CA2059136A1 - Coastal stabilization by fluidizing non-cohesive subsoil - Google Patents

Abstract

Coastal maintenance, such as for beaches or navigable channels.
Fluidized subsoil, whether from beach enhancement or from clearing a channel if not swept onto a nearby beach (Figs. 1, 2) may be fed into an alongshore current (Figs. 9, 10, 11, 12), or piping, and be transported elsewhere. Water is removed from subsoil underlying a beach (Figs. 13, 14, 16) via first foraminous pipes (71, 73) and is jetted (Fig. 15) via other foraminous pipes (81, 83, 87, 89), interconnected by a non-foraminous pipe (75), into adjacent offshore subsoil to fluidize it. As an alternative to continuous flow, fluidization via a piping array is augmented by sequential timing in a manner resembling peristalsis, to generate lateral flow (Figs. 7A, 7B, 7C; 8A, 8B, 8C). Valve-control means (Figs.
6) opens and closes individually valved water-jetting branch tubes (6; Figs. 3, 4) in accordance with a pre-set pattern of sequence and duration or sensors (3; Figs. 5A, 5B) of fluid flow and/or pressure.

Description

WO 91~1404, 2 ~ PCI-/US91/0148 COAST~ - $TA~ Z~TION BY FLUIDIZING NON--CO}iE:~ SUBSOIL

This invention relates to stabilizing coastal regions, ~ as by fluidizing offshore non-cohesive subsoil in deshoaling 6 harbors or navigable inlets or channels, and transporting 7 the fluidized subsoil elsewhere, as onto a beach to augment 8 or maintain it, with or without beach subsoil dewatering.

BACKGROUND OF THE INVENTION
ll Numerous methods have been suggested and many have been l~ used to prevent coastal erosion, and to encourage accretion 13 of sands or other subsoils that are non-cohesive when wet, 14 especially so as to enhance beaches and/or to stabilize navigable re~ions regardless of beach enhancement. Efforts 16 to overcome harm~ul effects of wave action or of alongshore 17 drift as by constructing groins, jetties, or other barriers 18 have often been unavailing, and frequently have occasioned l9 the opposite of what was sought, such as excess collection on the updrift side of sand that would have been shared with 21 a downdrift beach in the absence of such man-made obstacle.
22 Navigable inlet or channel maintenance traditionally is 23 attempted by dredging, repeated whenever nature fills in an 24 existing or former channel--usually more often than anyone anticipated. The necessity of periodic redredging may be 26 overlooked or, if considered, be optimistically minimized, 27 whereupon its actual cost may prove to exceed budget limits.
28 Accordingly, in many instances no effective action is taken, 29 or (if taken) becomes ineffective because of financial or technical limitations. Dredging is disruptive to underwater 31 landscapes and conducive to deleterious changes in e~isting 3~ currents or tidal flows or their effects. Dredging also may 33 necessitate costly transporting and redeposition of subsoil.
3~ Injection sf water into non-cohesive subsoil, such as sand, fluidizes it into a readily transportable slurry. Of f-3~ shore sandy subsoil can be so fluidized and be redistribu~e~
37 Dy water currents and wave action or ~ eduction pumpln~

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~O9l/l4047 2 ~ 5 ~ ~ 3 6 pcr/us9~ 482 1 Fluidization is well recognized in technical literature 2 as a supplement--or preferably an alternative--to dredging.

3 Contributors include Bruun in "Maintaining Tidal Inlet Chan-nels by Fluidization" J. Waterway etc. Enaineerina, ASCE, 110 (ww4) 117-120; Bruun and Adams in "Stability of Tidal 6 Inlets: Use of Hydraulic Pressure for Channel and Bypassi~g 7 Stability" J. Coastal Research 4 (1988) 687-701; and the 8 present inventor, as with Weisman and Collins, "Fluidization g as Applied to Sediment Transport (FAST) as an Alternative to Maintenance Dredging of Navigation Channels in Tidal Inlets"
11 Wastes in the Ocean vol II: Dredged Material Disposal in 12 the Ocean, Kester et al. (eds.) Wiley (1983). ~ -13 Accordingly, shoals in an otherwise navigable channel 1~ or similar waterway can be relocated downstream upon being fluidized. Optionally, if natural drift at a shoal location 16 is not favorable, but a not-too-distant region has favorable 17 prevailing currents, the fluidized subsoil can be co}lected, 18 be pumped to, and be released at the latter location for 19 natural redistribution. As the physical characteristics and behavior of non-cohesive subsoils become better understood, 21 fluidization doubtless will be recognized as the procedure 22 of choice, both technically and economically, to solve such ~`
23 environmental problems as shoaling of navigable channels.
24 Even such alternative channel clearing and maintenance :~
have relied upon the energy-intensive step of dredging to 26 enable the necessary piping to be buried preparatory to 27 fluidizing use. Prior art is represented by van Steveninck, 28 in U.S. Patent 3,695,049, wherein piping to be buried is sup-29 plied with one or more small accompanying pipes to fluidize underlying subsoil, sink~ing the pipeline together with the 31 fluidization pipes; and in "Pipeline Burial by Fluidi~ation"
32 Paper No. OTC 2276 of OFFSHORE TECHNOLOGY CONFERENCE of 33 American Institute of Mining, Metallurgical, and Petroleum 34 Engineers at Dallas, Texas in 1975, wherein a horseshoe-shaped device straddles piping to be emplaced and jets water 36 from openings in its hollow lower parts; the piping and the 37 straddling device sin~ into subjacent fluidized sandy soil.

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`~091/1404, ~ 3 ~ Pcr/us~l/0l482 1 The present inventor follows the precept that man has 2 to learn to use, rather than to oppose, nature in all such 3 environmental efforts. Elsewhere, as in his pending patent 4 application (PCT/US91/00421) he has described novel means and methods of emplacing foraminous piping for fluidization 6 and dewatering purposes.
7 Beach stabilization using dewatering foraminous piping 8 is a somewhat more recent development. Informative articles 9 about beach stabilization include "New Method for Beach Ero-sion Control" by Machemehl, Yrench, and Huang in Civil En-11 aineering in the Oceans/III (1975) 142-160 and "Experimental 12 Control of Beach Face Dynamics by Water-Table Pumping" by 13 Chappell, Eliot, Bradshaw, and Lonsdale in Engineerina Geol-14 ogy, 14 (1979) 21-40--both of which describe how water withdrawal from subjacent beach sand is conducive to deposi-16 tion of more sand. Vesterby U.S. Patent 4,645,377 teaches 17 such dewatering just below the mean high water level. A com-18 plex variation is suggested by Lin in U.S. Patent ~,898,495.

SUMMARY OF THE INVENTION
21 This invention utilizes subsoil fluidization to improve 22 harbor or navigable inlet or channel deshoaling and main-23 tenance and to improve beach enhancement and maintenance.
24 In general, these objectives are attained by fluidizing offshore subsoil (non-cohesive when wet) for transport from 26 an existing location to a preferred location in slurry form, 27 whether by natural flow of the adjacent water or assisted by 28 pumping. Water--as from onshore storage or withdrawn from 29 subsoil underlying a nearby beach--and/or air is jetted into such offshore (underwater) subsoil to fluidize it into a 31 slurry. Such jetting occurs steadily, intermittently, or in 32 patterned pulsed manner via foraminous piping for desired 33 fluidization. Other objectivess of the present invention, 3~ with means and methods for attaining the various objectives, will be apparent from the following description and from the 36 accompanying diagrams of preferred embodiments, which are 37 presented here by way of example rather than limitation.

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WO 91tl40~7 2 ~ ~ 9 ~ 3 6 PCT/VS91/01482 1 SU~MARY OF T~E DRAWINGS
2 Fig. l is a schematic perspective illustration of an 3 embodiment of fluidization of non-cohesive subsoil, as in channel maintenance, according to the present invention;
Fig. 2 is a schematic plan view of another e~bodiment 6 of fluidization by this invention, with subsoil removal;
7 Fig. 3 is a plan of supply piping, wit~ multiple 8 foraminous branch lines, according to this invention; and g Fig. 4 is a side elevation of a segment of the piping of Fig. 3, in a position for use according to the invention;
ll Figs. 5A and 5B are schematic end sectional elevations ~i~
12 of another embodiment of this invention, with buried piping, 13 shown before (Fig. 5A) and after (Fig. 5B) fluidization use;
14 Fig. 6 is a schematic representation of a control unit for individual valves of the foraminous fluidization piping;
16 Figs. 7A, 7B, and 7C are sequential plan views of a 17 piping array of the invention at }engthwise timed intervals;
18 Figs. 8A, 8B, and 8C are similar sequential plan views l9 of such array àt successive widthwise timed intervals.
20 Fig. 9 is a schematic plan of an eroded beach (at left) ', 21 and a shoaled navigation channel (at right):
22 Fig. l0 is a schematic elevation of the same eroded 23 beach and shoaled navigation channel, taken in Fig. 9 along 24 X-X onshore at the left and offshore at the right;
Fig. ll is a plan of the beach (at left) of Fiqs. 9 and 26 l0 enhanced by sandy subsoil from the shoaled channel; and 27 Fig. 12 is a sectional elevation of the previous chan-28 ' nel (Figs. 9 and l0) after de-shoaling by fluidization.
29 Fig. 13 is a side view of a beach and offshore vicinity (sectioned) embodying apparatus according to this invention;
31 Fig. 14 is a plan view corresponding to Fig. 13:
32 Fig. 15 is a sectional elevation taken along Xv-XV of 33 Fig. 14, looking onshore from (far right) offshore;
34 Fig. 16 is a sectional elevation similar to Fi~ but taken along XVI-XVI at an intermediate location;
36 Fig. 17 is a side sectional elevation of a variant of 37 the locality and apparatus of Fig. 13;

- . . ~ , , , ~091/l4W~ ~J~j9~ ~fi PCT/US91/01482 1 Fig. 18 is a side elevation of another embodiment of 2 foraminous piping (or jet tubing) useful in the practice of 3 the present invention:
4 Fig. 19 is a transverse sectional view of such piping embodiment taken at XIX on Fig. 18;
6 Fig. 20 is a side elevation yet another embodiment of 7 foraminous piping (or jet tubing) useful in the practice of 8 the present invention: and g Fig. 21 is a transverse sectional view of such piping embodiment taken at XXI on FigO 20.

12 DESCRIPTION OF ~OD~S OF THE INV~NTION
13 Fig. 1 shows schematically, in sectional perspective, a 14 first embodiment 10 of this invention as parallelepipedal block 11 of a channeled section of non-cohesive subsoil 15 16 having thexein several side-by-side mini-channels 17A, 17B, 17 17C. Three parallel fluidization pipes 16A, 16B, 16C--each 18 with a valve V therein--extend along the bottoms of the 19 respective mini-channels from the OFFSHORE or EBB area (arrow located at and directed to lower left) upgrade toward 21 the opposite ONSHORE or FLOOD direction (arrow located at 22 and directed to upper right). An arrow located at the lower 23 right but directed to the upper left indicates LATERAL DRIFT
24 or natural alongshore current flow direction. It will be understood that wave and tidal action are substantially per-26 pendicular to the shoreline, whereas alongshore drift is 27 more likely to be substantially parallel thereto.
28 The contouring illustrated in Fig. 1 conforms to cus-29 tomary fluidization results. As expected, the eleva~ion of subsoil between adjacent mini-channels is less than it is at 31 opposite sides of the entire channel. The rather angular 32 stylization of the drawing is for simplicity of the showing, 33 whereas in nature the edges and surfaces of non-cohesive sub-34 soils normally are rounded to a greater or lesser degree or extent. Fluid connections to the pipes are omitted as 36 within the skill of persons ordinarily skilled in the art.

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W091/l4047 ~ V ~ ~1 3 ~ PCT/US91/0~482 ~6-1 Fig. 2 is a schematic perspectlve of an additional 2 fluidization embodiment lo' of this invention viewed from 3 above and to one side. Instead of the three pipes of the ~ preceding view, two pairs of parallel pipes 16A' & 16B' plus 16C' & 16D' are spaced laterally apart, in non-cohesive sub-6 soil 15 (stippled). Upright exhaust pipe 19 rises above the 7 plane of the pipes and the horizontal parts of inlet tee 18 8 (with arrows)--located where the center of the middle pipe 9 was in Fig. 1. The exhaust pipe is broken off in a horizon-tal drift direction at the top (with arrow). An eductor 11 pump for producing exhaust flow in pipe 19 is not shown here 12 but will be understood to be connected to the exhaust pipe.
13 Fig. 3 shows in elevation (in a shipping orientation) 14 supply fluidization pipe or manifold assembly 16 featuring supply pipe 2 and spaced close above it a parallel row of 16 relatively shorter foraminous water~jetting tubes 6, each 17 offset from the larger pipe by intervening tube 4 and valve 18 5 at the junction between 4 and 6. The pipe may be thought 19 of as segmented by the intersecting tubes 4 with their as-sociated jetting means. It will be understood that the 21 detail shown here did not appear in preceding views because 22 of the considerable difference in scale.
23 Fig. 4 shows in elevation (in working orientation) one 24 segment of the assembly shown to a greater extent in the last preceding view with downwardly directed arrows indicat-26 ing the jetting of water from the openings (foramina) in the 27 tubes into the subsoil--not separately shown.
28 Figs. 5A and 5B show schematically fluidization embodi-29 ment 10" of this invention aftqr emplacement with the aid or fluidization by underlying pipes 6. Fig. 5A differs from 31 Fig. 5B by showing the top surface of sandy subsoil 15 at an 32 appreciable depth overlying the piping, as after burial but 33 berore going on-line, whereas the lower surface in Fig. 5B
34 accords better with relatively recent on-line fluidization.
Thus, eductor inlet tee 18 is also buried in Fig. 5A but a~
36 about the less well deflned Fig. 5B surface level.

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vo91/1404~ 2 Q ~ 9 :~ 3 ~ PCT/US91/014~2 l The embodiment of Figs. 5A and 5B also differs from the 2 Fig. 2 embodiment by showing fluidization jetting tubes 6 3 underlying respective supply pipes 16 A through 16F to which 4 they are connected (connections not visible here). Optional (dashed) intake tee with exhaust riser l9 is centered be-6 tween them in plan. Underlying and interconnected thereto 7 (interconnec~ion not shown) are corresponcling water-jetting 8 tubes 6. Supported above respective supply pipes on flexible g stalks l are sensors 3 responsive to water flow or pressure telectrical connections to sensors not shown).
ll Fig. 5B shows fluidization embodiment l0" similarly to 12 Fig. 5A, except after (instead of before) recent fluidiza-13 tion and similarly to Fig. l in that respect. Sandy subsoil 14 15 has been redistributed, resulting in a well defined open channel between banks at opposite sides at about the general 16 surface level in the last preceding view.
17 Fig 6 shows control apparatus 20 for the respective 18 valves of the water-jettin~ tubes of the preceding views.
1~ Peatured is CONTROL UNIT 21, which is provided with PROGRAM
INPUT means 23 and with DISPLAY means 25. SENSOR INPUT is 21 provided to the CONTROL UNIT as is indicated by the leftward 2~ arrow at the right, and control signals go from it TO VALVES
23 as is indicated by the leftward arrow at the left.
24 A main function of the program input is to time the opening and closing of fluidization valves so as to produce 26 the desired lateral transport of the non-cohesive subsoil.
27 Such programming may be done in advance or may be done in 28 real time by a human operator, as preferred. Valve control 29 is guided by a theoretical understanding of the physical con-ditions being dealt with and/or by monitoring of changes in 31 physical conditions as they are being achieved, preferably 3~ by both such types of input. Sensed water flow and/or pres- "~
33 sure can cons~itute suitable input signals.
34 In Fig. 6, the CONTROL UNIT conveniently is a digital computer, with one or more central processing units (CPUs), 36 also analog-to-digital modems to convert analog signals from 37 the sensors to digital signals for processing.

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WO91/140~7 2 ~ 5 ~ 1 3 ~ PCT/US91/01482 ~

The PROGRAM INPUT means shown schematically in Pig. 6 ~ includes a keyboard and also electrical and/or optical means 3 for reading program disks or the like. The DISPLAY MEANS in ~ Fig. 6 can show assumed or measured physical conditions, in-cluding the results of simulations provided by the cP~(s) in 6 the CONTROL UNIT and optionally real-time results being 7 monitored by the underwater sensors.
8 The next sets of diagrams show examples of lateral 9 transport of non-cohesive subsoil ~such as sand~ achievable by pulsed "peristaltic" control of the fluidization valves ll according to this invention. In these views stippling indi-12 cates respective fluidized subsoil areas.
13 Figs. 7A, 7B, and 7C are plan views of fluidization em-14 bodiment lO" at successive timed intervals, with the subsoil fluidized first in the top third, then in the middle third, 16 and finally in the bottom third (Fig. 7A through Fig. 7B).
17 As the pressure increases sequentially in such top-to-bottom 18 direction in these views, overlying water flow occurs along 19 the resulting gradient, which is mainly in the opposite direction along the piping--although also having a lateral ~l component toward the adjacent relatively undisturbed water.
22 Consequently, the fluidized subsoil above the piping array ~3 flows along that gradient until its imparted momentum drops, 24 or until it comes under the influence of another current.
Thus, where such pipes extend outward from the shoreline, 26 the subsoil may ~e so transported to a location far enough 27 offshore to intercept an alongshore drift effective to con-28 vey it away. The central region outlined in broken lines 29 between the trios of p.ipes is not required in this mode of operation but is included as useful for other operating 31 modes, such as the one shown in the next several views.
3. Figs. 8A, 8B, and 8C are plan views of e,nbodiment lO"
33 as in the preceding set of views except showing fluidization 3~ at successive widthwise timed intervals. In Fig. 8A the fluidization begins in the lengths nearest the broken-line 3~ showing between the pipe trios, then progresses to the ne~t 37 flan~ing pipes, and finally to the outermost pair or pipes.

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VO91/1404~ PCT/US91/01482 l Thus, pair of pipes 16C" and 16D" are pulsed first, 16B"
2 and 16E" are pulsed next, and 16A" and 16F" are pulsed last.
3 Such progression produces a double gradient from the outer ~ left and right toward the broken-line intermediate region.

5 Thus, the overlying water flows predominantly laterally 6 toward the centerline and carries wi~h it t:he fluidized sub-7 soil, which can be piped away by one or more exhaust risers 8 fro~ intake tees or interconnected foraminous intake pipes.
g Where only one intake tee is employed, the fluidization valve sequencing preferably proceeds outward from the center ll both laterally and longitudinally toward the perimeter, so 12 as to produce a counter-flow of fluidized subsoil from the 13 outer reaches of the array to a centralized eduction locus.
l4 Actual eduction accentuates the gradient in that direction.
In the absence of one or more eductor intakes along the 16 centerline, an opposite or outward-in fluidization sequenc-17 ing may be employed to transport the fluidized subsoil l8 progressively ~rom the centerline laterally outward. This l9 is conducive to a conventional channel configuration: low along the centerline and on both sides thereof for the 21 desired width of the channel. In such event an odd number 22 of parallel fluidization pipes may employed, with one in-23 serted along the centerline as in Fig. l.
24 Figs. 9 through 12, show deshoaling of a channel and restoration of an eroded beach according to this invention.
26 Fig. 9 shows, schematically in plan, a "split-screen"
27 view of BEACH 30 at the left and navigation CHANNEL 35 be-28 tween banks 39 at the right. ERODED SHORELINE 31 ~arks the 29 present extent of the beach. The channel is blocked by SHOAL 37 (broken lines because submerged) at mouth 32 31 thereof. An offshore arrow indicates LATERAL DRIFT (right 32 to left). An intermediate part of the view is broken away 3~ t.o suggest that its side portions are spaced laterally apart 3~ by an indefinite distance. Section line X-X superimposed on this view runs rightward substantially parallel to the 36 shoreline just onshore, then doglegs offshore and righ~ward 37 to cross t~e shoal similarly.

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WO91/14047 2 ~ ~ ~ 13 ~ PCT/US91/01482 l Fig. l0 again shows BEACH 30 at the left and C~ANNEL 3 ~ at the right, but this time in schematic sectional eleva-3 tion. The beach section is taken at an onshore location at X-X as already noted. Horizontal foraminous pipe 3~ ls shown just underneath the surface. Arrows pointing into ~he pipe 6 indicate e~traction of water from the beach soil, which is 7 saturated or nearly so most (if not all) of the time. The 8 channel section shows SHOAL 37 as a hu~p flanked by pair of 9 shallow dips 36 between banks 39.
Fig. ll shows BEACH 30 in plan with EN~ANCED SHORELINE
ll 33 in place of former ERODED SHORELINE 31 (broken lines).
l It should be understood that, at sea and on most bays and 13 many large lakes, wave action carries onto beaches tem-14 porarily supported subsoil and leaves some on the beach when washing back offshore, also usually removing some from the 16 beach at the same time. At times the amount deposited ex-17 ceeds the amount removed, and at other times (as in storms) 18 more is removed than is deposited. Judicious operation of a 19 dewatering pipe as illustrated can tip the balance in favor 20 of the beach, and over time can enhance beaches that other- `
21 wise tend to lose whatever sand other human efforts deposit ~;-22 thereon. As already noted, favorable drift may assist in 23 redepositing thereonto sand removed from elsewhere. -2~ Fig. 12 shows CHANNEL 35 in sectional elevation with fluidization pipes lying on a substantially flat bottom.
26 U-shaped contour 38 defines substantially the whole width 27 between the banks, as the former shoal has been removed. It .
28 will be understood that intermittent fluidization at timed 29 intervals usually can preclude shoaling, and that eduction pipes are unnecessary when alongshore drift is favorable, 31 though they aid in collection for alternative transport.
32 An eduction pipe may be supported on a barge, from a 33 crane, or by a platform rigged onshore or offshore. It ma~y 3~ be movable, as along a centerline between flan~ing fluidiza-3~ tion pipes. A pump is provided at or near the inta~e end, 3~ and may be supplemented by one or more along such length.
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~91/14~4, 2D~ 3~ PCT/US91/01482 1 Fluidization pipes do not have to be laid parallel as ~ shown and with both the supply pipe and the water-jetting 3 tubes mutually parallel, but such arrangements are often recommended. Although more complex patterns have their own merits and disadvantages in lnstallation and operation, any 6 way of providing the desire~ array, whether linear or areal, 7 can be effective if operated carefully with suitable timing ~ of both duration and interval and with appropriate pulsing.
9 Every site differs from every other site, and every sequence of events is unique, so experience, intelligence, and nature 11 all can contribute to success.
12 Selection of appropriate supply piping, valving (water 13 and/or air), and jet piping is within the skill of persons 1~ familiar with hydraulic (and pneumatic) arts. A uniformly foraminous plastic tube is suitable for a dewatering pipe, 16 but openings in a fluidization pipe are preferably oriented 17 primarily downward, and only secondarily sideward, to con-18 serve flUid used and energy consumed in pumping it.
19 Placement and retention of fluidization pipes and of dewatering pipes may employ fluidization of the subsoil to 21 embed them properly. Alternatively, they may be ditched 22 into place. Normally they can be left in place for years 23 without necessity for maintenance or repair bu~ should be 24 operated frequently--if only for short times--to keep them free of potentially clogging marine growth or deposits. The 2~ openings in foraminous pipes may be provided with suitable 27 one-way valves, may be grommeted with materials selected for 28 marine anti-fouling characteristics, be flushed ~rom time to 29 time with anti-fouling fluid, and/or be fitted with high-tech anti-fouling devices such as pulsed sound generators.
31 Programming of sequential fluidization has been con-32 sidered at some length herein, but as in most endeavors 3; there is no substitute for experience. A skilled human 3~ operator may become able to "play" the keyboard to produce 3, the most effective peristaltic action, with the benefi~ of a 36 graphical read~out or pictorial representation of the sense~
37 underwa~er flow or pressure c the fluidized subsoii.

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1 Selection of sensors for flow and/or pressure is within 2 the skill of persons familiar with hydraulic instrumenta-3 tion. Strain gages may be mounted above the supply pipes, ~ and their readings be fed to the central control unit for analysis or interpretation. The same or other suitable in-6 struments may be deployed in an array covering ~he area of 7 interest, which may be more extensive than the jet injectlon 8 fluidizing arrays, and be supported from floats or the like.
g A preferred arrangement for purposes of economy, simplicity, and effectiveness is to place the sensor on the top end of a 11 flexible stalk supported by piping underneath, to record its 12 sensed variations in position and/or water pressure, from 13 which flow data can be derived and currents be illustrated.
14 The concluding set of drawings illustrates beachfront dewatering and shows foraminous piping in more detail, along 16 with other useful hardware items.
17 Figs. 13 and 14 show in side sectional elevation and 18 plan section embodiment 50 of this invention in a setting 19 featuring beach 51, higher land 52 further onshore, and off-shore land 59 under water 58, shown temporarily at mean sea 21 level (MSL) 55. As also shown in plan in Fig. 14, MSL 55 is 22 flanked by mean high water line (MHW) 53 on the beach and 23 mean low water line tMLW) 57 on downs}ope 56.
2~ Earth anchor 61, having been screwed upright into the beach, has hook 62 exposed at its top end, helical auger 69 26 buried at its bottom end, and vertical body portion 65 inter-27 vening, mostly underground. At the left, extending from the 28 beach surface to pipe 47 ~retained by sleeve 67) is flexible 29 impermeable barrier sheet 45. Retained by similar sleeve 63 higher on the earth anchor body is foraminous pipe 71, which 31 func~ions as a dewatering pipe ~arrows pointing radially 32 toward it). Tee 72 (with plug 73 in its top opening) con-33 nects to that pipe and to pump Pl between it and pipe 75.
34 Pipe 75 interconnects to more complex fitting 79 from which foraminous pipes 81, 83, 87, and 89 fan out in substantially 36 horizontal directions, 81 and 89 parallel to the beach shore 37 line, and 87 and 89 extending obliquely farther offshore.

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l Figs. 15 and 16 show the apparatus of Figs. 13 and 14 2 as viewed looking onshore. Fig. 15 is taken along xv-xv on 3 Fig. 14 from a location completely offshore therefrom. Ar-~ rows headed downward from pipes 81, 83, 87, and 89 trace the initial path of the fluidizing fluid, which Stirs up the 6 sandy subsoil into the overlying water. Fig. 16 is taken 7 along XVI-XVI on Fig. 14 at a location between the aforemen-8 ~ioned pipes and dewatering pipes 71 and 73. Upward arrows g indicate the flow of water from the surrounding soil into dewatering pipes 71, 73.
11 Fig. 17 shows another embodiment in which plug 74 is 12 replaced by vertical pipe 91 (in place of previous plug 74) 13 extending from the top of tee 63 to pump P2 and valve 94 at 14 ground level, joined to connecting pipe 95, which rises alongside standpipe 90 and discharges from outlet 99 at its 16 top end into the top of the standpipe.
17 Fig. 18 shows in front elevation a first embodiment of 18 foraminous pipe, say pipe 81, suitable for dewatering and/or 19 fluidizing use. This pipe is furnished with vertical pipes 9l, valve(s) 94, and riser pipe(s) 95 at intervals along its 21 length. Spaced openings (foramina) l00 visible in the lower 22 edge of the pipe appear in more detail in the next view. It 23 should be understood that this type of foraminous pipe could 24 be used for fluidizing use generally (e.g., also for pipes 83, 87, 89) or for dewatering use (e.g., pipes 71, 73).
2~ Fig. l9 shows pipe 71 in transverse section taken at 27 XIX-XIX on Fig. 18 and on an enlarged scale. Opening l00 is ~8 seen to be a slot in the lower quadrant of the pipe wall.
29 The pipe itself is filled with aggregate, which not onl~
aids the burial of the pipe but also precludes sand from en-3l tering it and possibly getting to the pump (not shown).
32 Fig. 20 shows in front sectional elevation an embodi-33 ment of foraminous pipe, say pipe 71, also furnished with 3~ vertical pipe(s) 9l, valve(s) 94, and riser pipe~) g5 at intervals along its length--as pipe ~l was. The openings or 36 foramina here, designated ll0, are distributed more widely 37 than in the previous embodiment and appear in the next vlew.

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2 ~iy. 21 shows pipe 71 in transverse section taken at 3 XXI-XXI on Fig. 20 and on an enlarged scale. Opening llO
~ are seen to be distributed throughout the pipe wall. The pipe itself is shown filled with aggregate 95 just as pipe 6 71 of Figs. 18 and l9 was. As openings in the upper half of ? a foraminous pipe are less desirable for fluidizing use be-8 cause they provide an escape for the fluid before subjacent g soil is stirred up, this type of foraminous pipe is preferably used more as a dewatering pipe (pipes 71, 73).
11 operation of the last described apparatus of this inven-12 tion to practice the corresponding methods of the invention 13 is readily apparent from the foregolng description and the 14 accompanying diagrams. Wave onrush onto a beach followecl by backwash away from the beach usually produces a substantial 16 equilibrium of subsoil ~such as sand) transport onto the 17 beach and removal from the beach, ~ut abnormal conditions, 18 such as storms, may remove more sand from the beach than is 19 deposited thereonto. This invention affects the equilibrium just enough so that more sand is deposited onshore than is 21 removed normally--and excessive Iosses are minimized in more 22 unfavorable conditions.
23 Water from waves rushing onto the beach seeps down into 24 the subsoil and ~through its many openings) into the foraminous dewatering pipe buried under the beach. Water so 26 collected is pumped offshore via an interconnecting pipe and 27 into the foraminous fluidizing pipes, and jetted,t~erefrom 28 into adjacent non-cohesive sandy subsoil, fluidizing it.
29 The fluidized subsoil is carried by water currents and wave action alongshore and onto shore, where the concentra-31 tion of fluidized subsoil leaves a bit more than otherwise 32 would remain on the beach, as the dewatering pipe increases 33 water drainage from the saturated beach subsoil beyond what 34 would normally seep from the beach soil. Thus, the ap-paratus and method of this invention have tipped the e~ui-36 librium in favor of beach accretion, and a few thousand 37 waves a day will do the rest of the desired Herculean tas~.

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Use of an impermeable sheetlike barrier, to preclude draining water from further onshore, renders the process more productive, as well as conserving the onshore moisture, as is generally desirable.
In the final showing, instead of--or in addition to--pumping the collected water directly to fluidizing piping, the water is pumped at a relatively slow rate into storage, from which it can be retrieved rapidly by gravity flow, as when a storm may have shifted the prevailing equilibrium toward net removal of sand from the beach. Alternatively, when prevailing conditions favor accretion, fluidization will accelerate that desired process. Moreover, as nature provides most of the water movement and sand suspension, only enough water need be pumped to tip the equilibrium, rather than doing all the work, as is attempted by dredging.
The impermeable barrier is useful in this method as well.

INDUSTRIAL APPLICABILITY
Coastal management methods based upon dredging will be augmented in substantial part by addition or substitution of fluidization and dewatering techniques. Market demand for pumps, foraminous piping, and pipe-anchoring means will in-crease drastically. The resulting coastline stabilization, whether by beach enhancement or navigable channel or harbor deshoaling will become a recognized occupational specialty and will employ numerous people in supporting functions.
Early signs of such growth are becoming apparent in prominent coastal regions, such as California, Florida, and northeastern United States, as well as in Europe and Asia.
Preferred embodiments and variants of such embodiments have been described for this invention. Other modifications may be made, as by adding, combining, deleting, or subdivid-ing compositions, parts, or steps, while retaining at least some of the manifest advantages and benefits of the present invention--which itself is defined in the following claims.

Claims (9)

THE CLAIMED INVENTION:

1. Coastal stabilization method, comprising the steps of fluidizing offshore non-coherent subsoil by jetting fluid thereinto and transporting the fluidized subsoil elsewhere by natural or pump-assisted water flow.

2. Method according to claim 1, including the step of jetting fluidizing water, air, or a fluid mixture thereof into such subsoil continuously or intermittently.

3. Method according to claim 1 or 2, including jetting the fluid into the subsoil in a patterned pulsed manner.

4. Method according to any foregoing claim wherein the fluid is so jetted via foraminous fluidizing piping.

5. Method according to any foregoing claim wherein water so jetted is obtained by dewatering beach subsoil.

6. Method according to any foregoing claim wherein the fluid is so jetted from a substantially horizontal array of foraminous fluidizing piping pulsed in sequential patterned manner to flow fluidized subsoil laterally thereacross.

7. Method according to claim 6, wherein the pulsing produces lateral flow in any selected lateral direction.

8. Method according to claim 6, wherein the pulsing produces lateral flow beyond the plan extent of the array.

9. Method according to claim 6, wherein the pulsing produces multi-directional lateral flow.