Research On Design Theory Of Pipe Roof Reinforcement And Its Application For Weak-surrounding Rock Tunnels

Along the tunnel through the soft and broken surrounding rock slope and other location or processing scope of import and export,in order to ensure the stability of constraints and surface,prevent tunnel collapse,surface subsidence control,increase the safety of the tunnel excavation,will face a series of preliminary support of surrounding rock of special problems.One of such methods is the pipe roof reinforcement method.This method consists on installing,prior to the excavation of a length of tunnel,a series of pipes,either parallel to the tunnel axis or at a certain angle with it.By injecting grout through the pipes,the ground in between the pipes is stiffened and the pipes are connected,creating a kind of‘umbrella’above the area to be excavated.This technique combines the advantages of the modern fore poling system with the grouting injection method.In other words,the improvement of the mechanical characteristics and the impermeability of the ground around the tunnel can be achieved simultaneously.Through the preliminary support of the pipe roof in weak rock tunnel structure and the theory of bearing force and constraints in to do the preliminary support of the advanced cases stability study,make the building when can fully understand the theory of preliminary support method,so had a good guidance for the construction, is beneficial to reduce engineering cost and risks,is of great significance to ensure the engineering quality.In this paper, the main research work is as follows:①Overview of the tunnel is commonly used in domestic and foreign advanced technology,and to summarize the characteristics of various types of supporting and comments.②For the calculation of pipe roof stress load, through the comparison of common calculation of tunnel surrounding rock pressure calculation theory,so as to draw lessons from some of these theories knowledge,condition of buried depth,condition of surrounding rock and tunnel excavation and the characteristics of pipe roof as preliminary support structure such as factor analysis,the corresponding calculation formula.③In Pasternak created on the basis of elastic foundation beam theory mechanics analysis model of pipe roof,and the deflection curve differential equation,and get the pipe roof supporting structure angle,bending moment and the solution of the equation, the mechanical behavior of the preliminary support of the pipe roof is analyzed.④From the pipe roof structure,decorate a form, geometric parameters,etc,to carry out the optimization design of pipe roof.⑤Based on the engineering background of zunyi road tunnel,the preliminary support of the pipe roof structure model is established,and the analysis of the system.