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Tutorials for the Stabfront module

Read the general Stabfront manual here.

Consideration is given to a horseshoe-shaped abutment gallery. With a height of 4.5 meters and a width of 2.6 meters, the area of the face is equal to 11.4 m². No water table is considered, a surcharge of 20 kPa is applied at the surface, and the key is at the elevation of 37.9 NGF. The tunnel is excavated using the traditional method with an overbreak of 1.3 meters. A cohesive-frictional soil is considered, with the following horizons:

Name \(z_{top}~[mNGF]\) \(\gamma_{sat}~[kN/m^3]\) \(c'~[kPa]\) \(\varphi'~[°]\)
R 45.5 18 0 30
COL 40.05 21 25 35
MC 36.5 21 20 25
  1. Open the Stabfront tool from the Sandbox menu or from a project.
  2. Go to the Data tab, then the General Data sub-tab.
  3. Choose Traditional as the excavation method, then select a horseshoe-shaped tunnel. Adjust the overbreak and surface surcharge.
  4. Fill in the given dimensions and ensure that the 3D display has been updated.
  5. Adjust the key elevation to the given value. An error message will appear; this is normal as the ground has not been adapted to this elevation yet.
  6. Go to the Soil Settings sub-tab and modify this line to match the "R" layer. Verify that the error message has disappeared and that the 3D display is relevant again.
  7. Add a second layer using the "+" button below the table. Complete the new row with the "COL" horizon. Change the color.
  8. Repeat the operation with the "MC" horizon. Ensure that all three layers appear in both the 3D view and the stratigraphy.
  9. Go to the Water sub-tab and verify that the table is empty.
  10. Switch to the "Data Table" view: the various parameters are those entered, and automatic parameters can be consulted (coefficient set: Terzaghi & Jelinek (1954)).
  11. Go to the Calculation tab and run the program.
  12. Go to the Results tab. The Mechanisms sub-tab appears with two "half-bell" curves. The maximum is reached for approach 3, with a value of 47.8 kPa.

Consideration is given to a circular service gallery with a diameter of 2 meters. The water table level is at 29 NGF, a surcharge of 20 kPa is applied at the surface, and the key is at an elevation of 26 NGF. The tunnel is excavated using the traditional method with an overbreak of 0.5 meters. A cohesive-frictional soil is considered, with the following horizons:

Name \(z_{top}~[mNGF]\) \(\gamma_{sat}~[kN/m^3]\) \(c'~[kPa]\) \(\varphi'~[°]\)
R 39 18 0 30
A 37 19 7 0
S 31 20 1 25
  1. Open the Stabfront tool from the Sandbox menu or from a project.
  2. Go to the Data tab, then the General Data sub-tab.
  3. Choose Traditional as the excavation method, then select a circular tunnel. Adjust the overbreak and surface surcharge.
  4. Fill in the diameter and a failure dihedron as a "rectangle with the same area", and then verify that the 3D display has been updated.
  5. Adjust the key elevation to the given value. An error message will appear; this is normal as the ground has not been adapted to this elevation yet.
  6. Go to the Soil Settings sub-tab and modify this line to match the "R" layer. Verify that the error message has disappeared and that the 3D display is relevant again.
  7. Add a second layer using the "+" button below the table. Complete the new row with the "A" horizon. Change the color.
  8. Repeat the operation with the "S" horizon. Ensure that all three layers appear in both the 3D view and the stratigraphy.

  9. Go to the Water sub-tab, choose the description based on hydraulic head, and add two lines for elevations 39 NGF and 24 NGF. Assign them a head of 29 NGF. The chart is updated accordingly.

    Nota

    If the description mode is changed after entering these parameters, they are converted into the pressure system, and vice versa.

  10. Switch to the "Data Table" view: the various parameters are those entered, and automatic parameters can be reviewed (coefficient set: Terzaghi & Jelinek (1954)).

  11. Go to the Calculation tab and run the program.
  12. Go to the Results tab. The Mechanisms sub-tab appears with two "bell-shaped" curves. The maximum is reached for approach 3, with a value of 5.83 kPa.