Tunnelling simulated by the convergenceconfinement method in PLAXIS 2D

Question

Good morning. 
 On 17.01.2023 I followed the Coffee Corner: "Geotechnical Analysis (AM) - Tunneling simulated with the convergence-confinement method in PLAXIS 2D". 
 First of all, I congratulate you on the course which I think is very interesting. 
 I would like to ask questions: 
 1) Where can I find the file showing the example used in "Demonstration"? 
 2) It is indicated that in order to calculate the tunnel deformation before support installation taking into account the 3D arching effect, empirical formulas based on the work of Vlachopoulos ad Dierichs (Hoek et al. 2008) are used; where can I find this article? 
 3) The example is carried out considering a weightless ground and inserting vertical and horizontal stresses; Is the method used still applicable by inserting instead a ground having a weight and not inserting the vertical and horizontal tensions? 
 Thank you

Vasileios Basas · Answer

Hi Luigi, 
 I am thrilled to hear that you found the topic interesting! Regarding your questions: 
 
 The example shown in the Coffee Corner was taken from a course exercise. Unfortunately, we don't usually share those projects online. However, it should be relatively easy to recreate the model by following the steps shown in the recording. 
 I am referring to work by Vlachopoulos and Diederichs (2009). You can find their paper titled "Improved Longitudinal Displacement Profiles for Convergence Confinement Analysis of Deep Tunnel". Rock Mechanics and Rock Engineering. 42. 131-146. 10.1007/s00603-009-0176-4. 
 You absolutely can! The example shown in the presentation followed a stress field analysis with &sigma;1 = 30MPa and &sigma;3 = 15MPa. To achieve those principal stresses using the self-weight of the rock/soil, you would typically need an enormous model, as the tunnel would have to be buried at a much greater depth. However, This is not always optimal. In case you want to do something similar, you can follow the suggestion described in this forum question .