Analytical-Based Assessment of Effect of Highly Deformable Elements on Tunnel Lining Within Viscoelastic Rocks

Abstract

The utilization of highly deformable elements in lining has been proved to be an effective measure to control large deformations occurring in tunnels excavated in severe squeezing rocks. However, there exists no practiced method to transfer these benefits into engineering design. In this paper, the effect of highly deformable elements on tunnel responses is analytically conducted. The whole deformation of lining is divided into two parts to process, consisting of the first deformation of highly deformable elements and then that of segmental lining. Viscoelastic analytical solutions for lining pressure and tunnel displacement in the two deforming stages are derived, respectively. In addition, the analytical solutions are validated by comparing the predicted results with corresponding existing solutions. Good agreements between them can be achieved. Furthermore, a parametric investigation on the influence of highly deformable elements on tunnel performance is carried out. Results show that in linear viscoelastic rocks, there exists a linear relationship between lining pressure or tunnel displacement and length of the highly deformable elements with their numbers in lining remaining constant. The same lining pressure or tunnel displacement can be achieved under the condition of equal total length of highly deformable elements. Lining pressure or tunnel displacement linearly changes with Young’s modulus of highly deformable elements as well. This paper can provide a new trail to quickly and reliably evaluate the response of a tunnel where highly deformable elements are applied.