Road Double-arch Tunnel Surrounding Rock Stability And Construction Technology

With the development of highway at top speed, multiple arch tunnel as a structure style of highway tunnel has more and more been used in specific terrain condition for its merits such as plane line shape is smooth, floor area is small, choosing opening position is the more free, and easy to be in motion and do business. But it is necessary to study in a deep going way because the span of multiple arch tunnel is long, the structure is special and construction technique is complex.This article takes the geological conditions of multiple arch tunnels in Si-xiao express highway in Yunnan province as researching background and expound the deformation and failure mechanism of the country rock during construction according to the importance of the stability of country rock during tunnel designing and construction by means of the analysis the changing of the ground stress before and after excavation. Thus, the stability of country rock can be overall appraised. At base of this, the stress mechanics, construction method and construction organization are all be researched in order to supply theory basis and current significance for the tunnel constructed safely, fast and effectively.First, first stress field and second stress state are analyzed and researched starting with engineering geological factor that influenced the stability of country rock. Meanwhile, it shows clearly that the stability of country rock is influenced by geology, geological structure, ground stress, mechanical property of rock mass, groundwater and tunnel construction etc.Then, Comparing with the engineering geological background of the area researched, the major factors that influence the stability of country rock of multiple arch tunnels in Si-xiao express highway has been defined according to the major factors that influence the stability of country rock of underground cavern. The major factors include rock character, developmental condition of rock mass, ground stress, groundwater and excavation method etc. Meanwhile, at base of the failure mechanism analysis of country rock, combining with the self-stabilization time of country rock after excavation, we can judge that the stability country rock stability of multiple arch tunnels in Si-xiao express highway is between the bad stability and instability. The multiple arch tunnelswere mainly constructed by middle pilot drift method and local sector were constructed bythree-pilot drift method.After that, aimed at the middle pilot drift method, dynamic numerical simulation with FEM has been carried on for construction mechanics of multiple arch tunnels in order to analyze the law of change of ground stress during construction, stress state of mid-board, the development range of plastic zone and the .stress character of the whole lining structure. The results show it is reasonable for stress that the lining structure of multiple arch tunnels in Si-xiao express highway constructed by mid-pilot drift method which can satisfy the requirement of construction.At last, at base of researching on stability of country rock and construction mechanics of multiple arch tunnels, construction skill scheme of multiple arch tunnels in Si-xiao express highway in Yunnan province has been put forward, which provide reliable theory basis for the safe construction of whole tunnel and ensure the construction carried on smoothly.