| Dynamic response and failure characteristics of the slope in the portal section of tunnel under seismic load have been an important research topics in civil engineering and related fields.Especially,the tunnel is an important part in the economic lifeline of the Middle-western China,and the geological disasters induced by the earthquake often result in a large number of casualties and economic losses.Therefore,numerous of scholars and engineers have made a lot of research on the dynamic response of the slope of the tunnel portal section and the protection of slope in the portal section.In term of the limited reference of seismic field monitoring data about the tunnel and the slope of tunnel portal,the numerical calculation results showing the difference with monitoring data,and the defects of common model test has,such as gravity distortion effect,further research and data excavation are needed to study the dynamic response and failure characteristics of the slope in the tunnel portal section.The dynamic centrifuge model test can simulate prototype stress field and accurate the reveal seismic dynamic response,the slope in the tunnel portal section is as the research object to carry out dynamic centrifuge model test of the slope and the slope in tunnel portal.A complete set of design ideas and operating procedures for the dynamic centrifuge model test of the tunnel portal section is established,and the seismic dynamic response of the common slope at the tunnel portal section is revealed.The main results of this paper are as follows:(1)The acceleration time-history curve of each measurement point is consistent with the input seismic wave in the wave,but the difference is only on the order of magnitude.In the common slope model,the peak acceleration of slope shoulder and toe of slope is larger than that of the other locations.Due to the stress redistribution and stress concentration caused by the excavation of the tunnel,the acceleration response of the slope at the tunnel portal section is larger than that of the common tunnel model.Tunnel vault acceleration amplification coefficient amplitude reached 1.18 and acceleration dynamic response significantly,the peak acceleration of the slope shoulder,close to slope shoulder position,slope crest and tunnel vault is larger than that of other locations.(2)The peak amplification coefficient of acceleration is larger than 1.0,which indicates that the acceleration is amplified.In both vertical and horizontal direction,the acceleration response has obvious nonlinear superficial amplification effect.(3)Under the centrifugal acceleration of 50 g,with the corresponding prototype amplitude increased from 0.15 g to 0.3g,the acceleration amplification coefficient decreases linearly and the acceleration response decreases.(4)In the case of simulated prototype 0.15 g earthquake acceleration,with the increase of the centrifugal acceleration,the acceleration response increased.In the simulated prototype 0.25 g earthquake acceleration,the acceleration response decreases with the increase of the centrifugal acceleration.(5)With the increasing of elevation,the maximum amplitude of the dynamic earth pressure decreased linearly,the decreased amplitude of each stage is close;Dynamic Response earth pressure coefficient is the largest in tunnel lining vault,the least in 0.88 Relative elevation.(6)In the tunnel invert,the acceleration amplification factor is larger than that of the other parts below the tunnel vault,and the acceleration amplification coefficient is almost unchanged in the side wall and the tunnel invert.(7)Under the seismic load,the dynamic strain response of the tunnel vault is the largest,the circumferential strain response is significantly greater than the longitudinal response,and the longitudinal deformation and failure of tunnel lining are easily occur in tunnel vault;The maximum dynamic strain response of the tunnel model at the depth of 15 cm from the tunnel portal.(8)The deformation mechanism of the two models is creep-cracking. |
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