Research On The Supporting Performance Of Tunnel Invert Structure

With the rapid development of the cause of China’s highway in recent years, each grade highway mileage is growing, the number of road tunnel also increase dramatically. But with the construction of large-scale highway tunnel, a variety of engineering problems also appears. Especially in recent years cracked, broken plates, take water, subsidence, uplift and other diseases of tunnel pavement emerging made a serious impact on traffic safety and operations management. The invert, as the bottom of the tunnel support system, studies its support performance for improving or avoiding these diseases have an important role. Therefore, the paper focuses on the performance of the invert support structure, combined with variety of research methods,such as, theoretical analysis, similar tentative, numerical simulation test and so on, under the influence of the radius and thickness of the invert its bracing and Ⅴ grade rock conditions invert open digging pitches research. The main research work carried out as follows:(1) Combined with the analysis of a similar model test carried out on the effect of invert, clarify its effect of carrying capacity to improve support systems, constraining surrounding tunnel wall rock deformation, controlling surrounding rock plastic zone, optimizing the force status of supporting and so on.(2) Through the stress analysis of the tunnel invert structure, clarify the influence of the factors include invert structure radius, thickness and timing of construction, connection with the side wall structure, in which the tunnel surrounding rock strata properties and construction methods invert factors to the stress of the tunnel invert structure. And regard the invert structure as cylindrical shell on elastic foundation to simplify calculations.(3) By means of finite element analysis software research the invert structure in different radius and thickness, and recommends the radius of the invert take 2 to 2.5 times than the radius of the arch structure of the tunnel section, the thickness of the initial invert take 10~25cm when construction the tunnel in Ⅴ Grade Rock.(4) Based on the recommendation of the invert radius and thickness conditions, integrated numerical simulation analysis, invert trestle and the second lining trolley and other construction equipment size and the overall progress of the construction of the tunnel requirements, And recommends that excavated from the inverted arch in one take 4m when construction the tunnels in Ⅴ Grade Rock and invert part of the whole site excavation.