Deconfinement Level Assessment for Open face Tunneling, Part 1

In part one, we will focus on modeling a cable-reinforced tunnel that is conventionally driven through sandy rock formation in PLAXIS 3D and discuss the series of geo-structural responses that serve as a basis for the next stage workflow in PLAXIS 2D, where a calibration of deconfinement level takes place.

Estimation of the support required to stabilize a tunnel excavation, especially in the vicinity of the face, is essentially a four-dimensional problem. Time-dependent weakening of the rock will compound the three-dimensional redistribution of forces around the excavation. Given these constraints, it is valuable to have a general but still relatively simplified appreciation of the nature of the interaction between the rock mass and the installed support. The Convergence-Confinement method is a basic and commonly used tool for underground support structures in conventional tunneling during the preliminary stages of design. It was initially an analytical method for circular tunnels. Based on the analysis of stresses and strains around a tunnel, the Convergence-Confinement method provides insight into the interaction between the support and the ground by means of a plane-strain model of the tunnel excavation. It provides meaningful numerical results in a 2D analysis framework.

Prerequisites: PLAXIS 3D installed

Duration: 2 hours

Presented by: Xing-Cheng Lin