For this tutorial, we’ll use the relationship proposed by Vlachopoulos and Diederichs. The first step is to determine the amount of tunnel wall deformation prior to support installation. If any of these conditions are not met, choose a different support system and run the analysis again. Add the support and determine whether a) the tunnel is stable, b) the tunnel wall deformation meets the specified requirements, and c) the tunnel lining meets certain factor of safety requirements. Build a model that relaxes the boundary to the calculated amount in step 2 using either an internal pressure or modulus.Using either the internal pressure reduction method, or the modulus reduction method, determine the internal pressure or modulus that yields the amount of tunnel wall deformation at the point of and prior to support installation.Determining this deformation can be done using either a) observed field values, b) numerically from 3D finite-element models or axisymmetric finite-element models, or c) by using empirical relationships such as those proposed by Panet or Vlachopoulos and Diederichs. As a tunnel is excavated, there is a certain amount of deformation, usually 35-45% of the final tunnel wall deformation, before the support can be installed. Determine the amount of tunnel wall deformation prior to support installation.To design a support system, the following three steps must be performed: The goal of this tutorial is to design a reinforced concrete lining with a factor of safety greater than 1.4. The support is to be installed 2 m from the tunnel face. To compute the rock mass deformation modulus, the modulus ratio (MR) is assumed to be 400. The strength of the Schist can be represented by the Generalized Hoek-Brown failure criterion with the uniaxial compressive strength of the intact rock equal to 50 MPa, the GSI equal to 50, and mi equal to 10.

The major principal stress is horizontal, and the minor principal stress is vertical. The in-situ stress field has been measured with the major in-plane principal stress equal to 30 MPa, the minor in-plane principal stress equal to 15 MPa, and the out-of-plane stress equal to 25 MPa. Application of Joint Networks (with XFEM)Ī circular tunnel of radius 4 m is to be constructed in Schist at a depth of 550m.Effects of Thermosyphon on Shallow Foundation.3D Tunnel Simulation using Core Replacement.Drawdown Analysis for Tunnel Excavation.

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