Virtual Laser Target Board for Alignment Control and Machine Guidance in Tunnel-Boring Operations

Construction engineering and management research takes advantage of proven technologies and turns them into cost-effective solutions in the construction field. This paper describes our efforts in the development of a new alignment control and machine guidance system for tunnel-boring operations. Steering a tunnel boring machine (TBM) in tunnel projects normally relies on a laser station which projects a laser beam onto a laser target board mounted on the TBM. However, current practice lacks accuracy and requires tedious, time-consuming calibrations, thus potentially leading to quality defects, schedule delay, and cost overrun in tunnel construction. This research has developed an automated system called "virtual laser target board (VLTB)" in order to facilitate field construction. Through automation and technology integration, a commonly available survey tool -namely the robotic total station is transformed into a construction control robot, which is capable of precisely positioning and tracking the TBM in the underground space. By applying innovative computing algorithms, the exact coordinates of the cutter head center on the working TBM can be derived in millimeter-level accuracy. Thus, the invisible cutter head center can be visualized in a tablet interface in relation to the as-designed alignment. The VLTB system was field tested on a 1,000 m long sewage tunneling project in the city of Edmonton, Alberta, Canada. The tunnel test bed showcases the future of technology integration and automation in construction.