Abstract

Railway and subway tunnels have lengthy runs, long train operation times, high detection pressures, and critical structural safety concerns that affect tunnel service life, train safety, and passenger comfort. The current method of measuring the clearance convergence requires considerable manpower and equipment to identify defects, cannot measure the entire tunnel section, has poor operation efficiency, and provides noncomprehensive results. To address these shortcomings, three-dimensional laser scanning technology has recently been applied to tunnel structure inspection. This study therefore proposes methods for calculating the clearance convergence of a tunnel section, including the calculation of the shield tunnel convergence diameter, shield tunnel and mine tunneling method tunnel chord lengths, track gauge, guide height and offset of overhead lines, and vault clearance height. The tunnel point cloud data were acquired by the Capital Normal University (Beijing) mobile laser tunnel inspection vehicle and were processed using the algorithms developed in this study. The data indicate that the proposed method provides a repeatability and absolute accuracy within ±3 mm. The proposed method improves the efficiency of tunnel clearance convergence measurement by measuring the full section of a tunnel, providing technical support for the safe operation of subway and railway tunnels.