Investigating High-Strength Expanded Polystyrene (HS-EPS) as yielding support elements for tunnelling in squeezing ground conditions

Tunnelling and Underground Space Technology, vol. 140, pp. 105261

Abstract

Tunnelling conditions characterized by large and long-term deformations demand yielding support elements as a part of the shotcrete lining. The yielding support elements transform radial displacements into a tangential closure without compromising the lining system's support capacity and avoiding micro-cracking and overstressing of the shotcrete during the curing process. While products available on the market are satisfactory in performance, they are often heavy, difficult to handle on-site, and hence time-consuming for installation. A novel lightweight yielding support element made out of High-Strength Expanded Polystyrene (HS-EPS) is introduced to overcome these operational drawbacks. Unconfined compression tests on small- and large-scale samples were carried out to investigate the HS-EPS strength and deformation characteristics. Further, the combination of several HS-EPS panels with different stiffness properties allows the specific design of a yielding support element with optimum stress–strain behaviour for minor to severe squeezing conditions. Finally, deformation analyses with stress–strain curves and Digital Image Correlation (DIC) were carried out, and suggestions for the practical application on-site are given.

Authors 5

1. Manuel Entfellner corresponding
   Affiliation as printed

   Implenia Austria GmbH, Innsbrucker Bundesstrasse 67, 5020 Salzburg, Austria

2. Pooya Hamdi Aachen Department of Engineering Geology and Hydrogeology

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Department of Engineering Geology and Hydrogeology, Lochnerstrasse 4-20, 52064 Aachen, Germany

3. Xiaoyue Wang Aachen Department of Engineering Geology and Hydrogeology

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Department of Engineering Geology and Hydrogeology, Lochnerstrasse 4-20, 52064 Aachen, Germany

4. Helmut Wannenmacher
   Affiliation as printed

   Implenia Austria GmbH, Innsbrucker Bundesstrasse 67, 5020 Salzburg, Austria

5. Florian Amann Aachen Chair of Engineering Geology & Hydrogeology

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Chair of Engineering Geology and Hydrogeology, Lochnerstrasse 4-20, 52064 Aachen, Germany