Development of support system using pipe-jacking for the roof of the large caverns

In the urban area, many lifelines have been constructed in underground for many functions, such as electrical, gas, communication lines and water, sewer pipes. Due to this condition, it is demanded to construct for a new subway install at the deep underground with no disturbances on many existent infrastructures. In this case, the Pipe-Roof Method using steel pipes was applied for the support of the large cavern space at the new subway station, because no support drivage gave various influences to the upper existent lifelines. At this job-site, "Auger Type" machine for the general Pipe-Roof Method could not be adopted from the viewpoint of the difficulty, because the soil of this site consists of big cobble mingling gravel including maximum big cobble diameter 400mm with saturated underground water. So High Density Slurry Pipe Jacking method with cutter-face-pressure's control system was adopted for this pipe-roof construction as the new Pipe-Roof Method. This report discusses the example that the pipe jacking method was adopted for the advanced use in urban area's underground which the important structures are heavily crowded.