Analytic solutions for twin tunneling at great depth considering liner installation and mutual interaction between geomaterial and liners

Abstract

• Analytical solutions for twin tunneling are presented. • Solutions are valid for (1) newly constructed twin tunneling; (2) single tunneling influencing an existing tunnel. • Solutions are valid for the whole twin tunneling process (4 stages). • Twin tunnels with arbitrary geometry and arbitrary liner properties are considered. Analytic solutions for stress and displacement of twin tunneling at great depth considering liner installation and mutual interaction between geomaterial and liners are the key context in this paper. Twin tunneling is a continuous procedure, in which after one tunnel is excavated and lined, the other one is hysteretically excavated and lined. The presented solutions mainly focus on stress and displacement in geomaterial and liners for the hysteretical phases through an iterative combination of the complex variable method and the Fourier transform via the Schwarz alternating method. The presented solutions are verified by comparing to a corresponding numerical solution of a general case, in which a good agreement is observed after three iterations. Subsequently, a dimensionless parametric investigation is performed to investigate the influence of tunnel geometry (including twin tunnel spacing, relative angle of twin tunnels and relative size of twin tunnels), liner properties (including liner thickness and liner installation), and lateral stress coefficient on stress and displacement in both liners and geomaterial.