Stability of Geobags in Riverbank Erosion Protection Structures - Experimental and Numerical Study

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Sand-filled geotextile bags (geobags) are a comparatively new erosion protection system, however advantageous over traditional hard armour system, credited to their flexible and porous nature. Geobag riverbank protection structures have been implemented with success for about 15 years mostly in Asia, but there are remaining uncertainties about the element stability under various water-bag and bag-bag interface conditions. The main reason is that existing design formulae are made for hard material and do not consider the flexible nature of the geobags. The goals of the partnership between the University of Alberta and the Northwest Hydraulic Consultants (NHC) are to identify the key factors affecting geobag stability, enhance our understanding of the performance of geobag riverbank protection system, and develop a reliable design formula for sizing the geobags. The proposed research project will include a large-scale systematic laboratory experiments in conjunction with computational modeling. The relationships between hydraulic forces exerted on the bag surface and bag stability will be established, taking into consideration the flexibility of the geobags. The findings will be used to develop a sizing formulae and will be incorporated into guidelines. The improved knowledge will provide guidance and facilitate the development of a design standard for geobag riverbank protection structures. Combining filter properties with stability, geobags are ideal for temporary works that can be removed from the river system, as well as preparatory works that is incorporated later into the permanent works. This research will facilitate wider application of geobags which will greatly reduce the cost related to material, construction, flood damage and subsequent restoration work, as well as promote a sustainable erosion control across Canada.