WO2001036751A1

WO2001036751A1 - Barrier for coast protection

Info

Publication number: WO2001036751A1
Application number: PCT/EP2000/011341
Authority: WO
Inventors: Adriano Bertoldi; Massimo Abbiati
Original assignee: Adriano Bertoldi; Massimo Abbiati
Priority date: 1999-11-16
Filing date: 2000-11-16
Publication date: 2001-05-25
Also published as: ITMI992383A1; IT1313930B1; AU1521801A; ITMI992383A0

Abstract

The invention describes a barrier for coast protection, which can work also as breakwater barrier and has a low environmental impact and a high level of efficiency; said barrier consists of a series of basic modules (4) linearly assembled. The basic module (4) of the barrier consists of three elements: at least one float (1) setting under tension a submerged 'sail' (2), the latter being made of a material which is partially or totally impermeable to water and/or to sediments, anchored to the sea floor; the structure can be temporarily raised or supported, so as to adapt it to the natural answers and to the changing anthropic needs, until it is cancelled out by laying it onto the sea floor to be used as a consolidation element.

Description

BARRIER FOR COAST PROTECTION Field of the invention

The invention relates to a barrier for coast protection which can also be used as breakwater barrier. Prior Art

Emerging or supported breakwater barriers for coast protection are carried out at the state of the art: a) with natural rocks: taken out and thrown into the sea with or without foundation b) with concrete: laid down after carrying out suitable foundations obtained by heaping or gathering prefabricated elements, tripods or caissons c) with geo-textile fabric: pipes in geo-textile fabric filled with sand or ballasts and laid onto the beach or onto the sea floor d) by combining the three aforesaid techniques

In cases "a)", "b)" and "d)" the main disadvantages are: - Stiff elements, therefore destined to be destroyed or removed by the sea, and thus requiring a continuous and expensive maintenance.

Heavy elements, therefore tending to collapse if laid down onto sea floors which are not consolidated.

Expensive elements, both because of installation costs and because they re- quire foundations.

Non removable elements, having a strong permanent negative environmental impact, both from the aesthetic point of view and from the point of view of use and morphologic modification of the coast.

Elements which are impervious to sediments. In case "c)" the limitation results from the nature of the material, which enables to carry out only groins or small barriers, typically supported. Summary of the invention

The main aim of the present invention is to solve the aforesaid problems, in particular to provide a barrier with a low environmental impact and a high level of effi- ciency, said aim being reached by using new technologically advanced materials which replace traditional materials giving better results, a higher flexibility and therefore the possibility to adapt to the natural conditions and to the changed an- thropic needs (including the possibility to be removed, so that they don't become a permanent modification of the environment).

The main feature of said technologically advanced materials is lightness and an easy, cheap and fast (mechanical) assembly and installation. These features allow to vary the geometrical configuration of the structure so as to adapt it to the changing environmental conditions and anthropic needs (use), both during the year (seasonal) and through the years.

In particular, the position of the float and/or the height of the sail can be varied by changing the features of the barrier, i.e. by raising it, supporting it or temporarily eliminating it in case said float is laid onto the sea floor. The barrier length can also be varied by adding or leaving out basic modules. Said barrier is able to interact with the natural solid transport mechanisms regulating the formation, the growth and the permanence of beaches and can also work as a usual breakwater. In particular, said barrier can be an active barrier, i.e. it can help the natural re-growth of beaches by using the sediments in suspension carried by the sea.

The mechanism at the basis of said phenomenon is to carry out a sediment trap by means of a barrier having the features according to Claim 1 and which is permeable to their passage. Said "filter" can slow down and enable the deposit of the sediments in suspension by modifying the depths of the sea floors and its currents, thus starting a natural active process of coast re-growth.

Another object of the present invention is providing a low cost barrier for the coast protection and which doesn't sink in the sea (or water) floor; this problem is solved with a barrier having the feature of Claim 17. Claim 25 relates to a method for beach regrowth according a further aspect of the present invention.

Brief Description of the Figures

The invention will now be further described with reference to the enclosed drawings, characterized in that: Figure 1 shows a schematic perspective section of the barrier with the indication of a basic module 4.

Figure 2 shows a schematic axonometric view of the basic module with the indication of the three elements it consists of, i.e. float 1 , sail 2 and anchorage 3. Figures 2a, 2b, 2c, 3f show different embodiments of a basic barrier module according to the present invention.

Figure 3 shows a schematic section view of the basic module with the indication of the three elements it consists of, i.e. float 1 , sail 2 and anchorage 3. Figure 3a show schematically different anchoring means of a barrier basic module according to the present invention.

Figures 3b, 3c, 3d, 3e show schematically different ways to connect the sail to the anchoring of a barrier basic module according to the present invention. Figure 4 shows a schematic section view of the basic module with the indication of the action carried out by the barrier on the transport of sediments 5, their precipitation and their heaping 6.

Figure 5 shows a schematic section view of the basic module with the sail laid down onto the sediment heap 6.

Figure 6 shows a schematic section view of the basic module as a supported bar- rier.

Figure 7 shows a schematic section view of the basic module as a laid-down barrier.

Figure 8 shows a schematic transport of the basic elements. Figure 9 shows a schematic assembly of the elements: float 1 , sail 2, anchorage 3. Figures 10, 10a, 11a show a schematic basic module let down into the sea in the desired position with either an empty anchorage, or partly or completely filled with ballasts.

Figures 11 and 12a show a schematic anchorage 3 laid onto the sea floor in the desired position and filled. Figure 13 shows a schematic section view of several barriers according top the present invention arranged for re-growth.

Figure 12 shows a schematic section view of several barriers according to the present invention arranged so as to dampen the impact of a particularly violent breaker and/or sea storms. Figure 14 shows a schematic plan view of a coastline under erosion.

Figure 15 shows a schematic plan view of several barriers according to the present invention arranged for re-growth and/or to dampen the impact of a particularly violent breaker and/or sea storms.

Figures 16 and 17 show a barrier perpendicular to a shoreline made by several basic moduli of Figure 1. Description of the Preferred Embodiments Figure 1 shows a barrier consisting of a series of basic modules 4 linearly assembled. The basic module of the barrier consists of three elements (Figures 2,3): a float 1 setting under tension a submerged "sail" 2 which is anchored 3 to the sea floor (in the following description as "sail" a bidimensional object is meant, whose stiffness and flexibility will be determined by the skilled technician case by case, taking into account several factors like the energy and wavelength of waves, the water floor slope, the operating depth of the barrier etcetera; geosyntethics is a term known in the actual civil engineering and geotechnics and indicates a wide class of membrane and bidimensional elements usually buried to reinforce a soil or modify its permeability or impermeability property: the geosynthetic material class comprises geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, geocomposites etcetera. Newly developed materials are indicates sometimes as "geo-others", as the technical field keeps remarkably evolving; geotextiles are characterised by a woven or non-woven structure, geogrids and geonets have a bi- or three-dimensional reticular structure; in the following description the sev- eral therms are used with their usual meaning in the art, even if it's difficult to give exact definitions and the therm bounds are not always precise). The length and height of the barrier are suitable for the specific use, for instance length can vary from 10 m to hundreds of miles and height from 2 m to 25 m. The necessary length can be obtained by a linear assembly of a certain number of basic modules 4. The height, which depends on the sea depth, can be obtained by varying the height of the sail 2, which can involve a corresponding change in the size both of the float 1 and of the anchorage 3: the sail 2 and the anchorage 3 have such dimensions that the floating element 1 and/or the upper free end 20 of the sail 2 is kept preferably under the free water level, between the water level and the sea floor (Figures 6, 12). The upper free end 20 of the sail 2 can also reach the sea surface and float on it (Figures 1 ,3, 12, 13). According to an aspect of the present invention, the sail 2 is erected by the water hydrostatic lift (either hanging from one or more floating elements 1 or being self- sustaining, as it will be better described herein) and has a reticular structure so as to slow down the wave motion and filter the sediments in suspension in the water. The components: 1 ) The float 1 :

The float 1 can be carried out in three ways:

1 a) Pneumatic float: carried out with an air chamber, for instance in a rubberized fabric, inflated with air.

1.b) Stiff float: made of polymers, resins or metal, or with the same material of the sail and filled with air, foams or other materials with a specific weight lower than water.

The float 1 must be sized so as to keep the sail under continuous tension and to resist the impact of the wave-motion.

1.c) Distributed float: the floating effect to erect and lift the sail 2 is accomplished distributing one or several floats 1 along the whole sail height, or alternatively across or lengthwise the sail 2, as shown in Figures 2a, 2b, 2c, producing the sail

2 with floating materials or combining the three aforesaid methods of distributed floating. The hydrostatic lift on the sail 2 can also be increased with integral floating parts of the sail 2: in this case, some segments of geogrid rods are expanded (e.g. by foaming while producing the geogrid) until a specific weight of the part sufficiently low is reached. Eventually in this way the floats 1 described in items 1.a and 1.b can be no more necessary to lift the sail 2 in the water and the sail 2 with integral floating parts 1 can be self-sustaining in water. 2) The sail 2: The sail 2 is carried out in geo-synthetic materials like geo-net or/and geo-grid or/and geo-fabric or/and geo-composite and/or other materials partially or totally impermeable to water and/or to sediments in suspension in the active band (in the present description with "active band" we refer to the water strip in front of the shoreline in which the sediments carried towards the deep water by bottom streams can be brought towards the shore again by the surface waves; often, but not necessarily, the edge of such an active band is regarded the isobath at a -10 m depth; but it can be also a different isobath). The materials used for the sails 2 must be highly resistant and stable to atmospheric agents and to brackish water. The sail 2 is subject to a longitudinal tension, stretched between the float 1 and the anchorage 3, and to the pushing of the sea currents; therefore it is sized so as to resist the pressure of the wave-motion and the stress it is subject to because of the float oscillation. 3) The anchorage 3:

The anchorage 3 can be carried out in three ways: 3.a.1 ) Continuous anchorage The anchorage 3 is carried out with one or more tubular bags (as shown in Fig- ures 1-5) made of geo-net or geo-grid or geo-fabric or geo-composite, or other materials (preferably but not necessarily geosynthetic ones) which can retain the inert material filling said anchorage 3, having features of high resistance and stability to atmospheric agents and to brackish water. The filling is made of inert materials 7 having a specific weight similar to the sea floor, such as sea floor sand, river pebbles, inert materials from building demolitions. 3.a.2) Anchorage with plinths

The anchorage 3 can be carried out with one or more concrete plinths made with binders and aggregates, precasted or casted in-situ, having features of high resistance and stability to atmospheric agents and to brackish water. 3.b) Punctiform anchorage.

The anchorage 3 is carried out with two or more plinths 8 made with binders and aggregates precasted or casted in-situ, or micropiles 9 placed lengthwise along the sail width at such a distance that the sail fastening distributes uniformly the sail stresses, as shown in Figure 3a. The anchorage 3 is subject to three main mechanical stresses: a) The float 1 will tend to lift it transmitting vertical pulls because of its continuous oscillation. b) While stopping the sea current, the sail 2 will tend to move it horizontally. c) The sea floor can go down or settle, thus tending to collapse it partially or to- tally.

The anchorage 3 will be sized so as to resist the aforesaid forces by means of the three features now described: a') it will be heavy enough not to be lifted or to roll. b') it should have a support surface so as to exert a friction which can contrast the horizontal force tending to drag it.

C) it will have a height-to-width relation and it will be filled with materials having a specific weight similar to the sea floor, so as not to exert too high a pressure onto the floor and not to collapse.

The anchorage 3 could possibly be used as a foundation for other successive uses.

The elements constituting the basic module of the breakwater barriers float 1 , sail 2, anchorage 3 can be connected one to the other through connecting means which should resist the stresses they are subject to or, if necessary, have sufficient length to form an integral barrier.

The connection of the sail 2 with the anchorage 3 can be: 1 ) Continuous joint: 1.a) If the sail is carried out with geogrids or geonets, the connection can consist of a stiff bar of polymer-, plastic- and/or composite materials, or any other suitable material, fitted in the geonet or geogrid mesh, in such a way to carry a warping out, known per-se in the art.

1.b) In case the sail is carried out with geogrids, geonets or geofabric or geocom- posites, the connection must be carried out by sewing.

1.c) In case the sail is carried out with geogrids, geonets, geofabrics or geocom- posites, the connection can be carried out by burying the sail 2 in an anchorage 3 carried out with a concrete of binders and aggregates eventually casted in situ (Figure 3b). The zone where the sail 2 protrudes from the anchorage 3 is shaped in such a way that the sail can wave without sharp folds or causing friction. In order to reduce the friction between the sail and the anchorage and the bending stresses in the sail, the zone where the sail protrudes from the anchorage can consist of two templates 10 of polymers, plastic materials and/or composites or - any other suitable material, so that the sail bends over it while waving; said tem- plates (10, 10', 10"; Figures 3b, 3c, 3d) have suitable rounded shape to limit over a predetermined value the minimum bend radius of the sail during its movements; the value of said minimum bend radius is predetermined according to the maxi- mum stress and fatigue stress of each material of the sail. The templates 10, 10' or 10" can be buried in the concrete, as shown in Figures 3b, 3d or with a mechanic connection, as shown in Figures 3c, where an upper part 3' of the anchorage 3 presses and blocks the sail 2 against the lower part of the anchorage 3. 1.d) In case the sail 2 is carried out with geogrids, geonets, geofabrics or geocom- posites, the connection can be a hinge-like one, one example of which is shown in Figure 3e, obtained by winding the sail 2 around a stiff metal bar 11 (or polymer-, plastic- and or composite material bar, or made by any other suitable material) and fastened to the anchorage 3. The bar 11 is later connected or secured, according to the previous items 1.a and 1.b.

As can be inferred, the advantages with respect to the known art are to provide a barrier with three functions: a) It can dampen the wave-motion and its impact onto the coast. b) It can slow down (figure 4), filter and enable the deposit 6, 6' of the sediments 5 carried by the sea, both in front and behind the barrier element 4. c) It can be later used, if necessary (Figure 5), as a consolidation element for the sea floor and the deposited sediments 6, as will be better described further on. Let us now describe a preferable installation, referring to Figures 8-11 , 10a, 11a, 12a. The transport and installation of the breakwater barriers can be carried out in a cheap and fast way thanks to the features of the constituting elements and to the way they are assembled:

The float 1 , for instance, if made up of an air-chamber, will be inflated only when the installation has to take place as described later on, and/or, if made up of stiff polymers, it is dragged from the craft before assembly (and not loaded onto the craft).

The sail 2 is folded or wound or rolled so as to have the minimum overall dimensions. The anchorage 3 is folded or wound or rolled so as to have the minimum overall dimensions, and it is filled with the heavy and bulky inert material 7 only when it is let down into water, for instance as described later on. For instance, the installation takes place according to the following stages: The basic elements are made of light materials, which can be folded or wound, thus easily transportable from the production area to the dockyard or port or coast. The sail 2 and the anchorage 3 are assembled through connecting means or welded or glued or sewn or riveted in place (for instance in a dockyard or on the coast), and then loaded onto a craft (Figure 8), where the last assembly stage can possibly be carried out, for instance between the sail 2 and the float 1 and/or between the sail 2 and the anchorage 3, possibly starting to lay them down into the sea (Figure 9).

After carrying out all the assemblies between the elements and after having thus created the basic module 4, said basic module 4 is let down into the sea in the desired position with the anchorage 3 (Figures 10, 10a, 11a) empty, partially or totally filled with ballasts.

The anchorage 3 is laid down onto the sea floor in the desired position where its filling is completed (Figures 11 , 12a). If necessary, the float 1 can be permanently inflated or adjusted in height.

The basic module 4 of the barrier will begin to be active and play its function, waiting for another basic module to be added. Each basic module 4 which is added is tied to the previous one with connecting means. Possible settings and/or adjustments of the floats and/or of the connecting means between the various ba- sic modules 4 can be carried out after installing all the basic modules 4 to form the final barrier. If the barrier has to be permanently or temporarily collapsed, it will be sufficient to deflate the float 2 or to unhook it and/or to tie some weights onto the ends and position the sail 2 as shown in figure 5 or figure 7.

More barriers can be installed, one beside the other, so as to create a system as shown in figures 12,13 and 15.

Said systems can be of two types: a) A system of breakwater barriers for the following re-growth (figures 13 and 15) of a coastline LC under erosion (shown in Figure 14; curves L1 , L2 and L3 are different isobathes). b) A system of breakwater barriers to dampen the impact of a particularly violent breaker and/or sea storms (figures 12 and 15). a) The system of breakwater barriers for the following re-growth (figure 13 and fig- ure 15) provides for several barriers B1 , B2, B3 parallel to the coast LC, installed at given time intervals as described later on:

1 ) The first barrier B1 is installed, which causes a heaping of sediments generating the rise of the soundings until a limit re-growth situation occurs. 2) Now another barrier B2 is installed, farther from the coastline than the previous one. The first barrier B1 can thus be collapsed (for instance separating the floating elements 1 , if any, from the sail 2, or loading it with ballasts) so as to consolidate the grown sea floor, or it can be supported or left emerging. 3) This second barrier B2 can further raise the soundings (by means of the deposit of sediments 6) until the first one B1 , if it had been laid down onto the floor, is covered.

This procedure can be repeated until the desired coast growth is achieved, b) The system of breakwater barriers to dampen the impact of a particularly violent breaker and/or sea storms provides for the use of several barriers such as in figure 12 and figure 15, placed one beside the other parallel to the coast. The height of the floats 1 (or of the free ends 40) will be increasing starting from the outer barrier B3 (supported on the lower depth, for example -15m below the sea level) as far as the inner barrier B1 near the coast, which can be emerged. The waves are dampened and slowed down by the supported barriers which re- duce their periods and/or wavelength, and raise their widths increasingly as far as the last barrier against which said waves break, thus reproducing the effect of the sea floor onto the waves near the shore.

This system can dampen the direct violent impact of sea storms onto a single supported or emerged barrier gradually reducing their strength. System a) and system b) can both be used singularly and interact or integrate so as to increase efficiency and adjust the effects.

Both system a) and system b) can be arranged so as to reproduce the sea floor pattern (soundings) and the coastline (promontories, rocky areas, sandy areas or populated areas), providing for instance in some areas for a single barrier B1 to which, if necessary, others B2, B3 can be added (figure 15).

It should be noted that the present invention is subject to variations and changes made by any technician skilled in the art, without leaving aside the basic teaching of the invention and remaining within the framework of the claims: for example the barrier can slow the waveforms and filter the sediments in suspension by mean of two or several sails 1 , as shown in the Figures 3a, 3c, 3d, 3e and 3f (in Figure 3f the single floating element 1 is also constrained by the links 30, 30'); the barrier elements forming a breakwater system can be parallel (or along) the active band bound or facing (i.e. substantially perpendicular to) the predominant direction of waves, to maximize the breakwater effect; also the maximum slope direction of the sea floor can be taken into account while positioning the barriers in order to improve the sediment retaining effect. The barrier elements can be put to place also in rows perpendicular to the shoreline, as shown in Figures 16 and 17.

Claims

1 ) Barrier for beach protection comprising a sail (2) anchored on the sea floor to an anchoring element (3), said sail (2) being erected by hydrostatic lift, characterized in that said sail (2) has a reticular structure so as to slow down the wave- motion and filter the sediments (5) in suspension.

2) Barrier according to Claim 1 , characterized in that the sail (2) is hanging from at least one floating element (1).

3) Barrier according to Claim 1 , characterized in that the sail (2) is erected by the hydrostatic lift of a plurality of integral expanded and/or foamed portions of said sail.

4) Barrier according to at least one of the previous Claims, characterized in that said reticular structure is permeable to water and is apt to filter the sediments (5) in suspension in the active band.

5) Barrier according to claim 1 , characterized in that said sail (2) is made of geo- synthetic materials.

6) Barrier according to claim 5, characterized in that said sail (2) is made of at least one of the following materials: geo-net, geo-grid, geo-composites, geo-textile materials.

7) Barrier according to Claim 1 , characterized in that the anchoring element (3) consists of at least a plinth (8) and/or a plurality of micropiles (9).

8) Barrier according to Claim 1 , characterized in that said anchoring element (3) consists of a light tubular element filled with an inert material (7) substantially having the same specific weight of the sediments constituting the bottom onto which it rests. 9) Barrier according to claim 8, characterized in that said tubular element is made up of one or more tubular bags in geo-synthetic material.

10) Barrier according to claim 9, characterized in that said tubular element is made up of one or more tubular bags in at least one of the following materials: geotextiles, geo-nets, geo-grids, geo-composites. 11 ) Barrier according to Claim 1 , characterized in that the sail (2) is connected with the anchoring element (3) in at least one of the following ways: by fitting a bar element in the geosynthetic material mesh in a warp-like way, by sewing the geo- synthetic material, by burying the sail (2) in the anchorage element, with a hinge device (11 ), limiting the minimum bend radius of the sail making the sail bend over at least one template (10, 10', 10").

12) Barrier according to at least one of the preceding claims, characterized in that said sail (2) has such a height that said floating element (1 ) and/or the upper free end (20) of the sail (2) is kept under the free water level, between the water level and the sea floor.

13) Barrier according to claim 2, characterized in that said floating element (1 ) is made up of an air chamber and/or in rubberized fabric, inflated with air. 14) Barrier according to claim 13, characterized in that said floating element (1 ) is made of at least one of the following materials: polymers, resins, metal. 15) Barrier according to Claim 14, characterized in that said floating element (1 ) is filled with at least one of the following materials: air, foams, materials having a specific weight lower than water. 16) Barrier according to any of the preceding claims, characterized in that said anchoring element (3), and said sail (2) are reciprocally connected through releas- able fastening means allowing a mounting/demounting of the barrier.

17) Barrier for beach protection comprising a sail (2) anchored on the sea floor to an anchoring element (3), said sail (2) being erected by hydrostatic lift, character- ized in that said anchoring element (3) consists of a light tubular element filled with an inert material (7) substantially having the same specific weight of the sediments constituting the bottom onto which it rests.

18) Barrier according to Claim 17, characterized in that the sail (2) is hanging from a floating element (1 ). 19) Barrier according to Claim 17, characterized in that the sail (2) comprises a plurality of integral expanded and/or foamed portions suitable to erect the sail (2) by mean of water hydrostatic lift.

20) Barrier according to claim 17, characterized in that said tubular element is made up of one or more tubular bags in at least one of the following materials: geo-textiles, geo-grid, geo-net, geo-composite.

21 ) Barrier according to claim 17, characterized in that said tubular element is made of a material which can retain the inert material it is filled with, and that is highly resistant and stable to atmospheric agents and to brackish water. 22) Barrier according to claim 17, characterized in that said sail (2) has a reticular structure so as to slow down the wave-motion and filter the sediments (5) in suspension. 23) System of breakwater barriers, comprising a plurality of barriers according to at least one of the claims from 1 to 22 placed one beside the other, parallel to the coast (LC) or parallel to the active band bound or perpendicular to the predominant wave direction, characterized in that the level of the float (1) or of the free ends (20) of the sails (2) of the barriers starts, for the barrier (B1 ) near the coast (LC), from the water level and is constant, or it decreases until a predetermined depth for the barrier (B3) farther away from the coast, at which depth it can dampen waves.

24) System of breakwater barriers according to Claim 23, characterized in that said predetermined depth is 15 m from the sea level. 25) Method for beach re-growth, characterized in that it comprises the following stages:

- installation of a barrier consisting of a sail (2) anchored on the sea floor to an anchoring element (3) erected by the hydrostatic lift;

- formation of a sediment dune (6) between said barrier and the shore thanks to the interaction between the wave-motion and said barrier;

- collapsing of said barrier so as to lay down said sail onto the sediment dune (6) formed as a final consolidation of said barrier.

26) Method according to Claim 25, characterized in that said sail (2) is hanging from at least one floating element (3). 27) Method according to claim 26, characterized in that the collapsing stage provides for the separation of said floating element (1 ) from said sail (2).

28) Method according to claim 26, characterized in that the collapsing stage provides for the filling of said floating element (1 ) with inert materials having a specific weight equal to or higher than that of the water characterized in that said barrier is plunged.

29) Method for beach re-growth according to at least one of the claims from 25 to 28, further comprising the following stages: installation of one or more barriers between said first barrier (B1 ) and the shore, so as to form one or more additional sediment dunes covering the previous collapsed barriers and further raising the sea floor, thanks to the wave-motion interacting with the last barrier. 30) Method for beach re-growth according to at least one of the Claims from 25 to 28, further comprising the following stages: installation of one or more barriers as the previous one between said first barrier and the open sea, so as to form one or more additional sediment dunes covering the previous collapsed barriers and further raising the sea floor, thanks to the wave-motion interacting with the last barrier.

31 ) Method for beach re-growth according to at least one of the claims from 25 to 30, characterized in that said barrier is according to at least one of the claims from 1 to 24.