Conference paper
Floating (geogrid supported) geomembrane megabags for emergency water supply
Geosynthetics, Geosynthetics Conference, 2007, Use of Geosynthetics to Combat or Mitigate Acts of Terrorism and/or Natural Disasters, GRI Conference, 20, pp.94-108
01 Jan 2007
Abstract
Whether the cause is a natural disaster or an act of terrorism, a threat to a communitys potable water supply must be taken seriously. For communities which have ocean access, water can be temporarily transported from a clean source to the affected community by filling, towing, mooring of large polymer membrane megabags. Illustrated in this paper, and used as a design example, is a 30,000 metric ton megabag of approximate dimension of 450 feet long, by 78 feet width, by 39 feet in thickness; the latter two dimensions being in the form of a surface flattened ellipse. Using such a megabag filled with potable water and floating in ocean water results in the bag being approximately 5.5 feet out of the oceans surface and 33.5 feet beneath the oceans surface. To transport such an immense water-filled bag by directly tethering it to a towing barge has been the method used over the past 10-years since first considerations were given to this concept. The authors, however, feel that the water containing bag (made from polymer sheets heat welded together and prefabricated in a factory) is best cradled in a reinforcement geogrid for towing and mooring at both the filling and emptying terminal locations. This geogrid consists of longitudinal and transverse polymer ribs at right angles to one another. The ribs consist of high strength yarns of polyester, polyamide, or other polymers. In sequential steps, the paper has considered capacity assumptions, followed by filling rate and delivery/emptying rate considerations. Also addressed are towing forces, mooring and anchoring considerations. Lastly, navigation light requirements are addressed. The above stated, there are numerous additional design elements in need of further investigation. These involve, but are not necessarily limited to, the following: Hoop and longitudinal stresses in the geogrid containment system of the megabag. Methods of attachment of the end of the geogrid containment system to the towing barge. Method of fixity of the geogrid containment system to the ocean floor at both the filling and emptying ends of the journey. Details of the filling/emptying ports on the megabag itself insofar as stresses from the water transmission filling and emptying pipelines. Operational details of folding and/or wrapping of the empty megabag and geogrid support system for the journey back to the filling station. stimation of the number of reuses such as megabag and geogrid support system can reliably make so as to estimate costs and efficiency. The case histories cited illustrate that this emergency water supply concept is beyond the feasibility stage. Such activity is ongoing as mentioned in the introduction. What is new, and suggested herein, is to drastically scale-up the concept into the megabag category whereby huge quantities of water can be transported during each return voyage. This, it is felt by the authors, requires a separate support and towing system as can be provided by the identified geogrid enclosure, aka, a geogrid cradle. The actual details of this geogrid cradle will be the next step in the design process. In this regard, the possibility of wave tank experimentation is attractive and will be attempted in further development of this emergency water supply concept.
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Details
- Title
- Floating (geogrid supported) geomembrane megabags for emergency water supply
- Creators
- J. Richard Weggel - Drexel UniversityRobert M Koerner - Geosynthetic Institute (United States, Folsom)
- Publication Details
- Geosynthetics, Geosynthetics Conference, 2007, Use of Geosynthetics to Combat or Mitigate Acts of Terrorism and/or Natural Disasters, GRI Conference, 20, pp.94-108
- Publisher
- WTI-Frankfurt-digital GmbH
- Resource Type
- Conference paper
- Language
- English
- Academic Unit
- [Retired Faculty]; Civil, Architectural, and Environmental Engineering
- Identifiers
- 991022043982704721