Kleinmatterhorns, Zermatt – Rock cliff monitoring

The Alpin X project, implemented by Zermatt Bergbahnen, creates a tourist connection between Zermatt (Switzerland) and Cervinia (Italy) via the summit of the Klein Matterhorn. For this purpose, two new cableway mountain stations have been built at the summit at an altitude of 3820 m on the 50° to 70° inclined rock faces. In the serpentinite rock faces, extensive rock excavation of approximately 10,000 cubic meters and rock stabilization had to be carried out over 60m and a height of approx. 50m. Special challenges arose due to unstable rock sections near the surface and the prevailing permafrost conditions. The extent of the permafrost body within the Klein Matterhorn tends to decrease due to climate warming and local activities associated with new constructed facilities and structures.

Rock mechanical monitoring is used to record rock displacements, rock temperatures, and the rock anchorages' loads. The proposed solution was a vital part of ensuring safety during the construction work and the operation of the structure. Displacements on either side of existing intersecting rock discontinuities and potentially increasing rock temperatures are monitored using four boreholes, up to 30 m long and 4-point borehole extensometers with steel rods and four pieces of 4-point thermistors. The instruments were installed in boreholes inclined downward by 10°, drilled in the lowest levels of the excavation platform and directly under the support areas of the roofs.

So far, no significant displacements have been detected, while the temperatures in the rock are still below 0°C, but the monitoring system shows a slight increase in temperature. The high-performance, high-quality borehole extensometers and temperature sensors manufactured by Huggenberger have far ensured the safety and integrity of the structure. The systems will serve for the future as for long-term monitoring and will be an important part of the early warning system.