Boßler Tunnel: Influence of Rock Mechanics on the Tunneling Concept – Tendering and Execution

Credit/Quelle: DB Projekt Stuttgart–Ulm

1 Plan view of approval area (PFA) 2.2

Credit/Quelle: DB Projekt Stuttgart–Ulm

Credit/Quelle: WBI

2 Longitudinal section Boßler Tunnel

Credit/Quelle: WBI

3 Longitudinal section Boßler Tunnel, section in Brown Jurassic

Credit/Quelle: WBI

 4 Preliminary exploration, core photos of claystone interlayers of the Aalenium 2

Credit/Quelle: WBI

Credit/Quelle: WBI; Bochumer Eisenhütte Heintzmann

Squeezing rock mass and

yielding support

Credit/Quelle: WBI; Bochumer Eisenhütte Heintzmann

Credit/Quelle: WBI

6 Location of exploratory shaft and gallery

Credit/Quelle: WBI

7 Results of the uniaxial compressive tests on samples from ZOP/ZPU

Credit/Quelle: WBI

8 Horizontal bedding parallel discontinuity in the ZOP

Credit/Quelle: WBI

9 Exploratory shaft and gallery, detail of FE mesh

Credit/Quelle: WBI

10 Structural model of the Aalenium 2 and rock
mechanical parameters

Credit/Quelle: WBI

11 Eastern tube, photograph of the temporary face at tunnel meter 709.4

Credit/Quelle: WBI

Credit/Quelle: Arge Tunnel Albaufstieg

12 Longitudinal section with horizontal drillings at portal Buch

Credit/Quelle: Arge Tunnel Albaufstieg

Credit/Quelle: Bo-Ra-tec GmbH/Arge Tunnel Albaufstieg

13 Microgravimetric measurements at tunnel invert, measuring grid and execution

Credit/Quelle: Bo-Ra-tec GmbH/Arge Tunnel Albaufstieg

Credit/Quelle: Arge Tunnel Albaufstieg

14 Exploration drilling through segmental lining after tunnel heading

Credit/Quelle: Arge Tunnel Albaufstieg

Credit/Quelle: WBI/Arge Tunnel Albaufstieg

15 Cross-section with segmental lining division

Credit/Quelle: WBI/Arge Tunnel Albaufstieg

Credit/Quelle: WBI

16 Special segments with grouting nozzles for sealing structures

Credit/Quelle: WBI

Using the example of the Boßler Tunnel, the importance of careful rock mechanical investigations for the excavation concept of a tunnel is shown. The preliminary exploration revealed that squeezing rock conditions were to be expected in the middle section of the tunnel. In another tunnel section, karstification had to be expected. Towards this background, the tunnel was tendered for construction with conventional means (“shotcrete method”). Along the first 2.8 km, the use of a TBM was permitted. By driving an exploration shaft and gallery combined with accompanying rock mechanical investigations and numerical calculations, it was possible to create the basis for allowing for a TBM-excavation in the entire formation of the Brown Jurassic. In addition, the program for karst exploration was adapted to the requirements of a TBM heading.

1 Introduction

In the following, the importance of careful rock mechanical investigations for the excavation concept of a tunnel will be shown using the example of the Boßler Tunnel. On the basis of the results, it was possible to excavate a tunnel with a tunnel boring machine over its entire length, though the tender had limited TBM excavation to a minor length and predominantly foreseen conventional excavation.

2 Project

The 8.8 km long Boßler Tunnel consists of two tubes arranged at a distance of 30 m with circular cross sections and an inner diameter of approx. 10 m. The tunnel forms part of...