长隧道非一致激励振动台试验原理

Seismic damages of long tunnels have been frequently reported from recent happened earthquakes. Compared to the uniform seismic excitation, the non-uniform seismic excitation has a significant effect on dynamic response of long tunnels. Recent research on the non-uniform seismic input is limited to numerical simulations; however, it is difficult to realize the non-uniform seismic input via physical test due to its lack of theoretical basis. In terms of the features of long tunnels and in accordance with the interdisciplinarity of tunnel dynamics, earthquake engineering, and experimental mechanics, the multi-point and multi-dimension shaking table test technology for long tunnels subjected to non-uniform seismic excitations is systematically studied based on the combination of the theoretical analysis of discrete multi-point input mechanism and the multi-point seismic simulation shaking table test. The research proposal includes the following issues. The effective wave input method is proposed for the non-uniform seismic input. The theory of discrete multi-point seismic input mechanism for long tunnels is established, and the test equipment of assemble segmental model container is developed, which is used to convert the discrete multi-point shaking table input into the real continuous multi-point seismic input. This is done to efficiently solve the the continuous and discontinuous seismic input testing difficulties of the coupling interaction of long tunnels and surrounding medium subjected to non-uniform seismic excitations. Then the multi-point and multi-dimension shaking table model test is carried out to reveal the nonlinear dynamic damage mechanisms of long tunnels under non-uniform seismic motions. The proposed research benefits the development and improvement of seismic theory and model test method for long tunnels, and also provides scientific evidence for seismic design of long tunnels.

近年长隧道结构震害频发，考虑非一致激励作用对长隧道地震响应具有较大影响，目前研究仅限于数值分析手段，通过试验手段模拟长隧道非一致地震激励输入因缺乏理论基础而难以实现。项目针对长隧道结构的特点，交叉融合隧道动力学、地震工程学及实验力学等学科，采用离散多点输入机制理论分析和多点地震模拟振动台试验相结合的研究方法，系统研究非一致地震激励下长隧道多点多维振动台模型试验技术。包括建立考虑地震动空间非一致性的有效波动输入方法；建立长隧道离散多点地震动输入机制理论，研发可拼装式节段模型箱试验装置，利用离散多点振动台输入实现多点连续输入的转化，解决非一致地震作用下长隧道结构与环境介质动力耦合作用的连续与非连续地震输入试验技术难题；开展长隧道多点多维振动台模型试验模拟，揭示长隧道在非一致地震作用下的非线性动力灾变机理。项目研究有助于发展和完善长隧道结构抗震理论和模型试验方法，为长隧道抗震设计提供科学依据。

地震传播的行波效应对长大隧道的动力响应具有重要影响，因此在进行长隧道地震响应机制研究时需考虑非一致激励的作用效应。项目建立了可以考虑地震波传播相干效应和地层特征引起的局部场地效应等因素的空间非一致地震动输入方法；确定了多点非一致激励的地震动输入参数场及多点非一致激励场的主要影响。以实际连续多点地震动输入机制为基准，推导出模拟基岩面多个离散输入与连续输入的关联性，进而建立了台阵式振动台长大隧道非一致地震激励原理；研制了节段型模型箱及其联动装置，并优化设计了模型箱的尺寸、刚度、边界效应等关键技术指标，最终构建出振动台阵多个独立台面分区多点输入的非一致激励隧道地震试验平台；通过实际连续多点输入和多台面离散多点输入下基岩面动力响应的对比分析，进一步优化了非一致地震激励输入的离散多点输入机制；建立了多点振动台模型动力相似比设计理论，提出了以土-结构相对刚度比为控制指标的长大隧道地震响应物理模型的动力相似准则，在考虑结构所处场地特征的情况下合理模拟土-结构动力相互作用关系；开发了隧道多尺度物理模型和3D打印制作技术，可以模拟长大盾构隧道等复杂拼装式地下结构。通过空箱试验和自由场地试验，验证了该试验平台非一致地震激励的有效性，可以实现长度10km-级隧道-地层的强震非一致激励模拟。