Study On The Close-Range Photogrammetry In Tunnel Deformation Measurement

Deformation measurement is highly emphasized in tunnel project using NATM method. It is an important factor of enabling construction security and excavation efficiency. Tunnel design optimization also considers it as a significant reference. In conventional measurement work, total station, level, convergence gauge and other instruments are usually used. This method has the shortcomings such as slow speed, serious disturbance with the construction, finite object pionts,unstable measure quality and so on.Photogrammetry technology attracts more and more attention in recent years. With this technology, only simple equipments are required. It doesn't need to contact object points and has a high level of automation. Monitoring data is acquired rapidly. Considering that project demand is hardly met by conventional method, this paper introduces photogrammetry technology into measurement work on the basis of reviewing former study works and carries a research on the feasibility of non-metric digital camera use without control pionts. A deformation measurement system is developed to improve work speed, reduce project cost, and enable construction efficiency as well as security. The main work of the paper is outlined as below:(1) Infrared photography is introduced into tunnel measurement to solve the serious dust problem and distinct photos are obtained by this means. Aiming at the large lens distortion of non-metric camera, a rapid calibration method is also investigated to make convenience to field use.(2) A basic procedure for the pretreatment of digital photos is established based on computer graphics and a simple method of corresponding points matching is also proposed to adapt the practical measurement work in tunnel. Precise claculation of point coordinates and deformation value without fixed control points is achieved to solve the problem of non-existence of stable points in tunnel under construction and the unification of data obtained in different periods is realized based on free network adjustment theory, this work makes a good basis for wide use of photogrammetry in tunnel.(3) Programs are completed to realize various functions presented in paper and field tests are also carried out. Feasibility of photogrammetry appliance in tunnel is proved by the test.