Two case histories of underpinning bridge – piers are described, where a river flow velocity of 2 to 4 m/s and local turbulences had to be considered: In summer 1990 the common river pier of a highway and expressway triple-bridge settled 1.3 m due to a 14 m deep scouring which caused an international traffic chaos. The first and extremely urgent remedial measure comprised backfilling with rock material and grouting. This ,.special grouting method only was possible by placing “geotextile expander bags” into the boreholes. The second case history refers to the strengthening of ‘a bridge pier foundation in another river by installing jet grouting columns around the existing caisson. This measure required a temporary flexible cover of the river bed to prevent the cement grout from escaping which was achieved by placing geotextile mattresses filled with underwater concrete.
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