WO1991014047A1

WO1991014047A1 - Coastal stabilization by fluidizing non-cohesive subsoil

Info

Publication number: WO1991014047A1
Application number: PCT/US1991/001482
Authority: WO
Inventors: James Marshall Parks
Original assignee: James Marshall Parks
Priority date: 1990-03-05
Filing date: 1991-03-04
Publication date: 1991-09-19
Also published as: EP0483297A1; CA2059136A1; AU7488791A

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

COASTAL STABILIZATION BY FLUIDIZING NON-COHESIVE SUBSOIL

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

BACKGROUND OF THE INVENTION Numerous methods have been suggested and many have been used to prevent coastal erosion, and to encourage accretion of sands or other subsoils that are non-cohesive when wet, especially so as to enhance beaches and/or to stabilize navigable regions regardless of beach enhancement. Efforts to overcome harmful effects of wave action or of alongshore drift as by constructing groins, jetties, or other barriers have often been unavailing, and frequently have occasioned the opposite of what was sought, such as excess collection on the updrift side of sand that would have been shared with a downdrift beach in the absence of such man-made obstacle. Navigable inlet or channel maintenance traditionally is attempted by dredging, repeated whenever nature fills in an existing or former channel— sually more often than anyone anticipated. The necessity of periodic redredging may be overlooked or, if considered, be optimistically minimized, whereupon its actual cost may prove to exceed budget limits. Accordingly, in many instances no effective action is taken, or (if taken) becomes ineffective because of financial or technical limitations. Dredging is disruptive to underwater landscapes and conducive to deleterious changes in existing currents or tidal flows or their effects. Dredging also may necessitate costly transporting and redepoεition of subsoil. Injection of water into non-cohesive subsoil, such as sand, fluidizes it into a readily transportable slurry. Off- shore sandy subsoil can be so fluidized and be redistributed by water currents and wave action or by eduction pumping Fluidization is well recognized in technical literature as a supplement—or preferably an alternative—to dredging. Contributors include Bruun in "Maintaining Tidal Inlet Chan- nelε by Fluidization" J. Waterway, etc. Engineering, ASCE, 110 (ww4) 117-120; Bruun and Adams in "Stability of Tidal Inlets: Use of Hydraulic Pressure for Channel and Bypassing Stability" J. Coastal Research 4 (1988) 687-701; and the present inventor, as with Weisman and Collins, "Fluidization as Applied to Sediment Transport (FAST) as an Alternative to Maintenance Dredging of Navigation Channels in Tidal Inlets" Wastes in the Ocean vol II: Dredged Material Disposal in the Ocean, Kester et al. (eds.) Wiley (1983). Accordingly, shoals in an otherwise navigable channel or similar waterway can be relocated downstream upon being fluidized. Optionally, if natural drift at a shoal location is not favorable, but a not-too-distant region has favorable prevailing currents, the fluidized subsoil can be collected, be pumped to, and be released at the latter location for natural redistribution. As the physical characteristics and behavior of non-cohesive subsoils become better understood, fluidization doubtless will be recognized as the procedure of choice, both technically and economically, to solve such environmental problems as shoaling of navigable channels. Even such alternative channel clearing and maintenance have relied upon the energy-intensive step of dredging to enable the necessary piping to be buried preparatory to fluidizing use. Prior art is represented by van Steveninck, in U.S. Patent 3,695,049, wherein piping to be buried is sup- plied with one or more small accompanying pipes to fluidize underlying subsoil, sinking the pipeline together with the fluidization pipes; and in "Pipeline Burial by Fluidization" Paper No. OTC 2276 of OFFSHORE TECHNOLOGY CONFERENCE of American Institute of Mining, Metallurgical, and Petroleum Engineers at Dallas, Texas in 1975, wherein a horseshoe- shaped device straddles piping to be emplaced and jets water from openings in its hollow lower parts; the piping and the straddling device sink into subjacent fluidized sandy soil. The present inventor follows the precept that man has to learn to use, rather than to oppose, nature in all such environmental efforts. Elsewhere, as in his pending patent application (PCT/US91/00421) he has described novel means and methods of e placing foraminous piping for fluidization and dewatering purposes. Beach stabilization using dewatering foraminous piping is a somewhat more recent development. Informative articles about beach stabilization include "New Method for Beach Ero- sion Control" by Machemehl, French, and Huang in Civil En- gineerinσ in the Oceans/Ill (1975) 142-160 and "Experimental Control of Beach Face Dynamics by Water-Table Pumping" by Chappell , Eliot, Bradshaw, and Lonsdale in Engineering Geol- ogy, 14 (1979) 21-40--both of which describe how water withdrawal from subjacent beach sand is conducive to deposi- tion of more sand. Vesterby U.S. Patent 4,645,377 teaches such dewatering just below the mean high water level. A com- plex variation is suggested by Lin in U.S. Patent 4,898,495.

SUMMARY OF THE INVENTION This invention utilizes subsoil fluidization to improve harbor or navigable inlet or channel deshoaling and main- tenance and to improve beach enhancement and maintenance. In general, these objectives are attained by fluidizing offshore subsoil (non-cohesive when wet) for transport from an existing location to a preferred location in slurry form, whether by natural flow of the adjacent water or assisted by pumping. Water—as from onshore storage or withdrawn from subsoil underlying a nearby beach—and/or air is jetted into such offshore (underwater) subsoil to fluidize it into a slurry. Such jetting occurs steadily, intermittently, or in patterned pulsed manner via foraminous piping for desired fluidization. Other objectivess of the present invention, with means and methods for attaining the various objectives, will be apparent from the following description and from the accompanying diagrams of preferred embodiments, which are presented here by way of example rather than limitation. SUMMARY OF THE DRAWINGS Fig. 1 is a schematic perspective illustration of an 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 embodiment of fluidization by this invention, with subsoil removal; Fig. 3 is a plan of supply piping, with multiple foraminous branch lines, according to this invention; and Fig. 4 is a side elevation of a segment of the piping of Fig. 3, in a position for use according to the invention; Figs. 5A and 5B are schematic end sectional elevations of another embodiment of this invention, with buried piping, shown before (Fig. 5A) and after (Fig. 5B) fluidization use; Fig. 6 is a schematic representation of a control unit for individual valves of the foraminous fluidization piping; Figs. 7A, 7B, and 7C are sequential plan views of a piping array of the invention at lengthwise timed intervals; Figs. 8A, 8B, and 8C are similar sequential plan views of such array at successive widthwise timed intervals. Fig. 9 is a schematic plan of an eroded beach (at left) and a shoaled navigation channel (at right); Fig. 10 is a schematic elevation of the same eroded beach and shoaled navigation channel, taken in Fig. 9 along X-X onshore at the left and offshore at the right; Fig. 11 is a plan of the beach (at left) of Figs. 9 and 10 enhanced by sandy subsoil from the shoaled channel; and Fig. 12 is a sectional elevation of the previous chan- nel (Figs. 9 and 10) after de-shoaling by fluidization. Fig. 13 is a side view of a beach and offshore vicinity (sectioned) embodying apparatus according to this invention; Fig. 14 is a plan view corresponding to Fig. 13; Fig. 15 is a sectional elevation taken along XV-XV of Fig. 14, looking onshore from (far right) offshore; Fig. 16 is a sectional elevation similar to Fig. 15 but taken along XVI-XVI at an intermediate location; Fig. 17 is a side sectional elevation of a variant of the locality and apparatus of Fig. 13; Fig. 18 is a side elevation of another embodiment of foraminous piping (or jet tubing) useful in the practice of the present invention; Fig. 19 is a transverse sectional view of such piping embodiment taken at XIX on Fig. 18; Fig. 20 is a side elevation yet another embodiment of foraminous piping (or jet tubing) useful in the practice of the present invention; and Fig. 21 is a transverse sectional view of such piping embodiment taken at XXI on Fig. 20.

DESCRIPTION OF MODES OF THE INVENTION Fig. 1 shows schematically, in sectional perspective, a first embodiment 10 of this invention as parallelepipedal block 11 of a channeled section of non-cohesive subsoil 15 having therein several side-by-side mini-channels 17A, 17B, 17C. Three parallel fluidization pipes 16A, 16B, 16C—each with a valve V therein—extend along the bottoms of the respective mini-channels from the OFFSHORE or EBB area (arrow located at and directed to lower left) upgrade toward the opposite ONSHORE or FLOOD direction (arrow located at and directed to upper right). An arrow located at the lower right but directed to the upper left indicates LATERAL DRIFT or natural alongshore current flow direction. It will be understood that wave and tidal action are substantially per- pendicular to the shoreline, whereas alongshore drift is more likely to be substantially parallel thereto. The contouring illustrated in Fig. 1 conforms to cuε- tomary fluidization results. As expected, the elevation of subsoil between adjacent mini-channels is less than it is at opposite sides of the entire channel. The rather angular stylization of the drawing is for simplicity of the showing, whereas in nature the edges and surfaces of non-cohesive sub- soils normally are rounded to a greater or lesser degree or extent. Fluid connections to the pipes are omitted as within the skill of persons ordinarily skilled in the art. Fig. 2 is a schematic perspective of an additional fluidization embodiment 10' of this invention viewed from 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- soil 15 (stippled). Upright exhaust pipe 19 rises above the plane of the pipes and the horizontal parts of inlet tee 18 (with arrows)—located where the center of the middle pipe was in Fig. 1. The exhaust pipe is broken off in a horizon- tal drift direction at the top (with arrow) . An eductor pump for producing exhaust flow in pipe 19 is not shown here but will be understood to be connected to the exhaust pipe. Fig. 3 shows in elevation (in a shipping orientation) supply fluidization pipe or manifold assembly 16 featuring supply pipe 2 and spaced close above it a parallel row of relatively shorter foraminous water-jetting tubes 6, each offset from the larger pipe by intervening tube 4 and valve 5 at the junction between 4 and 6. The pipe may be thought of as segmented by the intersecting tubes 4 with their as- sociated jetting means. It will be understood that the detail shown here did not appear in preceding views because of the considerable difference in scale. Fig. 4 shows in elevation (in working orientation) one segment of the assembly shown to a greater extent in the last preceding view with downwardly directed arrows indicat- ing the jetting of water from the openings (foramina) in the tubes into the subsoil— ot separately shown. Figs. 5A and 5B show schematically fluidization embodi- ment 10" of this invention after emplacement with the aid of fluidization by underlying pipes 6. Fig. 5A differs from Fig. 5B by showing the top surface of sandy subsoil 15 at an appreciable depth overlying the piping, as after burial but before going on-line, whereas the lower surface in Fig. 5B accords better with relatively recent on-line fluidization. Thus, eductor inlet tee 18 is also buried in Fig. 5A but at about the less well defined Fig. 5B surface level. The embodiment of Figs. 5A and 5B also differs from the Fig. 2 embodiment by showing fluidization jetting tubes 6 underlying respective supply pipes 16 A through 16F to which they are connected (connections not visible here). Optional (dashed) intake tee with exhaust riser 19 is centered be- tween them in plan. Underlying and interconnected thereto (interconnection not shown) are corresponding water-jetting tubes 6. Supported above respective supply pipes on flexible stalks 1 are sensors 3 responsive to water flow or pressure (electrical connections to sensors not shown). Fig. 5B shows fluidization embodiment 10" similarly to Fig. 5A, except after (instead of before) recent fluidiza- tion and similarly to Fig. 1 in that respect. Sandy subsoil 15 has been redistributed, resulting in a well defined open channel between banks at opposite sides at about the general surface level in the last preceding view. Fig 6 shows control apparatus 20 for the respective valves of the water-jetting tubes of the preceding views. Featured is CONTROL UNIT 21, which is provided with PROGRAM INPUT means 23 and with DISPLAY means 25. SENSOR INPUT is provided to the CONTROL UNIT as is indicated by the leftward arrow at the right, and control signals go from it TO VALVES as is indicated by the leftward arrow at the left. A main function of the program input is to time the opening and closing of fluidization valves so as to produce the desired lateral transport of the non-cohesive subsoil. Such programming may be done in advance or may be done in real time by a human operator, as preferred. Valve control is guided by a theoretical understanding of the physical con- ditions being dealt with and/or by monitoring of changes in physical conditions as they are being achieved, preferably by both such types of input. Sensed water flow and/or pres- sure can constitute suitable input signals. In Fig. 6, the CONTROL UNIT conveniently is a digital computer, with one or more central processing units (CPUs), also analog-to-digital modems to convert analog signals from the sensors to digital signals for processing. The PROGRAM INPUT means shown schematically in Fig. 6 includes a keyboard and also electrical and/or optical means for reading program disks or the like. The DISPLAY MEANS in Fig. 6 can show assumed or measured physical conditions, in- eluding the results of simulations provided by the CPU(s) in the CONTROL UNIT and optionally real-time results being monitored by the underwater sensors. The next sets of diagrams show examples of lateral transport of non-cohesive subsoil (such as sand) achievable by pulsed "peristaltic" control of the fluidization valves according to this invention. In these views stippling indi- cates respective fluidized subsoil areas. Figs. 7A, 7B, and 7C are plan views of fluidization em- bodiment 10" at successive timed intervals, with the subsoil fluidized first in the top third, then in the middle third, and finally in the bottom third (Fig. 7A through Fig. 7B). As the pressure increases sequentially in such top-to-bottom direction in these views, overlying water flow occurs along the resulting gradient, which is mainly in the opposite direction along the piping—although also having a lateral component toward the adjacent relatively undisturbed water. Consequently, the fluidized subsoil above the piping array flows along that gradient until its imparted momentum drops, or until it comes under the influence of another current. Thus, where such pipes extend outward from the shoreline, the subsoil may be so transported to a location far enough offshore to intercept an alongshore drift effective to con- vey it away. The central region outlined in broken lines between the trios of pipes is not required in this mode of operation but is included as useful for other operating modes, such as the one shown in the next several views. Figs. 8A, 8B, and 8C are plan views of embodiment 10" as in the preceding set of views except showing fluidization at successive widthwise timed intervals. In Fig. 8A the fluidization begins in the lengths nearest the broken-line showing between the pipe trios, then progresses to the next flanking pipes, and finally to the outermost pair of pipes. Thus, pair of pipes 16C" and 16D" are pulsed first, 16B" and 16E" are pulsed next, and 16A" and 16F" are pulsed last. Such progression produces a double gradient from the outer left and right toward the broken-line intermediate region. Thus, the overlying water flows predominantly laterally toward the centerline and carries with it the fluidized sub- soil, which can be piped away by one or more exhaust risers from intake tees or interconnected foraminous intake pipes. Where only one intake tee is employed, the fluidization valve sequencing preferably proceeds outward from the center both laterally and longitudinally toward the perimeter, so as to produce a counter-flow of fluidized subsoil from the outer reaches of the array to a centralized eduction locus. Actual eduction accentuates the gradient in that direction. In the absence of one or more eductor intakes along the centerline, an opposite or outward-in fluidization sequenc- ing may be employed to transport the fluidized subsoil progressively from the centerline laterally outward. This is conducive to a conventional channel configuration: low along the centerline and on both sides thereof for the desired width of the channel. In such event an odd number of parallel fluidization pipes may employed, with one in- serted along the centerline as in Fig. 1. Figs. 9 through 12, show deshoaling of a channel and restoration of an eroded beach according to this invention. Fig. 9 shows, schematically in plan, a "split-screen" view of BEACH 30 at the left and navigation CHANNEL 35 be- tween banks 39 at the right. ERODED SHORELINE 31 marks the present extent of the beach. The channel is blocked by SHOAL 37 (broken lines because submerged) at mouth 32 thereof. An offshore arrow indicates LATERAL DRIFT (right to left) . An intermediate part of the view is broken away to suggest that its side portions are spaced laterally apart by an indefinite distance. Section line X-X superimposed on this view runs rightward substantially parallel to the shoreline just onshore, then doglegs offshore and rightward to cross the shoal similarly. Fig. 10 again shows BEACH 30 at the left and CHANNEL 35 at the right, but this time in schematic sectional eleva- tion. The beach section is taken at an onshore location- at X-X as already noted. Horizontal foraminous pipe 34 is shown just underneath the surface. Arrows pointing into the pipe indicate extraction of water from the beach soil, which is saturated or nearly so most (if not all) of the time. The channel section shows SHOAL 37 as a hump flanked by pair of shallow dips 36 between banks 39. Fig. 11 shows BEACH 30 in plan with ENHANCED SHORELINE 33 in place of former ERODED SHORELINE 31 (broken lines). It should be understood that, at sea and on most bays and many large lakes, wave action carries onto beaches tem- porarily supported subsoil and leaves some on the beach when washing back offshore, also usually removing some from the beach at the same time. At times the amount deposited ex- ceeds the amount removed, and at other times (as in storms) more is removed than is deposited. Judicious operation of a dewatering pipe as illustrated can tip the balance in favor of the beach, and over time can enhance beaches that other- wise tend to lose whatever sand other human efforts deposit thereon. As already noted, favorable drift may assist in redepositing thereonto sand removed from elsewhere. Fig. 12 shows CHANNEL 35 in sectional elevation with fluidization pipes lying on a substantially flat bottom. U-shaped contour 38 defines substantially the whole width between the banks, as the former shoal has been removed. It will be understood that intermittent fluidization at timed intervals usually can preclude shoaling, and that eduction pipes are unnecessary when alongshore drift is favorable, though they aid in collection for alternative transport. An eduction pipe may be supported on a barge, from a crane, or by a platform rigged onshore or offshore. It may be movable, as along a centerline between flanking fluidiza- tion pipes. A pump is provided at or near the intake end, and may be supplemented by one or more along such length. 1 Fluidization pipes do not have to be laid parallel as

2 shown and with both the supply pipe and the water-jetting

3 tubes mutually parallel, but such arrangements are often

4 recommended. Although more complex patterns have their own

5 merits and disadvantages in installation and operation, any

6 way of providing the desired array, whether linear or areal,

7 can be effective if operated carefully with suitable timing

8 of both duration and interval and with appropriate pulsing.

9 Every site differs from every other site, and every sequence

10 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

14 familiar with hydraulic (and pneumatic) arts. A uniformly

15 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

20 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 but should be

24 operated frequently—if only for short times—to keep them

25 free of potentially clogging marine growth or deposits. The

26 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 from time to

29 time with anti-fouling fluid, and/or be fitted with high- » 30 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

33 there is no substitute for experience. A skilled human

34 operator may become able to "play" the keyboard to produce

35 the most effective peristaltic action, with the benefit of a

36 graphical read-out or pictorial representation of the sensed

37 underwater flow or pressure of the fluidized subsoil. Selection of sensors for flow and/or pressure is within the skill of persons familiar with hydraulic instrumenta- 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- struments may be deployed in an array covering the area of interest, which may be more extensive than the jet injection fluidizing arrays, and be supported from floats or the like. A preferred arrangement for purposes of economy, simplicity, and effectiveness is to place the sensor on the top end of a flexible stalk supported by piping underneath, to record its sensed variations in position and/or water pressure, from which flow data can be derived and currents be illustrated. The concluding set of drawings illustrates beachfront dewatering and shows foraminous piping in more detail, along with other useful hardware items. Figs. 13 and 14 show in side sectional elevation and plan section embodiment 50 of this invention in a setting featuring beach 51, higher land 52 further onshore, and off- shore land 59 under water 58, shown temporarily at mean sea level (MSL) 55. As also shown in plan in Fig. 14, MSL 55 is flanked by mean high water line (MHW) 53 on the beach and mean low water line (MLW) 57 on downslope 56. Earth anchor 61, having been screwed upright into the beach, has hook 62 exposed at its top end, helical auger 69 buried at its bottom end, and vertical body portion 65 inter- vening, mostly underground. At the left, extending from the beach surface to pipe 47 (retained by sleeve 67) is flexible impermeable barrier sheet 45. Retained by similar sleeve 63 higher on the earth anchor body is foraminous pipe 71, which functions as a dewatering pipe (arrows pointing radially toward it). Tee 72 (with plug 73 in its top opening) con- nects to that pipe and to pump PI between it and pipe 75. Pipe 75 interconnects to more complex fitting 79 from which foraminous pipes 81, 83, 87, and 89 fan out in substantially horizontal directions, 81 and 89 parallel to the beach shore line, and 87 and 89 extending obliquely farther offshore. Figs. 15 and 16 show the apparatus of Figs. 13 and 14 as viewed looking onshore. Fig. 15 is taken along XV-XV on 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 sandy subsoil into the overlying water. Fig. 16 is taken along XVI-XVI on Fig. 14 at a location between the aforemen- tioned pipes and dewatering pipes 71 and 73. Upward arrows indicate the flow of water from the surrounding soil into dewatering pipes 71, 73. Fig. 17 shows another embodiment in which plug 74 is replaced by vertical pipe 91 (in place of previous plug 74) extending from the top of tee 63 to pump P2 and valve 94 at ground level, joined to connecting pipe 95, which rises alongside standpipe 90 and discharges from outlet 99 at its top end into the top of the standpipe. Fig. 18 shows in front elevation a first embodiment of foraminous pipe, say pipe 81, suitable for dewatering and/or fluidizing use. This pipe is furnished with vertical pipes 91, valve(s) 94, and riser pipe(ε) 95 at intervals along its length. Spaced openings (foramina) 100 visible in the lower edge of the pipe appear in more detail in the next view. It should be understood that this type of foraminous pipe could be used for fluidizing use generally (e.g., also for pipes 83, 87, 89) or for dewatering use (e.g., pipes 71, 73). Fig. 19 shows pipe 71 in transverse section taken at XIX-XIX on Fig. 18 and on an enlarged scale. Opening 100 is seen to be a slot in the lower quadrant of the pipe wall. The pipe itself is filled with aggregate, which not only aids the burial of the pipe but also precludes sand from en- tering it and possibly getting to the pump (not shown). Fig. 20 shows in front sectional elevation an embodi- ment of foraminous pipe, say pipe 71, also furnished with vertical pipe(s) 91, valve(s) 94, and riser pipe(ε) 95 at intervals along its length—as pipe Hi was. The openings or foramina here, designated 110, are distributed more widely than in the previous embodiment and appear in the next view. Fig. 21 shows pipe 71 in transverse section taken at XXI-XXI on Fig. 20 and on an enlarged scale. Opening 110 are seen to be distributed throughout the pipe wall. The pipe itself is shown filled with aggregate 95 just as pipe 71 of Figs. 18 and 19 was. As openings in the upper half of a foraminous pipe are less desirable for fluidizing use be- cause they provide an escape for the fluid before subjacent soil is stirred up, this type of foraminous pipe is preferably used more as a dewatering pipe (pipes 71, 73). Operation of the last described apparatus of this inven- tion to practice the corresponding methods of the invention is readily apparent from the foregoing description and the accompanying diagrams. Wave onrush onto a beach followed by backwash away from the beach usually produces a substantial equilibrium of subsoil (such as sand) transport onto the beach and removal from the beach, but abnormal conditions, such as storms, may remove more sand from the beach than is deposited thereonto. This invention affects the equilibrium just enough so that more sand is deposited onshore than is removed normally—and excessive losses are minimized in more unfavorable conditions. Water from waves rushing onto the beach seeps down into the subsoil and (through its many openings) into the foraminous dewatering pipe buried under the beach. Water so collected is pumped offshore via an interconnecting pipe and into the foraminous fluidizing pipes, and jetted therefrom into adjacent non-cohesive sandy subsoil, fluidizing it. The fluidized subsoil is carried by water currents and wave action alongshore and onto shore, where the concentra- tion of fluidized subsoil leaves a bit more than otherwise would remain on the beach, as the dewatering pipe increases water drainage from the saturated beach subsoil beyond what would normally seep from the beach soil. Thus, the ap- paratus and method of this invention have tipped the equi- librium in favor of beach accretion, and a few thousand waves a day will do the rest of the desired Herculean task. 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

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.

10. Method according to claim 9, wherein the pulsing produces multi-directional lateral flow toward an eduction location situated in plan within the extent of the array.

11. Method according to claim 10, including the step of educting fluidized subsoil from the eduction location.

12. Method according to claim 11, including depositing the educted subsoil onto an existing or prospective beach.

13. Method according to any foregoing claim, wherein the fluidized subsoil constituted a harbor obstruction or a shoal in an otherwise navigable inlet or channel.

14. Method according to claim 13, including the step of transporting the fluidized subsoil to clear the obstruc¬ tion.

15. Method according to claim 14, including the step of depositing transported fluidized subsoil onto a beach.

16. Method according to claim 15, including the step of enhancing a beach shoreline by so depositing the subsoil.

17. Method according to claim 16, including the step of maintaining such beach shoreline by dewatering its sub¬ soil as needed to preclude erosion of the beach shoreline.

18. Method according to claim 5 or claim 17, including the step of installing an impermeable sheetlike barrier be¬ tween the beach subsoil and adjacent further onshore subsoil so as to preclude dewatering such further onshore subsoil.

18. Method according to claim 5 or claim 17, including storing water obtained from beach subsoil dewatering during times when little or no offshore fluidizing is under way.

19. Method according to claim 18, including the step of storing water so obtained for subsequent gravity flow.

20. An identified coastal region stabilized according to the method of any of the foregoing claims.

21. Coastal stabilization apparatus, comprising foraminous means emplaced in an array in offshore underwater subsoil and adapted to jet a fluid therefrom into such subsoil to fluidize it, and valve means adapted to enable or disable such jetting from respective parts of the array in a sequential pattern.

22. Apparatus according to claim 21, including control means adapted to determine when respective parts of the ar¬ ray jet fluid into adjacent subsoil to fluidize it.

23. Apparatus according to claim 21 or claim 22, including sensor means distributed throughout the array and adapted to monitor a physical characteristic of fluidized subsoil overlying the array.

24. Apparatus according to claim 23, with the sensor means and the control means operatively connected to input values of such physical characteristic to the control means so that the control means can take such values into account in pulsing the valve means sequentially.

25. Apparatus according to any one of claims 21 to 24, including means programming the control means in response to values sensed by the sensor means and effective to induce peristaltic lateral currents in the fluidized subsoil.

26. Apparatus including any one of claims 21 to 25, including means adapted to transport fluidized subsoil else¬ where apart from the array.

27. Apparatus according to claim 26, including in the transport means an eductor pipe with an intake on a center line of the array and an outlet apart from the array.

28. Apparatus according to claim 26, wherein the inter¬ connecting piping means includes foraminous dewatering means in beach-underlying subsoil.

29. Apparatus according to claim 26, including an impermeable sheetlike barrier between the subsoil occupied by the beach subsoil dewatering means and adjacent further onshore subsoil to preclude subsoil moisture from further onshore from being drawn into the beach dewatering means.

30. Apparatus according to claim 21, including a plan array of fluid-jetting foraminous piping emplaced in an underwater region of non-cohesive subsoil, fluid-supply piping means connecting the foraminous piping to an external source of fluid, a multiplicity of valves interposed between the fluid- supply piping and the foraminous fluid-jetting piping at the water-jetting means. valve-control means adapted to open and close the respective valves in programmed order influenced by sensed conditions in the water overlying the array, sensing means at sensing loci in the water overlying the areal array and interconnected to the valve control means and adapted to input sensed values of such physical conditions to the valve-control means, and program input means associated with the valve-control means and adapted to enable the valve sequencing to induce peristaltic flow of fluidized subsoil overlying the array.