Applications of Geosystems as Retaining Structures in Marine Environments

Normal soil reinforced walls as a sole solution for marine structures may not be so effective in harsher marine environment due to severe hydrodynamic forces due to waves, tides and currents. It is more effective if used in combination with other geosystems. Geotubes and Geocontainers can be used to construct marine structures by itself or as a core of other geosystems. The stability of these systems can be further enhanced by using stacked geotubes, proper strapp ing system to keep number of tubes as single unit, adequate apron on headward side and suitable anchorage system. The static stability of such type of geosystem has been explored by 2 -D analytical modeling and substantiated by 3-D finite element modeling using FLAC. Closed form and approximate solutions for the cross -sectional shape and circumferential tension for stacked tubes were obtained for partial or full submergence, resting on deformable foundations, subjected to asymmetric loadings (as in dikes). Dynamic stability of geotubes against current and wave attack has also been investigated. A two-dimensional equilibrium and vibration analysis of a freestanding geocontainer is being done. Air and water are the two internal materials investigated. Three foundation variations are considered: rigid, Winkler, and Pasternak. Mathematica 4.2 was employed to solve the nonlinear equilibrium and dynamic equations, incorporating boundary conditions by use of a shooting method. The additional features of viscous da mping and added mass of the water were applied to the rigid foundation study of the vibrations about the freestanding equilibrium configuration. Results from the equilibrium and dynamic analysis include circumferential tension, contact length, equilibrium and vibration shapes, tube settlement, and natural frequencies. Natural frequencies for the first four mode shapes were computed.