地铁上盖超高层结构竖向振动台模型试验——考虑桩长的非振动控制模型研究

Study on vertical shaking table model test of super high-rise structure over subway: non vibration control model considering pile length

基于某地铁上盖120m高超高层结构的工程背景,分别对无桩基础结构、15m桩周降阻桩基础结构以及30m无侧摩阻力桩基础结构,进行了1∶30缩尺振动台试验。基于白噪声和7条地铁振动波不同峰值加速度激励下的结构响应,对比分析了三个振动台试验模型各测点楼层的振动响应。结果表明:桩基长度的改变可明显改变上盖结构的动力特性,上盖结构X、Y、Z三向频率呈现随桩基长度增加而减小的变化趋势,且桩基越长上盖结构的频率越低。相比于无桩基础结构,15m桩周降阻基础结构在避免地铁隧道下沉风险的同时,有利于降低上盖结构的振动响应。同时桩周降阻处理的桩基础改变了上盖结构的动力特性,使上盖结构楼层振动由高频向低频转移;而30m无侧摩阻力桩基础,对降低上盖结构的振动响应有限,且不影响结构楼层的振动频率分布。实际工程设计时,应综合竖向振动响应控制、地铁隧道沉降和桩基稳定性,合理设计桩周降阻长度。

Based on the actual engineering background of a 120 m height super high-rise structure above subway, the 1∶30 scale shaking table tests were carried out for structure without pile foundation, structure with 15 m resistance-reducing pile foundation and structure with 30 m non-lateral friction resistance pile foundation respectively. According to the structural responses of white noise and 7 subway vibration waves excited by different peak accelerations, the vibration responses of floors at each measuring point of three vibration table structures were compared and analyzed. The results show that the change of pile foundation length can significantly change the dynamic characteristics of the upper cover structure. The three-directional frequency of X, Y, and Z of the upper cover structure decreases with the increase of the pile foundation length, and the longer the pile foundation, the lower the frequency of the upper cover structure. Compared with structure without pile foundation, structure with 15 m resistance-reducing pile foundation is beneficial to reduce the vibration response of the upper cover structure while avoiding the risk of subway tunnel sinking. At the same time, the pile foundation treated with resistance reduction around the pile changes the dynamic characteristics of the upper cover structure, which makes the floor vibration of the upper cover structure transfer from high frequency to low frequency. The 30 m non-lateral friction resistance pile foundation has a limited response to reduce the vibration of the upper cover structure and does not affect the vibration frequency distribution of the structural floor. In actual engineering design, the control of vertical vibration effect, settlement of subway tunnel, and stability of pile foundation should be integrated to reasonably design the resistance-reducing length around the pile.