The Key Technology Researches Of The Large Section Pipe Roof-box Jacking Method

With the development of transportation rapidly, more and more large section and shallow buried tunnel will be constructed in city. Pipe roof-box jacking method is a kind of trenchless knowledge which has the advantage of little affect on ground activity and environment, especially for the case passing through road with heavy traffic and important zone. Based on the urban rapid highway between Zhengzhou and Kaifeng which crosses Jingzhu highway, this paper studies the mechanical effect of the pipe and the process of design and construction of the box such as establishment of reasonable spacing during the box jacking by means of analytical equation, numerical simulation, laboratory test and site measurement. The main job of this paper is listed as follows:1. The effect of analytical equation is limited because of the complex of the underground crossing program. So this paper uses the numerical simulation method and introduces application of FEM in the pipe roof-box jacking method taking Zhengkai program for example. And this paper completes the research of selection of reasonable construction process, the effect caused by different processes to box attitude and the effect caused by overexcavation to construction.2. This paper introduces the control model of vertical attitude of the box. It also proposes rectification measures to solve the problem of the box down during the construction.3. During the Pipe-Roof Box Culvert construction, more and more attention is paid to the spacing between pipes. If the spacing is too small, the construction will be difficult and also waste material; when the spacing is not so small, depending on the "micro arching effect", the soil above will not slip out of the pipes. Along with increment of the spacing, the "micro arching effect" decreases; when the spacing exceeds a critical value, the soil above will slip out of the pipes. Based on the "micro arching effect", this paper makes research about the spacing between pipes and put forward a formula for the spacing between pipes to maintain the effect of the "micro arching effect".4.Underexcavation and overexcavation models have been presented based on the elastic foundation beam theory and the corresponding deflection equations and other controlling equations have been deduced. When the settlement produced, the pipe roof can transfer some covering load from active sliding zone to stable zone and cause unloading effect. When the heave produced, the pipe roof can transfer some covering load to passive zone and cause unloading effect.Finally, the writer gives some advice for this paper to research further.