Research On Stability Of Surrounding Rock For High Railway Karsts Tunnel With Large Cross Section

In recent years, with the rapid development of high-speed railway, in theparticular geological and topographical conditions restricted areas, especiallyin the southwest Karsts tunnel development areas, building high speedrailway met with unprecedented challenges. In the southwest of the Karststunnel construction, often meet unknown geologic geological surroundingrock and complicate Karsts geological conditions, basically have cave，underground river， fault and fracture zone and other bad geological body.These factors not only affect the tunnel tunneling speed, and may causecollapse， large area of water gushing geological hazards, sometimes even cancause serious engineering accident.This paper as YunGui in high speed railway tunnel construction to growup-LiuLang Tunnel engineering background, in view of its big cross section,buried depth, wall rock broken and karsts development such complexgeological conditions. The karsts tunnel on geological radar and infrared TSP,agent comprehensive water the geological advanced prediction research.Advance geological forecast in the trial, the use of physical mechanicalparameters interpretation method Tunnel face surrounding rock characteristicsand structure characteristics of the front, and the geological forecast resultsand tunnel excavation of the actual geological condition after the analysis ofscience proposed parameters of surrounding rock reduction coefficientmethod, TSP and infrared agent of physical parameters water reductioncorrection, to decipher the analysis. Parameters of surrounding rock reductioncoefficient values the intimacy competency scale respectively in surroundingrock dry degree, have without fracture water and water content such as thesize of Ⅲ level, Ⅳ level of surrounding rock surrounding rock andsurrounding rock Ⅴ level is discussed and study, the forecast results and thepractical situation anastomosis as far as possible.Select the typical section of Karsts tunnel occurrence in the peripheralconvergence displacement， vault sink and surface subsidence etc, Withregression analysis and improvement of BP neural network model to predictsurrounding rock deformation values, Surrounding rock mass deformationprediction results show that the improved BP neural network model in thesmall sample cases prediction accuracy is higher than the regression. Software FLAC-3D based on finite difference simulation of tunnelingmethod in LiuLang Tunnel in step francs，full face，large side heading methodand double side heading method by four workers in the construction process,Surrounding rock of retaining structure and mechanical properties, revealslarge sections in karsts tunnel under different conditions and the supportingstructure displacement when mechanical distribution rule and optimized thelarge sections karsts tunnel construction methods. To optimize the project-meshshotcreting firstly method simulation research of the cave under thecondition of different occurrence of surrounding rock supporting structureand the deformation law of mechanical characteristics.Karts grouting treatment technology reinforcing, and sand filling slurry,filling clay pressure and Piece of stone method, the water concrete methodand the steel tube follow up the law is summarized. Through the monitoring ofthe surrounding rock before they might do the karsts deformation value, theanalysis after the treatment of karsts processing effect.