Study on Application of Digital Image Measurement Method to Monitoring System for Tunnel Construction Management

This paper introduces a new measurement system using digital images for tunnel construction management. This measurement technique that utilizes digital images brings the following benefits compared with conventional techniques. The 3-dimensional deformations and the area-wide distributions of many measurement points can be obtained through simple measurement work. As the image data are all in digital format, real-time monitoring is possible. Measurement involves photographing from a distance only, eliminating the need for sophisticated techniques to improve accuracy as in conventional measurement. The necessary measurement hardware consists of a digital camera and a PC only, which brings down measurement cost. This study first attempts to establish the theoretical framework for using images photographed from any position with a digital camera for measuring any object for which is difficult to set fiducial points, such as a tunnel and reproduce the 3-dimensional displacement of a tunnel with considerable decision. It then goes on to clarify the relation between various measurement parameters and measurement decision and includes experiments to evaluate the performance of the technique that is applied to deformation measurement system of jointed rock masses. As a result, the establishment of a new measurement system featuring simple measurement work and a high degree of decision was found to be possible.