Lötschberg Base Tunnel, Second Tube: Automated Cost Optimization of the Inner Lining

Credit/Quelle: BLS Netz AG

1 Layout of the Lötschberg Base Tunnel

Credit/Quelle: BLS Netz AG

Credit/Quelle: BLS Netz AG, Gruner AG

2 Photo from inside the tunnel (left) and visualisation of the triangular meshing from the 3D scan (right)

Credit/Quelle: BLS Netz AG, Gruner AG

3 Schematic section with two extreme values for the width of the insert

Credit/Quelle: BLS Netz AG, Gruner AG

4 Visualisation of the concept of subdivision of the enveloping into slices (a) and the subsequent clustering (b)

Credit/Quelle: BLS Netz AG, Gruner AG

5 View into the tunnel outline meshed with triangles and marking of the lower cutting edge (red line)

Credit/Quelle: BLS Netz AG, Gruner AG

6 Automatically generated rock volume of a tunnel slice

Credit/Quelle: BLS Netz AG, Gruner AG

7 Formula for calculating the objective function ƒ₁

Credit/Quelle: BLS Netz AG, Gruner AG

8 Formula for calculating the objective function ƒ₂

Credit/Quelle: BLS Netz AG, Gruner AG

9 Symbolic image of a particle swarm optimiser on a two-parametric cost function

Credit/Quelle: BLS Netz AG, Gruner AG

To realize the integrated synchronized timetables in long-distance traffic and to increase the capacity in freight traffic between Brig and Bern, the two-lane extension of the Lötschberg Base Tunnel (LBT) is necessary. This demands the installation of an inner lining over 14 km in the second LBT tube. Considering the excavation profile available, a skillful choice in the sequence of formwork carriage geometries (FCGs) can lead to optimization of the concrete volume to be installed, the feasibility of the build and the construction sequences. In the sense of a “proof of concept”, mathematical optimization algorithms are used to find a cost-optimal sequence of FCGs for a defined tunnel section. The article in tunnel 5/2021 describes the chosen approach and the results of the cost optimization.

1 Project Overview

The Lötschberg Baseline – comprising the 34.6 km long Lötschberg Base Tunnel (LBT) and the 2.6 km long Engstlige tunnel in the north – has been in operation since 2007. Due to limited financial resources during construction, the Lötschberg Baseline could not be completed over its entire length with two separate single-track tubes.

Currently, only the east tubes are in continuous operation (Fig. 1). The west tube of the LBT has been upgraded in the south over almost 14 km between the Raron south portal and the Ferden emergency stop. However, from the Ferden switch point to the...