US3075357A - Soil consolidator - Google Patents

Description

Jan. 29, 1963 J. H. CUNNINGHAM 3,075,357

SOIL CONSOLIDATOR Filed May 28, 1958 2 Sheets-Sheet 1 FIGURE I INVENTOR.

J. H. CUNNINGHAM Jan. 29, 1963 Filed May 28, 1958 J. H. CUNNINGHAM SOIL CONSOLIDATOR 2 Sheets-Sheet 2 FIGURE 3 IN V EN TOR.

J. .CUNNI GHAM' United States Patent Ofilice 3,675,357 atented Jan. 29, 1963 3,075,357 SOIL CUNSGLEDATOR Joseph H. Cunningham, PAD. Box 797, Beaumont, Tex. Filed May 28, 1958, Ser. No. 738,375 1 Claim. (Cl. 61-1) The present invention relates to a method for compacting soil or aggregate of deposition in such a manner as to provide steeper slopes than such soils are normally capable of supporting under the influence of water current and wave action. More particularly, it relates to a fiexible-base soil consolidator.

Silts and sands that are transported and deposited by the forces of water remain subject to such forces. The scouring force of water current is proportional to the square of its velocity with reference to the soilsbeing disturbed. Pressure fluctuations of ocean waves comblue with running currents to penetrate soils of deposition and set them into a fluid instability in depth neutralizing their value as ballast or even washing them away from current deflecting media to cause partial or total undermining of foundation beneath the Weight of a supported structure. In utilization of the density of such deposited aggregates for support of structural foundations and channel walls that are positioned off-shore, in beach uprush zone, on coastal locale subject to storm tides, in rivers cutting through a soil-type base and like areas, these inherent limitations must always be taken into consideration. In the past, attempts to obviate the problems presented have taken the form of elaborate and costly countermeasures or, alternatively, have been purcly temporary or high-risk expedients. Various remedies to prevent scouring and undermining of marine foundations have included, for example, using rigid barriers such as steel pilings or the conventional form of vertical scouring skirt, or surrounding the exposed areas of a supported structure with large size gravel, concrete blocks, sandbags, anchored villow mats and the like. The stone or sandbag method are flexible ones in that these elements fall into any attempts to underscour themselves and the foundation they are positioned to protect. However, they present high-friction surfaces to the water forces and are themselves attritioned in the performance of their duty. Usually, none are natural to the locale and must be transported and installed by the aid of equipment and labor which represents a costly capital investment.

I have now discovered a flexible-base means for preventing scouring and undermining of aggregate deposit which does not suffer from the common deficiencies of the prior art means and which has distinct advantages in that a minimum of materials, tools and labor are required in lending such protection giving it a vast economic advantage and more extensive applications over those in the prior art. My invention utilizes sheet materials of low surface tension and high tear resistance to enclose and densify soils against scouring dispersion, being designed in function to capture the desired amount of aggregate ballast and act as a flexible-base protective device which cannot be underscoured or attritioned. Essentially, I have discovered that films or sheets of material of low friction/ strength ratio will perform as a lubricant between bottom aggregate and the combined overhead vectors of current fiow and wave pressures acting to trip such forces as would disturb a soil consolidated in depth, i.e., that the dynamic liquid forces can be separated from the sediment on which they would act by friction contact by interposition of a friction-mitigating medium.

It is an object of the invention to provide means for giving water-agitated sands in tidewater a degree of bearing strength that equals or exceeds that of the damp sands above the uprush line. Another object of the invention is to consolidate deposited sand, silt or aggregate so that it has a supporting strength shoreward to any desired elevation or seaward to any desired depth. It is still another object of the invention to utilize available sands or soil for temporary groin or breakwater. A further object of the invention is to consolidate deposited soil to support steep-sided channeling through sand bar and to support abrupt sandy slope broadside to wave forces. Still another object is to utilize the dielectric qualities of the soil consolidator of the invention for mitigation of electrolysis at a metal-soil interface and as a concealed impedance station or route marker. Yet other objects are to permit extension of isolation time for sand cementing agents in a tidal zone to mitigate water damage during curing period and to capture all the secondary effects of the invention insofar as it influences the shoaling wave energies and alters the conditioning factors of sandy beach slope. These and other objects and advantages of the invention will become apparent from the following description together with reference to the accompanying drawings wherein:

. FIGURE 1 is a plan view of a type of flexible-base soil consolidator of the invention;

FIGURE 2A is a cross-sectional view of the position of the consolidator of FIGURE 1 as it appears immediately after placement on the supporting soil bed alongside a structure;

FIGURE 2B is a cross-sectional view of the position of the consolidator after it has been seated in the supporting soil bed by wave action;

FIGURE 3 is a pictorial representation of the supporting section of an off-shore drilling platform protected against scouring or undermining by means of the flexible-base consolidators of the invention and accessory equipment positioned outboard of the consolidators.

According to the invention, an area or section of deposited sand, silt, aggregate or the like can be locked against the scouring forces of water by positioning over that area a flexible-base soil consolidator. Such a consolidator shown in FIGURE 1 consists of a mat or pad 1 which is a sheet of waterproof material having a low coefficient of friction, low surface tension, and a density approaching that of water. Attached by sealing or bonding around the periphery of said mat or pad are anchor tubes 2, 3, 4, and 5, which are made of an identical or compatible material. Shown also is the weep drain 6 which is a filter tube atttched to the bottom surface of the mat and serves to permit removal of water of consolidation or gases from beneath. the consolidator when such removal is desirable. The tube anchors are filled with ballast, 8 in FIGURES 2A and 23, having a density equal to or exceeding the natural density of the soil or aggregate on which the consolidator is positioned, such ballast being a fiocculated sediment or sand of the locale, drilling mud, or the like. The anchor tubes are seated in the sediment or bottom aggregate by flushing out a seat mechanically or by means of natural scouring forces. These tubes serve to anchor the mat or pad and prevent encroachment from beneath the outer edges by the forces of wave and uprush. Since ballast contained in the tube anchors has a density equal to or exceeding that of the media in which it settles, it sinks in the bottom aggregate when the aggregate level is penetrated and fluidized by the natural scouring forces of current and wave action. Natural scouring forces do not penetrate to disturb ballast density within the anchor tubes and they possess great ability to withstand transient stresses in the horizontal plane. FIGURE 2A shows the position of the consolidator on the supporting soil bed, 9, alongside the structure, 7, to be protected in its initial completed lay, i.e., prior to any extensive action of water forces. FIG- amass? URE 213 represents the same consolidator after being seated in the supporting soil bed, 9, by storm forces.

Materials of construction applicable for the soil consolidator are waterproofed and have features of high strength/density and low friction/strength ratios. Such features are to be-found in conventional plastic sheeting and films such as polyethylene, plasticized polyvinyl chloride, neoprene-impregnated nylon cloth and the like. Likewise, a tight-weave steel chain mail would meet the requirements in some instances. Polyethylene is presently the preferred material because of its relatively low cost, availability in wide sheets, and ease of fabrication.

The thickness of the mat is not a critical feature. With polyethylene, for example, any thickness from 1 to 12 mils may be used. The preferred thickness depends upon the application and is readily determined based upon considerations and conditions under which the-installation is to be made;

The tube anchors are preferably fabricated from the same material as the mat but this is not a necessary requirement. They may be fashioned from different materials with the same general strength, low-friction, density characteristics as the mat as long as such materials can be satisfactorily sealed, bonded, or welded in a permanent manner to the mat.

The dimensional characteristics of the soil consolidator may obviously vary widely depending upon the particular application in which it is employed.

One simple method for fabricating the consolidator from polyethylene film is as follows:

A mill-supplied, 4-mil thickness width of six feet and with 12-inch is processed by bead sealing lengthwise along each of the two edgesof each of the two gussets so that lateral anchor tube casings of double-wall thickness .and circumference approximating 22 inches each are formed each side of a double-thickness mat. The assembly is continuous and unbroken to any predetermined required length. Both anchor tube casings are inflated and stressed with air pressure for inspection at the four weld beads and manual seal of any weak points. End tubes of the same dimension are then sealed into each end to complete requirements for a prefabrication that has the appearance of an air-inflatable. life raft but with each lateral tube projecting beyond the end tubes by an amount to provide facility for attaching filler lines. The two lateral tube ends at one end of the assembly are then tied off short at their cross tube and that end is positioned for rolling upon a 12-inch diameter pipe or mandrel of six foot length. The tubes are then evacuated of all air. A weep drain with one adhesive activated surface is oriented for adherence to the bottom side of the mat and the entire assembly is rolled upon the mandrel and given a protective shipping cover.

Upon installation the anchor tube casings may be pumped full of sand, silt or aggregate by water vehicle and compacted by flocculation and/or withdrawal of excess water by suction. Alternatively, materials exceeding density of the soil on which the consolidator is to be laid can make up the ballast of the anchor tubes. Loaded or contaminated drilling mud, for example, retains desirable density and flow characteristics. It is often desirable, too, to condition the mud by addition of tubing of flat lay a flocculating agent. A preferred type would have a timeblock coating such as polyvinyl alcohol and lead oxide to permit certain periods of dormancy before exerting its effect.

In order that the soil consolidator of the invention may be more completely understood, its use in protecting the supporting section of an off-shore drilling platform against loss of drilling attitude through the storm season will be described in detail with reference to FIGURE 3. The? supporting section of' the' platform, 11, below the legs, 10, locatedbelow the water line, 14, is ofsuch a type that it is without facilities forattaching a recoverable gussets at each edge type of flexible anti-scouring skirt. The figure illustrates a non-recoverable type of anti-scouring skirt designed for capturing and holding in position the aggregate of the supporting soil bed, 9, immediately adjacent to the structure. It consists of three soil consolidators horizontally positioned on the three exposed sides of the bottomed structure 11 of a size approximately ft. x ft. Each of the soil consolidators consists of an unbroken mat of polyethylene, 1, approximately four feet in width bounded by anchor tubes, 2 and 4, approximately 7 inches in diameter filled with drilling mud. The two longest consolidators approximate 192 ft. in length while the forward one is about 80 feet long. As added protection against possible unraveling of the horizontally positioned-skirt and to provide a safety factor, storm capes are positioned outboard "of the three consolidators so that they protectccorners formed by junction of the consolidators. .Anchored storm capes are also positioned within the wellhead, 13, where they function to capture migrating aggregate. A storm cape consists essentially of a tube anchor, 4, to which is attached one edge of a single sheet ofplastic, 12, which is permitted free flow cape action. Those represented in FIGURES have tubes approximately 7 inches in diameter and 30 feet long to which sheets 12 feet wide and 30 feet long are attached.

The installation of the soil consolidator components of the anti-scouring skirt illustrated together with the accompanying storm capes can be effected in any of several ways. One convenient method utilizes the forward end of the superstructure to be protected, its boat landings, a mud hopper with discharge valve and associated collapsible feeder hose, an underwater distribution station, a-self-priming water pump and suction hose. With atrained crew of two diversand-three deck hands, the entire installation is completed in twelve hours of fair sea weather wherein running currents do not exceed two knots.

It is standard procedure when a drilling platform is positioned on new location for a diver to walk the bottom and have removed any logs and debris and leveling off of any voids projecting beneath the bottomed structure. This is also a necessary preliminary to skirt installation.

The mandrel core upon which is rolled the prefabricated consolidator previously described is fitted into a simple lawn-mower-type handle assembly for ease in the unrolling operation alongside the structure. A 192 ft. long consolidator such as the starboard consolidator, for example, in FIGURE 3 has a diameter of approximately 26 in. and a net weight in air of about 94- lb. With the exclusion of all air bubbles, it will float in salt water because of its material density of 0.93.

i The consolidator assembly is then lowered into a positron alongside the platform just ahead of a tripod distribution assembly. This tripod assembly consists of a supporting brace leg to which is clamped a supported Y pipe arrangement having coupling hoses at both outlets thereof. The Y inlet is connected to .a collapsible feeder hose the upper end of which is attached to the discharge of a mud hopper, the hopper being in a fixed forward position on the superstructure. The hopper discharge is fitted with a remotely-controlled solenoid-operated valve and feeds mud by gravity fall into the collapsible feeder ose.

Seven separate charges of mud are required for the complete installation, two for each of the three cons'olidators' and one for the anchored storm capes. The calculated amounts of mud containing approximately 30% solids is charged to the hopper. Preferably, a flocculating agent is added to the mud in a crystalline form coated with a'timeblock of'a coating thickness and filler content to permit approximately one-hour dormancy. A. short burst of mud is dropped as a purging charge and the anchor tubes of the consolidator are then clamped in union with the Y coupling hoses. A control diver positioned at the tripod distribution assembly with remote push-button control in one hand feeds mud in short bursts, timing the interim between discharges by manually feeling the amount of back-pressure at the eeder hose with the other hand. The soil consolidator with a diver guiding it is propelled forward by the force of intrusion of the fluid ballast into the expanding anchor tubes. Completion of the lay is signified by unrelieved back-pressure at the feeder hose. Anchor tubes are tied ofi and the Y assembly is disconnected and allowed to drop any mud remaining in it. Both divers then inspect the lay of the skirt and manually adjust the tubes as required to assure that the inboard tubes lie in close proximity to the bottomed structure.

At the completion of flocculating action indicated by the feel of hardness at the base of the tube anchors, a suction tube is injected at one end of the tube anchor and the excess water of consolidation is pumped out. A final charge of mud is then injected in the manner described above, the open tube anchor ends are tied off short against the cross tubes and excess materials are trimmed at the knot. The ends are then seated into the sand or aggregate plane manually or by jetting action with use of a suction tube connected to discharge end of the water pump. This operation is repeated for laying of the other two consolidators. A complete scouring skirt installation requires the operation of the tripod station successively at each of the two forward corners of the structure and no equipment is required at the far end in this particular laying operation. Storm cape lay is effected in the same manner.

When weep drains are employed, the final step in the installation procedure is to give all weep drain tubes a common series connection with a suction hose connection to the pump. The weep drain, while not essential to the overall objective in the anti-scouring skirt application, appears to be a desirable feature because it acts to remove water of consolidation plus a great amount of water which is being wrung from beneath the weight of the bottomed structure, the hydrostatic pressures of which tend to rupture the natural consolidation of the outboard aggregate. It also serves another purpose. In practice, some instances of entrapment of animal and plant mat ter removed from their natural environment have resulted in gases of decay with potential lifting eifect on the assembly. Ordinarily and in most cases vapor pressures at the depth involved cause such rapid transmission of the gases through the 4-mil thickness of polyethylene as to make their eflfect inconsequential. However, the use of a weep drain obviates any possible undesirable effects from gas evolution in the area beneath the consolidators. Three days of operation of the weep drain has sufliced for destruction of organisms and plants and completion of drain so that its functioning is not required after this time.

Thus installed, the soil consolidators together with the storm capes provide a protective anti-scouring skirt which 6 stabilizes the structure over long periods of time in stormridden waters.

Consolidator design is adapted to emphasis on type of soil, combined burdens, and economic objectives. Protection for a highway paralleling a seacoast and occasionally subject to storm tides would be substantially at variance to component design for a recoverable scouring skirt positioned at the exposed sides of a transportable olfshore structure or for an expendable temporary type channel passage through a sand bar. Protection for concrete bridge piling subject to scourout would be identical in design for steel casing at an off-shore producing wellhead but objective would vary in respect that the steel casing is subject to severe stress electrolysis at the coincidental mud line and fulcrum point such that insulation qualities of the consolidator could well justify its use sorely on grounds of mitigation of corrosion.

What is claimed is:

The method of preventing underscouring of a marine foundation which comprises horizontally positioning over the aggregate plane alongside the structure on each of its exposed sides an assembly consisting of a mat of a resinous plastic material having a low coefllcient of friction and high strength bounded at its outer periphery by attached tubes of the same material as said mat and having attached to its bottom surface a tube adapted for withdrawing liquid from underneath said sheet, anchoring said assembly by filling said tubes with ballast of a density at least equal to that of the aggregate on which it rests, seating said tube-s in said aggregate plane whereby said sheet of plastic material captures the encompassed and covered aggregate plane against disturbing penetration by current and wave forces, positioning outboard from the corner junctions of said assemblies, storm capes consisting of tubes of a resinous plastic material having a low coeificient of friction and high strength filled with ballast of a density at least equal to that of the aggregate in which they are positioned and having attached thereto free flowing sheets of the same material, and seating said storm capes in the aggregate plane.

References Cited in the file of this patent UNITED STATES PATENTS 283,369 Bartlett Aug. 21, 1883 1,039,579 Neames Sept. 24, 1912 2,390,403 Van der Rest Dec. 4, 1945 2,870,609 Siebenhausen Ian. 27, 1959 2,895,301 Casagrande July 21, 1959 OTHER REFERENCES World Oil Magazine, pages 108, and 112, Feb. 1, 1950, F. Briggs.

Engineering News Record, pages 43 and 44, May 25, 1950, D. Appel.

US. Bureau of Reclamation Linings for Irrigation Canals, Office of Chief Engineer, Denver, Colorado, July 1952.

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