Due to ground excavation 13 m from a gas holder at Rhyl, North Wales, the gas holder settled 60 mm. The settlement was at least in part due to piping of sands deep below the foundations of the holder.
Grouting to recompact sands loosened by the piping stabilized the ground and allowed pressure grouting to be used to restore the gas holder to its original levels. Little response to the grouting was seen until a substantial proportion had been pumped when a sudden change indicated the onset of a second phase of the process, the restoration of effective overburden pressure being followed by a controlled ground rise.
- © The Geological Society 1984