Construction techniques used to automatically pass standard box girders through special passenger-line tunnels

When a box girder passes through a rail tunnel erected for special passenger lines, the box girder frequently exceeds the inner profile of the lining, making it difficult to travel through a tunnel without collisions. After comparing several methods for accommodating vehicles used to transport box girders when they pass through rail tunnels, reducing the height of filled concrete in the inverted arch was determined to be the most suitable option. In addition, analysis of associated problems such as the need to maintain the height of the filled concrete in the inverted arch, running speed of girder-transporting vehicles, space geometry in tunnels, and safety of girder-transporting vehicles carrying box girders while passing through tunnels was carried out. An automatic control system was designed according to the construction process in this study. Inspection tests were carried out by use of a trestle-built model and after actual box girders, meanwhile the safety and viability were determined. The system detected distances using signals from ultrasonic and laser ranging devices. The system can be switched to the automatic drive mode. The control system automatically adjusts the direction and speed. These steps allow the 129 components found on standard box girders to pass through the tunnel safely and successfully.