏于轴向,随弯曲变形增大逐渐向竖向偏转,且其峰值存在临界坡度和临界深度。线弹性分析便于认识防渗墙的受力-变形-应力规律,但不适用于评估复杂条件下墙体的防渗性能。损伤分析能描述混凝土的材料特性,反映墙体结构的破损特征,其损伤因子可与防渗性能建立联系,用于评价防渗墙安全更加合理和准确。更多还原

【Abstract】 The performance of concrete cut-off walls in overburden of earth dam foundation is crucial important to dam design and safety evaluation. However,it is difficult to carry out in-depth study because the traditional numerical methods are limited to nonlinear elasticity theory. In this paper,a systematic numerical simulation by 3 D nonlinear FEM is firstly conducted to study the three-dimensional valley effect mechanism, focusing on the deformation mode and the spatial characteristics of stress distribution in the wall.Then,a 3 D plastic-damage model for concrete and an adaptive-incremental iterative algorithm for collaborative analysis with rock-fill were developed,the damage-stress characteristics of the wall was revealed. Finally,The analysis methods for evaluating the performance of concrete cut-off walls were discussed. This research indicated that the 3 D valley effect on the wall is outstanding due to the combined effect of bending deflection of the wall and negative resistance aroused by overburden. The direction of the tensile stress is orients axially,trends to the vertical gradually with the increasing deflection. In addition,there exists critical valley slope and valley depth of tensile stress. It is good to understand the force-deformation-stress rule of the wall with elastic analysis,but has no application to evaluate the performance of the wall in complex conditions. The material behavior of concrete and the damage features can be described and captured with damage analysis. Moreover,the damage index has the ability to build connections with anti-seepage performance. It is more reasonable and accurate to evaluate the performance of cut-off walls with damage analysis.更多还原