Week 8 Tunnelling & TBM Course: Jet Grouting & Forepoling

Week 8 (10th March to 14th March) of the Tunnelling and TBM course was dedicated to Ground Reinforcement using Jet Grouting and Steel Pipe Umbrella. Prof. Peila explained us the recent trends and the commonly used methods for the design of Steel Pipe Umbrella as Tunnel Supporting structure.

Two main design approaches of Steel Pipe Umbrella were discussed:

1. Equivalent 2D model by considering each Steel Pipe individually deducing bending moment and reaction forces (as shown below):

More on this topic to be discussed in future blogs.

2. 2D Numerical Model, by considering an area of improved Geomechanical properties. This topic is discussed in Hoek's 2000 Terzaghi Lecture (more details here)

3. 3D Model by modelling individual elements in rockmass.

During this week, we also had an opportunity of hands-on experience with the Rock testing, Prof. Peila organized a visit to Rock Mechanics Laboratory in Politecnico di Torino.

Shear Test on Discontinuities

High Pressure Triaxial Apparatus (HPTA)

Triaxial Apparatus for Gravels

Geothermal Model

References:

[1] Oreste, P. P., and D. Peila. "A new theory for steel pipe umbrella design in tunneling." Tunnels and Metropolis. Proceedings of The World Tunnel Congress on Tunnels and Metropolises. Vol. 2. 1998.

[2] Pelizza, Sebastiano, and Daniele Peila. "Soil and rock reinforcements in tunnelling." Tunnelling and underground space technology 8.3 (1993): 357-372.

[3] Peila, D., and S. Pelizza. "Ground reinforcing for tunnelling the example of Steel pipe umbrella." AITES-ITA Training Course Tunnel Engineering. Istanbul, Turkish (2005).

[4] E. Hoek, “Big Tunnels in Bad Rock - 2000 Terzaghi Lecture,” ASCE J. Geotech. Geoenvironmental Eng., vol. 127, no. 9, pp. 726–740, 2001. (PDF is shared in Hoek's corner, here)