CASE STUDY ON THE LARGE DIAMETER PIPE JACKING FOR UTILITY TUNNEL IN MODERATELY WEATHERED SILTSTONE

Pipe jacking has been widely used in utility tunnel constructions as an environment-friendly method in China. This study is focused on the critical technologies used in the pipe jacking for the utility tunnel in Huanggang Mingzhu road. The inner and outer diameters of this utility tunnel are 4m and 4.8m respectively, which is the largest circular pipe jacking project in China at present. This utility tunnel is designed under the urban main road with heavy traffic, so the control accuracy of pipe jacking construction is required to be high. According to the characteristics of the project and actual construction technical measures, the key construction technologies including pipe jacking equipment selection, launching of small spacing, slurry circulating, drag reduction technology, and the control of surface settlement are discussed in this paper. Meanwhile, the jacking force and surface settlement during pipe jacking construction are monitored. The results show that the selected pipe jacking machine has good adaptability to the geological conditions of the project. The actual jacking force is much smaller than the theoretical value, and the two intermediate jacking stations are not activated. In addition, the road surface deformation is -8 - 5mm during the whole process of pipe jacking construction, which has no impact on surface traffic.