Jacking precision control of pipe roof and large box culvert below urban expressway-a case study of a large underpass in Shanghai

Abstract Pipe roof-culvert box method is an effective way for shallow buried tunnel passing beneath important facilities. In soft ground, the culvert can be jacked under the pre-reinforcement of pipe roof. This paper presents an investigation on the precision analysis and control of a large- scale pipe roof jacking (the scale of this structure is 21.648m*8.148m) of an underpass, which passes beneath the Mid-Ring expressway in Shanghai. The conclusions drawn from this paper show that: (1) In this project, more than 70 percent of the deflection values of jacking machines and pipes are controlled within 20mm. (2) During the process of pipe jacking, the deflections of pipes tend to lag behind the machines’ about 3~10m. 68 percent of the rangeability of pipes’ deflection are 50%~100% of the corresponding machines’ deflection. (3) Due to Stiffness effect of pipeline, posture of pipe is difficulty to be rectified during the stages of pipe starting and receiving. A compelling rectification will result in overlarge deviation and increase the difficulty of subsequent operation. (4) For two adjacent pipes, the posture of latter pipe is positively related by the stiffness of prior pipe. The Pearson correlation coefficient of horizontal pipes and vertical pipes can be 0.46 and 0.68 respectively. (5) Considering the interspace between top pipes and box culvert, the control criterion of vertical deviation of box culvert is recommended as 5cm.