Settlement Behavior of an Avalanche Protection Gallery Founded on Loose Sandy Silt

by Walter Steiner, (M.ASCE), Balzari & Schudel AG, Bern, Switzerland,

Document Type: Proceeding Paper

Part of: Vertical and Horizontal Deformations of Foundations and Embankments


An avalanche protection gallery located in the Swiss Alps was founded on alluvial ground close to the steep rocky mountainside. The rear retaining wall, at a variable distance of a few to twenty meters from the wall of rock, was founded on a strip footing. The footings for the face columns were placed on pile caps supported by driven piles of more than 20 meters length. The settlement and inclination behavior of the rear wall was monitored during backfilling. At the southern end of the structure the observed settlement substantially exceeded the anticipated settlement. Therefore, an additional boring was drilled and in-situ flat dilatometer (DMT) tests were performed. The much thicker and more compressible layer of loose silt and sand encountered explained the settlement of the rear wall and column footings. Computed settlements with dilatation moduli from DMT-tests agree well with the observed settlements. An in-situ coefficient of secondary settlement Cα = 0.28% was obtained.

Subject Headings: Soil settlement | Footings | Structural settlement | Field tests | Avalanches | Silt | Soil properties | Soil compression | Alps

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