【作者】 黄明； 付俊杰； 陈福全； 江松；

【Author】 HUANG Ming;FU Jun-jie;CHEN Fu-quan;JIANG Song;College of Civil Engineering,Fuzhou University;

【机构】 福州大学土木工程学院；

【摘要】 随着我国路网的迅速发展,诸如渝黔铁路复线周家湾大桥等类似工程,其地处地震活跃带而桥桩又位于溶洞之上的情况时有出现。基于分离相似设计方法确定了岩质材料、模型桩和地震波的主控参数,并通过19组配比试验最终得到振动台试验用的岩体相似材料配比指标,通过开展不同顶板厚度及溶洞直径下的岩溶桩基小型振动台模型试验,对溶洞顶板在桩端荷载及地震共同作用下的动力特性和破坏特征进行了研究。结果表明:1)随着地震波加速度的增强,模型内部裂纹增多而使阻尼比逐渐增大,振动主频随之降低;地震波通过溶洞之后,部分波段频率明显增强,而不经过溶洞的地震波对应测点的频率成分保持稳定,溶洞的存在改变了模型的局部基频和动力特性。2)波的频谱变化与上部荷载大小无直接关系,而溶洞顶板在桩端荷载和地震共同作用下产生的桩端裂隙,造成了地震波整体幅值的下降,引起了模型基频的变化。3)相同类型地震波之间仅幅值有所差别,而不同类型地震波作用下的频谱分布差异较大,模型的第一主频发生了改变,模型结构的频谱特性产生不同程度的影响,与模型主频相近的波段频率有所提高。4)各测点的应变均随地震峰值的增加而增大,溶洞正上方的岩体应力集中现象显著,离桩越近应变越大;溶洞直径较小时顶板临空面处易发生剪切破坏,而溶洞直径较大时表现为整体的冲-剪破坏。更多还原

【Abstract】 With the rapid development of Chinese road network,such as Zhou-jiawan Bridge of Chongqing-Guizhou double-tracking railway and other similar projects,which is located in the active earthquake zone and the bridge pile is located in the above of the cave have emerged,the main control parameters of rock materials,model pile and the seismic wave were obtained using the separation similarity method.And the mix proportions of the rock similar material for the shaking table test were suggested by 19 times of test.The shaking table tests mainly focused on the dynamic properties and failure characteristics of the karst roof under pile load with various thickness of roof and diameters of cave.It was shown that cracks of the rock increase as the increment of the seismic accelerated velocity,which leads increment of the damping ratio,and the main vibrating frequency of the model also decreased.When the seismic wave cross the karst cave,part of the frequency increased obviously.On the contrast,frequency component without crossing maintains the same.Partial fundamental frequency and dynamic properties of the model was changed due to the karst cave.In addition,change of the frequency spectrum is not directly related to the pile load,but the cracks of roof occurring nearby the pile will induce the decrement of the wave amplitude and change the fundamental frequency.Variation of the same kind of seismic wave only alters the wave amplitude,but different kinds of seismic wave will lead the distribution change of fundamental frequency and the first main frequency of the model.What’s more,the wave frequency increases even if with the same frequency of the model.Strain of the monitoring point increases as the increment of the peak of seismic wave,and strain nearby the pile is larger than that in other part because of the stress concentration.Shearing failure of the karst roof occurs when the diameter of the cave is small,but punching-shearing failure happens as the diameter of karst cave is larger.更多还原