Design and Construction of Trenchless Directional Drilling for the Natural Gas Pipeline Project Crossing Zhantian Lake

Part of natural gas pipeline network project of Changde Huayou Gas Co., Ltd needed to cross the Zhantian Lake about 216m, and the pipe diameter was 200mm, the pipe material was PE. The strata which the pipeline crossed was artificial fill, silt, silty clay, mucky silty clay, round gravel layer in order. After comparing the several programs, trenchless guided drilling was selected for installing the section of the pipeline. For the long lake crossing distance and the complicated strata, No-Dig rig KSD∼25 with a large drag force was chosen to carry out the pilot bore construction, and then the pilot bore was enlarged through four times reaming pass until the drilled hole diameter was 500mm, Finally, pipe laying and grouting were done. The application of trenchless guided technology in the engineering was the focus of this paper, for example, the pilot bore trajectory design, pullback reaming, pipe laying process design, construction technology and control. Meanwhile, some technical difficulties such as measurement while drilling, drilling fluid preventing hole wall from collapse were studied and discussed. After field testing of the actual construction of the project, the precision of pipe laying meeted the requirements, no-dig construction process was smooth, and then the project was successfully completed within the stipulated construction period and with less construction cost.