US3653167A

US3653167A - Anchorage apparatus

Info

Publication number: US3653167A
Application number: US11249*A
Authority: US
Inventors: Louis F Menard
Original assignee: Compagnie Francaise des Petroles SA; TECHNIQUES LOUIS MENARD
Current assignee: Total Compagnie Francaise des Petroles SA; TECHNIQUES LOUIS MENARD
Priority date: 1969-02-07
Filing date: 1970-01-29
Publication date: 1972-04-04
Anticipated expiration: 1989-04-04
Also published as: GB1298863A; NL7001043A; FR2031804A5; DE2005066A1

Abstract

For an anchorage in the ground, an anchoring head is provided which can be driven into the ground in an orientation providing a small frontal area and small resistance to the driving-in force. Attached to the head at a point laterally offset therefrom is a rod or cable through which the anchoring force is to be transmitted. When the head has been driven in to the anchorage depth, tension is applied to the rod or cable which, by virtue of said offset, tilts the head into a different orientation in which it presents much greater resistance to pull-out forces.

Description

0 United States Patent [151 3,653,167 Menard 1 Apr. 41, 1972 [54] ANCHORAGE APPARATUS 2,941,636 6/1960 Cordes ..52/164 3,468,085 9/1969 Jones..... [72] Inventor: Louis F. Menard, Paris, France 23 97 3 19 4 pruynm [731 Assignees: Techniques Louis Menard, Longiumeau; 972,306 10/1910 WllCOX ..52/l63 ggmngzgnie Francaise des Petroles, Paris, Primary Examiner price C Jr.

Attorney-Breitenfeld & Levine [22] Filed: Jan. 29, 1970 [21} App1.N0.: 11,249

[57] ABSTRACT 30 F A ti P it Data For an anchorage in the ground, an anchoring head is proorelgn pp lea on y vided which can be driven into the ground in an orientation Feb. 7, 1969 France providing a mall frontal area and mall resistance the driv. ing-in force. Attached to the head at a point laterally offset [52] US. CL. 2/l62, 52/l66 therefrom is a rod or cable through which the anchoring force [51] Int. Cl ..E02d 5/30 is to be transmitted. When the head has been driven in to the [58] Field of Search ..52/162, 166, 155, 156, 158, anchorage depth, tension is applied to the rod or cable which,

52/159, 160, 161, 163, 164, 165 by virtue of said ofiset, tilts the head into a different orientation in which it presents much greater resistance to pu11-out [56] References Cited forces.

UN lTED STATES PATENTS 6 Claims, 9 Drawing Figures 1,052,700 2/1913 Warrick ..52/163 PATENTEDAPR 4 I972 3,653,167

SHEET 2 [IF 2 ANCHORAGE APPARATUS This invention relates to an anchorage apparatus to a method on anchoring.

An anchorage in foundation soil, for example, serves to withstand forces tending to pull the anchorage out of the soil and caused, for instance, by water pressure below a foundation raft, overturning moments due to wind, by currents and thrusts on sheet piling, and by the action of the sea on floating platforms.

Most conventional anchorage processes are based on either drilling a hole in the ground in which a rod or cables are sealed with mortar, or driving into the ground a tube with or without a widened head and with or without concrete injection.

Driving systems are the most used in loose soils and are relatively reliable and economical. They have the disadvantage of needing very powerful driving equipment, since the penetration resistance of a smooth tube or of a tube having a widened heat is something like twice or three times the pull-out resistance at normal anchorage depths. Consequently, a required pull-out resistance of 100 tons means that the driving equipment must be able to deal with a penetration resistance of from 200 to 300 tons.

It is an object of this invention to enable low-cost driving means to be used to install anchorages having very high pullout resistances.

To this end, according to the invention, a special form of anchorage head is driven into the ground and, after arrival at the anchorage depth, the anchorage head is tilted by a pull applied from the surface to change the head position, so that the pull-out resistance of the head is greater than its previous penetration resistance. An anchorage head is used whose orientation in the anchorage position can be varied by a pull applied to the head by a pulling member articulated to the head at a point laterally offset from the main axis of the head in the direction of penetration into the ground, i.e., eccentric of the head center of gravity if the said axis normally passes through the center of gravity.

For instance, the head may comprise at least one plate, the point of articulation being offset from one side of the plate and by which the head is connected to the pulling member. The articulation can have a pivoting axis parallel to the plate. It may be a pivot pin.

Advantageously, the head can comprise two plates; for instance, two plates arranged in a V around a central tube, the articulation preferably being disposed substantially in the plane of symmetry of the two plates and possibly comprising a pivot pin disposed perpendicular to such plane.

Certain embodiments of the invention will nOW be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a simple form of anchorage head according to the invention, the head being assumed to be in the position for driving;

FIGS. 2 and 3 are views, in planes perpendicular to one another, of the head of FIG. 1;

FIG. 4 is a diagrammatic view of apparatus for installing the anchorage;

FIGS. 5 and 6 are diagrammatic views showing the start and end, respectively, of the pulling operation;

FIG. 7 shows another form of anchorage head;

FIG. 8 shows a further form of anchorage head; and

FIG. 9 shows how the invention can be used to stabilise. soil.

The anchorage head shown in FIG. 1 comprises a metal plate 1 whose dimensions are suitable for the required anchoring force and which has a transverse member 2. A pulling member 4, such as a cable or rod, is secured by an articulation 3 to the outer end of the member 2. The articulation, which is shown as a pivot pin, is such that the plate can rotate around the pin and take up any position imposed by external forces. The member 2 of this embodiment takes the form of parallel flat arms disposed perpendicularly to the plate 1.

This form and similar forms of head construction present a very low penetration resistance when the head is in a position in which the various planes which define it are parallel to the penetration direction, for penetration resistance is then caused merely by friction on the surfaces of the head and on the pulling cable; the frontal resistance is relatively slight since the frontal area consists merely of the edges of the various plates. A head of this kind can therefore be driven in by relatively low-power driving means acting by way of a small slotted metal rod or tube 5 which knocks against the plate 1 and at the same time maintains the plate vertical.

FIG. 4 is a diagrammatic view by way of example of an installation wherein an anchorage head of the kind shown in FIGS. 1 to 3 is driven into the ground by a lorry-mounted piledriver 6 which strikes the head by way of a tube 5. When the head has reached the required anchoring depth, which depends upon the nature of the soil, the required anchoring force and the dimensions of the plate 1, the tube 5 is removed and a pull is applied to the head by jacks which bear on the soil surface and which act on the pulling member 4. This pull applies a tilting moment to the plate because the force is applied to the plate off-center. This tilts the plate into a position which is substantially horizontal and, at the pulling-force limit, exactly horizontal. The pull-out resistance which can be provided is therefore very high, since the bearing surface when the plate is in the horizontal position is from 3 to 10 times what it was when the plate was vertical.

FIGS. 5 and 6 are diagrammatic view showing the start and termination, respectively, of the pulling of the plate by jacks 7, 8 acting on the cable 4, on the assumption that the final position of me plate is horizontal. The pull-out force which a system of this kind can withstand is very much greater than the drive-in force, the difference being from 2- to 6-fold depending on the dimensions of the plate and upon the depth.

It is not always necessary to perform the operation of tensioning the anchorage by jacks before the normal anchoring force is applied; this previous tensioning is given only to obviate the movements of a few tens of centimeters during the first application of the normal anchoring force. No such pretensioning is needed for the anchorage of a floating platform, or for pylon guying, for example.

The anchorage can be temporary or permanent; if it is permanent the metal thicknesses may be greater than if it is temporary, to allow for possible corrosion in the soil.

The anchorage head diagrammatically shown as a plate 1 can have other shapes in accordance with the conditions in which the anchorage is to be employed in practice. For instance, for ease of piledriving it is convenient to use a head in the shape of an H section beam with wide flanges, as shown in FIG. 7. In this case, the pulling member, e.g. a chain 9, is attached preferably to the lower part of one of the flanges 10, 11 of the beam, the piledriver or the like acting on the web 13 of the beam.

Piledriving can be omitted in some cases if the head is lowered to the bottom of a shaft, e.g. of from 20 to 50 cm. diameter, and if the shaft immediately above the anchorage is filled, e.g. with sand-gravel mixture, to form a plug. When tension is applied to the head, the head is tilted in just the same way as if it head been driven in.

The anchorage according to the invention has the advantage of simplicity of design and ease of use, a drive-in to pull-out ratio well below unity, in contrast to conventional systems, no concrete or like injection of any kind, immediate use of the anchoring force, low cost and reliability. Possible uses are many, e.g., soil slip stabilition consolidation of canal and river banks and anchorage of facilities for pile testing.

The method is very advantageous for underwater use, making possible the use of reasonable sized piledriving or vibropenetration facilities which are easy to handle on board a ship or pontoon. It has been found that anchoring forces of several hundreds of tons can be achieved economically.

A description will now be given by way of example of tests with 15/35 anchorage heads (15 tons of useful strength, 35 tons breaking strength) of the kind shown in FIG. 8 in the tilted-over position. The head is connected to a medium-hard steel rod T of 25 mm. diameter, and comprises two 11 mm.

thick plates P welded to a 49 X 63 mm. guide tube and strengthened by 8 mm. plates. The head is connected to the rod T by a pivot pin A. When the anchorage has been tilted over in the ground, the efiective surface area is 690 cm". The head is driven in by means of a boring tube nested in the central tube 5. Penetration resistance is therefore very low, consisting merely of friction on the walls and on the strut and of a relatively frontal resistance. Once the head is at the required depth, the boring tube is removed and the anchorage is prestressed by jacks which pull on the rod T and which bear on the soil surface.

I ANCHORAGE IN SANDY SOIL Once the head had been driven in and the pivot pin A was at a depth of 2.70 m., it was found that substantial refusal was met with in soils having a high resistance (there is no lateral friction supplementary to the piledriving above the height of the plates P). Head pulling was then started by means of two jacks of 40 tons, the jacks being operated by a hand pump; the head started to tilt at 12 tons and could be assumed to have tilted completely over at 15 tons with a 15 cm. displacement. After this value of 15 tons had been attained so that the anchorage had been stabilized, variations of from i to 10 tons were made and substantially resilient deformations were found (maximum losses at each stroke and recoil 0.2 mm., damped). The forces were increased to tons without breakage occurring, and a motor-driven hydraulic pump had to be used to pull out the anchorage at a force of tons apparent.

II ANCHORAGE IN CLAYEY SOIL The same anchorage was given a similar test in clayey soil. The head was driven in by vibro-penetration without difficulty. The pull tests showed that the head could be tilted through 30 cm. with very reduced forces 5 tons), that subsequent movements were very slight up to 13 tons (1 cm.) and that a force of 15.9 tons was required for rupture.

III USE FOR SOIL SLIP The method according to the invention is very well suited to countering soil slip since it can be carried out using very light driving equipment on sloping ground even if the ground is still moving; the anchorage is secured to the top of reinforcedconcrete plates of standard dimensions and is immediately ready for use to stabilise the soil.

In this case, what may be used is more particularly l5-35 anchorage heads fitted with 32 mm. diameter rods; the heads can be driven in vertically or at up to 45 to the horizontal with a conventional light ram of the kind used for trial boring.

When soil slip is found, the thickness of the moving iayer, and the mechanical characteristics of the substrate to which the heads will be secured, should be measured. Depending on circumstances, it is recommended to anchor at from 2 to 3 meters in the layer in situ and, possibly, to drive in the anchorage with simultaneous injection at the tip to assist penetration, taking care to avoid any premature false refusal.

In a first approximation, in the absence of accurate knowledge of the actual forces required to stabilise the slip, one 15/35 anchorage is put in per 10 m? of moving surface. Where blocks or lumps larger than 30 X 30 cm. are present in large numbers (in cliff slides, for example), a driven-in system of this kind is unsuitable.

This use of the method is illustrated in FIG. 9, where the driving-in phase of the operation is shown at (a), the tilting phase of the operation is shown at (b) and the locking of the rods T by means of elements B, e.g. concrete plates, at (c).

Variants of the heads hereinbefore described by the use of equivalent technical means may be made without departing from the invention.

What I claim as our invention and desire to secure by Letters Patent is: 4 4

l. Anchorage apparatus comprising: an anchorage head adapted to be forced into the ground in a first orientation affording low penetration resistance, said head affording pullout resistance greater than said penetration resistance when in a second orientation tilted with respect to said first orientation; articulation means laterally offset from said head; pulling means connected to said articulation means for tilting said head from said first orientation into said second orientation; said head comprising an anchor plate which is flat, rectangularly shaped and provided with a transverse member comprising a transverse plate fixed at one end to one side of said anchor plate perpendicularly to said anchor plate, said articu lation means being at the other end of said transverse plate.

2. Anchorage apparatus according to claim 1 wherein said transverse member includes another plate which is parallel to said transverse plate.

3. Anchorage apparatus according to claim 1 wherein said anchorage head includes a second rectangular plate connected to said transverse member parallel to the anchor plate.

4. Anchorage apparatus according to claim 1 wherein said articulation means includes a pivot parallel to said anchor plate.

5. Anchorage apparatus according to claim 1 wherein said pulling member is a chain.

6. Anchorage apparatus according to claim 1 wherein said pulling member is a rod.

Claims

1. Anchorage apparatus comprising: an anchorage head adapted to be forced into the ground in a first orientation affording low penetration resistance, said head affording pull-out resistance greater than said penetration resistance when in a second orientation tilted with respect to said first orientation; articulation means laterally offset from said head; pulling means connected to said articulation means for tilting said head from said first orientation into said second orientation; said head comprising an anchor plate which is flat, rectangularly shaped and provided with a transverse member comprising a transverse plate fixed at one end to one side of said anchor plate perpendicularly to said anchor plate, said articulation means being at the other end of said transverse plate.