Silverstone race circuit maintains a significant internal road network which provides access and transportation for staff, workers and members of the public. During racing events it is crucial that these roads are in good condition as service vehicles may need to access the track. One such road, adjacent to a two-meter high grass bank, was continuously flooding and the integrity of the road was being undermined as the road surface itself was sinking due to the amount of water present underneath the tarmac. Also, the pooling water was also flooding a communication duct which carries live cabling. GWD were chosen to deliver a drainage and ground stabilisation solution which would remove the standing water, stop the continuous flooding, enabling the ground to dry out and the road to be resurfaced.
Following a site survey it was established that there was enough room between the side of the road and the grass bank for the drill-rig to drill the required bore holes. The design itself used the “linear formation” of 6 metre lengths of Energy-passive Groundwater Recharge Pumps (EGRPs). At depths of 6 meters and beyond, 3 x 6 metre lengths of EGRP are interconnected and then capped to form a much more powerful groundwater pump. Three additional 6 metre EGRPs were installed on the other side of the road to form a defensive barrier to sub-surface water which was moving underneath the road and adding to the problem.
The 770 acre estate is situated on the Blisworth Clay Formation – Mudstone and bordered by Limestone
The installation involved drilling 20 bore holes at 1.5 metre centres to a depth of 6.1 metres and then inserting the EGRP as soon as the augers were finished drilling and the drill-rig was out of the way. In such wet ground conditions recently drilled bore holes can quickly collapse leading to a complete re-drilling exercise. The EGRP system was positioned 100mm below ground level and a free draining top dressing was used to close off the bore hole before gravel was spread out on the surface along the road side.