Client
Opus Joynes Pike and Metropolitan Housing Trust
Location
St Aidans Court, Old Basford, Nottingham
Overview
Ground collapse revealed a buried man-made cave in a Nottingham Castle Sandstone Formation of the Sherwood Sandstone Group of Triassic age.
Problem
A ground collapse within the patio area of a tenanted housing association property caused Metropolitan Housing Trust to evacuate the tenants for their safety.
TBL Solution
TBL assisted Opus Joynes Pike (then Joynes Pike & Associates Ltd) by facilitating full confined space entry of the Nottingham man-made cave.
The works were undertaken in two phases, firtsly a photographic and video survey to investigate the nature, size, and extent of the cave, followed by it's vented grout filling.
Following evacuation of the tenants, TBL facilitated a full confined space entry by setting up a steel/timber 'safety cage' at the point of collapse, and lowering it using hand excavations to the cave floor level. Further 'safe-zones' were progressed into the cave using 'tied' steel acrow supports until sufficient access was available for the geotechnical appraisal. A tunnel section and other voids were captured with TBL's pole mounted cameras.
The cave was understood from the 1989 BGS Technical Report WA/89/27 (Register of Nottingham Caves) to have been used as an air-raid shelter originally accessed from Park Lane, with an emergency exit to the rear.
With voids close to house foundations, the remedial works consisted of pumping a G4 grout in stages over two days to prevent excessive loadings onto the old entrance retaining wall. Venting ensured the void was adequately filled.
Benefit
With entry design, risk assessments and method statements completed within 24 hours from instruction, and all confined space entry resources 'in-house', TBL were able to mobilise quickly and minimise both the inconvenience to the tenants and re-housing costs for the client.
