US2789419A

US2789419A - Method for forming reinforced foundation piles with an enlarged base

Info

Publication number: US2789419A
Application number: US269701A
Authority: US
Inventors: Pickman Edgard
Original assignee: Frankignoul Pieux Armes
Current assignee: Compagnie Internationale des Pieux Armes Frankignoui SA
Priority date: 1952-02-04
Filing date: 1952-02-04
Publication date: 1957-04-23
Anticipated expiration: 1974-04-23

Description

April 23, 1957.

E. PlcKMAN 2,789,419 METHOD FOR FORMING REINFOR FOUNDATION PILES WITH AN E RG BASE Filed Feb. 1952.

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METHOD FOR FORMING REINFORCED FOUNDA-` TION PILES WITH AN ENLARGED BASE Edgard Pickman, Brussels, Belgium, assigner to Compagnie Internationale des Pieux- Armes Frankignoul, Societe Anonyme, Liege, Belgium Application February 4, 1952,`Serial No. 269,701

` 3 Claims. (Cl. 61-57) The invention relates to`a method and a device for forming foundation piles from reinforced concrete or the like which are provided with an enlarged base moulded in the ground. More particularly, the invention has for its object to form a pile of the type aforesaid, having its enlarged base built up to a controllable height and volume, while securing a pile having a high tensile strength. The term .concrete is used to indicate any running or plastic material suitable for the formation of foundation piles. The method of the invention is essentially characterized by the fact that, upony driving the tube to the required depth, a predetermined, relative axial motion is brought.

about between the tube and a rigid body extending at least over a large portion of the free cross area at the foot of 'the tube, and so `that the said rigid body is located at a predetermined distance under the base ofthe tube, the said distance being maintained while the concrete poured into'the tube is being rammed so as to be driven out laterally into the ground, the said rigid body forming a deflector, until an enlarged base of required height and volume has formed between the said body and the lower end of the tube, whereupon the formation of the pileis completed in any suitable manner.

According to the invention, the said rigid body, which is preferably made from concrete, is conveniently connected to longitudinal reinforcement members protruding beyond the upper end of the tube, the said reinforcement members being rendered stationary with respect to the tube when the distance apart between the said body and the foot of the tube -is reached. The upper surface` of the said body is preferably of conical or like shape in order that the concrete may be pressed out more easily in the lateral direction.

In case the rigid body, under the effect of the ramming, descends beneath the tube, up to a distance which is smal-ler than the required height of the enlarged base, the tu-be will be raised by a corresponding vertical distance and will be maintained in its new position until rthe enlarged base is completed.

However, it often happens that, as a result of the ramming, and While the tube is held in position, the rigid body would continue its descent, with no appreciable broadening of the pile base occurring. The latter drawback is avoided by the invention which makes provision for rendering stationary the reinforcement members, which are fast with the rigid body, after the latter has been lowered up to a predetermined distance beneath the tube, whereupon the reinforcement assembly will not be released unless an enlarged base `has formed, having the required volume and height as may be exactly predetermined.

Further according to the invention, the rigid body is preferably positioned on the top of a layer of concrete located in the lower end of the tube and which may be easily driven out therefrom.

A few examples of carrying out the invention will be hereinafter described by way of illustration, with reference to the accompanying diagrammatical drawings, in which:

Figs. 1 and 2 are two vertical cross-sectional views taken prior and subsequent, respectively, to the formation of the enlarged base of a pile in the course of being cast by means of a tube driven through the medium of a tight concrete plug formed at the lower end thereof.

Figs. 3 and 4 are similar fragmentary views referring to the case where the tube rests upon a'rigid point and is driven by direct blows applied on the tube.

Figs. 5 and 6 show two further modied embodiments.

In the example shown in Figs. 1 and 2, the tube 1 has been driven into the ground by striking upon an adherent, tight plug 2 formed of concrete or similar compressed material. When the required depth is reached, the tube 1 is held stationary and the striking upon the plug is continued until the latter is partly expelled, oreven fully expelled, in case water or silt are not likely to enter the tube. Thereupon, the rigid body 3 is introduced, such body being conveniently made from concrete in which reinforcement rods, such as 4, 5, have been firmly anchored, lthree `or four of them e. g., the rods may be interconnected by any convenient binding means such as 6.

A certain quantity of concrete is poured on the top of the body 3 and ramming is continued so as to expel the 4body 3 and the concrete from the tube 1. Pouring the concrete. and striking the latter are continued until the body,3 has descended a predetermined distance A beneath the tube, corresponding to the height of the enlarged base tov be formed. At that time, the

reinforcement members

4, 5 are held stationary in order to avoid any additional descent of the body 3, which might occur should the latter `not be held stationary, the ground being supposed to be of a nature-e. g. clay-which would not offer a resistance sufficient to prevent such descent to occur under the effect of ramming.

Moreover, holding the reinforcement members stationary is always advantageous, and applies also to the case where the rigid body would not tend to descend to a greater depth, and even though it should be necessary to raise the tube slightly in order to obtain the desired spacing between the lower end thereof and the rigid body. In

l fact, if the reinforcement members were left free they might bend outwardly under lthe effect of the ramming, which should be detrimental and would not enable accurate control of the height of the enlarged base, since the relative axial motion between the reinforcement members, and the upper end of the tube would not more accurately correspond to the distance between the basel of the tube and the rigid body. n

The further batches of concrete that will then be poured into lthe tube and rammed, will be forced laterally into the ground, with the body 3 acting as a detlector. To this end, the upper face of the said body will be conveniently of conical, rounded or similar shape. It will be understood that, by controlling 'the volume of the charges of concrete, the volume of ,the enlarged base, to be formed to the height A, can be determined with accuracy.

The concreting of the pile is then completed in the usual way, either by withdrawing the tube 1, or by leaving it in the ground the case where it is intended to act as perma nent sheath.

The reinforcement assembly may be held stationary, during the formation of the enlarged base, by any suitable means, e. g. through the medium of hooks 7 formed atv the upper ends oftheA

reinforcement members

4, 5, which Ihooks come to rest upon the head of the tube 1 when the body 3 has descended beneath the tube by the distance A. All that need be done to release the reinforcement assembly after the enlarged base has been formed is to shear off the hooks. The hooks need not be sheared oif in the case of a sheath to be left in the ground. Moreover, the reinforcement assembly may be provided at the upper end thereof with a stiffening ring which may be held station,

Patented Apr. 23, 1957.

ary withl respect to the tube when the enlarged base is formed. In the case of a permanent sheath, the said ring may show a diameter corresponding to lthat of the sheath, so 'that it will come to rest upon the latter. Such anarrangementV is shown in Fig. 4 (ring 8.)

The use of the invention is particularly advantageous when the driving is effected by means of a concrete plug, as described above, or through the medium of a mandrel or core resting upon both the head of the tube and a sealing plug from concrete or the like located therein. The invention, however, is also applied with advantage where other driving` methods are used.

In the example shown in Figs. 3-4, the tube 1 rests upon a driving point 9 and is lowered into the ground e. g. `by striking directly upon the tube. Prior to placing thev body 3 and the reinforcement assembly d, 5, 6 in position, a quantity of concrete 10 is poured into the tube. When the desired depth has been reached the concrete 10 is expelled, which takes place either prior to introducing the body 3 or subsequent to such introduction and to pouring a certain amount of concrete on top of the body. Thereupon, the enlarged base is built up as described with reference to Figs. 1 and 2.

The mass of concrete 10 will form the lower portion of the enlarged base, in the same manner as did the plug 2, thus completely coating the lower surface of the body 3 and eliminating any risk of water seeping along the surface of the body and, therefore, any risk of the reinforcement members getting destroyed at their point of attachment to the body 3. Thus, one may be assured that a perfect anchorage of the reinforcement assembly in the base of the pile has been provided, at the same time as a high tensile strength as regards tensional stresses tending to separate the shaft from the base and which occur in earth upheavals, which are frequent in clayish soils.

It will be understood, however, that the invention also applies to thecase where the body 3 is placed directly upon the point 9, and to the one where the said body is made integral with such point, i. e., where the reinforcement members 4, are anchored directly in the point 9, as shown in Figs. 5 and 6, the said point being provided in this insatnce with a conical or rounded upper face.

In order to oppose bending of the reinforcement members outwardly along the free vertical distance between the tube and the rigid body when the concrete is being rammed to form the enlarged base, the invention provides for strengthening the reinforcement members at least along that free vertical distance. Moreover, in order to reduce the number of lobes of which the enlarged base is to be made up owing to the presence of the reinforcement rods, which inevitably oppose the concrete being driven out laterally, it is advisable to reduce the number of such rods e. g. to three, which is a minimum in view of preventing the body 3 from tilting, the thickness of the said rods being suitably increased. Consequently, the use of a small number of reinforcement rods of large cross section is greatly advantageous. The reinforcement rods for the shaft of the pile may be provided in a larger number. Figs. 5 and 6 show such embodiments.

In Fig. 5, the reinforcement assembly includes a small number of thick rods 11 anchored in the rigid body acting as a deflector, and a certain number of thin rods 12 65 which are terminated at approximately the foot of the tube 1 all the rods being interconnected by a bonding 6. The point 9 and the body 3 (Fig. 3) are combined to a single body 13.

As shown in Fig. 6, the reinforcement basket for the shaft of the pile includes thin rods 12 with at least some of the latter having attached to their lower ends, such as by welding, rods 14 of greater thickness, which are anchored in the body 13.

What I claim is:

l. In a method of forming a reinforced foundation pile with an enlarged base by means of a tube which is driven into the ground, the steps of arranging a rigid body at the lower end of the tube so that it is disposed over at least a large portion of the cross-sectional area of the tube, mounting reinforcement members for the pile axially in the tube close to the inner periphery thereof with said rigid body being carried by the lower ends of the members, axially moving the rigid body and the tube relative to each other when the tube has been driven to the required depth until the rigid body is located at a predetermined distance under the tube while ramming pile forming material through the tube during such relative axial movement, positively connecting said members to the upper end of the tube to immobilize the members relative to the tube and maintain the tube and the rigid body in such attained position, ramming pile forming material laterally into the ground between the lower end of the tube and the rigid body which acts as a dellector, until an enlarged base of the required volume and the predetermined height has been formed.

2. In a method as claimed in claim l, the step of introducing a layer of pile forming material into the lower end of the tube before introducing the rigid body.

3. In a method of forming a reinforced foundation pile with an enlarged base by means of a tube which is driven into the ground while resting on a driving point, the steps of arranging a layer of pile-forming material on the top of the driving point, arranging a rigid body on said layer at the lower end of the tube so that it is disposed over at least a large portion of the cross-sectional area of the tube, mounting reinforcement members for the pile axially in the tube close to the inner periphery thereof with said rigid body being carried by the lower ends of the members, axially moving the rigid body and the tube relative to each other when the tube has been driven to the required depth until the rigid body is located at a predetermined distance under the tube while ramming pile forming material through the tube during such relative axial movement, positively connecting said members to the upper end of the tube to immobilize the members relative to the tube and maintain the tube and the rigid body in such attained position, ramming pile forming material laterally into the ground between the lower end of the tube and the rigid body which acts as a deflector, until an enlarged base of the required volume and the predetermined height has been formed.

References Cited in the tile of this patent UNITED STATES PATENTS 1,501,643 Blumenthal et al. July 15, 1924 1,604,722 Rotinoi Oct. 26, 1926 2,184,514 Cleesattel Dec. 26, 1939 2,497,377 Swann et al. Feb. 14, 1950 2,512,831 Holmes lune 27, 1950 FOREIGN PATENTS 593,620 Germany Mar. l, 1934 556,367 Great Britain Oct. 1, 1943