Seismic Response Analysis Of Shallow-depth Tunnel And Vibration Absorption Measure

With the quickly development and utilization of underground space, the anti-seismic performance of underground constructions is being paying close attention to increasingly, the anti-seismic analysis of tunnel become more important. It has strategic meaning that how to assuring the tunnel working well during earthquake. However due to the lack of basic information, a perfect method for the seismic design code for the subway (currently being developed) in our country isn't yet comprehensive. These make the research about the seismic design of underground structure more- important and urgent.In this paper the summary of worldwide typical instances of tunnels behavior during earthquake and research developments & methods is briefly described, the characteristics regarding the tunnel damages during earthquake and classification are summed up, the damage mechanism of action from earthquake is described too. Based on the data of the Qin Ling tunnel of the national highway 108 , the transient dynamic method of ANSYS compute software is used:1.Taking a shallow-depth tunnel as an example, a two-dimension model of rock and tunnel lining construction systems is build up to study the their interaction, such as the different lining thickness, different lining rigidity, different geologic conditions and different depth. Results of the analysis reflects that the seismic response of lining construction have the following properties.(1) In response to the seismic response analysis, the arch springing of tunnel are easier to have a large stress and deformation, take place breakage most easily.(2) The depth of tunnel has a great influence to its dynamic interaction. In a certain scope, the depth of buried structure is larger; the seismic response is safer.(3) The thickness of liner has a great influence to its dynamic interaction too. The liner of tunnel with a bigger thickness has better anti-seismic capability in the upper part of the structure. The displacement and stress from arch invert to arch springing augment the anti-seismic ability worsening.(4) The change of liner rigidity has no influence to the low of tunnel's distortion. The tunnel bears a bigger earthquake load, producing a smaller displacement when the liner has bigger rigidity. 2. Taking a shallow-depth tunnel as an example, build up a two-dimension model of rock & vibration absorption layer and tunnel lining construction systems is to study the mutual action principles of the liner. Analyzing and comparing the seismic response of lining construction with different vibration absorption layer thickness and different rigidity, Results of the analysis reflects that the seismic response of lining construction have the following disciplinarians when vibration absorption layer exist.(1) The vibration absorption layer can deliver earthquake load to rock. The liner bears a less earthquake load, producing a smaller relative displacement when the vibration absorption layer existed.(2) The thickness of vibration absorption layer has influence to the liner's dynamic interaction. The tunnel beats a less earthquake load, producing a smaller relative displacement when the thickness is bigger.(3) The rigidity of vibration absorption layer must less than the liner's. The vibration absorption layer with less rigidity improves the anti-seismic ability of liner.