Proposed design of local 2D geodetic network for the construction of the tunnel part of the Belgrade metro

Abstract

This paper presents a method of optimization of the underground network for the construction of the Belgrade metro. In the process of optimization, the method of preanalysis was used. The theoretical basis of the mathematical model of the preanalysis is given, which is based on Gauß-Markov model of geodetic networks adjustment, as well as the theoretical basis for calculating the tunnel breakthrough precision. Based on the construction standards, the calculation of the required breakthrough precision was made, as the fundamental criterion of precision for the development of the underground tunnel network. Depending on the technical parameters of the Belgrade Metro Line 1 alignment, related to the position of the axis and the longitudinal profile of the tunnel, the design of the underground tunnel network was defined. In the process of optimization, different plans of observations were analyzed, as well as the results obtained from the preanalysis for each plan individually. Based on the set criterion of maximum transverse error of the tunnel breakthrough, which is 4.5 cm, the third plan of observations was adopted as the final plan, by which the breakthrough error of 3.5 cm was achieved. The adopted plan of observations includes planned measurements of horizontal directions, azimuths, and distances, with the assumed standard deviation of 1" for horizontal directions, 3.2 " for azimuths, and (1 mm; 1 ppm) for distances.

Keywords

• Local geodetic networks
• optimization
• Gauss Markov model
• preanalysis
• tunnel breakthrough precision