| Biased tunnels are caused by asymmetric rock formation geology,which causes asymmetric loading on both sides of the tunnel structure.Under earthquake action,the biased tunnel structure is more likely to be damaged than conventional tunnels.The severity of the earthquake damage of the bias tunnel under different working conditions is also different.In this regard,based on the conditions of different slope ratios,combined with the seismic damage investigation,shaking table model test and finite element numerical simulation of the tunnels with different slope ratios,the dynamic response characteristics and resistance of the tunnels with different slope ratios under earthquake action are studied.Effect of shock absorption measures.The main research contents and results are as follows:(1)The investigation results of the seismic damage of the biased tunnel show that the seismic damage characteristics of the biased tunnel are mainly manifested in the tunnel entrance and the tunnel body.The types of earthquake damage in the entrance section of the biased tunnel are:collapse of the side slope,burial of the opening,cracking deformation of the slope,and damage to the gate wall;Bulge,etc.The factors influencing the seismic damage of the bias tunnel are summarized and analyzed.(2)By inputting different peaks of seismic waves,a shaking table model test is conducted to analyze the peak internal force and peak acceleration of each monitoring point.The results show that:the peak internal force at each monitoring point of the lining increases with the increase of seismic wave acceleration,and the peak internal force at the dome and arch foot is obviously larger;The coefficient increases between g and 0.4g,and the acceleration increases between 0.3g and 0.4g,and the acceleration amplification coefficient decreases between 0.4g and 0.5g;the acceleration amplification coefficient of slope and surrounding rock increases with the acceleration of the seismic wave,Undergoing the process of decreasing first,then increasing to the peak,and then decreasing;the effect of elevation on the slope acceleration amplification factor is greater than that of the surrounding rock,and the acceleration amplification factor of the monitoring point of the surrounding rock appears after the elevation reaches a certain height The phenomenon that the acceleration amplification factor decreases.(3)Through finite element numerical simulation,the bias conditions of different slope ratios(0°,30°,45°,60°)are simulated,and the changes of peak internal force,acceleration peak and displacement peak at each monitoring point are summarized and analyzed.The results show that as the bias angle increases,the peak internal force at the monitoring point increases first and then decreases,and the peak value of the internal force at each monitoring point reaches a maximum value at 300bias,indicating that there is a critical bias angle that makes the lining at each point The peak value reaches the extreme value;the peak value of the internal force at the lining arch foot is obviously greater than the peak value of other monitoring points,and the arch foot between the arch foot and the side near the mountain is more vulnerable to damage.The arch shoulder is the weak part of the bias tunnel;the peak acceleration and formation displacement increase with the increase of the bias angle,which is positively correlated,and the peak is closer to the ground.(4)Through the numerical simulation to study the shock absorption effect of the anti-seismic joint and the shock-absorbing layer,it is found that the anti-seismic joint and the shock-absorbing layer have certain damping effect;the smaller the bias angle,the more obvious the damping effect;The damping effect of the shock-absorbing layer on the peak lining internal force is greater than that of the anti-seismic joint;when the bias angle is large,the damping effect of the anti-seismic layer and anti-seismic joint is equivalent,and there is no obvious difference. |
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