US3636717A

US3636717A - Pile anchoring method and apparatus

Info

Publication number: US3636717A
Application number: US873429A
Authority: US
Inventors: Ivo C Pogonowski; Paul D Carmichael; Richard H Griswold
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1969-11-03
Filing date: 1969-11-03
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25

Abstract

The invention relates to a method and the apparatus therefor for the pile anchoring of a structure in a relatively shallow or underconsolidated substratum. The method includes the initial introduction of an anchoring pile to a desired depth into the normally incompetent substratum. A series of longitudinally spaced peripheral projections are then formed in the substratum adjacent the pile external wall, at discrete intervals to define an irregular holding surface on the otherwise uniform sided pile. The annular projections comprise a precipitated mass of a polymerized methacrylate that has been introduced as a liquid through the pile, dispersed into solution with a solvent. Cavities in which the projections are built, are formed by the pressurized injection of an aqueous fluid whereby to displace and wash away substratum material in a desired pattern.

Description

[451 Jan.25,'1972 United States Patent Pogonowski et al.

[54] PILE ANCHORING METHOD AND FOREIGN PATENTS OR APPLICATIONS 703,654 2/1954 Great APPARATUS Primary Examiner- David J. Williamowsky Assistant Examiner- David H. Corbin AltorneyThomas H. Whaley and Carl C. Ries [73] Assignee:

[22] Filed:

ABSTRACT [2i] Appl. N0.:

The invention relates to a method and the apparatus therefor for the pile anchoring of a structure in a relatively shallow or 1/53,6 1/46 5 underconsolidated substratum. The method includes the ini- E02d 5/54 tial introduction of an anchoring pile to a desired depth into 1 /295;61/35 36 465 535 the normally incompetent substratum. A series of longitudinally spaced peripheral projections are then formed in the 51 rm.c|..............

[58] Field of Search substratum adjacent the pile external wall, at discrete intervals Refercnces i d to define an irregular holding surface on the otherwise uniform sided pile. The annular projections comprise a precipitated mass of a polymerized methacrylate that has been introduced as a liquid through the pile, dispersed into solution with a solvent. Cavities in which the projections are built, are formed by the pressurized injection of an aqueous fluid UNITED STATES PATENTS '166/295 whereby to displace and wash away substratum material in a desired pattern.

2,025,948 Jorgensen 6 X 2,555,359 6/195l Montague... ...61/53.6 X 2,670,048 2/1954 Menaul....... 3,078,920 2/1963 ten 3,324,665

6/1967 Robichaux et al....................61/5368 3.9 am 6 awinefisatse FILE ANCHORING METHOD AND APPARATUS BACKGROUND OF THE INVENTION The use of piles as foundation or anchoring members is widely used in many facets of industry. The well-known purpose of such piles is to provide a solid base or foundation element in a substratum that is otherwise incompetent to support a structure. The ability of a pile imbedded into the substratum to support any structure is contingent at least in part, on the character of the substratum and on the extent of the piles holding surface.

In the petroleum industry, piles are used extensively for supporting drilling and production platforms at both land based and offshore locations. In the instance of the latter, the anchoring ability of the substratum to hold a pile is often adversely affected by the prevalence of water both in the substratum, and the pressure exerted by the latter in the water depth at which the pile is anchored.

The common means for rigidly positioning offshore platfon'ns in a body of water is to drive elongated piling downwardly through vertical platform legs and into the substratum. Where the latter comprises a relatively underconsolidated mass, the holding ability of the soil is generally poor, consequently greater lengths of piling must be used. Altemately, rather than resorting to deeply buried piles, additional members such as skirt piles or the like are often utilized to achieve the desired anchoring effect. In either instance, it is often impossible to economically utilize long piling such as where the piling has only a limited depth of underconsolidated substratum in which to be imbedded.

Toward providing more substantial holding power to a pile of any length, the latter may be cemented into place thereby affording an irregular external surface connection with the substratum, and also greater weight to the pile. This method however entails many drawbacks including difficulty inherent in handling fluidized cement while conducting the latter from the waters surface to the pile lower end. Of further consideration is the tendency of the cement to harden and form voids to a greater or lesser degree, which voids decrease overall hold ing ability.

It is further well known in the prior art particularly in the petroleum industry, that the production rate of crude oil from a well, can under certain conditions be improved by lessening the flow of such undesirables as water and/or sand. Flow of the latter maybe minimized and even completely overcome through the medium of consolidation of the soil about the well through which the water and/or sand would normally pass from the substratum and into the well casing.

Consolidating agents adapted to the above purpose usually are passed through the well and injected into the surrounding oil bearing strata thereby forming a rigid though porous mass. An example of the soil consolidation technique adapted to the above stated purpose is disclosed in US. Pat. No. 3,078,920,

K. C. ten Brink, entitled Treating Underground Formau'ons.

Here the patentee teaches that a suitable treatment will result in the consolidation of a substratum by the method of introducing a treating agent to the underground formation. Said treating agent includes a solution of a normally solid, polymerized methacrylate. Functionally, the polymerized methacrylate is dispersed within a solvent, the mixture being introduced by way of the well structure to the underground substratum. Thereafter, contact with the normally aqueous environment within an oil or water bearing well, causes an immediate precipitation of the methacrylate since the solvent is completely miscible in the water.

However, while such a method as disclosed by the patentee does tend to bind an otherwise underconsolidated substratum, this does not of itself constitute a suitable vehicle for affording a firm anchorage to an anchoring pile. It is felt to the contrary, that soil consolidation as above noted will leave the soil particles and composition in a condition less fit to provide a firm grip on a pile introduced into the consolidated strata.

It is therefore one of the objects of the invention to provide method and apparatus adapted to provide a positive economical foundation anchoring for a structure. A further object is to provide a pile anchoring method and apparatus adapted to form a firm foundation for a structure in a relatively underconsolidated substratum. A still further object is to provide a method and apparatus for removably anchoring a foundation pile by increasing the holding surface of the pile subsequent to the latter being imbedded. Still another object is to provide a method and apparatus for removably imbedding a foundation pile by use of a precipitatable mixture including a polymerized methacrylate which is carried in solution through the pile. Still another object is to provide a method for fostering the anchoring and removing ability of foundation piling by providing the latter with radial projections which extend outwardly from the pile and into the surrounding substratum whereby to more firmly position the pile, or foster its removal.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an offshore platform of the type contemplated utilizing anchoring piles as herein disclosed for anchoring the platform in a body of water.

FIG. 2 is an enlarged segmentary view in partial cross section illustrating one of the legs of the platform shown in FIG. 1.

FIG. 3 is an enlarged, segmentary view in cross section taken along line 3-3 of FIG. 2.

FIGS. 4, 5 and 6 illustrate a pile of the type contemplated going through the sequential steps which terminates in the fully imbedded unit.

PILE IMBEDDING METHOD The invention briefly stated, relates to a method for imbedding a foundation pile into a substratum such as beneath an offshore body of water that would ordinarily be incapable of retaining the pile. Such a substratum can be classified into any one of several categories. For example, a relatively shallow layer of underconsolidated sediment overlying a rocky base would require either drilling through the rock, or using a large number of shorter piles driven into the overlying layer, to develop pile pullout resistance against overturning loads.

Generally, any form of substratum characterized by a greater or lesser holding characteristic can have its pile gripping ability improved by use of the herein disclosed method and apparatus. For the purpose of the present disclosure, the anchoring pile as shown in the drawings, comprises an elongated cylindrical member. The latter is normally formed of a plurality of shorter members which are end welded or fastened into engagement as the pile is progressively driven into a holding substratum.

operationally, the upper end of the pile is grouted or welded to a member of the structure to be supported. The pile lower end depends downwardly from the structure and is forced into the substratum where it is retained essentially by a frictional hold on the pile outer surface.

Referring to FIGS. 1 and 2 in the herein disclosed method, anchoring pile 10 extends downwardly from the offshore platform 11 and is initially driven such as by hammering, by its own weight, or by jetting whereby the pile is imbedded to a predetermined depth into the substratums. In anticipation of such an anchoring operation, it is the usual practice to predetermine the consistency of the soil into which the pile is to be imbedded. Such a determination will then afford an indication to the operator, of problems which might be encountered as the pile is progressed to its desired depth.

Toward improving anchoring ability of pile 10 in the substratum, the pile outer surface is provided after being imbedded, with one or more radially projecting

protuberances

12, 13 and 14 which in effect grip the pile surface and simultaneously adhere to the materials comprising the substratum. These radially spaced protuberances are formed by initially evacuating a plurality of external cavities at discrete intervals along and about the pile length. The cavities can be formed by the forceful injection of water, or other fluid downwardly through the pile center passage and thence radially outward through orifices 16 formed in the pile wall. The forceful injection into the underconsolidated portions of the substratum will cause formation of one or more voids immediately adjacent to each orifice.

Preferably, the void forming medium comprises a pressurized jet of water directed radially through a sufficient number of orifices 16 to form an annular cavity, or a plurality of individual cavities adjacent to and contiguous with the pile outer surfaces. Each cavity is of course determinable by the size of the respective orifices l6 and the direction at which they are disposed whereby to outwardly direct a plurality of cavity forming streams.

The respective cavities defining an aqueous environment,

are provided with a liquefied mixture of the polymerized methacrylate dispersed in a solvent. Said mixture is characterized by remaining in the liquid phase by itself, but being precipitatable only when in the presence of water. Thus, as the mixture under pressure is injected into the respective water occupied cavities, contact of the water with the solvent causes immediate commencement of the precipitation step. This is achieved by absorption of the miscible solvent into the aqueous atmosphere thereby causing the polymer to precipitate out and form preferably a plurality of annular ringlike projections about the pile outer surface.

To avoid premature precipitation of the polymer from injected mixture prior to the latter entering the preformed cavities, water used in the cavity evacuating process is displaced by injecting an initial purge flow of solvent down through the pile conduits. Thereafter, the precipitatable mixture introduced through said conduit passes into the cavity. As previously noted, solvent will be immediately washed from the introduced mixture by the water in the cavity whereby the solid precipitate ring or series of projection will be formed.

Orifices or apertures 16 formed in the wall of pile are spaced at sufficient longitudinal intervals to lie within the underconsolidated layer. and to form a series of the desired radial holding rings l2, l3 and 14. Each series of orifices at a particular depth is provided with an annular manifold l7, l8 and l9which extends about the pile inner wall to define a fluidtight conduit.

APPARATUS Referring to FIG. 1, offshore platform 11 is illustrated in a body of water, which platform normally utilizes pile anchors of the type contemplated for maintaining the unit at a desired location. This is achieved by driving one or more piles 10 through the platform upstanding legs 21 whereby the piles are imbedded into the ocean floor immediately beneath the platform.

It is understood that the following description of the apparatus in general relates to a unit applicable to the disclosed method. The method however can be applied as well to a land based well or drilling operation for anchoring a structure above the well.

Platform 11 shown in FIG. 1 includes in general a deck 22 nonnally disposed above the surface of the water and holding equipment ancillary to a drilling or crude oil producing operation. Deck 22 further embodies a plurality of vertical corner openings which incorporate jacking mechanisms not presently shown. The latter are so arranged with a vertical opening to register a leg 21 and form a tight, releasable grip on the latter in such manner as to position the deck with respect to the water: surface. Elongated support legs or columns 21 depend downwardly from deck 22 toward the ocean floor and generally terminate at, or a slight distance above the latter.

Each leg 21 as herein shown includes at least one hollow steel pile which, during imbedment, is passed downwardly through a leg center passage and driven into the substratum by a pile driver, by a jetting operation, or by virtue of the weight of the pile itself. Normally when the pile 10 has been imbedded a sufiicient distance into the substratum it is unitized with the platform leg 21 by welding or cementing such as by a cement collar disposed intermediate the pile wall and the leg 21 lower end.

Referring to FIGS. 2 and 3, pile 10 is formed with a relatively thick outer wall 24, being made up of shorter lengths of cylindrical casing 26 usually between about 18 to 36 inches in diameter. The pile lower end is provided with a tapered edge to foster movement of the pile into the substratum. Further, although not presently shown, a jetting mechanism can be incorporated at the pile lower end for hydraulically displacing soil thereby forming a passage for the pile as the latter is lowered. During imbedment, the pile is normally suspended and its length added to by welding short sections of casing 26 to the pile upper end.

Referring again to FIGS. 2 and 3, pile l0 embodies the novel feature of orifice means 16 transversing the casing wall at the pile lower end. Said orifice means includes a plurality of spaced-apart apertures formed by a relatively constricted port 27 at the casing inner wall which is connected by outwardly divergent sidewalls 28 and which terminate in a wide opening at the casing exterior surface.

Apertures 16 are preferably arranged peripherally about casing 26 and spaced radially equidistant one from the other, each series of apertures being spaced longitudinally apart along the pile wall. Thus, as the pressurized fluid stream is passed through the respective apertures, there will be a forcible displacement of the underconsolidated material outwardly adjacent to the apertures to form cavities l2, l3 and 14, preferably defining an annular space about the casing. Each series of longitudinally spaced apertures positioned to form an annular cavity in the substratum about the pile, is such as to open into a particular layer of the substratum. Thus, the subsequently formed radial projections will define in effect an outer corrugated surface on the pile homogeneously connected with the polymerized methacrylate penetration of the soil. The latter is thereby more rigidly held in the imbedding soil over a greater exterior surface.

As shown in FIGS. 2 and 3, each series of peripheral apertures 16 formed in a segment of casing 26 is provided with a manifold as 17, 18 and 19. The latter defines an annular passage 31 preferably about the pile inner wall and sealably fastened to the latter by welded

joints

32 and 33 at the upper and lower ends respectively. Manifolds l7, l8 and 19 are spaced longitudinally one from the other in accordance with spacing between series of peripheral orifice 16. Each manifold, 17 for example, includes an inlet 35 having a connection fitting 34 depending therefrom providing passage to the manifold interior. Each manifold is further provided with an individual riser or conduit-36 being coupled to the inlet through fitting 34 or the like. Riser 36 includes a plurality of short pipe lengths coupled one to the other as the length of pile and riser increases to the deck 22.

The respective distribution manifolds are disposed preferably at the upper end of each length of casing 26 although each of said lengths may be provided with a manifold at opposed ends thereof. Thus as the respective varied length casing segments are added to the pile, the distance between the respective groups of apertures may be varied in accordance with the disposition of the stratum into which the pile is to be imbedded.

As shown in FIG. 2, the respective risers 36 extend upwardly from

pile manifolds

17, 18 and 19 to the waters surface, and communicate with a fluid distribution system. The latter comprises in essence a plurality of tanks or storage vessels represented by 38, 39 and 41, holding constituents necessary to the operation of the present method such as a liquid flushing material, solvent, and polymerized methacrylate. Exemplary of the distribution system, three individual tanks are here shown having pumping means therein to direct streams of material as required downwardly through the riser system, manifolds and the various control valves 42, to the pile orifices 16.

In an example of operation of the present method and referring to FIGS. 4 to 6, a pile 46 is initially positioned to a predetermined depth in the substratum in accordance with the known composition of the substratum which is usually predetermined by test borings and the like. A plurality of annular cavities 47, 48 and 49 are formed about pile 46 outer surface by actuating the surface positioned control means to communicate the respective risers 51 simultaneously with a pressurized stream of water.

The latter is passed downwardly through the risers and into the manifolds 52. The high-pressure water streams are then directed through the peripherally arranged constricted apertures 53 whereby to displace the soil from about the respective apertures and define the series of cavities. With continued excavation and displacement of soil, the individual cavities will ideally merge into a single annular cavity.

Since precipitation of the polymerized methacrylate will commence virtually immediately upon contact of the injected mixture with water, a pressurized flow of solvent is passed into the respective risers 51 to forcibly purge water therefrom. Thereafter, the flow control means is adjusted to communicate the respective solvent holding risers with an anhydrous solution of the polymerized methacrylate and solvent, which mixture is introduced under pressure to the respective cavities by way of the circularly arranged apertures 53. Upon contact of the precipitatable mixture with the water environment within the respective cavities 47, 48 and 49, the solvent, which is completely miscible in the water will be drawn from the latter thereby leaving a residue in the form of a precipitated solid in and about the area adjacent to the respective apertures.

Over a period of time, with an absence of solvent, the precipitate will harden to form a desired bond to consolidate the soil immediately adjacent to the pile, and to form a bond with the pile exterior thereby to establish a continuous rigid connection through the respective apertures 53. The overall effect is to provide a plurality of radially extending anchoring projections which depend from the pile wall and into the surrounding substratum thereby giving a desired pile gripping efficiency.

When at a subsequent time it becomes feasible or desirable to remove the platform to a different location, the piles, rather than being destroyed and scrapped, can be salvaged by removing the same from the substratum for subsequent use. This is achieved by exposing the precipitated solid ring, or the individual projections, in cavities 47, 48 and 49 to the solvent which is introduced down the respective risers and conveyed to the manifolds.

Injected solvent will thereby dissolve and disperse the precipitated mass from the manifold, from the apertures 53 and from the area adjacent to the apertures. This pressurized solvent injection in one effect dissolves the bond between the pile and the substratum whereby the former may be withdrawn through the application of a lifting force exerted from above.

A preferred mixture of the constituents of the presently disclosed precipitatable solution includes a polymerized methacrylate such as methyl methacrylate. Any of a number of water miscible solvents are effective to function as a vehicle into which the methyl methacrylate is dispersed which solvents include glacial acetic acid, acetic anhydride, anhydrous propionic acid, also a number of the normally elastic ketones such as acetone, methyl ethyl ketone and the like.

Obviously, many modifications and variations of the invention, as hereinafter set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. Method for firmly and removably embedding an elongated anchor pile into an underconsolidated substratum, said pile having longitudinally spaced lateral openings formed therein and being selectively connected with a fluid distribution system including a pressurized source of water, which method includes the sequential steps of;

l. embedding the lower portion of said pile into said un derconsolidated substratum,

2. forming a plurality of longitudinally spaced water filled cavities in the substratum adjacent to thewalls of said anchor pile, said cavities being formed by injecting water into the substratum.

3. selectively communicating the respective pile lateral openings with a pressurized source of liquefied mixture from said distribution system, said mixture comprising polymerized methyl methacrylate dissolved in liquid solvent,

4. injecting said liquefied mixture into said water filled cavities,

whereby said solvent will be adsorbed into said water to precipitate methyl methacrylate within said cavity and form a bond between the substratum and said pile, and

selectively communicating said respective pile lateral openings with a pressurized source of said solvent material subsequent to the injection of water through said lateral openings, whereby to purge water from said pile lateral openings prior to the introduction of liquefied mixture thereto.

2. In an anchor pile adapted to form a firm releaseable grip in a normally underconsolidated substratum, said pile being selectively connectable to a source of a precipitatable mixture, and a flushing liquid respectively, which anchor pile comprises;

an elongated casing having an outer wall terminating in the pile lower anchoring end,

orifice means at said casing lower end including longitudinally spaced-apart apertures transversing said casing wall and opening at the exterior side thereof,

conduit means communicating said respective orifice means with said source of precipitatable liquid mixture, and flushing liquid respectively, and

flow control means integral with said conduit means, and being actuatable to selectively communicate said orifice means with said respective sources of precipitatable liquid mixture and flushing liquid for sequentially directing said flushing liquid and said mixture to said orifice means, and a manifold carried at the elongated casing inner surface and being disposed substantially normal to the pile axis, said manifold enclosing at least one of said orifices means in said casing lower end, said manifold being communicated with said conduit means.

3. In an anchor pile as defined in claim 2 including; a plurality of said normally disposed manifolds defining closures across said spaced-apart apertures, each of said manifolds being separately communicated with conduit means.

Claims

2. forming a plurality of longitudinally spaced water filled cavities in the substratum adjacent to the walls of said anchor pile, said cavities being formed by injecting water into the substratum.
2. In an anchor pile adapted to form a firm releaseable grip in a normally underconsolidated substratum, said pile being selectively connectable to a source of a precipitatable mixture, and a flushing liquid respectively, which anchor pile comprises; an elongated casing having an outer wall terminating in the pile lower anchoring end, orifice means at said casing lower end including longitudinally spaced-apart apertures transversing said casing wall and opening at the exterior side thereof, conduit means communicating said respective orifice means with said source of precipitatable liquid mixture, and flushing liquid respectively, and flow control means integral with said conduit means, and being actuatable to selectively communicate said orifice means with said respeCtive sources of precipitatable liquid mixture and flushing liquid for sequentially directing said flushing liquid and said mixture to said orifice means, and a manifold carried at the elongated casing inner surface and being disposed substantially normal to the pile axis, said manifold enclosing at least one of said orifices means in said casing lower end, said manifold being communicated with said conduit means.
3. In an anchor pile as defined in claim 2 including; a plurality of said normally disposed manifolds defining closures across said spaced-apart apertures, each of said manifolds being separately communicated with conduit means.
3. selectively communicating the respective pile lateral openings with a pressurized source of liquefied mixture from said distribution system, said mixture comprising polymerized methyl methacrylate dissolved in liquid solvent,
4. injecting said liquefied mixture into said water filled cavities, whereby said solvent will be adsorbed into said water to precipitate methyl methacrylate within said cavity and form a bond between the substratum and said pile, and selectively communicating said respective pile lateral openings with a pressurized source of said solvent material subsequent to the injection of water through said lateral openings, whereby to purge water from said pile lateral openings prior to the introduction of liquefied mixture thereto.