05/485255

11/25/1975

07/02/1974

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Doris C. G.

405/31

E02B3/06; E02B3/06

61/3,4,5,1,46,49

Shapiro, Jacob

Daniel, William J.

This is a continuation-in-part of my co-pending U.S. patent application Ser. No. 324,305 filed Jan. 17, 1973

I claim

1. Protective system against the heaving action of waves of water comprising a bulky obstacle means having a spreading-out surface and providing a substantially uninterrupted impingement area of substantial extent athwart the wave path and exposed to the impact of successive surges of the heave to induce along said spreading-out surface alternate ascending and descending motions of a mass of water of a thickness greater than a boundary layer of water, and means providing a plurality of energy dissipating material elements in front of said spreading-out surface at a distance sufficient to penetrate into said mass of water beyond said boundary layer, said elements serving to slow down ascending and descending water motions and phaseshift the same with respect to the heave, said bulky obstacle means comprising a bulky wall structure having a closed contour and exposed to the impact of said successive surges of the heave, and said energy dissipating material elements comprising an energy dissipating structure arranged in closed contour around the bulky wall structure and comprising a plurality of beams and a plurality of posts supporting the beams in vertically spaced relation at a distance from the bulky wall structure sufficient to dip into said mass of water beyond said boundary layer.

2. Protective system as claimed in claim 1, in which the bulky wall structure comprises a cylindrical wall having a vertical centerline.

3. Protective system as claimed in claim 1, in which the bulky wall structure comprises a lobate wall having a vertical centerline.

4. Protective system as claimed in claim 1, in which the beams project radially outwardly of the posts.

5. Protective system as claimed in claim 1, in which the beams have radially outer surfaces which are substantially flush with radially outer surfaces of the posts.

6. Protective system as claimed in claim 1, in which the beams are supported with at least about 1 meter clearance between adjacent beams, in vertical direction.

7. Protective system as claimed in claim 6, in which the clearance is about 2 meters.

8. Protective system as claimed in claim 1, in which the beams have a width in the range of between about 0.50 meter and about 1.50 meter in radial direction of the energy dissipating structure.

9. Protective system as claimed in claim 8, in which the beams have a height less than said width.

10. Protective system as claimed in claim 9, in which the beams have diamond shaped cross-sections.

11. Protective system as claimed in claim 9, in which the beams have bevelled cross-sections.

12. Protective system against the heaving action of waves of water comprising a bulky obstacle means having structure spreadingout surface and providing a substantially uninterrupted impingement area of substantial extent athwart the wave path and exposed to the impact of successive surges of the heave to induce along said spreading-out surface alternate ascending and descending motions of a mass of water of a thickness greater than a boundary layer of water, and means providing a plurality of energy dissipating material elements in front of said spreadingout surface at a distance sufficient to penetrate into said mass of water beyond said boundary layer, said elements serving to slow down ascending and descending water motions and phaseshift the same with respect to the heave, said bulky obstacle means comprising a reinforced concrete wall structure having a closed contour and exposed to the impact of said successive surges of the heave, and said energy dissipating material elements comprising an energy dissipating structure arranged in closed contour around the wall structure and comprising a plurality of reinforced concrete beams, and a plurality of reinforced concrete posts supporting the beams in vertically spaced relation at a distance from the bulky wall structure sufficient to dip into said mass of water beyond said boundary layer, at least one platform supported by the wall structure above the water level, a plurality of reinforced concrete radiant braces connecting the energy dissipating structure to the wall structure; and prestress steel units passing through the wall strcture and through the beams, posts and braces.

The invention covers protective systems against wave and heave effects and especially applies to the protection of port facilities and offshore facilities.

The development of problems raised by such facilities, especially related to the development of oil industry and the exploitation of sub-marine deposite, created an increased need for adequate systems which can protect marine facilities against heave and wave effects. In the existing systems, one mainly attempts to dissipate wave and heave energy, for instance between the blocks of rough stones in a conventional breakwater or through the apertures of a perforated caisson breakwater. This invention permits an efficient protection to be achieved using various means which can be used in combination with a breakwater of a known type in order to improve the protection provided by the latter.

It is well known an important effect of an obstacle opposed to heave (for instance a vertical wall opposed to a heave normally oriented to its plane) is the heave reflection on the obstacle against the incident heave. It results in an amplification of the incident heave amplitude on the obstacle, the latter creating a force field which increases the incident energy. A protective system against heave effects will then have to reduce the reflection of the incident heave.

The invention is based on the remark that the reflection occurs while the fluid which has been projected upwards at the time of a surge impact is falling down, and the invention consists in slowing down the energy restitution to the heave by dissipating the energy of the fluid while it is raising up, then falling down in front of the obstacle. The raising and falling fluid energy along the obstacle is therefore partially absorbed and phase-shifted with respect to the incident heave.

To do this, according to the invention, ascending and descending motions of the fluid are opposed to by energy dissipating members arranged in front of the obstacle so as to dip into the water mass under motion beyond the boundary layer thereof.

The energy dissipating members can be material elements resting over the surface of the obstacle or arranged against this surface and projecting in front of the obstacle. They must slow down the projection of a water mass well above the incident heave peak level, then slow down water fall along the obstacle. The geometric shapes of the material elements which can be obtained in sculpturing them out of the obstacle or in securing on its surface separated elements, shall be selected so that these elements will rather deeply penetrate beyond the boundary layer to the water moving up and down along the obstacle to efficiently reduce its energy. The sculptures and all other material elements should not create still water zones covered by a boundary layer beyond which the running fluid is moving without encountering any obstacle. This is a problem well known in thermal exchanges between a fluid and a thermal wall, the solutions of which can be used, save on the scale, to solve the above mentioned difficulty. The material elements of the invention may comprise separated and discontinuous elements which constitute structures permitting water drainage, and which can be made under the form of discontinuous inclined slots, studs or bars projecting from the obstacle surface and arranged in staggered relation as eddy generators or sending the fluid towards shocks against other elements or against other portions of fluid, with cancellation of the trend to create a limit layer.

In an embodiment, the system of the invention includes a wall provided, on its front face exposed to heave action, with projecting studs arranged in staggered relation and preferably unevenly distributed. These studs can show, on straight section, asymmetrical profiles and/or inclined profiles over the general direction of the ascending and descending motions of the fluid (i.e. inclined over the vertical line), so as to introduce into these motions a circulation generating fluid deviations and end eddies at the stud ends and therefore an instability of the stud boundary layer likely to prevent building up of the boundary layer.

The projecting studs can be easily derived, in constructive manner, from other anti-heave systems. They can consist, for instance, in pipes draining water through the apertures of a perforated wall of a breakwater of the perforated caisson type.

In another embodiment, studs can be replaced by a system involving linear slots and baffles. According to the wall construction mode, it can be easier to provide discontinuous linear force motion fendering devices arranged in such a way that they prevent the wall limit layer from being created. For instance, these motion fendering devices can be similar in shape, save on scale, to heat exchanger blades or centrifugal gimblets.

Also in another embodiment, the protective system of the invention involves a plurality of separate obstacle members arranged in staggered relation to provide a substantially uninterrupted impigement area for the heave, a colonnade, for instance.

In another embodiment, the obstacle is a bulky wall structure having a closed contour --such as a cylindrical or lobate structure with a vertical centerline--, and the energy dissipating members comprise a plurality of beams supported in vertically spaced relation by a plurality of posts arranged in closed contour around the wall structure. The bulky wall structure is exposed to the impact of successive surges of the heave to induce along the wall structure ascending and descending motions of a mass of water of a thickness greater than a limit layer of water, and the beams are supported at a distance from the bulky wall structure sufficient to dip into the mass of water beyond the limit layer, the beams serving to slow down said ascending and descending motions and phase-shift the same with respect to the heave.

Preferably, the clearance between adjacent beams is at least about 1 meter in vertical direction and the width of the beams is in the range of about 50 centimeters and about 1.50 meter in radial direction of the structure, to produce a significant energy dissipating effect. Still more preferably, the vertical clearance is about 2 meters.

The beams preferably have a cross-section which is flattened to be wider than high, such as a diamond shaped cross-section or a bevelled cross-section.

The following description completed by attached drawings given as non limitative examples, will help in explaining how the invention can be achieved.

FIG. 1 is a partial view, in vertical crosssection, of a heave protective wall provided with studs;

FIG. 2 is a partial elevation view of the wall shown on FIG. 1;

FIG. 3 shows a partial view similar to that shown on FIG. 2, showing a modification;

FIG. 4 shows a perspective view of a stud represented on FIG. 3;

FIG. 5 shows a partial view similar to that on FIG. 1, showing another modification;

FIG. 6 is a partial view similar to FIG. 2, showing another modification;

FIG. 7 is a vertical cross-section following line VII--VII of FIG. 6;

FIG. 8 shows a partial perspective view of a modification to the embodiment of FIGS. 6 and 7;

FIG. 9 shows a plane view of a protective system including a vertical colonnade;

FIG. 10 shows an elevation view of a modification to the protective system of FIG. 9;

FIG. 11 shows an elevation view of a protective system involving horizontal drums;

FIG. 12 shows a vertical cross-section following line XII--XII shown on FIG. 11;

FIG. 13 shows an elevation view of a protective system involving vertical and horizontal drums;

FIG. 14 is a cross-section following line XIV--XIV shown on FIG. 13;

FIG. 15 is a top plan view of a protective system comprising a cylindrical wall structure having a vertical centerline and an energy dissipating structure involving a plurality of horizontal circular beams supported in vertically spaced relation around the wall structure;

FIG. 16 is a larger scale cross-section following line XVI--XVI shown on FIG. 15;

FIG. 17 is a perspective view of a part of the protective system shown on FIGS. 15 and 16;

FIG. 18 shows a protective system comprising a lobate wall structure having a vertical centerline, and an energy dissipating structure involving a plurality of horizontal circular beams supported in vertically spaced relation around the wall structure, in cross-section following line XVIII--XVIII of FIG. 19;

FIG. 19 is a cross-section following line XIX--XIX of FIG. 18;

FIG. 20 is a perspective view of a part of the protective system of FIGS. 18 and 19, at a larger scale;

FIG. 21 is an enlarged view of a part of FIG. 18, showing a modification;

FIG. 22 is cross-section following line XXII--XXII of FIG. 21;

FIG. 23 is a view similar to FIG. 22, showing a further modification.

FIGS. 1 and 2 show the upper part of a protective wall 1, whose front surface 1a exposed to heave 2 provides an impigement area therefor and is provided with a plurality of studs 3 arranged in several horizontal rows 3a, 3b, 3c irregularly spaced over a vertical distance. Studs 3 can be arranged in regular staggered relation, as shown, or each stud can be horizontally shifted with respect to the studs included in all other rows. More generally, stud arrangement on surface 1a can be of any other type (i.e. other than horizontal rows); however, vertical distances between the adjacent studs are preferably irregular. In the embodiment shown, studs 3 are projecting over the same length l in front of surface 1a, but in other embodiments, length l could vary from one stud to another.

When a wave is such that the heave arrives against solid wall 1, a part of its energy is transformed into an ascending vertical motion along surface 1a. Should the wall be smooth (i.e. should it not include studs 3 or equivalent asperities), water would go up, as shown in 5a in dotted line, to a considerable height and would then fall down so generating (or contributing to generate) the well known reflection or underset phenomenon which considerably increases the incident heave energy and aggressiveness.

Studs 3 have a noticeable length l, as shown on the Figure, so that they extend beyond the boundary layer of the fluid which is vertically moving along surface 1a. In other words, studs are not short asperities, the purpose of which would only be to slow down a rather thin fluid layer moving against surface 1a to make it a still water layer in which they would be fully sunk, but they penetrate into the wave beyond this layer. Studs 3 so generate in water going up following arrows 6 (FIG. 2) eddies 6a which reduce its motion, so that the water only reaches a reduced height as shown on FIG. 1, in 5. Water which goes down then along surface 1a following arrows 7 is falling from a reduced height and therefore with a smaller energy which is still reduced by eddies 7a which are created around studs 3.

In the modification shown on FIGS. 3 and 4, studs 8 having asymmetrical profiles with respect to the general vertical direction of the ascending and descending fluid flows introduce in a well known manner a circulation of such flows, as shown by ascending current lines schematically drawn in 9. This circulation will increase the energy dissipation and result in fluid deviations and eddies at the stud ends (Prandtl end effect). These eddies have been schematically shown in 10 on FIG. 4, for the descending flow, the deviations and these eddies contribute to the instability of the stud limit layer.

On FIG. 5, wall 11 is the front wall, face 11a of which is exposed to heave effects, of a perforated caisson which reduces the heave energy, in a well known manner, leaving water flowing through holes 12 between face 11a and the caisson included between the other face 11b of the wall and another wall which is not shown in the Figure. According to a particularity of the invention, holes 12 are made in wall 11 (which is made of concrete, for instance) by pipes 13 projecting on face 11a of the wall, so constituting studs which absorb a part of the ascending and descending flow energy, as it is the case in the embodiments shown on the previous Figures and which modify the flow through holes 12 in attenuating the Borda phenomenon. The ends of pipes 13 can be bevelled as shown in 13a, so permitting the hole output to be modified (preferably in increasing their output while ascending water motions take place, as shown by arrow 14) and eddy generation to be favoured, at pipe ends as shown in 14a.

FIGS. 6 and 7 show an embodiment in which studs have been replaced by discontinuous linear blade sections 15 projecting on face 16a of wall 16. These linear blade sections are inclined laterally and define a plurality of slots 17 therebetween. The inclined and discontinuous arrangement of these blades prevents water from generating still water zones in slots 17.

When the arrangement of the wall or obstacle on which these blades are resting so permits, blades such as blades 15 are spiral wound, so that ascending and descending flows are subject to a centrifugal effect which prevents still water zones from being generated in the slots and boundary layer from building up on the blades. For instance on FIG. 8, blades 18 are spiral wound over outside surface 19a of a circular wall 19 designed to protect an offshore structure.

In the embodiment shown on FIGS. 1 through 8, the spreading-out surface of the system, providing the impigement area for the heave and energy dissipating material elements, is a wall face. However, it could be of advantage to arrange the material elements on a plurality of separate obstacle members staggered in a direction perpendicular to the system spreading-out front surface, to provide the substantially uninterrupted impigement area. For instance one can see on FIG. 9 a colonnade made of several vertical columns 20 arranged in regular staggered relation and provided each with energy dissipating elements 21 which can be studs or any other type of elements as described on the previous Figures. A larger and efficient wet surface is then obtained.

In other embodiments, the obstacle means involves one or several colonnade areas and one or several solid areas. On FIG. 10 for instance, this is a wall which alternatively includes solid horizontal strips 22 and horizontal strips 23 made of colonnades similar to those shown on FIG. 9. This arrangement permits a cheaper cost and reduces the difficulty likely to be encountered when constructing the obstacle means in placing the most efficient part thereof approximately at the medium water level in calm weather, the said most efficient part extending over the tide range with an appropriate margin for heave amplitude. It goes without saying that the columns can be of any section, polygonal with rectilinear sides, convex or concave for instance, and that a more or less strict alternation can be provided between solid portions and colonnades.

The colonnade shown on FIG. 9 or the colonnade areas such as those shown on FIG. 10 can be replaced by several horizontal drums 24 arranged in regular staggered relation (FIGS. 11 and 12) or by horizontal drums 25 crossed with vertical drums 26 (see FIGS. 13 and 14).

The protection constituted by colonnades, horizontal or crossed drums, or by their alternation with solid zones will follow the contour of the structure to be protected, at a convenient distance from the latter. This structure could be a beach, a wharf or a tank which will be enclosed by the protective system. The distance between the structure and the system will be defined taking into account the residual heave reflected by the structure, on which the protective system operates from its rear face to reduce it. This distance can be small.

When the structure to be protected (wharf or tank, for instance) includes a vertical or almost vertical wall, it can constitute with the protective colonnades installed behind it a kind of caisson acting as a perforated caisson in order to contribute to the heave energy dissipation.

It should be noter that in a protective system made of concrete, including solid portions alternating with colonnades or horizontal or crossed drums zones, the columns or drums can be used to pass prestress steel reinforcing elements ensuring the strength of the structure and columns proper (or drums). These steel reinforcing elements can be cables passing through pipes which are then filled of concrete to obtain the columns or drums. This remark especially shows that in addition to their heave reducing effect, horizontal drums can also play a very useful part in the structure strength.

FIG. 15 shows a circular wall 27 designed to protect an offshore structure (not shown on the Figure). At a distance around wall 27, a plurality of posts or columns 28 have been arranged in a circle to support a plurality of horizontal circular beams or string-courses 29 forming with the columns a kind of grid, as shown on FIG. 17. The edifice including wall 27 and grid 28, 29 is completed by a plurality of braces 30 connecting the wall and the grid. The edifice is made of reinforced concrete and, to facilitate building operations, columns 28, string-courses 29 and braces 30 are rectangular in section. Grid 28, 29 is capped by an upper circular beam or roofing 31 which is also rectangular in section. Prestress steel reinforcing units 32 pass through the columns, beams and braces.

AS the waves impinge against circular wall 27, they will induce ascending and descending motions of a mass of water which will in turn wash a number of the horizontal circular beams 29, 31 and the latter will generate energy dissipating eddies like the material elements of the embodiments already described.

It will be appreciated that, in FIGS. 15 to 17, the circular beams are supported cantilever in front of the posts, so that the full cross-sections of the beams project radially outwardly of the posts. This construction makes it possible to obtain a good energy dissipating effect with a short spacing of the posts, because the full lengths of the beams are useful for this purpose.

FIGS. 18-20 show an energy dissipating structure of easier construction, in which the radially outer and inner surfaces 33a, 33b of horizontal circular beams 33 are flush with the radially outer and inner surfaces 34a, 34b of posts 34, respectively. This construction mode does not reduce significantly the energy dissipating effect of the beams, because the spacing of the posts is much greater than in FIGS. 15-17, and the beams can work along substantial lengths between the posts.

Moreover, the bulky impigement structure of FIG. 18 comprises a lobate wall structure 35, that is to say a wall made of a plurality of part-cylinder portions 35a, 35b, 35c, 35d, 35e, 35f having vertical centerlines to form a festooned cross-section as shown. The posts are connected to the wall structure by a plurality of pairs of braces 36, 37 joining at the intersections 38 of the lobes.

Wall 35 is designed for supporting a double decked platform 38 above the surface of the sea 40, to receive offshore industrial plants such as an oil winning or processing plant. Wall 35 and posts 34 are built upon a common foundation raft 41 which is made to rest on the bottom of the sea 42.

Here again, wall structure 35, beams 33, posts 34 and braces 36, 37 are made of reinforced concrete, and are used for the passage therethrough of prestress steel units 32.

As already stated, the horizontal beams should have a substantial width in radial direction and should be substantially spaced in vertical direction, in order to dissipate energy of the waves to a considerable extent. For example, in an embodiment of FIGS. 15-17, beams 29 are one meter wide and the vertical clearance between adjacent beams in 1 meter as well. In an embodiment of FIGS. 18-20, beams 33 are 1 meter wide and the vertical spacing is 2 meters.

The height of the energy dissipating beams is immaterial, and the beams preferably have a cross-section which is flattened to be wider than high. In other words, the horizontal beams may be given a height less than their radial width, in order to reduce the horizontal thrust or pressure applied thereto by the waves. Also, the posts may be flattened or streamlined in cross-section, i.e. have a relatively thinner width circumferentially to the energy dissipating structure than radially thereto, in order to reduce the horizontal thrust or pressure of the waves. FIGS. 21-23 show embodiments in which both the beams and posts have such flattened corss-section. In FIGS. 21 and 22 both beams 43 and posts 44 have diamond shaped cross-sections. In FIG. 23, beams 45 have bevelled cross-sections.