Seismic Response And Seismic Perfromance Analysis Of Composite Prefabricated Utility Tunnel

With the popularization and application of fabricated structures in underground engineering,the stacked composite prefabricated utility tunnel has become one of the important development direction of integrated utility tunnel construction.At present,there have been certain achievements in the seismic research on cast-in-place composite utility tunnel.But the research on the seismic response law and damage mechanism of the composite prefabricated utility tunnel is still at the initial stage,seriously lagging behind the actual construction of the fabricated utility tunnel.In order to study the seismic response characteristics of composite prefabricated utility tunnel,a three-dimensional finite element model of nonlinear static-dynamic coupling interaction system between soil and composite utility tunnel is established by numerical simulation method using finite element software ABAQUS in this paper,and the seismic response law and damage mechanism of the interaction system are analyzed.The main work includes:(1)The key issues involved in the modeling process of the refined finite element model of the soil-composite fabricated utility tunnel were determined,including the material comstitutive model,the setting of soil-structure contact surface,the setting of the old and new concrete composite surface,the mesh division,the seismic wave input and the static-dynamic artificial boundary.The “cohesion-friction” mixed model was used to simulate the coherence-slip behavior between the old and new concrete surfaces,the correctness of the model parameter selection is verified.Free field calculation examples based on viscoelastic artificial boundary condition and infinite element boundary were established,and the accuracy of two equivalent load input methods for ground motion was investigated.Finallly,the viscoelastic artificial boundary condition and its equivalent seismic load input method were selected as the artificial boundary conditions and the ground vibration input method used in the model.(2)The soil-composite prefabricated utility tunnel structural model was established,and its seismic response analysis was carried out to explore the effects of several factors on the seismic response of the utility structure,including different structural forms,structural burial depth,concrete strength,and ground vibration incidence direction.Under the action of ground motion,the force characteristics and damage evolution of the composite prefabricated utility tunnel structure were similar to those of the cast-in-situ integrated utility tunnel,which can be considered as equivalent to the cast-in-situ,but its seismic response is greater than that of the cast-in-situ integrated utility tunnel.Due to the effect of frictional slip on the contact surface,the cast-in-situ main part of the composite prefabricated utility tunnel structure is damaged before the prefabricated part,which presents a certain layered damage.The tensile damage of the prefabricated part is higher than the cast-in-situ main part,and the connection between the prefabricated side walls and the top and bottom plates is the weak parts of the structure.There is an unfavorable burial depth position of the composit prefabricated utility tunnel,and increasing the concrete strength grade,especially the cast-in-situ concrete part,can reduce the seismic response of the composite prefabricated utility tunnel.(3)The superposition surface transfer mode will directly affect the Mechanical performance of the utility tunnel structure.Under the vertical seismic excitation,the force transmission mode of the utility tunnel structure is extrusion at the top plate position,extrusion at both sides of the bottom plate and tension in the middle,and each side wall is mainly tensioned at both sides and extrusion in the middle.Under the horizontal seismic excitation,the force-transmission mode of the top and bottom plates and side walls of the utility tunnel structure is tension on both sides and extrusion in the middle.Under the action of two-way earthquake,the force transmission is mainly dominated by horizontal ground vibration,the force transmission mode of utility tunnel structure is open on both sides of the top and bottom plate and extruded in the middle,and the side walls are open on one side and extruded on the other side.(4)Based on the relationship between story drift limit,the degree of seismic damage and the degree of damage to the composite surface,the seismic performance level of the composite utility tunnel under horizontal earthquake and the physical description of seismic damage are preliminarily presented.The seismic level of composite prefabricated utility tunnel can be divided into five seismic levels of structural soundness,slightly damage,moderate damage,severe damage and complete damage.