回填EPS混合土的防滑悬臂式挡墙地震稳定性分析
Seismic stability of anti-sliding cantilever retaining wall with EPS composite soil
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摘要: 以一种带防滑齿的“T”型悬臂式挡土墙为对象,采用振动台模型试验揭示了分别回填EPS混合土和天然南京细砂时的挡墙地震稳定性特征。分析并比较了墙-土体系的地震反应以及墙背动土压力分布,重点讨论了试验的防滑悬臂式挡墙位移模式以及回填土性质对墙背动土推力的影响。试验结果表明,回填EPS混合土时,填土地表加速度反应相对更小。回填土的动土推力对墙体转动位移的贡献随激励峰值的增大而增大;墙-土惯性相互作用效应与回填土的动力变形模式密切相关。两种回填料下的墙背动土压力分布形态具有显著差异;砂土-挡墙体系的动土推力与地表峰值加速度间趋向非线性关系,作用点接近2/3墙高。回填EPS混合土时两者更接近线性关系,且动土推力作用点接近1/3墙高。两种体系的动土推力作用点随地表峰值加速度增大均略有下移。基于试验结果与几种经典的解析方法预测结果比较,给出了EPS混合土柔性挡墙抗震分析的几点建议。Abstract: Shaking table tests are conducted on the inverted T-shape cantilever retaining walls with an anti-sliding tooth to comparatively study the seismic stability characteristics using EPS composite soil and Nanjing fine sand as backfills, respectively. The seismic responses of wall-soil system and dynamic earth pressure distribution behind the wall are comparatively analyzed. The influences of displacement modes of retaining wall and the properties of backfill on dynamic earth thrust are emphasized. The experimental results indicate that when using EPS composite soil as backfill, the acceleration response on the backfill surface is relatively small. The contribution of dynamic earth thrust to the wall rotation increases with the increasing input peak excitation. The inertial interaction between wall and soil is closely related to the dynamic deformation mode of backfill. The distribution of dynamic earth thrust behind the wall when using sand as backfill is obviously different from that using EPS composite soil. The relationship between the dynamic earth thrust and the peak ground acceleration for sand-wall system is nonlinear, and the acting position of earth thrust is approximately 2/3 wall height. A linear relationship exists for EPS composite soil-wall system, and the acting position is close to 1/3 wall height. The acting position of earth thrust slightly moves down as the peak ground acceleration increases for the two test systems. Based on the comparison between test results and several classical analytic solutions, some suggestions are proposed regarding the seismic analysis of flexible retaining wall when using EPS composite soil as backfill.