The concrete production in focus

At the construction site of the second Gotthard Tunnel tube in Göschenen, numerous behind-the-scenes processes converge to ensure that tunnel excavation proceeds precisely and efficiently. A central role is played by the support services, which ensure the entire construction site is supplied with all necessary materials while also managing their disposal. Ivo Bölsterli, site manager for logistics services on the north side, is responsible for this.

The production facilities in the Eidgenössisch area include both above-ground structures and underground facilities. The main production facility, however, is located inside the mountain, in a large cavern excavated specifically for this purpose. This cavern is approximately 148 meters long, 18 meters wide, and up to 16 meters high. With a total volume of approximately 40,000 cubic meters, it forms the heart of the concrete supply for the Göschenen construction site.

Underground production offers several advantages. It saves space on the surface, allows for weather-independent processes, and reduces noise impact on the local population. At the same time, it meets the site’s specific requirements: the area is located in a zone that has been affected by avalanches in the past. For this reason, it was decided to build the main production facilities inside the mountain, where they are better protected.

An essential element of the system is the reuse of excavated material. The material from both construction sites is transported to Stalvedro, on the southern slope of the Gotthard, and then brought back by train to Göschenen. Here it is unloaded from the railcars into a hopper and transported via conveyor belts, through a tunnel, directly into the silo of the concrete mixing plant located inside the mountain.

The concrete produced is used for numerous applications on the construction site. In addition to the production of segments, it is also used for the construction of the inner lining, for securing the excavation during blasting operations, for the components of the utility ducts, for the intermediate slabs, the platforms, and the ventilation stations inside the mountain. During peak periods, approximately 5,000 cubic meters of concrete are produced per week. This corresponds to approximately 500–600 truckloads.

A major application of concrete is the production of segments. Segments are concrete elements that are installed on the tunnel boring machine to permanently stabilize the rock mass. A ring consists of six segments and is two meters long.

These elements are also produced underground. The production process begins with the reinforcement. This is placed in the clean formwork before the formwork is filled with concrete. The surface is then finished, partly with a finishing machine and partly by hand. The segments are then moved to the curing chamber, where they harden for about eight hours.

In the next step, the elements are demolded and transported using a vacuum lifter. They then cure for another 24 hours in a tent. Only then are they transferred to the above-ground segment storage area. There is space there for about 560 rings of segments, or over 3,000 individual elements. From this storage area, the segments are loaded onto the vacuum plate, transported on segment carriers, and finally taken into the mountain for final installation.