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Description of the project:
For the historic Irsee monastery (Bavaria, Ostallgäu district), an escape staircase system with a basement in solid construction was created as an external extension to the multi-storey studio building.
ICP Altusried was commissioned with the subsoil investigation and the preparation of a foundation concept.
The particular challenge in this project lay in the difficult subsoil conditions for which the town of Irsee and also the site of the monastery are known. Above a clay marl sequence of the Tertiary period, which is deconsolidated to soft clay in the upper part, with a sloping erosion surface that carries back water, lie Quaternary, largely unconsolidated and water-bearing limestone tuffs up to more than 5 m thick. The limestone tuffs are very susceptible to settlement and highly sensitive to groundwater fluctuations. The monastery building was partially founded on these compressible soils and has been showing recurring settlement damage for decades. It can be assumed that the subsidence and redistribution processes in the subsoil have still not subsided despite the building's existence for over 200 years (after reconstruction in the 18th century).
Attaching the staircase to the existing building structure with load transfer via the existing wall and foundation construction was ruled out for structural and monument preservation reasons. The structure was therefore built as a self-supporting construction that is movably attached to the existing building structure. This means that settlement differences are compatible with the structure.
The foundation was made using a base plate placed on small bored piles. The bored piles tie into the Tertiary clay marl with a semi-solid consistency, which is present from a depth of approx. 6 to 7 m below the compressible overburden with a tendency to slide.
Construction time: 2014
Services performed by ICP:
Subsoil investigation by means of small pile driving boreholes, soil mechanics field and laboratory tests, geotechnical report with foundation concept, specification of design values for the pile foundation, consulting during construction.
Client: Swabian Educational Centre Irsee, Klosterring 4, 87660 Irsee, Germany