Stresses in the concrete lining of tunnels located in heterogeneous mountain massifs

Abstract

The presented studies confirmed stress formation patterns in concrete supports, which are the sum of gravitational, tectonic, and variable components, especially in areas with active geodynamics. The problem of the underground workings lining reliability is due to the need to solve problems of determining the stress-strain state level, taking into account all the listed components of the forces and the concrete lining strength properties. The main stress parameters in the transport tunnel support are determined using the unloading deformations. For unloading, a borehole is drilled with core sampling. In the drilling process, linear deformations of the core are measured in three directions, for which a delta socket of strain gauges is installed on the concrete lining surface. The core taken from the borehole is also used to determine the actual concrete strength class and modulus of elasticity. Principal deformations and principal stresses are determined analytically. As a result of the measurements, were identified tunnel sections that work mainly on rock pressure and sections with a significant contribution of horizontal stresses, and a relationship was also established between the main stresses of the lining and the tectonic fault cracks trajectories in the mountain massif. In practice, it is proposed to take into account when designing the contribution of horizontal tectonic components and variable stresses, determined with special scientific support, and, accordingly, reinforce the concrete lining. During operation in areas with active geodynamics, to ensure reliability and lining safety, it is recommended to use automated deformation control of changes in its stress-strain state.