筋-土界面刚度软化对加筋土挡墙动力特性的影响

Effect of Stiffness Softening of Reinforcement-soil Interface on Dynamic Characteristics of Reinforced Retaining Wall

加筋土挡墙被广泛应用于公路工程、铁路工程、水利工程、边坡等支挡结构中,筋土界面的动力剪切特性对加筋土挡墙的稳定性和耐久性有重要的影响。采用室内直剪试验研究了不同剪切频率(1 Hz,2 Hz,3 Hz)和不同竖向压力(50 kPa,100 kPa,150 kPa)条件下粗粒土与格栅界面的循环剪切特性。通过对循环剪切试验数据的拟合分析得到了筋土界面剪切刚度变化的经验公式,然后编制fish语言将该公式导入FLAC3D软件。通过分析考虑筋土界面剪切刚度变化规律的加筋挡土墙三维计算模型,并与振动台试验的试验数据进行了对比验证,发现了考虑筋土界面刚度软化的模型更符合实际情况。采用验证以后的三维计算模型对地震作用下考虑筋土界面和不考虑筋土界面剪切刚度软化的加筋土挡墙动力特性进行了对比分析。结果表明:考虑筋土界面剪切刚度的软化对地震作用下加筋土挡墙有明显的影响,在地震峰值加速度为0.4g时,考虑软化后墙体水平位移比不考虑软化增大了8.8%,加速度放大系数比不考虑软化增大了1.76%,筋材的最大拉力比不考虑软化的减小了6.9%。因此筋土界面的剪切刚度软化对地震作用下加筋土挡墙的影响不可忽略。

The reinforced retaining wall is widely used in highway engineering,railway engineering,hydraulic engineering,slopes and other supporting structures.The cyclic shear behavior of the soilgeogrid interface has an important influence on the stability and durability of the reinforced retaining wall.The cyclic shear characteristics of the soil-geogrid interface were studied at different shear frequencies(1 Hz,2 Hz,and 3 Hz) and normal stresses(50 kPa,100 kPa,and 150 kPa) by using a large-scale direct shear apparatus.Through fitting analyses of the cyclic shear test data,the empirical formula of the shear stiffness of the soil-geogrid interface is obtained.Then the FISH script is compiled into the software FLAC3 D,and a three-dimensional calculation model of the reinforced retaining wall is established considering the variation law of the shear stiffness of the soil-geogrid interface,which is compared and verified with the test data of the shaking table test.It is found that the model considering the softening of the soil-geogrid interface is more in line with the actual situation.After verification,the three-dimensional calculation model is used to investigate the influence of shear stiffness softening on the dynamic characteristics of the reinforced retaining wall.The results show that the softening of the shear stiffness has a significant effect on the reinforced retaining wall under seismic loads.When the peak acceleration of the earthquake is 0.4 g,the horizontal displacement of the wall is 8.8%larger than that without considering the stiffness softening.The acceleration amplification factor is increased by 1.76% compared with that neglecting the stiffness softening effect.Simultaneously,the maximum internal force of the geogrid is reduced by 3.8%.Therefore,the shear stiffness softening at the soil-geogrid interface is not negligible for the reinforced retaining wall under seismic loads.