WO1998000609A1

WO1998000609A1 - Pile joint and method of producing this pile joint

Info

Publication number: WO1998000609A1
Application number: PCT/SE1997/001201
Authority: WO
Inventors: Gunnar Lundqvist
Original assignee: F O Peterson & Söner Byggnads Ab
Priority date: 1996-07-02
Filing date: 1997-07-02
Publication date: 1998-01-08
Also published as: SE9602621D0; AU3637797A; SE9602621L; SE506910C2

Abstract

A pile joint comprising two pile tubes (1, 2) with end surfaces in mutual contact (at 8) and a jointing sleeve (7) arranged inside the joint, wherein the ends (3, 4) of the pile tubes (1, 2) are widened cylindrically and coaxially with the extension of the pile tube to an internal diameter corresponding to the internal diameter of the pile tube increased with 1/2 to 2 times the thickness of the material in the pile tube. The jointing sleeve (7) has an external diameter substantially corresponding to said widened internal diameter, and in the joint sleeve (7) has a length that is less than the total length of the diameter-widened parts of the two pile tube ends (3, 4), and a method of producing the pile joint.

Description

PILE JOINT AND METHOD OF PRODUCING THIS PILE JOINT

The present invention relates to a pile joint comprising two pile tubes with the end surfaces in mutual contact and with a jointing sleeve inside the joint, and a method of producing said pile joint. Background

Piles made of steel tubes are used i.a. for foundation reinforcement of existing buildings and for other foundation works with reference to other buildings, plants and activities. The use puts special demands on leniency at the installation of the piles, which in turn has led to the development of a special kind of piles - high-strength, corrosion protected steel tube piles, driven with light-weight high-velocity hammers. They have been developed and used since the end of the 1970 -ies. They are characterized by a small diameter, 50-150 mm, thin material thickness and high quality steel, all with the object of minimizing the amount of installed material for a given load-bearing capacity. The piles always have a rust protection, either in the form of organic or inorganic cover or in the form of an extra thickness for rust (which thus is anticipated to disappear by corrosion during the life time for which the pile has been dimensioned) .

Driving is accomplished with light hammers with a very high hitting velocity and a high hit frequency but a small energy content for each hit . Verification of the load-bearing capability is made by hitting to a stop with the same kind of hammers. This way of hitting piles secures good penetration ability and minimizes deleterious vibrations in the ground and the environment.

The dimensioning theory has been developed in parallel with the commercial use of the pile type and the development of sufficiently advanced measuring instruments, which allows measuring of the very quick tension and acceleration processes in a pile during driving. These piles, as well as others, are dimensioned in ultimate stress condition for the three main cases material rupture under the load of the supported construction or because of load in connection with the installation, rupture in the ground underneath and around the pile, flexure rupture from the axial load in soft soil (breaking) . The piles are dimensioned and installed under specific quality systems, which in this connection has allowed for a very high use of available material strengths.

The type of use (often indoors) for this type of pile gives short joint lengths, i.e. the joints are lying close to each other. The important demands on a joint for this type of pile is to secure that the ends of the pile tubes stands exactly on each other after completed installation, not to reduce the strength of the pile at the joint, - not to (too much) dampen the driving force of the hammer, not to reduce the rust protection of the final pile, allow checking of the integrity and the straightness of the installed pile over all its length, to be tight against penetration of soil and subsoil -water during the driving of the pile, and to be simple, quick and inexpensive to produce at the site of the piling. Known technology

The most common technique for this kind of pile joints uses jointing sleeves in the form of a steel tube for application outside of the pile having such dimensions that the pile tube fits with a small clearance in the hole of the sleeve.

The sleeve can be welded to any of the pile tube ends in the factory. At the site of the piling the male end of a following tube is put into the sleeve so that the driving can be continued to the next joint etc.. This joint performs well. Its disadvantages depend on the fact that the high velocity hammers gives, and has to give, a shock wave with a very high particle acceleration at the front of the shock wave, in the order of 1,000 g. A sleeve with a permanent attachment to the pile tube is then subject to very high inertial forces under the driving, which put very high demands on the quality of the weld. The high hitting frequency can in addition thereto result in fatigue of the strength of the weld. Welding per se can result in a reduction of the strength of the pile tube to the extent that it depends on cold working of the steel during the manufacture of the tube. The weld is a sudden cross- sectional change of the pile tube and thus an indication of fracture. Other kinds of fixed connection - bolts, rivets, pins, etc. - can in principle not take up the big inertial forces without rupture of the material (in the sleeve or in the pile tube) .

The joint is not automatically tight. The tightness can be improved by making the inside hole of the sleeve and/or the lower part of the pile tube weekly conical, so that the joint is wedged together. This puts high demands on the tolerances. Transfer of forces must take place between the ends of the pile tubes, not through the sleeve, wherefore the pile tubes in each joint safely must be able to be hammered together.

Conical joints give in principle ring (tensional) strains in the sleeve and from this reason reduce the ability of the sleeve to withstand the strains resulting from the driving of the pile. The joint of the steel plastic pile, EP-C-0 337 543, comprising an outside joint sleeve on a pile tube with rust protection in the form of extruded PE does not exhibit the above mentioned disadvantages, since the sleeve is connected to the pile tubes only through a thin layer of plastic material. This dampens the acceleration of the sleeve during driving and results in a tight joint. This joint also functions well, but has the disadvantage that the corrosion protection of the joint (hot zinc coating) is less good than for the rest of the pile, the tolerance demands are high and the jointing procedure at the site of the piling is a bit time consuming.

An improvement is illustrated in the Swedish patent application SE-A-9503477-3 wherein PE sheathed pile tubes is performed with an inner tube-shaped sleeve. The rust protection will then be intact at the joint, but instead the inner sleeve has to be fixed in the pile tube against full inertial forces. This is made by providing the sleeve with a thickening, which partly passes out between the ends of the pile tubes in the joint. This thickening must in practice be formed with high precision in order to, on the one hand, have sufficient strength, on the other hand, not be so big that the steel in the pile tubes at the laying together of the joint cannot be upset around the thickening. In principle this kind of joints can be improved with weekly conical sleeves etc.. In order to securely fix the sleeve right before the joint between the pile tubes the described thickening is necessary, which thickening "hooks" between the pile tubes. The invention The pile joint according to the invention is defined in claim 1 and a method of producing the joint according to the invention is defined in claim 3.

The invention resides in that the joint is made so that the ends of the pile tubes is expanded with an adapted tool on a requisite distance. The expansion is cylindrical and coaxial with the remaining part of the pile tubes. The increase of the inner diameter is small, in the order of half the material thickness of the pile tube to twice this thickness. This operation is performed on an industrial scale. At the site of the piling an internal tubular jointing sleeve is introduced into the upper end of the pile tube having been driven into the ground, whereupon a new pile tube is placed over the jointing sleeve, whereafter the driving is taken up again.

The external diameter of the jointing sleeve is adapted to the locally increased internal diameter of the pile tube and its length is slightly less than the total length of the part with increased diameter in the two combined pile tubes. With this the objects are achieved, that both loads from the building and loads from the driving is transferred completely through the ends of the pile tubes. The expansion of the tube ends gives a soft transition without such a cross-sectional change that an indication of fracture arises and without the risk of strength reduction and fatigue, which comes with welding in the pile tube . The sleeve has not any fixed connection to the pile tube. During the driving the sleeve will instead be able to move to a certain extent inside the pile tubes between the points where the internal diameter in these changes over to normal cross section - the sleeve will "bounce" between the constrictions. The sleeve will never be able to pass up any substantial distance in the pile tubes but instead it will, during the whole driving and during the use of the pile be right before the pile tube joint. Therewith the function of always mutually centering the pile tube ends is secured.

With this joint the corrosive protection of the pile tubes will be the same at the joint as for the rest, irrespective if the protection consists of an outer coating or rust tolerance on the pile tube. According to a preferred embodiment of the invention the joint is provided with an organic coating between sleeve and pile tube with the object of either sealing the joint or provide a better fitting and less freedom of movement for the sleeve in the pile tubes. The pile tubes can be steel plastic piles, i.e. have a PE sheath. Hereby is achieved that the life of the pile does not have to be dimensioned to a less good corrosive protection (hot-galvanized, rust tolerance) than for the pile tubes.

With the invention it is achieved that there is no welding joint between sleeve and tube section, which means that there is nothing that may break at high-velocity driving, neither welding joint nor any material of the tube affected by welding. Further the pile joint will be very inexpensive in production, there are no problems in providing the joint at the site (contrary to welding) , it will be very straight, the sleeve is rust protected and if the tubes are also rust protected the pile can be guaranteed a very long life.

The invention is described below with reference to the accompanying drawing, in which the figure shows a longitudinal cross-sectional view through the pile joint according to the invention.

The pile joint, a cross-section of which is shown in the figure, comprises two pile tubes 1,2 with expanded end parts 3,4. The expansion of the pile ends is cylindrical and coaxial with the extension of the pile tube. Preferably the widening or broaching is performed with a special tool which secures a soft diameter change, illustrated at 5,6. Hereby it is achieved that the change does not form an indication of

Claims

1. A pile joint comprising two pile tubes (1,2) with end surfaces in mutual contact (at 8) and a jointing sleeve (7) arranged inside the joint, characterized in that the ends (3,4) of the pile tubes (1,2) are widened cylindrically and coaxially with the extension of the pile tube to an internal diameter corresponding to the internal diameter of the pile tube increased with ^*v_ to 2 times the thickness of material in the pile tube, that the jointing sleeve (7) has an external diameter substantially corresponding to said widened internal diameter, and in that the jointing sleeve (7) has a length that is less than the total length of the diameter-widened parts of the two pile tube ends (3,4) .

2. A pile joint according to claim 1, characterized in that an organic coating is applied between sleeve (7) and pile tubes (3,4) with the object of sealing the joint or to give a better fitting and less freedom of movement for the sleeve in the pile tube.

3. A method of producing a pile joint comprising two pile tubes with the end surfaces in contact with each other and with a jointing sleeve arranged inside the joint, characterized in that the pile tube ends with a special tool are widened cylindrically and coaxially with the remaining part of the pile tubes corresponding to an increase of the internal diameter with half % to 2 times the thickness of the material in the pile tube, in that, at the site of the piling, an internal tube shaped jointing sleeve is entered into the upper end of a driven pile tube, whereupon a new pile tube is placed over the jointing sleeve and the driving is restarted, whereby the external diameter of the jointing sleeve is adapted to the locally increased internal diameter of the pile tube and its length is slightly less than the total length of the diameter-increased part of the two pile tubes.