Dynamic Response Of Tunnel Entrance Structure Of Sunken Plaza Under Earthquake

The construction of underground structure is growing with the development of underground space.All this time,underground structure has been considered to have better seismic performance because of restriction from surrounded rock and soil mass.But many phenomenon of earthquake disasters show that the existing underground structures are not safe,and even seriously damaged.Especially,the formations with weak constraint in the mouth of underground structure,shallow buried structure and large cross section structure,the probability of failure is generally higher.A large number of sunken-plaza-style underground structure are developed and utilized in underground space and transport hub in recent years.The entrance section of it is the throat in the underground engineering,but very little researched on dynamic performance under earthquake action and rarely guiled by systematically seismic guidelines.Under this background,based on the finite element time history analysis method of ANSYS and indoor physics resemble simulation shaking table test,the entrance/exit section of the underground structure with sunken plaza under different influence factors were researched on earthquake dynamic response characteristics and law.Meanwhile,the influence of earthquake action direction and intensity,lithology,buried depth,sunken plaza form and space shape of underground structure on dynamic response characteristics were studied.On the basis of these,the dynamic response characteristics and earthquake weak parts of entire underground space structure with sunken plaza were analyzed.And the influence law and mechanism of interaction between rock and soil mass and structure on structure were further discussed.Firstly,on the basis of summarizing function and structure form of existing sunken square,the three forms of sunken plaza are proposed for seismic dynamic research,and providing reasonable model for further study on this style structure.Subsequently,basic underground structure unit with sunken plaza under horizontal and vertical earthquake action was analyzed by dimensional numerical simulation analysis.Characteristics of stress,displacement and acceleration of structure are obtained.The results show that the stress component in earthquake action direction determines the stability of underground structures,different earthquake direction causes different structure seismic response,the effects of vertical seismic is lesser,but the extreme value are bigger,and the impact of vertical earthquake on underground structure should be considered.The influence of different factors on seismic dynamic response of underground structure with sunken plaza was studied.Stability of structure is worse with earthquake intensity being increased.The detailed influences are response of structure especially high stress zone is greater,structure interlayer rupture increases and acceleration amplification effect is more apparent.With lithology increased,deformation of structure is reduced but stress is increased and obvious traveling wave effect of structure is also caused.When shallow buried depth,horizontal displacement between values of structural is smaller,and buried depth is shallower,the acceleration amplification effect of the structure is more obvious.Response laws of the underground structure with different sunken plaza form and structure space shape are obtained.Different sunken plaza form and increased an underground structure are all cause the change of stability of underground structure.The change of the underground structure space length and cross section can lead to the distribution change of underground structure seismic weak parts and affect the dynamic stability of underground structure.Complex 3D underground space structure with sunken plaza is established.And the distribution regularities of the structure stress,extreme value,anti-seismic weak positions,interlayer displacement,and acceleration amplification effect are disclosure,and provided some reference for studying the dynamic stability and evaluation of this style of underground structure.On this basis,the dynamic response of underground structure is obtained under considering the interaction between rock and soil mass and structure.By analyzing contact status and contact stress of nonlinear contact pairs,the influence mechanism of the interaction is preliminary explained.Finally,based on the common electric vibration table system,a physics resemble simulation test is designed and the acceleration and deformation law of underground structure are found under horizontal seismic action.The results are consistent with the numerical simulation,which shows that the resemble model and testing are feasible,and rationality the numerical simulation method and results are verified.