Stress-strain Study Of Double-arch Tunnel Excavation Process

Large number of studies have shown that the double-arch tunnel is not only very high economic benefits in linetype, engineering quantities,costs and daily management;but also small amount of vegetation destruction, facilitate to evacuate and manage emergency traffic, can improve the safety of construction and daily use, and has high environmental and social benefits.However, due to the large span complex structure,cumbersome construction procedure,the application and research of double-arch tunnel structure is still not mature, research of it is a complex and systematic issues, relates to mechanics, materials, systems and other aspects, so far there is no uniform design and construction regulations or norms. Researches of the double-arch tunnel excavation methods have been many, but most were forms of excavation of the tunnel section. The research on the impact of one side of the main tunnel excavation on the other side is still not common. Using the parameters of the structure form,the wall rock and the supporting of yumujianggou ,and in different construction procedures, This paper founded the Three-dimensional elastic-plastic finite element numerical model,and made analysis and comparison. Further studied the vertical and longitudinal stress and displacement on the key positions:the arch crown,the arch foot,the arch bottom and the arch waist ,on the impact of double-arch tunnel excavation and surface settlement affected by the tunnel excavation.This paper is composed by The introduction, The double-arch tunnel finite element calculation methods, The engineering situation of YuMuJiangGou double-arch tunnel,The simulatons parameters'determination methods,The numericl simulation analysis of the doble-arch tunnel,and conclusion and suggestions etc six parts. The first part System introduced the characteristics of double-arch tunnel, the theoretical research of double-arch tunnel, the contents of this paper, programs and technical routes. Part of The double-arch tunnel finite element calculation methods in-depth exposited the numerical calculation methods constitutive model and yield criterion, Numerical simulation of double-arch tunnel prototype overview summarizes the main numerical analysis of the prototype (YuMuJiangGou double-arch tunnel) of the construction technique. It combines on-site investigation and survey, research and analysis of engineering geological conditions and identifies the surrounding rock lithology, stratigraphic occurrence, groundwater, geological structure, stress, topography and other engineering geological conditions for the double-arch tunnel provides a numerical simulation based on parameters. Double-arch tunnel some three-dimensional numerical simulation of various parameters in order to ensure true and reliable, relying on all the parameters works Yumujianggou tunnel on the three-dimensional numerical model, a major study of vertical construction in the tunnel face with two different depth of excavation under the process of vertical on the surrounding rock stress and strain influence. Calculation conditions due to space constraints and the computer can not simulate all the details of the tunnel, just select the carpenter tunnel on the lot depth of 25 meters. Rock level is III. Considering the program as a large excavation to level advance to the Peak, the model selected for the flat top condition. Yu Carpenter tunnel is the double-arch tunnel, 243 meters long total, 155 meters long of bored tunnel section, excavation section of the single arch span12.5m, height 7.9 m. It is shallow tunnels. Three-dimensional plane strain numerical model for elastic-plastic model, the initial stress only consider the surrounding rock mass weight, calculation model to take a single arch span of the border around 4 times 50 meters, vertical direction, take the free surface boundary, the boundary to take Diameter 4 times 50, calculate the length of 45 meters. It is full-face excavation method of calculation. To minimize the simulation step, the pilot tunnel excavation using a one-time and one-time placement in the wall. Excavation around the main tunnel of the right and left posterior simulation points first two options to proceed with the simulation, analysis of the tunnel under the program in two key parts of the surrounding rock stress and displacement distribution.The conclusions of the research have some important theoretical significance and reference value on the double-arch tunnel construction and a related aspect has. The findings show:⑴During the construction process the rock stress concentration zones mainly distributed in the arch foot, the and its top and bottom surrounding rock areas. The tensile stress areas mainly distributed in the arch crown,the arch bottom, the Internal of the middle-wall.Forces in the top and bottom of the middle-wall surrounding rock are very complex,and these areas are the poor stability parts of the double-arch tunnel. And these areas should be protected carefully to prevent them from being injured.⑵Constructing double-arch tunnel In the rock level III. about digging holes in different circumstances of construction cycle, the main tunnel's excavation one side on the longitudinal impact rock mainly concentrated in the same side range, within about 1.5 to 2 times the main tunnel diameter. Less influence on the other side of the tunnel. The two holes in the same construction cycle tunnel ,the faces move forward together, the main hole of the longitudinal impact the surrounding rock mainly within the 2.5 to 3 times single-hole span construction cycle. The major impact on the surrounding vertical assembly area in the wall reinforcement, the mechanical analysis of the tunnel should be key considered in the reinforced area.⑶Digging oneside hole of shallow double-arch tunnel. The maximum surface settlement appears in the side of excavated tunnel.As the other side of the main tunnel excavating, the location of maximum surface settlement transferring to the top of the middle-wall surface. Digging the two holes of the double-arch tunnel , the maximum surface settlement is located in the top of the middle-wall surface. The final settlement value of the surface on the top of the middle-wall surface are symmetry ahout the middle-wall axis but the corresponding symmetry point,but symmetry points in the corresponding, Laters are bigger than the earlier.