US3757528A

US3757528A - Method for producing a bearing pile of reinforced concrete

Info

Publication number: US3757528A
Application number: US00289879A
Authority: US
Inventors: U Finsterwalder; K Finsterwalder; T Herbst
Original assignee: Dyckerhoff and Widmann AG
Current assignee: Walter Bau AG
Priority date: 1971-09-21
Filing date: 1972-09-18
Publication date: 1973-09-11
Anticipated expiration: 1990-09-11
Also published as: IT974954B; CH549133A; DE2147051A1; FR2153956A5; NL152950B; NL7212275A; CA958236A; ATA803072A; AT335922B

Abstract

Method for producing a bearing pile of steel reinforced concrete in a bore hole where armoring is placed in the bore hole which is filled with hardening material such as concrete and where the armoring is a steel pressure element of compact, particularly round cross-section provided with profiling on its surface to increase the adhesion between the filling material and where after setting, but prior to hardening the filling material is impregnated with cement sludge or grouting through an apertured conduit that is disposed between the steel pressure member and the wall of the bore hole.

Description

ted States Patent Finsterwalder et al.

1451 Sept. 11, 1973 METHOD FOR PRODUCING A BEARING PILE 0F REINFORCED CONCRETE Inventors: Ulrich Finsterwalder,

Munich-Obermenzing; Klemens Finsterwalder, Socking near Starnberg; Thomas F. Herbst, Munich, all of Germany Assignees: Dyckerhoii- & Widmann Aktiengesellschaft, Munich, Germany Filed: Sept. 18, 1972 Appl. No.: 289,879

Foreign Application Priority Data Sept. 21, 1971 Germany P 21 47 051.9

us. Cl 61/5362, 61/5362, 61/56, 61/565, 52/155, 52/740 Int. Cl E02d 5/62, E02d 5/80 Field of Search 61/5352, 53.62, 6l/53.6, 53.64, 53.66, 56, 56.5; 52/155, 740, 742

[56] References Cited UNITED STATES PATENTS 3,312,035 4/1967 Van Koot 52/740 3,717,966 2/1973 Reichert 61/53.62

FOREIGN PATENTS OR APPLICATIONS 970,760 10/1958 Germany 6l/53.62

Primary Examiner-Jacob Shapiro Attorney-Robert H. Jacob [5 7] ABSTRACT Method for producing a bearing pile of steel reinforced concrete in a bore hole where armoring is placed in the bore hole which is filled with hardening material such as concrete and where the armoring is a steel pressure element of compact, particularly, round cross-section provided with profiling on its surface to increase the adhesion between the filling material and where after setting, but prior to hardening the filling material is impregnated with cement sludge or grouting through an apertured conduit that is disposed between the steel pressure member and the wall of the bore hole.

6 Claims, 2 Drawing Figures METHOD FOR PRODUCING A BEARING PILE OF REINFORCED CONCRETE BACKGROUND OF THE INVENTION The invention relates to the production of piles used for supporting building structures. More in particular, the invention relates to a method for producing bearing piles of reinforced concrete where first a bore hole is made into which armoring is placed, and then the bore hole is filled with a hardening material such as concrete, cement mortar or the like.

In the foundation of building structures, poles or piles are frequently used for transmitting forces of compression into lower layers of ground that have greater carrying capacity. In this connection prepared piles or stakes are known which are in finished condition rammed, pressed or flushed into the subsoil and which can be subjected to loads immediately, and stationary piles which are produced in situ in a hollow space prepared in the ground and require a certain hardening time prior to being subjected to the load. The invention relates to bore piles made of steel reinforced. concrete, i.e., piles for which the hollow space is produced by boring and is subsequently filled with concrete.

With known bore piles the concrete transmits the forces of compression into the ground. Due to the diff":- culties attending the filling in of the concrete, faulty places frequently cannot be avoided in the piles, so that the permissible concrete pressure tensions cannot be fully exploited. Frequently it is not possible for the ground to absorb greater tensions, or they are only absorbed in connection with considerable slippage. The concrete pressure tensions that are permissible are relatively low due to the high safety factors and require large pile diameters in order to take up the heavy loads which occur. For the production of such piles expensive boring tools are required, which are neither suitable to economically penetrate obstacles in the ground such as pieces of rock or the like, nor for producing bore holes having relatively large inclinations.

This disadvantage of boring technique is avoided by piles referred to as root piles. These are considered bore piles having a small thickness, up to about inches, the bore holes of which can be produced by the boring method with relatively simple boring tools. Armoring is placed in the bore holes; then during withdrawing of the boring pipe the concrete is filled in in steps and is compressed with compressed air. By these means a'good connection is obtained between the concrete and the ground, and high compression of the hard core filling is obtained.

Owing to the small diameter of the bore hole, however, the concrete cross-section of these root piles is so much reduced that the pile strength necessarily remains low. The pile strength cannot be essentially increased by strengthening the armoring, because the conventional armoring cages cannot be optionally strengthened due to the small bore hole diameter, without causing installation difficulties. Heavy loads can only be achieved with a small bore hole diameter if considerably higher pressures can be effected in the cross-section of the pile.

SUMMARY OF THE INVENTION It is an object of the invention to provide a possibility of applying higher pressures in the pile cross-section and to make it possible in this manner to absorb heavy loads with relatively small pile diameters.

In accordance with the invention this problem is solved in that a'steel pressure element is used as armoring which has a compact, particularly a round, cross section and which is provided at its surface with profiling in order to increase the adhesion with the fillmaterial, and after setting but before the hardening of the fill material, a compressed body is produced by single or multiple injection of compressing material, for example cement grouting, through compression conduits having compression openings reaching into the depth of the bore hole which material extends over the entire or the greatest part of the length of the steel pressure member. Fibrous substances, for example, mineral or plastic fibers, can be added to the fill material.

The advantages of the bore pile produced with the method in accordance with the invention as compared to known bore holes may be seen in that the force of compression is essentially absorbed by the steel pressure member alone, while the fill material, i.e., the concrete or the cement mortar, take up the forces by adhesion and transmit them into the ground while protecting the steel pressure member against corrosion.

With the high loads obtainable with small pile diameters due to the great strength of the steel pressure member as compared to concrete, the problem of buckling of the pile becomes very important. Lateral evasion of the steel pressure member is avoided in that as a result of subsequent compressing by means of the pressure conduits, the ground surrounding the pile is so strongly secured, respectively it is so strongly consolidated with ground that cannot be injected, that it can impart the required lateral stiffening to the steel pressure member that is exposed to the danger of buckling.

The admixture of mineral or plastic fiber to the filling material for the filling of the bore hole results after setting of the fill in an improvement of the combiningv characteristics between filling material and the steel pressure member by increasing the annular tensional forces. Thereby also the filling material between the steel pressure member and the wall of the bore hole can be relied on as a supporting aid.

In a further embodiment of the method in accordance with the invention a steel pressure member is used which consists of a known armoring rod which is provided with hot rolled ribs disposed along a helical line. As a connection with the foundation body a force distributing plate may be provided. However, the connection may also be by way of a butt connection. Finally, the steel pressure member may also be butted within the pile in one or several locations.

A pressure pile having greatcarrying strength made in accordance with the method of the invention is in many respects superior to the known bore piles. Besidesthe advantages already mentioned, it may be used to particular advantage, due to its simple anchoring possibilities, when a steel is employed that has a thread extending over its entire length, for alternate loads combined of tension and pressure, which plays a considerable role in connection with most foundations. Finally, in groups of piles, piles may be pre-loaded in simplest manner in that the neighboring piles are subjected to pull or tension. Such a reversal of the load is not possible with known piles. Finally, the thread makes it possible, for example, when foundations rise, to set the foundation by way of the thread to any desired levelling value or factor.

DESCRIPTION OF THE INVENTION The invention is described more in detail hereinafter with reference to an embodiment illustrated in the drawings in which:

FIG. 1 is a sectional view of a bearing pile in accordance with the invention, and

FIG. 2 illustrates the upper part of the bearing pile in an enlarged section.

In a bore hole 1 surrounded by filling material 2, for example, concrete or cement mortar, there is disposed a steel pressure member 3. The steelpressure member 3 is located centrally in the bore hole and is secured in this position by spacers (not illustrated). In the example illustrated, it consists of a single armoring rod which is provided on its surface with profiling in the form of hot rolled ribs disposed along a helix. These ribs constitute a thread upon which an anchoring or connection element which has a corresponding counter thread may be threadedly mounted. in the example illustrated, the pressure member 3 consists of two rods which are abutted by a threaded sleeve 4. The steel pressure member 3 may also be composed of several individual rods which during installation are combined to form a unit.

A compressing conduit 5 reaches down into the depth of the bore hole 1 which is installed simultaneously with the compression member 3. In the embodiment the compressing conduit 5 is in the form of an annular conduit having an entrance opening 6 and a discharge opening 7 and is provided over the entire length of the compression member with compressing apertures 8. In lieu of the annular conduit it is also possible to provide a pipe or a similar device, which in any event must be so constructed that due to the pressure injecting of compression material, for example cement grouting, in several successive working operations under high pressure into the compressing conduit in individual sections along the pile or the entire length of the pile, so that compressed material is introduced and the surrounding ground is consolidated and is partly also injected The compression apertures'8 are provide with valves for this purpose.

When the method in accordance with the invention is used, the bore hole 1 is first produced by means of a conventional method adapted to the existing ground conditions;then the steel pressure member 3 is inserted together with the compression conduit 5, and the fill material 2 is introduced. After setting, but before hardening of the fill material 2, a compression material, for example, cement grouting, is pressed in at high pressure after injection into the compression conduit 5, and that either through the entrance opening 6 while the discharge opening 7 is closed, or throughboth openings. Since the bore hole I is closed towards the top by the filling material 2, very high pressure can be obtained in the compression conduit 5, which results in that the filling material 2 is forced against the: earth or ground and that the compression material either enters the ground and secures it in the area surrounding the pile or consolidates it with lateral pressure in ground that cannot be injected. Increasing compression pressures indicate in this connection the degree of the improvement in carrying capacity of the ground.

The connection of the building structure or of the foundation body to the steel compression member 3 may also be effected by a pressure distributing plate 9, which has an extenion provided with an internal thread which can be threaded onto the thread of the steel pres sure member 3. The connection may also be effected in an analogous manner by way of abutment connections or by friction adhesion along the part of the pressure member that extends above the pile.

A further use of the method in accordance with the invention is also afforded with the sinking of well or spring foundations having open caissons. Frequently they must be founded in strong rock, which in excess water pressure was heretofore only possible by means of air pressure caissons. If for foundations pressure piles are used that are made in accordance with the invention, these may take over the anchoring in the rock in that they elongate the caisson wall into the rock, as it were, by points, without it being necessary that the caisson actually has to reach the edge of the rock. The anchoring of the pressure rods in the rock as in the caisson wall is effected in accordance with the invention by injection of cement grouting with the compression conduits mentioned above.

Having now described our invention with reference to the embodiment illustrated, what we desire to protect by Letters Patent of the United States is set forth in the appended claims.

We claim:

1. Method for producing a bearing pile of steel reinforced concrete comprising the steps of producing a bore hole, placing into said bore hole armoring in the form of a steel pressure member having a compact, particularly round cross-section with profiling at its surface to increase the adhesion with filling material, placing compressing conduit in said bore hole between said steel pressure member and the walls of the bore hole, pouring filling material such as cement mortar into said bore hole around said steel pressure member and said compressing conduit, and after setting and before hardening of the filling material, forcing compression material, such as cement grouting or sludge, through said compressing conduit into the filling material to constitute a compressed body extending around and substantially over the length of the steel pressure member.

2. Method in accordance with claim 1 where the filling material includes fibrous substances such as mineral or plastic fibers.

3. Bearing pile of steel reinforced concrete constructed in a bore hole comprising armoring in the form of a steel pressure member in said bore hole, said steel pressure member having compact, particularly round cross-section with profiling at its surface, a compressing conduit in said bore hole between said steel pressure member and the walls of the bore hole, filling material such as cement mortar disposed around said steel pressure member and said compressing conduit and said filling material having cement grouting or sludge injected therein.

4. Bearing pile in accordance with claim 3 where said steel pressure member is an armoring rod having ribs disposed along a helical line.

5. Bearing pile in accordance with claim 4 having a pressure distributing plate mounted on the top of said steel pressure member.

6. Bearing pile in accordance with claim 3 where said steel pressure member comprises abutting sections.