This project involved foundation repair works through pressure grouting or ground improvement. The homeowner had become concerned about fresh cracking to her property and contacted Substruck.
The subsidence investigation required testing of the drainage and water supply and trial holes. The drains were found to be leaking to varying degrees around the property. However, the worst leakage was at the rear which corresponded to the movement at the corner of the building.
As the structural damage was not significant, pressure grouting at 7 nr locations along the area of distress was considered a reasonable approach. Ground improvement or pressure grouting, termed ‘permeation grouting’ by CIRIA C514 (2000), is applied in low risk buildings in areas of loose permeable soils. A neat cementitious grout is pumped or filled into the subsoils to fill voids, increase strength and reduce compressibility of the underlying soils to stabilise the structure. The grout is very mobile and whilst following the path of least resistance, travels through the voids providing both compaction and densification, therefore increasing the bearing capacity of the soil. 0.73 tonnes of cement grout was injected and good relief pressure was observed at all locations.
The drains and water supply were replaced and tested on completion to satisfy certification requirements of the Consulting Engineer. However, whatever the requirements, all drainage installed by Substruck is tested before any reinstatement works commence.
Our foreman, XXX, got to show off his finishing skills once again and the new concrete driveway and footpaths are looking fantastic.