Photogrammetry Technology: Towards A New Testing Method Of Concerte’s Appearance Quality Of The Railway Tunnel Lining

In recent years, as the high-speed railway and passenger dedicated lines such as Beijing-Shanghai, Beijing-Shijiazhuang, Shijiazhuang-Wuhan, Wuhan-Guangzhou,and Zhengzhou-Xi’an had been opened, the total length of China’s high-speed railway has up to7531kilometers, ranking first in the world. That indicates that China has entered a new era of high-speed railway. Accordingly, the safe operation which was directly decided by the quality of railway tunnel lining has become an important issue. Therefore, the railway tunnel lining quality detection technology has great social and economic value.The railway tunnels lining quality disasters are water seepage, leakage, spalling, concrete block reinforcement honeycomb, pitted, crack and etc. Among these factors, the tunnel lining crack influenced the safety most. The length and different forms of crack suggests tunnel lining deformation has produced by force from different direction. At present, the detection of tunnel lining quality was carried out mainly by artificial means with supplementary auxiliary equipment, which makes the long detection cycle and low detection accuracy, as well as omission phenomenon inevitably. Image detection system has been widely applied on bridge and road engineering, but railway tunnel as its specificity. A set of tunnel lining quality inspection system was developed based on railway tunnel considering the characteristics of it. This paper explains the system principle of work and procedure, after the hardware equipment selection, assembly and debugging was completed in the laboratory, basically achieved the expected results.In this paper, a high resolution CCD camera (Canon EOS5D Mark II) and two millimeter laser rangefinder were installed on a rotating shaft through precision machining equipment. A fine adjustment through the precision optic products makes the light axis. Under a specific motion state, the servo motor and PLC control system get the tunnel lining scan imaging. Calibrating of the lens was made before image acquisition and the parameter was used in the later image processing. After calibration, keep the camera parameters unchanged, roughly confirm the lens optical center position, and fine adjustment was made by built indoor control field and the precision of the machine product. After all calibration work completed, the fixed equipment was preceded into the tunnel test. In view of the limitation of experimental conditions, the system only simulated the indoor static test. This paper mainly studied system internal selection based on the accuracy analysis of the hardware, the assembly and debugging, and the digital image processing and analysis later. With the rapid development of sensor and processor, the application of image processing technique to detect the quality defects of railway tunnel lining has broad prospects.