Tunneling technology development in China brings great achievement in rail way construction industry. Beijing underground railway line along the diameter of buildings, structures intensive, beneath the Metro Line 2, 4 km section parallel thereto, recently just 1.7 meters, but also beneath the Metro Line 4 Xuanwumen station; Closely through Zhengyang door, front door watchtower, China Railway Museum, Ming City Wall and a number of important cultural relics; important buildings along the State-owned Assets Supervision and Administration Commission, the Communist Youth League central office building; Tianning Bridge, West Bridge would, also accompanied by a moat and other important structures tunnel diameter line; all kinds of underground rainwater, sewage, water, heat, gas and other pipeline clouds. Beijing through three subway trunk and can not interfere with its operations, sensitive areas to control the settlement within three millimeters, which weighs 1,600 tons of shield machine is easier said than done, almost demanding standards. He Feng head “sword of Damocles,” the project manager immersive abyss, treading on thin ice, pins and needles.

When the air cushion slurry shield tunneling, first with a certain pressure of the high viscosity of the mud in front of the cutter and shield full body around, along with the rotary blade cutter cutting rock, mud blocked the formation pervasive gap in the surface of the formation being cut forming a layer of mud wrap. In support of pressurized mud, mud always “meticulous” to support the formation, secure working space.

At the same time, the cabin air is compressed mud precisely control the pressure can be accurate to 0.1 kilograms per square centimeter, so that the settlement under different circumstances to achieve precise control. Muddy water pressure and air pressure, according to the effective model is determined by the technical staff for different environments, effective computing model by project department and Tongji University joint research technician OK. At the same time, the project department technical staff also timely in the process of driving the gap behind the tube sheet synchronize backfill grouting and secondary reinforcement grouting. Coupled with work surface, middle and bottom are equipped with sensors measuring device shield tunneling construction on settlement precise control becomes ease.