Study On Construction Mechanics Behavior Of Shallow Buried Large Section Highway Tunnel In Single Side Heading Method

With the comprehensive development of social economy and transportationenterprise in our country,there are more and more big section highway tunnels in trafficengineering construction in our countryin order to alleviate the increasingly congestedtraffic,and many cross section tunnelsis more shallow buried and bias of bad geologicalenvironment.It has important significance that we research on the geological conditionsof shallow buried side,the process of large cross section tunnel excavation andsupporting construction mechanical behavior of surrounding rock and supportingstructure,the shallow buried and bias,separately carries on the discussion of shallowburied large section of bias tunnel design and construction.In this paper,it used the large cross section tunnel in GuiYang HuaguoyuanSonghua road as the engineering background,mainly uses the construction method ofthe single wall pilot tunnel method,through theoretical analysis and numericalsimulation,the main content and research results were as follows:①We set up the elastic-plastic numerical model of big section highway tunnel,simulate and calculate the construction process of single side of Songhua road tunnelheading method.Construction process of shallow buried large section of bias tunnelconstruction mechanical behavior is analyzed.In this case we concluded that the upperleft pilot tunnel after excavation is the biggest displacement value in this phase,thetunnel vault subsidence maximum towards the buried depth of the tunnel deep side,inconclusion,the upper left of the pilot tunnel excavation is the weakest link of theconstruction.②End of the tunnel arch uplift springback is biased towards the maximum depthof shallow side.Tunnel roof tensile stress appears.Arch feet on one side of the deepburied depth and the tunnel arch camber line on one side of the shallow depth tunnelhave a different degree of stress concentration.The surrounding rock of Tunnel burieddepth on the deep side releases more pressure than on one side of the shallow burieddepth obviously,and the stress concentration phenomenon is severe.Through thesimulation of tunnel excavation process,we concluded that the axial force of sprayedconcrete in early support in the excavation of the side is greater than after theexcavation side,so we can have a rational bias design of supporting structure. ③Under the construction of the single wall gate bias tunnel of shallow buriedlarge section,compare and analysis the two kinds of working condition of the simulationcalculation:First excavation deep excavating and first excavation shallow excavatingburied side,we reached the conclusion,In particular bias conditions,the stability of thetunnel surrounding rock and the supporting structure are more advantageous to excavatethe shallow buried large section tunnel firstly.Taking Songhua road tunnel as prototype,modeling the embedment depth and theground slope changes,we calculated and analysis the tunnel construction mechanicalbehavior and the variation characteristics, and compared the influence of surroundingrock and supporting structure.We reached the conclusion that when the embedmentdepth increases gradually,the tunnel surrounding rock pressure is increasing on thewhole,and overall bias pressure effect will decrease.When the Local surface slopeincreases gradually,the deep tunnel embedment depth of the surrounding rock pressureincreases more obvious than, and bias effect is more obvious.