Research On The Servest Ground Motions Of Near-Fault Tunnel Based On Damage Potential

Earthquake is natural disaster caused by rupture of active fault.China has a vast territory and is located between the Asia-Europe earthquake zone and the Pacific Rim earthquake zone.Earthquakes are widely distributed,in high frequency and intensity and own shallow sources.These characteristics are the basic national conditions of China.The reality that corresponds to the basic national conditions of frequent earthquake disasters is: China has become the country with the largest number,the largest scale,and the most rapid development of traffic tunnels.A large number of traffic tunnels under construction or proposed are located on active fault zones in the southwest,northwest,north and southeast regions of China where earthquakes occur frequently.Near-fault ground motions have significant features such as velocity pulse,hanging-wall effect,and permanent displacement and its damage to the tunnel is obviously different from far field ground motions.This paper relies on the National Natural Science Foundation of China “Study on the seismic damage mechanism and structural earthquake-resistant adaptability of traffic tunnel in near-fault area” and based on damage potential of ground motion,the following work has been done on the study of the severest ground motions for tunnel structure near active fault:(1)Based on the empirical mode decomposition method,this paper proposes a method for extracting the velocity pulse from near-fault pulse ground motions.The lower limit of the pulse identification index PI is determined as 0.2.On the basis of achieving identifying pulse quantitatively,the method of identifying multi-pulse ground motions is promoted.(2)Based on the wave theory,ground motion input is achieved considering the numerical model using visco-elastic artificial boundary in the finite element software.The correlation between the characterization parameters of damage potential of ground motion and the evaluation parameters of the tunnel is calculated.According to the correlation coefficient size to determine the optimal characterization parameter of damage potential of ground motion and then proposing a method that comprehensively estimating damage potential of ground motion for tunnel engineering.It provides a reference for selecting the severest design ground motions for tunnel near active fault.(3)Based on the wave theory,oblique incident ground motion input is achieved considering the numerical model using visco-elastic artificial boundary in the finite element software.According to the influence of the incident angle of the ground motion on the damage potential for the tunnel,the critical angle of near-fault pulse ground motion is determined.The critical angle of P wave is 30°.The critical angle of SV wave is 15°.