Research On Construction Mechanics Behaviour Of Spatial Cross-Subsidiaty Structure And Shaft In Tunnel

At present,there aren't many studies on cross-tunnels in China.while cross-tunnels,as a special kind of tunnel layout,are gradually transmitting to the general separation of tunnel with "Y"shape type bifurcation on the plane show from the hole-span tunnel,multi-arch tunnel and tunnels with small spacing within a short distance.Due to safety requirements and terrain constraints,the new mechanical and electrical, ventilation and emergency parking aggregate demand of the new-built tunnel must be considered.Therefore,ventilation shafts,cross holes and other ancillary structure must be built.However,the existence of these important ancillary structures caused that the overall structure of the tunnel showed great heterogeneity and the connect of sub structure and the main parts of tunnel became the weakest link.In this paper,some domestic key projects such aLs Lianghekou hydropower station 4# traffic tunnels,Xiamen East Channel and the Nanjing Yangtze River Tunnel were as reseatch object,FLAC3D as an analytical tool,in order to simulate the effect of actual excavation of the tunnel cross section on the stress and deformation of the cross section,evaluat the program, improve the design and construction technology based on the experience at this stage,and ensure safety and success of construction.The following aspects were studied mainly.(1)The numerical simulation methods was adopted to study the stability of the cross-section of the tunnel cross section changes,a large arch section,the stability of small spacing and the rock excavation engineering methods and key indicators such as support parameters of the corresponding section,and put forward rock reinforcement directly.(2)Since the main tunnel and traffic Xiang'an tunnel cross section is large excavation, some cross holes were in the rock section of V-class,complex and geological condition was complex,numerical simulation analysis was used to study the stability of the spatial cross structural of the cross-hole,the main tunnel and service tunnel of Xiangan tunnel,ensure the safe and smooth of cross-structure of the tunnel construction of space,the reasonable force of tunnel structure support,and provide a reliable basis for the design optimization.(3)Numerical simulation was used to study the effect of shaft set on the structural stiffness of the main shaft,the mechanical characteristics of binding sites between shaft and main tunnel,the impact of the tunnel shaft construction on the main structure and vicinal geologic strata,and analyze and evaluate the overall stability of the settings on the tunnel.