Study On Seismic Dynamic Response Of Unsymmetrically Loaded Tunnel Under Strong Earthquakes

When tunnel through the mountains, in the shallow area, Due to topography, lining structure is very susceptible to be in a biased state. When the unsymmetrically loaded tunnel in the alpine region, temperature in winter is low,and in summer is relatively high,so the tunnel will withstand adverse effects that freeze-thaw cycle caused.Therefore, study on the seismic dynamic response of unsymmetrically loaded tunnels and the impacts of temperature factors on unsymmetrically loaded tunnel has an engineering significance.This paper analyzed the seismic dynamic response of unsymmetrically loaded tunnel with the numerical simulation method, and studied the effects of temperature field to the dynamic response of unsymmetrically loaded tunnel. The main research work and achievements are as follows:(1) Based on the damage data collection of mountain tunnels, clear the importance of the study on the influence of unsymmetrically load and temperature field on the seismic dynamic response of unsymmetrically loaded tunnels.(2) Analysis of dynamic response of the unsymmetrically loaded tunnel portal portion under single rock conditions, the following conclusions are concluded:unsymmetrically load can increase the entrance length. In IV Grade Rock, slope angle 30°conditions, the entrance length magnify 1.5-fold with not considering the terrain bias.(3) Through analysis of the 30m cross-section from the entrance, studied the seismic dynamic response of tunnel lining and the surrounding rock under different slope angle. The peak moment, peak shear force appear in the left abutment, The peak axial force appears in the right spandrel. In IV Grade Rock, the depth of Dome is 15m, The critical slope inclination of unsymmetrically loaded tunnel and symmetrically loaded tunnel can be taken 20°under earthquakes.(4) Studied tunnel dynamic response in different slope soil thickness. With the increase of the slope soil thickness, asymmetry of the dynamic response of the tunnel waning. The critical soil thickness under dynamic conditions is about 1.84 to 1.96 times that under static conditions,which based on the pressure arch theory.(5) Studied the effects of freeze-thaw cycles on the dynamic response of the unsymmetrically loaded tunnel. Studies have shown that freeze-thaw cycles have no effects on duration law of displacement and internal force of the tunnel,it justs change the peak of displacement and internal forces.When considering the freeze-thaw cycles, displacement and internal forces response peak of the tunnel structure under dynamic conditions has increased compared with not considering the freezing thawing cycles.