Theoretical modeling of the pre-cutting system performance for the tunnel face stability in very weak rock masses

Abstract

By forming continuous pre-lining around the tunnel's perimeter, pre-cutting is a recognized tunneling technique that enables full-face excavation of a tunnel even in unfavorable ground conditions. In this study, a theoretical method is put out to simulate the performance of this kind of pre-support in squeezing conditions. The loading distribution on the pre-cutting shells is determined for this purpose using the LDP of an unsupported tunnel, and the non-linear stiffness of the pre-cutting shell is then determined using the shell theory. The convergence confinement method is used to calculate how much the pre-supported tunnel isdeformed. The non-uniform loading distribution also results in the tangential and longitudinal bending moments on the pre-cutting shell. To show the effectiveness of pre-cutting shells in extremesqueezingconditions, several examples are solved. As a result, a few graphs for the preliminarydesign of a tunnel using this technique are given. The graphs show the overall tunnel displacement for various pre-cutting shells under various geological conditions. The outcomes demonstrate good agreement between FALC 3D resultsand the ones by thesuggested analytical model. A preliminary design can be made using the assessment of the proposed methodonthe loads on the pre-cutting system.