Study On Information Construction And Numerical Simulation Of High Railway Karsts Tunnel With Shallow Buried And Large Cross-section

In recent years, with the development of high-speed railway in China, to construct arailway tunnel in Karsts area is increasing steadily. The stability of tunnel in Karstsarea has also become a prominent construction problem during construction. In orderto work smoothly, geological disaster and impact which caused by Karsts must bestudied. This article is background with Dongfeng Tunnel with Karsts which locatedat railway passenger line from Yunnan to Guangxi, Karsts features and distributedrules are discussed in detail, tunnel geological prediction，risk evaluation, on-sitemonitoring measurement and numerical simulation in Karsts tunnel construction areapplied，information construction and simulation study on optimize construction inDongfeng Tunnel with Karsts are researched. The following conclusions can beconcluded by research the system of Dongfeng Tunnel with Karsts:(1) Based on summarized basic features in Karsts tunnels, main features ofshallow buried Dongfeng Tunnel with Karsts and large section has discussed, that isfeatures of Karsts and developing Karsts water. Ground Karsts is main with peaklongitudinal, Karsts depression, funnel, shaft, hole fell into water and so on, whileunderground is main performance with Karsts gap, Karsts, and underground river.Based on this, main engineering geological problems at shallow buried DongfengTunnel with Karsts and large cross section has analyzed, that is bursting water,bursting mud problem, collapsed Karsts ground, collapsed Karsts cave, lost stabilityof filled cave and so on.(2) To deficiency of traditional method of TSP203geological prediction, madeintegrated P wave, SH and SV wave, wave ratio of longitudinal wave and transversewave, poison ratio, dynamic elastic modulus and so on, with these parameters totranslate lithology and structure of tunnel. And combined the GPR with infrareddetector to mutual validation and predict the reliability surrounding rock of tunnel,the research results has applied successfully in predication work of Dongfeng Tunnel;based on water runoff module method and simple balanced method have donecalculation forecast of normal inflow water in tunnel and maximum inflow forecast inrainy season respectively, provide reliable parameters for the tunnel construction riskevaluation. Through study risk evaluation on Dongfeng Tunnel with Karsts, revealedthat risk levels exists in Dongfeng Tunnel is above high of initial risk, it isparticularly with risk of landslides and water gushing and mud.(3) Vault settlement, around convergence, steel support internal force and so onhas carried out monitoring measurement at typical developing Karsts section in Dongfeng Tunnel, has revealed that ⅲ level surrounding rockis reached stabilitybasically in about12days after it early supported with anchor spray measures(combination anchor rod, hanging reinforced network tablets and C25Jet concrete);IV level surrounding rock is reached stability in about14days after it early supportedwith anchor spray measures(steel support, combination anchor rod, hangingreinforced network and C25Jet concrete). Steel supporting structure has little changeand trend to stable in about14days.(4) The simulation result of Karsts distribution impact on construction of largecross section tunnel indicates that when clamp thickness is a constant, it is not goodfor stability when karsts cave located near the hance of tunnel, destroyed plastic zonein surrounding rock is large, bolt axial force distribution differences are large; whilekarsts cave located at the vault surrounding rock of tunnel has little influence onstability. Simulation on surrounding rock deformation results indicate that whenkarsts cave located near the hance, it has good effect when tunnel backfilled withadding length and density clip rock beltings.Large cross section Karsts tunnel geological conditions is complex, surroundingrock stability is different, bursting water and bursting mud phenomenon happenedoften. Karsts geological features has analyzed, geological prediction has researched,construction risk evaluation has evaluated, on-site monitoring measurement hasanalyzed and construction numerical simulation has calculated in this article, karstsgeological distribution features, surrounding rock and support structure of mechanicalcharacters during construction process have revealed, these can be guide for largecross section karsts tunnel how to construct, provides reference for similarengineering.