Pre-support Technology Of Pipe Roof In Karst Tunnel And Its Application

With the rapid development of highway construction in China,tunnel construction has become an inevitable choice across mountains and mountains.At the same time,the construction of tunnel engineering is also challenged by the complexity of mountain strata.The harsh surrounding rock conditions lead to the difficulties in the construction of the tunnel,and even affect the construction safety and delay the construction period.In order to guarantee the stability of tunnel surrounding rock,special supporting method of surrounding rock can be adopted to guarantee the safety of tunnel construction.Therefore,it is necessary to carry out research on this technology.In this paper,based on the presupport technology of pipe Roof in juntian tunnel of yongji highway through karst area,the application of pipe Roof presupport in karst tunnel is studied according to the surrounding rock environment,construction conditions and characteristics of the tunnel.This paper introduces the mechanism and construction process of the pipe Roofpresupporting,applies midas-gts to establish three-dimensional model analysis,and makes corresponding evaluation on the effect of the pipe Roofpresupporting support,seeks the most practical presupporting scheme under various supporting conditions,and makes analysis on the key points of the construction method under the pipe Roofpresupporting protection.The effect of karst on the tunnel under the support of pipe Roofwas analyzed.The main research work is as follows:1)This paper summarizes and analyzes the mechanism and construction process of the pipe Roofpresupport,makes a brief survey of the classified use of the pipe Roof presupport and its structural parameter design,and analyzes the problems and causes that tend to occur in the pipe Roofconstruction,and gives the corresponding disposal methods.2)Based on the junetian tunnel project of yongji highway,this paper analyzes and summarizes the geological,hydrogeological and geological characteristics of the tunneling area.Using midas-gts software to carry out 3d numerical simulation,the effects of different pipe Roofpresupporting states and different construction methods on tunnel displacement and stress are analyzed,and the application effect of pipe Roofpresupporting is discussed.3)Combined with the case of juntian tunnel project,three-dimensional numerical modeling was carried out based on the funnel-shaped karst holes existing in the arch roof,and its effects were analyzed and compared on the changes of stress,displacement and plasticity in the surrounding rock of the tunnel after the treatment of karst caves and untreated karst caves.Based on the location of karst caves,the effect of karst caves on tunnel displacement and stress is analyzed.