Engineering geological investigations of T-11 tunnel along Burdur-Antalya high-speed railway

Abstract

Tunnels are underground structures constructed by cylindrical boring of the rock masses with certain proportions and methods. One of these methods is the new Austrian tunnelling method (NATM). The first and most important principle of this method is to preserve the strength of the rock mass and form a supporting circle in the surrounding rock mass around the tunnel. This method enables the construction of the tunnel to be both safe and economical. This paper aims to analyse geological and geotechnical properties of the 2045-m-span T-11 tunnel, which is planned to be constructed within the scope of Turkey Burdur-Antalya high-speed railway project. In this study, the data from borings LB (Lithology Borehole)-501, TB (Tunnel Borehole)-18, CB (Cut Borehole)-19 and discontinuity measurements were used. The laboratory results of these borings were also analysed. In total, five on-site discontinuity measurements were used in Dips v5.0 to generate the required data. The acquired data was used to analyse whether the limestone will be stable or unstable in the case of tunnel boring. The results of the analysis suggest that unstabilities are not expected. Evaluation of rock masses regarding the tunnel entrance was executed. In this study, the rock masses were evaluated with only rock mass rating (RMR) calculation. In order to compute RMR values, LB-501 boring data were used to calculate the uniaxial compressive strength and average point load strength. The limestone unit of Beydaglari Formation had an RMR value of 35 and was classified as a poor rock.