The UKPN Capital Delivery Alliance installed 500mm diameter HDD bores for 132kV electrical cables at Under Track Crossings beneath Network Rail tracks and assets in south London. Problems were encountered during HDD works, and claims had been lodged by the specialist drilling sub-contractor. The problems included large unexpected heave of the tracks, drilling fluid loss by frac-out to the surface and wedging of the product pipe during pull-through.
GCG was commissioned to independently review all the available records, including the ground conditions, the design documents, construction records, drilling mud information, HDD operational parameters and monitoring data, augmented by GCG’s own desk study. On this basis, we provided an independent opinion on the validity of the contractor’s claims in respect to unforeseen Ground Conditions and presented a technical explanation of the events that had occurred.