Civil Engineering May 2021 | Vol 29 No 4

local suppliers manufacture geocontainers with varying attributes. Using available formulae to calculate the theoretical volume of a geocontainer filled with air, without any elongation, and available research pertaining the influence of geocontainer elongation on the hydraulic stability of a structure, relating to the sand fill ratio, it was estimated that a percentage of elongation greater than 15% could influence the integrity of a geocontainer revetment structure. Due to the emergent nature of the project, it was decided not to restrict the elongation properties to a maximum of 15% for the possible risk of time delays in sourcing the geocontainers. However, for future projects, the impact of higher deformation/elongation shall be investigated in more detail. Extent of new revetment and configuration Along the northern portion of the site (in front of the life-saving club), the foundation of the gabion structure is now protected by a new geocontainer scour protection toe. In the southern portion (in front of the pedestrian walkway and sewer line), the gabion structure was removed and replaced by a new geocontainer revetment. In total, the revetment is 178 m long – 58 m in front of the life-saving club, and 120 m between Big Bay and Small Bay. The revetment comprises a double layer of geocontainers and was con- structed in stretcher bond fashion with overlap. The crest elevation of the geocon- tainer revetment varies between +4.2 m and +4.8 m mean sea level (MSL); crest width of 2 m, to foundation level of +0.5 m MSL and 45 degrees slope. A non-woven, continuous filament polyester geotextile material with a minimum weight of 770 g/‌m 2 was placed between the exca- vated slope, behind and underneath the proposed geocontainer revetment. Scour and toe protection Typically, scour protection of geocontainer revetments use a special type of geocontainer referred to as a “Dutch-toe-bag” and comprise a standard size bag with an added piece of material which is then tied back into the structure. The “Dutch-toe-bag” was placed seawards and at the same depth as the toe of the structure (bottom, seawards row). Should the beach erode down to the toe of the structure, the function of the Dutch-toe-bag is to slide down (fall) into any erosion cavity and therefore prevent the structure toe itself from moving. However, due to the limited allowable footprint for the new structure, which in turn impacted the maximum founding depth, the foundation had to be limited to +0.5 m MSL. In order to prevent undermining of the foundation, the contractor recommended placing an additional geocontainer under the Dutch-toe to allow for additional mitigation against erosion at the toe, in the event of storm erosion. Gabion edge It was decided to incorporate a gabion edge between the geocontainer and Construction of the geocontainer revetment (Credit: Bruce Sutherland, CCT) Civil Engineering  May 2021 15 The revetment comprises a double layer of geocontainers and was constructed in stretcher bond fashion with overlap.