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 Aktuelle Projekte / Bern, enlargment of the Rathaus parking facility
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The enlargement of the parking facility requires a 15.5-meter deep excavation with anchored pile walls in top-down construction method. The garage structure is constructed on the hillside between the river Aare and a row of old historical houses located very close to the excavation.
The first 8 to 15 meters of the excavation consisted of soil contained debris from demolished houses following a large fire. Under this debris layer was approximately 9 meters of glacial sediments that followed the slope of the hill. The debris cover was loosely to moderately compact and the glacial sediments were rather impermeable and possibly pre-consolidated. Below this is a layer of moraine material.
Construction for the parking facility enlargement results in potential vertical and horizontal movements. A long-term monitoring system is installed to measure both geotechnical and geodetic movements during the construction phase. A motorized total station (TCA) is used to automatically measure 45 points on the row of old houses and additional reference points beyond the influence of the construction. Online, real-time calculations are used to determine the position of the TCA itself and of the 45 points on the houses in the horizontal x- and y-directions as well the vertical z-direction. The monitoring system also measures borehole extensometers providing real-time movements along the axis of the boreholes. Periodic manual measurements using a Sliding Deformeter and the borehole inclinometer provides a meter by meter profile of displacements in vertical and horizontal directions in the subsoil between the excavation and the foundation of the houses. |
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