Low investment concrete-casting geometries, modeled for stability, are the primary focus of this web page. Concrete geometries are studied through 3D CAD for bottom applications like aqua culture pens. The suggested advantage of this concrete approach is low cost as compared with coated metals or alloys, when deployed on a large scale.
First a flexible netting application is presented followed by other more rigid structures for pens. The first picture -- visualizes a netting system to contain sea organisms of interest and keep out predators. It is held in place by concrete anchors, lines and submerged buoys. Elongation characteristics of all flexible members are selected and proportioned to allow preferred levels of flexing and positioning under stress. The first model below is conceived very large with many spaced out buoys on top and many anchors inside, on the sand bottom. The submerged buoys are modeled long for less resistance to current surges (pictured on right side).
Next below are theoretical, rigid structures for fencing to be made with non-ferrous reinforced concrete, made heavy for stability in sub surface current. In the visualization below, the fencing is conceived as movable, large, rectangular sections, bound to the concrete pyramidal frames and also bound, each section, one to another. A variety of mesh products could be considered and pyramid details can be modified as well, (since the proposed construction method, linked below, is so very versatile). Still further below are additional structures which could be adapted as posts or cage supports.
An apex extension was added for more head room within each cage, while not increasing pyramid size. Further stability might be achieved by sinking the pyramidal bases down into the sand by means of water-jetting the sand. Such burial is expected to reduce the gradual sand-gouging by wave currents. Such effects are observed as slight "funneling" around hard objects in sand, (which could complicate fence-containment). Such effects might also be further reduced by slimming the framework near the "framework ankles" and thickening the framework in base (to maintain massiveness). In any case, it may be found necessary to extend fencing somewhat beyond all thick members, to prevent escape or predation. Methods for latching together two pyramidal halves has also been worked out, asked for more details.
Next visualized below are anchors, primarily for the flexible sea netting concept above. Dodecahedron based geometries can be built partially hollow. These can be cast in molds, in part using various available balls. Many sized balls are available for re-usable forms. These can be adapted to form almost any large sized, concrete, root-like anchor. A proposed experimental method is considered to penetrate the sand bottom for concrete based anchorage. Ample water or compressed air may jet out through each pod , while the dodecahedron sinks into a sandy bottom. Methods to tie onto the anchor have yet to be added.
Next below, following similar thinking, a vortex concrete anchor may otherwise work better. The vortex geometry uses slanted flutes, both as a means for "bored out" sand to escape and also for final "grip" as may be had from eventual gravity compaction of sand (around the flutes and fins).
Next below follows a dome concept for comparison, again intending to employ the least costly materials possible. The below visualization depicts a self-standing domed cage structure. As modeled, the concrete volume is near to a cubic yard or meter and the weight will be around a ton, (depending actually on the concrete aggregate). This cage features a concept of embedding the cage mesh directly into the molded concrete. The embedded mesh becomes part of the concrete reinforcement.
For the easiest experimental approach, sand casting of the above concrete structures is recommended. Please see this linked page for further information. Very few tools are required and training is available. From experience, the author suggests that any of the above models could experimentally be sand cast in remarkably little time. Where rigging equipment is not available, individual concrete-members could be cast separately and tied together underwater, (with at least one unskilled but physically strong helper). This may help prove the features of interest before greater production is attempted. A land based production facility, using floated forms is modeled here.
Next are visualized (more challenging) ring-module space frames which are applicable as sub-surface "fence posts" or marine cage supports. Material savings are
combined with broad cross sections to achieve more stability. Differing approaches for reinforcing ring segments can be found on this link. First some variations on hexagonal arrangements are visualized.
Simple concrete material alone could possibly be adequate. It is proposed that these space frames may additionally encourage coral and eco-system growth. Small organisms may benefit from such structures. It is assumed that increased habitat will enhance aquaculture. Next the simplest "chain Link" style of space frames are considered.
For applications where less forceful surge currents are encountered, much more concrete surface area may be employed. This would allow more framing members or struts. Above is a triangular ringed framing truss example which offers stability and possibly also a coral reef substrate for sea organisms. These truss examples could potentially be set upright and "planted" in sand. While that geometry must be formed intact, a nesting geometry is pictured below and seen from two ends for distinction.
Simple, low cost reinforced concrete adapts well to small modular sections. Short sections reduce the normal concrete shrinkage problems.of longer concrete sections. Nesting assemblies provide lateral stability when set upright like aqua culture fencing posts. Nesting upright assemblies simplifies installation of fairly strong structure. Form work for these ringed structures might be adapted from motor-cycle tires, combined with sand beds.
The red "pillows" represent "mortar" to lock the truss work together. For underwater work, the "mortar" would be bagged to prevent dilution under water, during the initial 24 hr cement cure. (A non-toxic, slowly- soluble bag material could prevent sea creatures like turtles from accidentally and harmfully eating plastic). The bag also will aid compact forming and installation in fast work cycles. The colors are chosen only for schematic distinction. For aquatic fish pen posts or cage supports this installation would proceed in an upright posture.
Additional ring structure concepts are found on the "ringforcement study". Again, concrete bonding of the meshes and rings are described in more details with many practical examples. The rings make complete use of the wire, so that no reinforcement material is wasted.
Questions For Further Research
Fencing wires freely-pass the water currents much better than large concrete members (which must withstand considerable wave or current energy). The question is then, how do the combined surface-resistances add up in compared models? If contiguous cages are put together, which approach drags the wave-currents more? Which less? Which will prove more stable in the sand? Will local sand formations become negatively impacted? Which will cost less in production and deployment? What other design issues are important?
For more committed production of concrete in the marine environment, this page is offered for consideration. Water born production may well prove expedient with widely adjustable equipment and a moderate training investment.
The sustainability of marine farming is unknown in the long term. Is this farming sustainable if it relies on harvesting wild marine life to feed marine life in captivity? Will it improve or enhance food production if it relies upon already stressed land farming? Will GMO feed stock introduce new issues? If world fisheries are already, largely depleted, will farming improve fish harvest yields? Can the costs of this farming really prove profitable over long periods of time? Will smaller cages and pens ultimately out perform larger fenced in tracts of sea floors? If protein production is the objective, how will aquaculture compare to other protein production methods?
Public perceptions of marine projects may increasingly tangle with human sources of waste. For example, here are some noteworthy instances of human trash at sea. A publication of the National Oceanic & Atmospheric Administration (NOAA), U.S. Department of Commerce. Human trash at sea has already earned some nicknames:
"North Pacific gyre"
"Great Pacific Garbage Patch"
Plastic trash stresses and ruins marine life. Harvesting the floating plastic trash for incineration fuel invariably produces CO2 pollution, (an added source of global warming, to say nothing of considerable harvesting costs). Could these countless tons of floating waste be more productively woven or baled together, in order to build flotation platforms with favorable marine uses?
Comments are invited. Consultancy or constructive cooperation is offered.
Note: These pages are placed in the public domain and are furnished "as is". The author assumes no responsibility for the use or misuse of the concepts in this series. All authorities should be satisfied first, as might be required, by relevant laws, before any building proceeds.
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