Displacement measurement of the soil nail walls by using close range photogrammetry and introduction of CPDA method

Displacement measurement of the soil nail walls is a very important task in monitoring tiny movements in excavations to prevent disastrous accidents like wall collapsing. In building construction projects, this is usually done by either micro-geodesy or accurate instrumentation methods. In this research, for the first time, the use of close range photogrammetry in displacement measurement of the soil nail walls has been proposed and experienced. For this, a photogrammetric system was designed, implemented and evaluated. Proposed system with three separate methods for displacement measurement, which one of them was submitted for the first time (CPDA), was implemented. The evaluation results the accuracy of 3 mm is achievable in determining the point coordinates with a precision of 8 mm in displacement measurement of soil nail walls. Due to the efficiency, low cost, high accuracy, high speed of observations along with the simplicity of implementation of close range photogrammetry, it is suggested as a proper alternative to the traditional methods.