Verification and Comparison of Direct Calculation Method for the Analysis of Support–Ground Interaction of a Circular Tunnel Excavation

Abstract

A direct algorithmic process can deal with the solution of the support–ground interaction in a circular tunnel excavation through the convergence-confinement method (CCM) with the concept of increment. This process is the so-called direct calculation method (DCM) that can find solutions, the mobilized support pressure and the convergence, in the analysis of CCM. To achieve the solution, using two linear equations in the elastic region and Newton’s recursive method to find the roots in the plastic region are proposed and realized by a calculated spreadsheet. The validity of the algorithmic process for the analytical solutions was investigated and verified by the finite element computation, and compared with the published results, Rocksupport (2004), Oreste (2009), and Gschwandtner-Galler (2012). The results obtained between DCM and related studies show no significant differences.

An Improved Incremental Procedure for the Ground Reaction Based on Hoek-Brown Failure Criterion in the Tunnel Convergence-Confinement Method

“…The increase in stress can be accounted for as part of the stress gradient using confinement losses. (7) The proposed incremental procedure can deal with the influence of the nonlinear failure criterion of rock mass and can not only be a useful tool for the analysis of circular tunnels in an isotropic stress state but may also be applied to the simulation of the ground behavior of the tunnel under anisotropic stress conditions in the next stage of research. However, this method also has its limitations; namely, the CCM analysis can only be used for the excavation of circular deep tunnels.…”

“…That is to say, the impact of the unsupported distance on the advancing excavation of the working face is to consider the changes in stress and displacement caused by a certain observation section in the front after the continuous excavation of the tunnel. Based on the relevant basic research [6,7], using the tunnel convergence measurement data, a statistical regression analysis is used to establish a function related to the effect of tunnel face advancing excavation and to estimate the confinement loss. The function of this confinement loss curve (CLC) is shown in Figure 2.…”

“…This is an important principle and concept used in the theory of the convergence-confinement method. The change in this stress can be described by the following expression [6,7]:…”

“…When a tunnel is excavated, the primary stress in the rock mass is redistributed, causing the rock to deform and converge toward the opening. This convergence can lead to displacements, deformations, and potentially unstable conditions if not properly controlled [6][7][8][9].…”