Study On Construction Mechanics Effect Of Shallow-Buried Bias Tunnels With Small Interval

With the large-scale increasing of transportation infrastructure construction, tunnelengineering widely been promoted, restricted by the model selection, line router and geologicalconditions, shallow-buried bias tunnels with small interval were increasingly adopted in projectpractice. Due to the influence and restriction of various factors, its mechanics effects,construction difficulties and construction safety were far more complicated than generaltunneling engineering, to understand the mechanism of construction mechanical effects anddeformation failure mechanism was very critical for construction and running of tunnel. Giventhis, this paper is supported by the research experience of the key project of Jiang Su provincialgovernment of Communications-Key Technology of Mountain Tunnel under ComplicatedGeological Condition, construction mechanics of shallow-buried bias tunnels with small intervalwere studied by theoretical analysis, numerical analysis and field investigation, mechanism ofdeformation and failure of tunnel structure and slope were focused on. The chief contents of thispaper as follows.(1) Analysis of construction mechanical and its influence factors of shallow-buried biastunnels with small interval.By simplifying reasonably engineering, desuperposition equivalence principle was used tosolve surrounding rock stress field distribution, influence of various factors were discussed.Given this, through the computation model, the significance of factors has been analyzed,deformation of the surrounding rocks and stress of the supporting structures have beensystematic and deep researched in different terrain bias, different tunnel buried depth anddifferent tunnel interval.(2) Analysis of dynamic construction in shallow buried Bias tunnels with small intervaland its stability evaluation.Back analysis model was built by finite element method and neural network, BP NeuralNetworks is adopted to constitute mapping of rock parameter and rock displacement andcalculate rock displacement in back analysis of rock parameter. On this basis, three-dimensionalanalysis model was built on the basis of construction step, simulation and calculation of thewhole-process dynamics construction mechanics was achieved, the deformation of thesurrounding rocks and stress of the supporting structures have been systematic and deepresearched, analyzing the interaction mechanism between slope of tunnel entrance andsurrounding rock, they are mutually respond to each other, the deformation of surrounding rockis the main factor causing slope failure, and excavation by backstroke.will also cause slopedeformation, therefore, the main measure is to control the deformation of surrounding rock in tunnel entrance, displacement of surrounding rock is the key factor for stability of tunnel-slopesystem, excavation and slope cutting were risk factors. Meanwhile, based on the concept ofsystem, the paper studies the technology of digging hole on the typical slope at tunnel entrance inBeigushan Tunnel.(3) Failure mechanism and disaster control technology of surrounding rock-slopesystem.On the basis of surrounding rock-slope system, counter the characteristics of disaster inBeigushan Tunnel entrance, through analyzing of the engineering geological survey, interactionbetween tunnel structure and slope, real-time monitoring, technology system of caveconstruction about shallow-buried bias tunnels with small interval were established, the principle,process, techniques and construction of main points of the system were described systematic.Taking utility and technological feasibility into account, reasonable reinforcement measures toensure slope and tunnel structure stability were proposed, results showed that the structure safetyof existing tunnel and the construction of following tunnel were assured.