Provost Driver Court Remedial works
Geobear was contacted to investigate settlement issues affecting the pumping stations at the end of Provost Driver Court in Renfrew. Settlement was presumed to be a direct result of a loss of ground and groundwater into the sewerage system.
A dewatering scheme was chosen to artificially increase rigidity and in turn densify the loosened silty sands which were contributing to the problem. This would allow for accelerated settlement in a completely controlled environment and ensure both speed and precision.
As dewatering methods were being used, manhole chambers in the local area could have been impacted through mobilised settlement and tilt. To combat this, fourteen ejector wells were positioned in a circle with a diameter of 20m and the assumed point of ground loss was located in the centre.
Our solution
We installed injection tubes directly into the soils below manhole chambers to allow for the lifting and relevelling of manholes during dewatering. This treatment allowed chambers to be lifted and placed and level off sand strata whilst staying within a pre-agreed tolerance.
As the work progressed, there became a requirement for us to carry out water sealing works around pipes connecting the manholes, as well as void filling, works to stem water flow to the site. Additional operations were specified after work had commenced and which illustrates the versatility of our operations.
The Engineering Department submitted a full technical proposal document in order to procure the operations. On top of this, the works and potential issues were discussed with a wide range of professionals and local residents, keeping everybody informed.
To achieve these objectives, a geopolymer resin, specially developed to be highly effective where water is involved, was used. Characteristics such as high expansion and rapid gel time meant that works could be completed efficiently, quickly and cleanly.
RESULT
All works were successfully completed and manholes were suitably relevelled. Visual inspections of relevelling and water sealing works were carried out to verify quality. Void filling was subject to dual validation. Pre-verification in the shape of void volume calculations and geopolymer rise density to determine how much should be injected. A check was also carried out on reactions felt on the injection pumps, an increase in back pressure showed that void filling was successful.
