The East Coast of the North Island includes extensive areas of fine-grained soils. High rainfall and rolling terrain rising inland means that these low permeability soils are mostly saturated. Many banks of these soils continue to creep. Gisborne District includes more than 1,800 km of generally low volume roads, and several locations are affected by creeping banks. The result can be encroachment onto the road, undesirable realignment of road or more seriously dropouts with the loss of road width. A cost-effective solution has been developed over the past 17 years. This involves trenching into the underlying hard pan and backfilling with alluvial material. More than 80 slides have now been arrested using this process, and this paper describes the simple technique, which has strong emphasis on worker safety, and the observed effectiveness. (a) For the covering entry of this conference, please see ITRD abstract no. E212706.
Abstract