STRESSED STATE OF A SYSTEM OF THREE PARALLEL TUNNELS WITHOUT DRAWING FROM OWN WEIGHT OF AN ANOTROPHONE ROCK MASSIF

Abstract

Objectives. The aim of the study is to carry out a parametric analysis of the stress state of an anisotropic rock massif on the contours of the workings of a system of three parallel circular tunnels without lining due to the mass of the massif, for various ratios of the elastic characteristics of the rock massif in orthogonal directions, and at different distances del transverse isotropic medium. Method. The calculation of a system of three parallel tunnels without a large extension lining, laid in a strong transversely isotropic rock massif, is reduced to the problem of plane deformation of the theory of elasticity for a transversely isotropic medium containing parallel workings. A model of a transversely isotropic medium (a special case of an anisotropic medium) is used, in which the rock massif in one plane has the characteristics of an isotropic medium (the isotropy plane), and in the perpendicular direction, characteristics different from the isotropic medium. The stress state was investigated by the finite element method using the ANSYS software package. The sizes and type of the finite element suitable for calculation on the basis of the solution in the program complex of the verification task were previously determined. The Kirsch problem was accepted as the verification problem. Result. The relative tangential stresses on the contours of three parallel tunnels were determined depending on the degree of anisotropy of the rock mass and depending on the distance between parallel tunnels. The influence of the distance between the tunnels on the stress state on the contours of three parallel tunnels was evaluated, depending on the degree of anisotropy.Conclusion. The results of a parametric analysis of the system of three parallel free-flow tunnels without lining, depending on the degree of anisotropy of the rock mass and the distance between the tunnels, show that the stress state is significantly affected by the degree of anisotropy of the elastic properties of the soil massif and the distance between the tunnels. When designing underground structures, it is necessary to take into account the anisotropy of the elastic properties of the soil mass. It is also necessary to determine in more detail the physical and mechanical properties of rocky soils and pay special attention to elastic characteristics. As studies have shown, taking into account transverse-isotropy and the distance between the tunnels leads to both an increase and a decrease in tangential stresses on the contours of parallel tunnels. At some ratios of elastic characteristics in orthogonal directions, regardless of the distance between the tunnels, there are no tensile stresses on the contours of the tunnels, which favorably affects the operation of the hydraulic tunnel.

Keywords

• deformation modulus
• poisson’s ratio
• transversely isotropic medium
• system of three parallel tunnels
• theory of elasticity