基于边界位移法的地下结构推覆试验可行性研究

Feasibility study of pushover test of underground structure based on boundary displacement method

地震过程中地下结构变形主要受周边土体变形控制。基于该思想,现已提出一种在土-结构有限元模型侧边施加土体变形的地下结构抗震简化分析方法——边界位移法,但缺乏相关试验研究。为探索土体侧边施加推覆位移的试验方法可行性,以自行研制的岩土综合试验模型箱为试验平台,以1:10缩尺的大开车站区间隧道为研究对象,开展了大型土-地下结构系统推覆试验。通过应变、位移和应力的分析,揭示了试验过程中地下结构及周边土体的反应特性。结果表明:由于土体材料的强非线性特征,土体侧边施加的倒三角形变形在传递过程中会产生衰减,地下结构受到剪切变形和挤压变形的耦合作用;中柱与底板交接处是整体结构中的抗震薄弱位置;水平基床系数与土层位移水平及结构侧壁的破坏阶段相关;结构整体刚度大于等代土体,两者的侧向变形比值小于1。随着推覆水平增加比值逐渐增大,通过变形特征能够量化土-结构相互作用,有效填补了土-结构相互作用系数试验研究的空白。试验方法与结论,对地下结构抗震分析及推覆试验可行性研究具有重要指导意义。

The deformation of underground structure during earthquake is mainly controlled by the deformation of surrounding soil.Based on this idea,a simplified seismic analytical method,namely the boundary displacement method,was proposed for underground structure by applying soil deformation to the lateral boundary of soil-structure finite element model,while there is a lack of relevant experimental research.To explore the feasibility of the test method of applying pushover displacement to soil lateral boundary,a large-scale pushover test of soil-underground structure system was carried out taking the self-developed geotechnical comprehensive test model box as the test platform and the 1:10 scale Dakai station section tunnel as the research object.Response characteristics of underground structure and surrounding soil in the process of test were revealed based on the analyses of the strain,displacement,and stress.The results show that due to the strong nonlinear characteristics of soil materials,the inverted triangle deformation applied on the side of soil will attenuate in the transmission process,and the underground structure is subject to the coupling effect of shear deformation and extrusion deformation.The junction between central column and bottom plate is the seismic weak region in the whole structure.Horizontal coefficient of subgrade reaction is related to the level of soil displacement and the failure stage of structural side wall.The integral stiffness of structure is greater than that of the equivalent soil,and the ratio of lateral deformation between structure and soil is less than 1,which gradually increased with the increase of the pushing level.The soil-structure interaction could be quantified through deformation characteristic,which effectively fills the gap in the experimental study of soil structure interaction coefficient.The test method and conclusions have important guiding significance for seismic analysis of underground structure and feasibility study of pushover test.