Soil Nail System for the Extension of A14 Trunk Road

Near the city of Cambridge in Great Britain, the trunk road between Girton and Histon is being widened by one lane per direction. The A14 is an important national highway that connects the Port of Felixstowe on the east coast with the British road network.

A number of steep sidehill cuts had to be comprehensively stabilized within the scope of the A14 widening. Soil nails were installed top down in accordance with the side hill cuts that were carried out in individual stages, and the cut face was secured immediately as construction progressed.

To install the R25 9-15m long soil nail, the bore holes were drilled with two rigs working concurrently to maintain progress consistent with the tight time frame. Afterwards, the soil nail system were installed using spacers to centralize the bars within the holes, and then grouted via a tremie pipe from the bottom to the mouth of the borehole. This ensured full column bonding of the soil nail to the ground.

The soil nail system was ideal for top down construction in this project because they provide a permanent, safe and economic reinforcement of slopes without the requirement for additional support. The soil nail system installed featured galvanized protection, which provides comprehensive corrosion protection for soil nailing applications. This application of soil nail system had great benefits, not only economic ally, but also technically.