ABSTRACT:

It goes without saying that every building activity leaves its mark on the existing natural conditions, often with surprising consequences. One of the few "safety" aspects generally taken for granted during the building of a structure is stability in space and time. In some cases, however, even this is not achieved. This is the case for construction in the landslide area located in St. Moritz in the Swiss Alps.

SITUATION AND GEOLOGY

The Brattas-Fullun landslide is located on the northern slope above the village of St. Moritz. The landslide is composed of a 600 m wide clastic flow and is bounded on both sides by parallel shear surfaces. The detachment zone is located on the southern edge of the terraced surfaces of the Val Saluver at an altitude of 2400 m a.s.l., and the area stretches over a horizontal distance of 1.5 km to a lower altitude of 600 m. The clastic flow may be divided into two zones (Figs. 1 and 2). The upper zone, which extends from the detachment zone between Sass Runz.l and Sass da Muottas to the crest at an altitude of approximately 2100 m, is composed of a rockfall. The lower zone, which is the actual Brattas-Fullun landslide, is composed of a thick soil mass which is moving downhill but is blocked at its foot by the Hotel Kulms rock ridge, after which the movement stops. The amount of material in motion is enormous and has been estimated to be about 10 million cubic metres. A drill hole was carried out at one location in the upper zone of the slope which revealed the main sliding surface to be at a depth of 60 m and the thickness of the entire sliding mass to be 87 m.

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