C-Tunnel: a Cetu-itech software
C-Tunnel is the result of the collaboration between CETU, the French research centre dedicated to the design, construction, maintenance and operational management of road tunnels, and itech, professional in FEM calculations and distributor of CESAR-LCPC, the software package dedicated to Civil Engineering computation.

The dedicated field of application of C-Tunnel is the pre-design of tunnels. It was developed to responds to two main issues identified by the CETU:
  • the pre-design of tunnels may require the analysis of a great number of alternative scenarios,
  • the large majority of preliminary studies can be performed on a restricted number of standard geometries.
C-Tunnel: software using CESAR-LCPC solver
C-Tunnel is a new product that is using CESAR-LCPC solver. It allows geotechnical engineers to automate most of the steps of the model generation process, from the definition of the tunnel geometry to the publishing of the report.

The usual modelling steps specific to the finite element method such as meshing, definition of the boundary conditions and application of the loads are here fully automated and according to finite element best-practice.
C-Tunnel: a very simple wizard
Selection of standard tunnel sections depending on the need for reinforcement, bottom slab…
Selection of standard tunnel sections
depending on the need for reinforcement, bottom slab…


Automatic meshing
 Automatic meshing
  description d'une section type The model definition is quick and easy:

  • 1st step: Selection of a standard tunnel section from a wide range of possible templates.

The definition of the geometry is parametric. An optimal finite element mesh is automatically generated.

Toolbox for parameter setting of the model
Toolbox for parameter setting of the model

  • 2nd step: Input of material properties: Soil, reinforced soil, lining, support, lateral pressure coefficients and long-term effect coefficient.

  • 3rd step: Input of the confinement loss coefficient "lambda": user defined or assessed using C-Lambda, the specific tool based on the "convergence-confinement" method.
C-Lambda: convergence-confinement method
C-Lambda : module convergence-confinement The module "convergence-confinement", linked to C-Tunnel, has been designed in relation with the CIH department of EDF (French electricity provider). It may also be used as a separate module. The convergence curve of the soil is assessed by selecting one of the four following material behaviors :

  • Mohr-Coulomb.
  • Mohr-Coulomb with softening,
  • Hoek et Brown.
  • Hoek and Brown with softening.

The displacement curve at the time of the support installation is defined from one of the two following methods:

  • Elastic method (AFTES).
  • Similarity principle

méthode élastique, méthode de Corbetta Based on geometrical data and material properties, the convergence-confinement curves are calculated and plotted in the toolbox .

   C-Lambda : module convergence-confinement
C-Tunnel: a dedicated software
Extract from a C-Tunnel report Extract from a C-Tunnel report
  

C-Tunnel : note de calcul C-Tunnel Beyond its great user-friendliness, its fit-for-purpose design makes of C-Tunnel an extremely valuable tool for all the professionals of the tunnelling industry.

In particular, the presentation of the results in an automatically generated report ensures reliability and saving of time.

Result overview is presented in the following format:

  • Charts of displacements and stresses in the soil; charts of displacements, stresses and forces in the lining and the support in given tunnel sections;
  • Graphs presenting the deformed mesh, stress tensors and plastic zones;
  • Curves of displacement normal to the tunnel wall and of the efforts in the lining and the support.

For support and lining design, the non-reinforced concrete criterion of AFTES (French professional Tunnel Society) is introduced.
C-Tunnel : hauteur du piédroit, cohésion du sol, épaisseur du soutènement  The software C-Tunnel is an easy-to-use and didactic product. It allows carrying out parametric studies in a simple and accurate manner. The varying parameter may be a geometrical property or a material property, for instance the height of the abutment, the soil cohesion or the lining thickness, etc.

C-Tunnel is also a good starting point to initiate students or qualified engineers to the application of the Finite Element method to a practical design problem.