St. Moritz Brattas-Fallun, Chesa Corviglia, 22 years landslide and structural health monitoring.
Located above the northern part of the town of St. Moritz in Switzerland, there is a 600m wide and about 1500m long clastic flow type landslide. At the sides bounded by parallel shear zones and at the lower end constrained, the Brattas-Fullun landslide is composed of a thick soil mass which is moving downhill with different velocity and even stops at the Kulm rock barrier.
The residential building Chesa Corviglia has suffered from the landslide effects since it was built in the 1990. A massive anchored pile wall, separated from the house, was constructed and meant to be founded in stable rock. Due to difficulties related to the prognosis of the location of the stable rock, both, the pile wall and the house, move downhill with different velocity, causing that the gap between the house and the retaining wall is closing and so endangering stability of the wall and house.
Already in 1995 a monitoring system was established and since then operated, that included anchor force measurements, subsoil and geodetic deformation measurements and sensors to measure relative displacements between the house and the retaining wall. During summer and autumn 2016 the retaining structure was reinforced and intensified by installing additional and longer ground anchors. The existing, over 20 years old, Sisgeo monitoring system has then been refurbished and expanded to meet the needs for future long term monitoring. Actually the system includes:
• anchor load monitoring on 23 anchors;
• convergence extensometers at 7 point monitor displacement between the retaining wall and the house;
• at 5 points water pressure behind the retaining wall is recorded to ensure that the drainage is releasing water pressure.
The OMNIAlog data logger takes measurements every 4h and sends out the results every day. A project website enables the engineers and the owner to overlook the situation of the automatic taken readings but also of manual taken inclinometer measurements and geodetic displacement measurements.