ABSTRACT
Leakage of sand and water through a diaphragm wall for the Vijzelgracht station of the Amsterdam North South line at a depth of 12m — NAP led to settlements up to 0.15m of the adjacent buildings. These buildings are founded on end bearing piles that were installed with their tip in the first sand layer (at the same depth as the leakage). The leakage led to a local ground loss and decrease in density of the sand underneath the piled foundations. Corrective grouting was performed initially to restore the capacity of the pile foundation. Although the lifting of the building was successful, it appears that for these conditions (loose sand due to ground loss) the efficiency of the corrective grouting process is rather low. Injections of up to 600 litres/m2 led to a heave of only 10mm at maximum. Although the original stiffness of the load bearing sand layer was completely restored, ongoing settlements were found up to at least 5.5 months after finishing the compensation grouting.
Keywords: Corrective grouting; case history; heave; long term settlements.
