Discontinuity Controlled Deformation Estimation in Small Diameter Tunnels

Abstract

Tunnel projects are carried out in tunnel construction by evaluating the soil and rock profiles obtained from the exploration drillings along the route, groundwater level, and structural elements. In practice, there are some differences between the geological sections foreseen according to the exploration drillings and the structural elements encountered during tunnel construction. This study has modeled a tunnel, through intermediate to weak and very weak rocks, between Ankara and Istanbul, obtained the deformation amounts by numerical analysis. To get the principal stresses, deformation forces, and surface settlements on the tunnel lining in each excavator were used Phase2D. The total displacement amounts were calculated with the numerical analysis. After, during tunnel manufacturing, were measurement deformations to control projects' adequacy. Thus, the results of the analysis and deformation amounts encountered during the tunnel between Ankara and Istanbul opened were compared. At the end of the study, when the discontinuity properties are taken into account in the calculation, it was seen that the deformations obtained and the deformations obtained from the numerical analysis gave very close values. As a result, it was concluded that discontinuity data that was not seen at the project stage for cost-effective tunnel design in tunnels should be collected and added to the analysis as much as possible. It was concluded that corrections should be made in the support system during the manufacturing studies with the back analysis method. © 2022, TUBITAK. All rights reserved.