- Client: Graham Construction Ltd
- Engineer: JWH Ross / Fairhurst
- Value: £120,000
- Location: Kirkcaldy, Fife
- Duration: 2 Weeks (Test Grouting phase); 6 Weeks (Consolidation phase)
- Dates: April 2020 and March/April 2021
GBLE were commissioned by JWH Ross on behalf of Graham Construction to undertake test grouting and bulk infill consolidation of shallow unrecorded mine workings in the Jersey and Lochgelly Splint/ Parrot Coals beneath the site of a proposed new orthopaedic centre at Victoria Hospital in Kirkcaldy, Fife, in order to ensure the long-term stability of the development.
The site of the hospital was known from historic investigations to be underlain by old uncharted workings and had been subject to previous drilling and grouting works by others. However, subsequent investigations for the proposed development indicated that the past consolidation works may have been inadequate, with residual void space being evident at the level of both worked horizons.
In order to clarify the extent of the problem, GBLE undertook a phase of test drilling and grouting across the footprint of the development whereby 17no rotary percussive openholes were drilled and pressure grout injection was undertaken into both seams under strictly controlled test conditions. The results of this test phase helped to define the areas of the site where the old workings required further treatment and those where the previous consolidation works could be considered adequate.
Under a second mobilisation to site, GBLE carried out bulk infill drilling and grouting on a grid of boreholes at 3m centres beneath the eastern half of the site where the workings had been found with significant residual void space. Treatment holes were required to target both the Jersey and the Splint/ Parrot coal horizons, as well as an anomalous worked seam overlying the Jersey Coal in the far east of the site which was identified during the course of the drilling works. After the drilling of 220 holes and the injection of 480 tonnes of grout, subsequent pressure injection testing confirmed that the old workings had been successfully remediated to the satisfaction of the Engineer.
Both the test and infill grouting phases were carried out as “essential works” during the COVID 19 pandemic and as such required to adhere to strict distancing and other safety protocols. Additionally, the sensitive nature of the site close to the A&E department of the hospital meant that careful environmental and logistical controls required to be implemented to maintain the safe and effective running of both hospital and site operations in tandem.