The mainshock-aftershock has a profound influence on the seismic resilience of tunnel. However, it is very dangerous to consider only the influence of the mainshock in the current seismic research of tunnel. This stud...
详细信息
The mainshock-aftershock has a profound influence on the seismic resilience of tunnel. However, it is very dangerous to consider only the influence of the mainshock in the current seismic research of tunnel. This study is based on the resilience evaluation framework under multiple disturbances to study the resilience of the tunnel against mainshock-aftershock. A 3D finite element tunnel model was established based on Longdongzi tunnel. Eight real earthquakes were selected to construct the mainshock-aftershock sequence by the repeated method, and the seismic load was input into the tunnel model by the high-precision wave input method. The failure ratio of surrounding rock and transverse convergence of lining are used as performance indexes to evaluate the tunnel resilience. The results show that aftershocks can significantly amplify the damage of the tunnel structure damaged in the mainshock, and the equivalent plastic strain of surrounding rock after aftershocks can increase by 253% at most compared with that after the mainshock, and the lining cracks will expand from microcracks to through cracks and eventually lead to the collapse of the tunnel lining end. The decreased value of resilience indicator DRe of tunnel surrounding rock after the aftershock is generally more than two times of that after the mainshock alone, and the highest DRe can reach 4.231 times. The resilience of each section of the lining structure experiences a certain loss after the main shock, and the loss of resilience is intensified after the aftershock. The resilience of the severely damaged section after the aftershock decreases remarkably, and the reduction range can reach about 50%. The hard surrounding rock can improve the resilience of the tunnel against the mainshock-aftershock, while the soft surrounding rock can cause the lining to deform greatly in the mainshock and continue to degrade in the aftershock.
The determination of the incident angle of an earthquake is one of the critical research issues in modeling the seismic input mechanism at a dam site and it is also for geological exploration. At present, the incident...
详细信息
The determination of the incident angle of an earthquake is one of the critical research issues in modeling the seismic input mechanism at a dam site and it is also for geological exploration. At present, the incident angle calculation methods mostly rely on accurate geological models, complex theoretical formulations, and complicated procedures. To this end, an incident angle estimation method using dam vibration response data and a machine learning algorithm is presented in this study. First, a three-dimensional finite element gravity damfoundation system model is constructed. A wave input method based on the viscous-spring artificial boundary is used to simulate the multi-angle incidence of P and SV waves. The vibration responses of key dam points are obtained. Nine features that have geometric interpretation are constructed by the response data and the new data are substituted into a stacking ensemble algorithm for training. Finally, the angles of obliquely incident P and SV waves are estimated using the trained stacking ensemble estimation model. The results reveal correlation between dam responses and the incident angle with the average R2 values of the estimation model of 0.996 (P waves) and 0.996 (SV waves), and the average root mean square errors of 1.765? (P waves) and 0.546? (SV waves). It is thus confirmed that the estimation model integrated multiple features from several measurement points with high accuracy and stability. In addition, the proposed method can be extended to other types of large structures because of its universality.
暂无评论