Ten Walls in Ten Weeks: Case studies in the use of Launched Soil Nail Supported GCS walls in the Far North District

During both March and July, 2007 the Far North district of the North Island in New Zealand was hit by a series of severe storm events, which caused over 60 large slope failures along the roading network. Faced with the challenge of remediating such a large number of slips in the minimum amount of time, FNDC and GHD looked to some innovative technologies, recently introduced to New Zealand, to ensure the shortest possible remediation time. In addition, all solutions proposed needed to be sufficiently robust and cost-effective when compared to conventional retaining wall options.

This paper will present several case studies and will discuss the extent of site investigation carried out at these sites, as well as outlining the general design assumptions used which allowed for Geosynthetically Confined Soil (GCS) walls, typically 2m wide and up to 6m high to be designed using the additional contribution of launched soil nails (LSNs) to extend the overall width of the reinforced soil block. This combination allowed for 10 walls, up to 200m² face area, to be constructed in 1ess than 10 weeks.