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Tutorials for the Tunren Module

You can find the general Tunren manual here.

Tutorial 1: Short-term tunneling in a Mohr-Coulomb material

On is considering a tunnel with a radius \(R=4\) m. The initial isotropic stress is set at 1 MPa, and the temporary support considered consists of HEB200 (\(E=210 000\) MPa , strength limit at 240 MPa, safety factor of 0.75) and 25 cm of shotcrete (\(E_{CT}=10 000\) MPa) MPa, \(\nu_b=0.2\), strength of 25 MPa, and safety factor of 0.67). The support is applied in passes of 1.5 m, positioned 25 cm from the face.

The characteristics of the ground are as follows:

| Parameters | Value | |-----------|--------| |$E$ (MPa) |400 | |$\nu$ |0.25 | |$c$ (kPa) |90 | |$\phi$ (°) |34 | |$\psi$ (°) |0 |

We also choose to work based on Panet's LDP (1995) and with the implicit method of Nguyen-Minh & Guo.

  1. Open Tunren and go to the Data tab.
  2. Expand the Calculation Options accordion. Choose a determination of \(\lambda_d\) based on a longitudinal profile if it's not already the case, and select Panet's LDP from the dropdown menu. Activate the Nguyen-Minh & Guo implicit method by checking "Yes."
  3. Expand the General Data accordion. Enter the values for initial stress, distance to the face at the support installation \(d_1\), advancement step, and excavated radius. Choose to calculate the unsupported distance based on the mean displacement.
  4. Expand the Terrain accordion. Choose a Mohr-Coulomb behavior law and complete the parameters.
  5. Expand the Reinforcement accordion. Check "Concrete ring" and "Metallic hangers." Provide the information. The spacing of the hangers corresponds, in our exercise, to the advancement step. Choose the HEB200 profile from the dropdown list.

At this stage, the calculation is completed (it is updated as you go along). Users can then extract the data they want from the image and tables, or generate their report from them.

Tutorial 2: moving from the short to the long term

"We are focusing on a tunnel with a radius of \(R=8\) m. The isotropic initial stress is set at 0.75 MPa, and the support/lining is considered to be made of a concrete ring. The ring has a thickness of 40 cm. Its Poisson's ratio \(\nu\) is set to 0.2, and a safety factor of 0.667 is considered. The short and long-term Young's modulus is taken as 20000 MPa and 10000 MPa, respectively. For the concrete strength, it varies from 19 MPa to 12 MPa. The advancement step is 2m, with a minimum unsupported distance of 20cm."

The ground has the following characteristics:

| Parameters | Value CT | Value LT | |-----------|-----------|-----------| |$E$ (MPa) |500 |300 | |$\nu$ |0.25 |0.25 | |$c$ (kPa) |50 |40 | |$\phi$ (°) |30 |25 | |$\psi$ (°) |0 |0 |

We also choose to work with the Vlachopoulos & Diederichs LDP and the implicit method of Nguyen-Minh & Guo.

Note

The implicit method directly affects only short-term equilibrium: its purpose is to consider the effect of support at the back of the face on displacements (at installation and equilibrium). In the long term, its only influence corresponds to the choice of the initial point: short-term equilibrium.

  1. Open Tunren and go to the Data tab.
  2. Expand the Calculation Options accordion. Choose a determination of \(\lambda_d\) based on a longitudinal profile if it's not already the case, and select the Vlachopoulos & Diederichs LDP (2009) from the dropdown menu. Activate long-term calculation and the Nguyen-Minh & Guo implicit method by checking "Yes" for both options.
  3. Expand the General Data accordion. Enter the values for initial stress, distance to the face at the support installation \(d_1\), advancement step, and excavated radius. Choose to calculate the unsupported distance based on the mean of the distances.
  4. Expand the Ground accordion. Choose a Mohr-Coulomb behavior law and complete the CT (short-term) and LT (long-term) parameters.
  5. Expand the Reinforcement accordion. Check "Concrete ring." Provide information for both short-term and long-term considerations.

Note

If the maximum allowable long-term support pressure (LT) is less than the value reached at short-term (CT), a horizontal line is drawn at the limit value between the short-term equilibrium displacement (CT) and the intersection with the long-term GRC (Global Resultant Curve). In this case, it occurs when the thickness is set to 20cm.