既有圆形深坑边坡、结构共同作用大型振动台试验研究

Shaking table test studies on interaction of existing round pit slope and structure

城市周边废弃矿坑逐渐被利用起来用以建设大型公共服务项目,建筑群以边坡作为基础引发了新的技术难题。采用大型振动台试验对地震作用下既有深坑边坡、单跨和多跨框架结构的动力特征、响应规律和共同作用进行研究。试验结果表明:随激振次数和幅度的增加,边坡的自振频率趋于减小,阻尼比趋于增大;结构模型在整个激振过程中均处于弹性阶段,自振频率略有减小,阻尼比略有增大。边坡的动力响应随着坡体位置的升高而增大;边坡材料具有非线性特征,边坡动力放大效应随着振幅的增加而减小;模型的动力响应均与激励波的类型和方向有关,低频波较高频波对边坡引起的动力响应大,与激振同向的动力响应较其他方向大。以边坡为基础的结构动力响应随基础位置的升高而增大;由于连梁的影响,多跨结构的坡中结构动力响应较坡顶与坡底结构大。结构顶的动力响应由基础及上部结构耦合而成,因而始终大于底板。底板的动力响应因上部结构的动力反作用而始终大于周边地基。边坡、结构存在着共同作用,整体稳定性较好、刚度较大的多跨结构可以提高地基的抗震性能,地基动力响应应减弱10.4%~24.3%;而整体稳定性较差、刚度较小的单跨结构会降低地基的抗震性能,地基动力响应放大12.3%~51.1%。研究结果可为既有深坑地下空间开发利用的岩土工程设计提供指导作用。

Abandoned mine pits around city are gradually used for the construction of large public service projects with the basis locating on slopes,which is causing new problem. A large-scale shaking table test was carried out to study the dynamic characteristics and response of pit slope,single and multi-span frame structures,and interaction between slope and structures. The results show that,with the increase of vibration time and amplitude,the self-vibration frequency of slope model tends to decreases,while the damping ratio tends to increase. The structure models are in elastic stage during the vibration process,and its self-vibration frequency decreases slightly,while the damping ratio increases slightly. Slope dynamic response increases with slope position rising. Due to slope material nonlinear characteristics,slope dynamic amplification effect decreases with the increase of vibration amplitude. Moreover,model dynamic response is associated with the type and direction of wave excitation. Low-frequency waves have greater influence on slope than high-frequency waves,and dynamic response in excitation direction is stronger than that in other directions. Dynamic response of structures increases with base location rising. Due to the influence of coupling beam,dynamic response of middle part of multi-span structure is stronger than that of other parts. Dynamic response of the structure top,which is coupled by foundation and upper structure,is always larger than the bottom plate. Dynamic response of bottom plate is always greater than around ground due to dynamic reaction of superstructure. In addition,there is notable interaction between slope and structure. Multi-span structures with good stability and high stiffness can improve seismic performance of surrounding ground,and ground dynamic response decreases 10.4%–24.3%. In contrast,single-span structures with poor stability and low stiffness probably reduce seismic performance of surrounding ground,and ground dynamic response increases 12.3% – 51.1%. The research results can provide guidance for geotechnical engineering design of development and utilization of existing pit underground space.