Dynamic Response Analysis Of Tunnel-working Shaft Structure Under Earthquake Action And Research On Shock Absorption Technology Of SMA Tunnel

In recent years,many catastrophic earthquake have occurred many times all over the world.People pay more attention to the earthquake resistance of underground structures because of the damage of tunnels in earthquakes.As a Abrupt stiffness structure of the tunnel,the working shaft usually has the phenomenon of stress concentration or displacement amplification in this part of the area due to the change of structural type.It is one of the weakest parts of the seismic performance of the whole tunnel structure.In order to ensure the safety of tunnel working shaft structure,it is necessary to study the seismic response of tunnel working shaft under extremely rare earthquake and how to improve its seismic performance.Based on the working shaft of a large underwater shield tunnel project,combined with the dynamic response theory of underground structure and shield tunnel,this paper establishes a refined three-dimensional finite element model that can reflect the stress and deformation characteristics of tunnel working shaft structure.In the process of modeling,we discussed the key of tunnel structure in finite element analysis,and analyzed the dynamic response of structures under super intensity earthquake and multi-directional earthquake.In order to solve the problem of stress concentration at the tunnel working shaft joint and the relative displacement between tunnel pipe rings exceeding the design value,we designed a damping device using shape memory alloy(SMA)as damping and energy dissipation material.It was installed at the connection between the working shaft and the tunnel shield section.We have carried out mechanical performance tests on SMA damping materials,and studied the damping effect of SMA damping device by simulation.At last,we discussed the feasibility of SMA damping device used in tunnel working shaft structure.The specific research contents and conclusions are as follows:Under the action of extremely rare earthquake and the multi-directional input of ground motion,the tunnel internal force had an obvious sudden change at the connection between the working shaft and the shield section and the open excavation section,the structure was seriously damaged by tension and compression,resulting in stress concentration,and the maximum stress value exceeds the cracking stress value of concrete.The opening amount of the pipe near the design ring exceeded a certain allowable range;We designed a damping device with shape memory alloy rod as energy dissipation and damping material,and carried out the mechanical property test of SMA rod and the realization of damping device in finite element.It was found that the mechanical behavior of SMA could be simulated by using the connector in ABAQUS.The designed damping measures had good damping effect.SMA damping device improved the stress of tunnel working shaft structure and the displacement difference between two tunnel rings.After setting the damping,the stress value at the joint decreased,and the relative displacement between rings in a certain range near the damping node was concentrated at the flexible damping device,while reducing the relative displacement between rings in this area.