Week 6 Tunnelling & TBM Course: Shotcrete and Lining Design

Week 6 (24th Feb '14 to 28th Feb '14) of 2nd Level specializing course in Tunnelling and TBM was on Shotcrete and Design of lining, including the use of support interaction capacity curves. Majority of this week's time was spent on understanding the evolution of design philosophy for tunnel liners using shotcrete and steel-sets. 

Initial Support & Lining System Used in Current Practice [1]

It is understood from the above figure that the application of Shotcrete + Steelsets is used for wide range of ground conditions and is one of the most widely used support system. 

Concepts of three main design methods: Distributed ground pressure approach, subgrade reaction approach and Ground-support interaction approach were discussed. The paper on composite supports (Steel-sets + Shotcrete) by Hoek's research group (Carranza-Torres et al) [2] was helpful in understanding the concepts of Capacity diagrams.

Other paper which was reviewed during this week was Oreste (2007) which is on Hyperstatic reaction (numerical method) to simulate interaction between the support and rock surroundings using springs. Based on several calculation using Hyperstatic Reaction Method (HRM), design tables are presented for dimensioning support system (with Steel-sets + Shotcrete).

For complete understanding of shotcrete usage and admixtures used, we had invited lectures by  Mr. Enroco Dal Negro, Carlo Pistolesi and Cristiano Maltese (from Maipei) on practical aspects of shotcrete use in a site and on Concrete Technology.

Also during this week,  we had a special lecture by Mr. Juha Kukkonen (from Sandvik) on Drilling Jumbos and tools. This is in continuation with the Drill and Blast lecture series which was covered during Week 4 of this course.

Mr. Juha Kukkonen and Mr. Giovanni De Mattia from Sandik

References:

[1] Transportation Research Board (2006). "Making Transportation Tunnels Safe and Secure", NCHRP Report 525, Vol. 12.

[2] Carranza-Torres, C., and M. Diederichs. "Mechanical analysis of circular liners with particular reference to composite supports. For example, liners consisting of shotcrete and steel sets." Tunnelling and Underground Space Technology 24.5 (2009): 506-532.

[3] Oreste, P. P. "A numerical approach to the hyperstatic reaction method for the dimensioning of tunnel supports." Tunnelling and underground space technology 22.2 (2007): 185-205.