填土加筋对悬臂式挡墙地震响应影响的模型试验研究

Model tests for effect of fill reinforcement on seismic response of cantilever retaining wall

为探讨墙后填土加筋对悬臂式挡墙抗震性能的改善效果,开展了缩尺比1∶4的悬臂式挡墙及墙后填土加筋的振动台模型试验。采用小震0.11g、中震0.24g、大震0.39g的简谐波激励模型结构,获得加速度、位移、土压力等响应量,分析了填土加筋对模型自振频率和阻尼比的影响,对比加速度放大系数、振动位移、墙-土相互作用等地震响应差异,讨论了填土加筋的减震效应随加载幅值变化特征。试验表明:填土加筋可提高墙-土体系的整体性、减小振动伤损,自振频率和阻尼比在历经振动后的变化幅度相对未加筋模型更小;加筋措施可使小震和中震下墙体惯性力与地震土压力产生明显相位错峰,大幅降低不利位移状态时墙体承受的地震土压力,但大震下墙体水平位移小于填土,墙-土挤压作用显著,减震效应发挥欠充分。

Here,to investigate improvement effect of fill reinforcement behind wall on aseismic performance of cantilever retaining wall,shaking table tests for a 1/4 scale model of cantilever retaining wall and fill reinforcement behind wall were conducted.The simple harmonic excitation model structure with small earthquake of 0.11g,medium earthquake of 0.24g and large earthquake of 0.39g was used to obtain response quantities,such as,acceleration,displacement and earth pressure.Effects of fill reinforcement on natural vibration frequencies and damping ratios of the model were analyzed.Differences of seismic responses including acceleration amplification coefficients,vibration displacements and wall-soil interactions under different earthquakes were analyzed contrastively,and characteristics of fill reinforcement’s seismic mitigation effect with loading amplitude variation were discussed.The test results showed that fill reinforcement can improve the integrity of wall-soil system,reduce vibration damage,and variations of natural frequencies and damping ratios after vibration are smaller than those of the unreinforced model;reinforcement measures can cause obvious phase staggering peaks between wall inertia force and seismic earth pressure under small and medium earthquakes,and greatly reduce seismic earth pressure on wall body under unfavorable displacement conditions;but horizontal displacement of wall body is less than that of fill under large earthquake,wall-soil squeezing effect is significant,and damping effect is not fully played.