In this thesis, we address tunnel convergence measurements within operational tunnel monitoring. The most commonly used methods for monitoring convergence or changes in the geometry of the tunnel inner profile are presented. A more detailed description is given of the method for measuring convergence distances using a tape extensometer, which is the most frequently used method in Slovenia. In the following section, we propose a method for measuring convergence distances using an electronic total station and reflectors. A mathematical model is presented for the direct computation of convergence distance from measured quantities, and the accuracy of the computed distance is determined using the law of propagation of variances and covariances. To enable the transition between the two methods, we first define characteristic points of each method and their geometric relationships. We then present three approaches for the transition. The first is an empirical approach, in which the convergence distance is determined using both the existing and the new method. The second approach is based on an analytical model in which we use linear algebra to determine relationships between position vectors of characteristic points, and we compute the convergence distance as the distance between selected points in a local coordinate system. The third approach is based on the coincidence of characteristic points of both methods, ensuring that the convergence distances obtained by both methods are identical. This coincidence is achieved using a specially designed adapter and ball prisms. A dedicated chapter is devoted to determining the optimal geometry of the measurement network. For different positions of the instrument setup (along the tunnel axis and off axis), we determine the optimal distance to the measurement profile and the optimal geometry of the measurement triangle. We also compute the required accuracy of measured quantities to achieve the prescribed accuracy of convergence distance determination. Finally, we present a practical case study involving measurements and computation of convergence distances on two test profiles, and we compare the results obtained using both methods.
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