Computational Approach to As-Built Tunnel Invert Survey Based on Processing Real-Time TBM Tracking Data

By taking advantage of cost-effective technology and elegant computing algorithms, turning invisibility into transparency provides field crews with peace of mind and substantially improves controllability and efficiency of construction operations. In current practice, the as-built information of a tunnel is generally collected as a separate effort after tunnel construction is completed, which requires special surveying expertise and incurs significant resources and time. The main contribution of this research lies in the formalization of a simple, computationally efficient computing approach that can be implemented as real-time analytics to determine the coordinates of the invisible tunnel invert point based on analyzing the visible tunnel boring machine (TBM) tracking points during tunnel-boring operations. In addition, Monte Carlo simulation is applied to characterize error propagation on the computing algorithm due to measurement errors of total station, which provides input data collection means for the computing approach. The practical feasibility of the proposed approach was evaluated by conducting field testing over six months on a 1-km-long and 2.34-m-diameter drainage tunnel project in Edmonton, Alberta, Canada. (C) 2014 American Society of Civil Engineers.