含倾斜强风化带及局部边坡复杂场地的动力响应及破坏模式研究

Dynamic response and failure mode of the complex site with tilting strongly weathered layer and local slopes

基于大型振动台模型试验,研究了含倾斜强风化带及局部边坡场地在地震波作用下的动力响应特征,同时结合边际谱理论分析、土层内部应变和边坡位移规律,探究了场地内部的损伤发展过程。试验结果表明:模型加载El Centro地震波时,基岩和基覆内加速度放大系数随高程增加而增大,当加载地震波幅值大于0.33 g时,输入幅值越大,加速度放大越小;强风化带处加速度峰值削弱明显,加载幅值越大,削弱程度越大。模型加载3 Hz正弦波时,边际谱能量识别显示场地损伤从平台与局部边坡拐角下的强风化带开始,此后局部边坡底部强风化和平台中部下的强风化带出现损伤,平台与局部边坡拐角处强风化带的损伤逐渐与顶部损伤贯通;土层应变、坡面位移规律印证了场地损伤的发展过程;由破坏现象、边际谱损伤发展分析、土层应变及边坡位移规律可知,该含倾斜强风化带场地的破坏模式表现为拉裂–剪切–滑移以及拉裂–剪切–破碎2种破坏模式。

The article researched the dynamic response of complex site with tilting strongly weathered layer and local slope with a large-scale shaking table model test. The damage progress of the site was studied through the analysis of marginal spectrum,the strain variations of the soil and the displacement of the slope surface. When the El Centro wave is loaded,the amplification coefficients of acceleration at the points in the bedrock and cover layer increase with increasing of elevation. The amplification coefficients of acceleration decrease with the increasing of amplitude（0.33 g）. The accelerations at the point in the strongly weathered layer decrease sharply and decrease more with the increasing of earthquake amplitude. When the 3 Hz sine waves are loaded,the energy identification of the marginal spectrum implies that the destruction of the site starts from the strongly weathered layer at the corner of local slopes. Then there appears damage in the strongly weathered layer at the bottom of local slopes and the middle of the site. The destruction of the strongly weathered layer at the corner of local slopes connects gradually with the damage at top. The damage progress is verified by the strain changes in the soil and the displacement changes on the slope surface. The failure modes of the site are cracking-shearing-slippage and cracking-shearing-crushing