Expanded Longitudinal Deformation Profile in Tunnel Excavations Considering Rock Mass Conditions via 3D Numerical Analyses
Open Access
- 10 June 2021
- journal article
- research article
- Published by MDPI AG in Applied Sciences
- Vol. 11 (12), 5405
- https://doi.org/10.3390/app11125405
Abstract
In the convergence–confinement method, the longitudinal deformation profile (LDP) serves as a graphical representation of the actual tunnel convergence (both ahead of and behind the face); therefore, it is considered important for determining the distance of support installation from the face or the timing after excavation in this method. The LDP is a function of the rock mass quality, excavation size, and state of in situ stresses; thus, obtaining the LDP according to the rock mass conditions is essential for analyzing the complete behavior of convergence during tunnel excavation. The famous LDP shows that the best fit for the measured values of tunnel internal displacement reported simply expresses the ratio of the preceding displacement as approximately 0.3. This can lead to an error when predicting the ratio of the preceding displacement while neglecting the rock conditions; consequently, a complete tunnel behavior analysis cannot be realized. To avoid such error, the finite difference method software FLAC 3D is used to develop an expanded longitudinal deformation profile (ELDP) according to the rock mass conditions. The ELDP is represented by graphs featuring different shapes according to the rock mass rating (RMR), and the empirical formula of the LDP best fitted for the tunnel convergence measurement values is expanded. This expanded LDP formula is proposed in a generalized form, including the parameters α and β from the empirical equation. These parameters α and β are expressed as functions of the RMR and initial stress. Statistical analysis results of the 3D numerical analysis of 35 cases were analyzed in the ranges of α = 0.898–2.416 and β = 1.361–2.851; this result is based on the empirical formula of Hoek (1999) (α = 1.1, β = 1.7), which was expanded in the current study according to the rock quality and initial stress conditions.Keywords
Funding Information
- Korea Agency for Infrastructure Technology Advancement (21UUTI-B157787-02)
This publication has 7 references indexed in Scilit:
- Extension of tunneling quality index and rock mass rating systems for tunnel support design through back calculations in highly stressed jointed rock mass: An empirical approach based on tunneling data from HimalayaTunnelling and Underground Space Technology, 2018
- Review of Rock-Mass Rating and Tunneling Quality Index Systems for Tunnel Design: Development, Refinement, Application and LimitationApplied Sciences, 2018
- Plastic radii and longitudinal deformation profiles of tunnels excavated in strain-softening rock massesTunnelling and Underground Space Technology, 2012
- Improved Longitudinal Displacement Profiles for Convergence Confinement Analysis of Deep TunnelsRock Mechanics and Rock Engineering, 2009
- Effect of Poisson's ratio on the normalized radial displacements occurring around the face of a circular tunnelTunnelling and Underground Space Technology, 2003
- Application of the Convergence-Confinement method of tunnel design to rock masses that satisfy the Hoek-Brown failure criterionTunnelling and Underground Space Technology, 2000
- Contribution à la méthode convergence-confinement par le principe de la similitudeRevue Française de Géotechnique, 1991