We are proud of the end-to-end services and project management that our GRM teams can provide for developers, and with it the benefits in relation to reduced time, cost, and confusion.
One recent example of this was the provision of multiple services to a national housebuilder for a large development project near Telford. The site had a long and complex coal mining history, with extensive workings of Carboniferous coal seams using opencast and shallow underground adit and shaft techniques.
The Coal Authority (recently renamed the Mining Remediation Authority) had identified 19 mine entries within or adjacent to the site. Underground pillar and stall mine workings had been used to exploit three main coal seams to depths of 27m. The opencast extraction had been backfilled with unconsolidated fill in excess of 20m below ground level.
The resultant conceptual ground model identified a complex range of risk elements, all of which required some form of mitigation before construction could begin.
Over 1000 probe holes were drilled to a maximum depth of 39m in order to confirm the extent of the underground mine workings. These were then filled and stabilised using conventional techniques which included the injection of nearly 9000 tonnes of grout.
Six of the 19 mine shafts warranted further investigation by rotary probe drilling methods. Three of these shafts were subsequently treated, and in addition one unrecorded mine shaft was also identified, investigated and treated.
The unconsolidated opencast fill was subject to numerous exploratory techniques during the site investigation phase. This data was used to delineate the former highwalls to the opencast workings and for extensive analyses using established theoretical techniques to look at settlement of the backfill material.
Calculations showed that settlements in excess of 100mm were to be expected. A ground improvement phase was trialled at the site which showed that settlements could be kept within acceptable limits, thereby minimising the amount of piling required at the site. This provided significant cost savings for the client.
GRM were also involved in the foundation designs, generating significant cost savings by demonstrating to the warranty providers that a mix of traditional, pile and ground improvement foundation solutions could be used at the site. This included the use of a number of zone load tests across the site (as shown in image).
If you have any development or construction projects, then please get in touch to find out how we can help save both time and costs. Please use your main point of contact at GRM or for new enquiries email richard.upton@grm-uk.com or call 01283 551249.