The Italian Art of Tunnelling

Literature survey will show that the fundamentals of modern tunnelling were already well understood during 19th and 20th century. The basic processes were almost completely understood by then and the only actual innovations have been in the use of new materials (shotcrete, high-strength steel, steel fibre reinforcements, admixtures, etc).

Based on the country of origin and underlying principles, there have been many classification of "tunnelling methods". It is quite obvious that differentiation of various "tunnelling methods" is sometimes difficult and they often overlap with each other. More often, a combination of "methods" offers an optimal solution for the problem at hand. However, for the case of classification, the classical tunnelling methods can be broadly divided into:

• German Tunnelling Method - Core method
• The English Tunnelling Method - Longitudinal beam/ trestle method
• Belgian Tunnelling Method - Underpinning method
• The (old) Austrian Tunnelling Method - Upraise tunnelling
• The New Austrian Tunnelling Method (NATM) - Thin-walled support to relieve ground pressure
• The Italian Tunnelling Method - ADECO-RS (Lunardi Method)

This post covers some salient points of the Italian tunnelling method.

Italian - Packing method in squeezing condition [4]

Traditionally, the Italian tunnelling method referred to packing method. It is used to overcome very difficult geological conditions (strongly squeezing rock with water ingress). Excavation is done in parts with immediate installation of packing material (even within the finished dimension of tunnel) and later broken out after ring closure. Later, the tunnelling method developed by Dr. Lunardi and Prof. Pelizza was referred as New Italian method, which was called ADECO-RS (Analysis of COntrolled DEformation in Rocks and Soils). The intention was to develop a process, which can conter the disadvantages of the NATM in regard to safety and cost-effectiveness in squeezing ground conditions.

While the Austrian method calls for partial excavation to increase face stability, the Italian method advocates full face excavation but with advance face support using methods like glass fibre anchors, jet grouting etc. This results in early ring closure than with the excavation of the entire cross-section in parts and keeps the deformation of the rock mass low. In addition, it also permits the use of large and powerful machines and hence faster production rates.

Lunardi [3] summarizes that the ADECO-RS approach emphasis to:

• Analyse the deformation response of the ground both ahead of and down from the face (using experimental, full scale, numerical, empirical tools etc)
• Controlling the susceptibility to deformation of the ground ahead of the face (advance core) by using appropriate stabilization techniques (various face stabilization techniques proposed in Dr. Lunardi's paper are shown below).

Choice of face stabilization methods [4]

While it may seem very similar to the New Austrian Method of measurement and control, Lunardi [3] clearly summarizes the difference in design and control using the pictures below:

Difference in analysis approach

Difference in control approach

Elaborate explanation about ADECO-RS method is given in Dr. Lunardi's book [1].

References:
[1] P. Lunardi, Design and Construction of Tunnels: Analysis of Controlled Deformations in Rock and Soils (ADECO-RS). Springer, 2008.

[2] Pelizza, S.; Peila, D.: Soil and Rock Reinforcements in Tunnelling. In: Tunneling and Underground Space Tech. 8 (1993), No. 3, S. 357–372.

[3] P. Lunardi, “The design and constrution of tunnels using the approach based on the analysis of controlled deformation in rock and soils,” Tunnels & Tunnelling International, no. May, pp. 3–30, 2000.

[4] Maidl, Bernhard, Markus Thewes, and Ulrich Maidl. Handbook of Tunnel Engineering I: Structures and Methods. Vol. 1. John Wiley & Sons, 2013.