Underwater Anchoring Apparatus

The present invention is concerned with apparatus for raising high density solids such as gravel in bulk from the bed of a river or a seabed, particularly in depths beyond the range of normal dredging apparatus. A further application of the techniques and apparatus of the invention is a means for establishing an underwater anchorage such as for a surface vessel or for any other structure such as a well-head.

According to the present invention an underwater anchoring apparatus includes a substantially hollow structure submersible in a volume of water and having at least one intake passageway located in the lower region of the structure, the apparatus also including collection means whereby in operation water from the lower strata of the volume of water on or adjacent the bed of the liquid may be induced into the interior of the structure through the intake passageways with sufficient momentum to carry into the interior solid matter from the water bed to cause the structure to become at least partially buried in the water bed.

Preferably the collection means includes a vent passageway located in the upper region of the structure and through which liquid may be extracted from within the interior of the structure by suction means.

The structure might also include an air inlet passageway through which air under pressure may be fed into the interior of the structure to act in conjunction with the vent passageway as an air-lift pump for the extraction of air/water from within the interior of the structure.

In one arrangement of the invention the substantially hollow structure includes a lower platform region with a series of intake passageways arranged in the base of the platform such that solids induced into the structure by the collecting means substantially fill the interior of the platform region and cause it to become at least partially buried in the bed material.

In order that the present invention may be more fully understood an embodiment thereof will now be described by way of example only with reference to the accompanying drawings which illustrate vertical sections through the apparatus of the invention.

FIG. 1 shows the anchoring apparatus on the surface,

FIG. 2 shows the flooded anchoring apparatus submerged and resting on the water bed,

FIG. 3 shows the submerged anchoring apparatus being evacuated of water, which is being replaced by material from the water bed, and

FIG. 4 shows the anchoring apparatus partially buried in the water bed thereby providing a secure anchorage.

Referring to FIGS. 1, 2, 3 and 4 the underwater anchoring apparatus in the form of a hollow structure 10 floats on the surface of the water as shown in FIG. 1 until it is located above the site where it is to be anchored. The hollow structure 10 is then flooded and sinks to the water bed as shown in FIG. 2. The water contained within the structure is then expelled in any one or more of a number of ways; for example, by connecting the interior of the structure to the suction pipe of a pump, either submerged or mounted above the surface of the water, or by a water jet ejector, or by an air-lift pump.

As shown in FIG. 3 the water within the hollow structure 10 is expelled through a pipe 13 connected to a water pump 15 whereby liquid is induced into the structure through open substantially unobstructed intake passageways 14 located in the lower region of a platform-like lower portion of the structure 10. The momentum of the water entering through the intake passageways 14 is arranged to be sufficient to carry over solids from the water bed, with which the external portions of the intake passageways 14 are in contact or are adjacent to, into the interior of the structure 10. The velocity within the structure 10 is arranged to be sufficiently low for heavy solids to settle out of suspension once they have entered the structure through the intake passageways 14. This action continues with the platform-like lower portion of the structure 10 gradually filling with material from the water bed and at the same time being buried deeper in the water bed to form a firm anchorage. If the means for expelling the liquid from the interior of the structure is able to handle solids then the process can continue after the structure 10 is full of solid material from the water bed, excess solid material passing out through the pipe 13 and the pump 15 and settling on top of the structure which continues to bury itself, thereby increasing the effectiveness of the structure as an anchorage.

One advantage of using this method to establish an anchoring point is that comparatively little material need be used to construct the structure, the majority of the mass of the anchoring device being provided by the material dredged up from the water bed. Although illustrated as being sunk into bed material beneath relatively shallow water, the anchoring apparatus can obviously be used also in deep water to provide the totally submerged anchorage point. The actual size of the anchorage may vary enormously as the artisan skilled in the art will readily appreciate. At one extreme the anchorage might for example be used to provide a secure mooring for a small boat while at the other extreme the anchorage might constitute for example the whole or a substantial part of an oil rig platform.