Seismic Analysis Of The Cross Joint Of Underground Utility Tunnels

In recent years,with the rapid development of the construction of the utility tunnel,the seismic performance of the utility tunnel,especially the cross joint,has been widely concerned.Earthquakes occur frequently in China.It is of great significance for seismic design to conduct seismic analysis of utility tunnels and their cross joints.In this paper,a finite element software ABAQUS is used to establish the seismic analysis model of the cross joint of the utility tunnel.Firstly,a linear dynamic analysis model is established,and the size of the final seismic analysis model is determined by analyzing the deformation.On the basis of the model size determined,taking the utility tunnel under the thick soil layers in Tianjin as a case,using viscous-spring artificial boundary and equivalent nodal force as seismic input,considering the nonlinearity of materials,the non-linear dynamic analysis model is established.Through the analysis of internal forces,the influence scope and influence effect of the cross joint are studied.Subsequently,considering the nonlinearity of soil spring and material,the non-linear quasi-static analysis model is established by using soil spring.The influence range and effect of the cross joint are also studied by analyzing internal force and compared with dynamic analysis.The research shows that,in the model of the cross joint of the utility tunnel,the internal force of the utility tunnel along the axial vibration increase,which bending moment becomes the control internal force of the cross-section.The internal force of the utility tunnel which vibrates along the vertical axis decrease except for the joint area,while shear and torque are generated,and torque becomes the control internal force of the section.The increasing effect of internal force is most obvious at the junction position,and the lower corner of the utility tunnel is the the most disadvantageous position of the section.The influence range and effect of joints in dynamic analysis and quasi-static analysis are similar,but the internal force value in dynamic analysis is larger.Quasi-static analysis can be used instead of dynamic analysis if we only study the influence effect of the cross joint.