EP0246589A1 - Precast concrete pile and method and apparatus for introducing it into the soil - Google Patents

Abstract

A precast concrete pile (10) for pile foundations has a helical rib (16) on its outer surface so that it can be screwed into the subsoil (12) by a drilling head (32) which can in turn be moved by a hydraulic operating cylinder (48). The pile reinforcement (18) is helical, the direction of rotation being opposite to that of the helical rib. …<IMAGE>…

Description

The invention relates to a prefabricated concrete pile and a method and a device for its introduction into the ground.

In the past, there were two alternatives for pile foundations: Either a hole was drilled in the soil at the desired location, which was filled with in-situ concrete, or a prefabricated concrete pile was driven into the soil using a ram. The first alternative is time-consuming, the second alternative is associated with a high level of noise pollution.

It has already been suggested (magazine "Construction Machine and Technology", 9th year, 1962, pages 253 ff.) To screw a prefabricated concrete pile into the ground like a self-tapping screw. The forces required for this are generated on the one hand by constant axial pressure being exerted on the concrete pile, which does not generate any noise, and in part by turning the concrete pile, which is associated with only slight noise pollution. In other words: When a concrete pile is screwed in, the force required to push the pile into the ground is largely derived from a rotational movement, the conversion into an axial force being carried out by the helical rib arrangement. Turning the pile around its longitudinal axis also has the effect that only the smaller sliding friction has to be overcome between the pile and the ground. When driving piles, however, the high static friction between the outer surface of the pile and the soil must be broken up with every impact. This static friction is very large because the part of the earth in which the pile penetrates is in must be displaced laterally so that the soil in the immediate vicinity of the pile is highly compressed and under high tension. If the helical rib arrangement cannot convert the rotary drive movement into an axial feed movement (start of insertion if the pile initially only slightly engages the ground; loose or very soft ground), the required axial feed force can be transferred directly from one to the top At the end of the concrete pile working linear drive can be provided, for example a hydraulic cylinder.

The screwing in of concrete piles is comparable in terms of noise development to the alternative mentioned at the beginning, in which a hole is drilled and the latter is poured with in-situ concrete. However, it can be practiced much faster at the place of use, in particular the mechanical and time expenditure which has to be done to remove the cuttings, the drill or the tubular formwork for the pile is eliminated. Pile foundations can thus be completed in a very short time, and the piles placed in the ground are immediately fully load-bearing. In the case of construction work that is to be carried out in the vicinity of buildings or streets, this results in a considerable reduction in the impairments associated with the work. In this way, piles can also be founded inclined strongly to the vertical.

With the second alternative mentioned at the beginning, in which prefabricated concrete piles are rammed into the ground, screwing in has the advantage in common that the quality of each individual concrete pile can be controlled and monitored more precisely during prefabrication in a factory.

When screwing concrete piles with a spiral rib arrangement into the ground, very high torques often have to be removed Pile are transferred. The present invention is therefore intended to develop a concrete pile according to the preamble of claim 1 in such a way that it is particularly well capable of transmitting high torques from its upper, driven end to its lower end.

With the pile design according to the invention it is achieved that large torques exerted on the upper end of the pile are safely passed down in the pile, since such torques cause the helical reinforcement part to contract (in the sense of a spiral spring "trying to" pull up "), thereby causing him to enclosed concrete volume is subjected to compression. However, the concrete material can withstand such compression loads well, so that overall safe torque transmission in the concrete pile is guaranteed.

Advantageous developments of the invention are specified in subordinate claims.

A concrete pile according to claim 2 contains only as much reinforcement as is necessary for transmitting the torque at a particular point on the pile. This allows the pile to be manufactured inexpensively overall.

The development of the invention according to claim 3 enables the use of the invention even in hard and stony surfaces. As a rule, it is sufficient if only the lowest aisles of the helical rib arrangement are provided with a wear-resistant, cap-like protective rail protecting their back.

The development of the invention according to claim 5 is advantageous with regard to a free cutting of "thread turns" in the ground and also with regard to a locking of the pile inserted into the ground in the angular direction: spring back the elastically displaced soil in the radial outward direction when the rotary movement exerted on the pile is ended.

The latter advantage is also obtained by developing the invention according to claim 6.

According to the proposal specified in claim 7, an overall large length concrete pile in several axially consecutive segments can be brought into the ground one after the other, which allows the use of a screwing device with a small working stroke, which is cheaper to manufacture and can be transported more easily.

The developments of the invention according to claim 9 is advantageous with regard to the use of the solution according to the invention on such substrates in which a mere turning of the concrete pile, at least in the first phase of its penetration into the ground, would result in the rib arrangement similar to the ground Milling cutter crushed so that no guidance of the rib arrangement in the ground would be obtained.

According to claim 11, at the same time as the concrete pile is brought into the ground, information is obtained as to how firmly the pole is actually seated in the ground. The measured torque is in fact directly associated with the pile's circumferential lubrication of the pile's penetration force into the ground, which in turn dictates the load-bearing capacity of the pile; if the pile is not lubricated on the circumference, the measured torque is representative of the penetration resistance, as just explained, in combination with the circumferential static friction between the pile and the ground. These forces are also characteristic of the later load-bearing capacity of the pile. When using the method according to the invention, one is not at blanket estimates and the results are not exact Penetration point of a pile of test holes made.

• Figur 1: eine seitliche, teilweise geschnittene Ansicht eines vorgefertigten Betonpfahles sowie einer Vorrichtung zum Hineindrehen dieses Pfahles in das Erdreicht;
• Figur 2: ein schematisches Blockschaltbild der Hydraulikanlage der in Figur 1 gezeigten Vorrichtung;
• Figuren 3 bis 5: seitliche Ansichten abgewandelter Betonpfähle, welche in das Erdreich hineingedreht werden können;
• Figur 6: eine Aufsicht auf eine gemeinsame Kopfplatte, durch welche die von den oberen Enden benachbarter Betonpfähle getragenen Formschlußmittel drehschlüssig verbunden sind;
• Figur 7: einen vergrößerten Teilschnitt durch eine der Rippen des in Figur 1 gezeigten Betonpfahles; und
• Figuren
• 8 und 9: transversale Schnitte durch Betonpfähle mit in Umfangsrichtung veränderlicher Rippengeometrie.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this show:

• Figure 1: a side, partially sectioned view of a prefabricated concrete pile and a device for screwing this pile into the ground;
• Figure 2 is a schematic block diagram of the hydraulic system of the device shown in Figure 1;
• Figures 3 to 5: side views of modified concrete piles, which can be rotated into the ground;
• FIG. 6: a plan view of a common head plate, by means of which the positive locking means carried by the upper ends of adjacent concrete piles are connected in a rotationally locking manner;
• FIG. 7: an enlarged partial section through one of the ribs of the concrete pile shown in FIG. 1; and
• characters
• 8 and 9: transverse cuts through concrete piles with rib geometry that can be changed in the circumferential direction.

In Figure 1, a prefabricated concrete pile is shown partially screwed into a base 12. The device used for this purpose, which exerts an axial force on the concrete pile 10 and at the same time rotates it about its longitudinal axis, is designated by a total of 14 in FIG. The concrete pile 10 has a helical rib 16 running on its outer surface and is provided with a helical reinforcement part 18 on the inside. The latter is shown in the drawing as if it were made from a tape; in practice, the reinforcement member 18 can be made in the usual way from bent and intersecting reinforcement bars, like conventional reinforcements of concrete piles. In addition to the reinforcement part 18, the concrete pile 10 can comprise further reinforcement parts which are not shown in the drawing and which, in a known manner, have reinforcement bars running in the axial direction and running in the circumferential direction.

The upper end of the reinforcement part 18 is welded to a cage-like reinforcement head 20, which in turn is firmly connected to a square drive 22.

The square drive 22 is positively received in a drive opening 24 of a drive ring 26. The latter is rotatably and axially supported between two end plates 28, 30 of a total of 32 designated drilling head. The end plates 28, 30 are kept at a distance by a front end plate 34 and a rear end plate 36 and by side plates 38 and, together with the latter, delimit a gear chamber. In the latter, a pinion 40 meshing with the drive ring 26 rotates, which sits on the shaft of a rotating hydraulic motor 42.

The entire drill head 32 can be moved on extensions of the side plates 38 on a drilling mast 44. For this purpose, the piston rod 46 of a long hydraulic working cylinder 48 is articulated on the upper end plate 28, the housing of which is supported on a projecting arm 50 of the upper end of the drilling mast 44.

The drilling mast 44 itself is connected via articulated struts 52, 54 connected to a vehicle, not shown, and can be transported from one location to another by the latter. By moving the struts 52, 54, the drilling mast 44 can also be adjusted in its inclination.

As can be seen from FIG. 2, a linear position transmitter 56 is mechanically coupled to the piston rod 46 or a part that moves rigidly with it. Similarly, the rotation of the drive ring 26 is detected by an angle sensor 58 which is mechanically coupled to the shaft of the hydraulic motor 42 and which can be formed by a multi-turn potentiometer or a stroboscopic disk with a counter connected downstream.

The position transmitter 56 and the angle transmitter 58 are also connected to inputs of a control unit 60, as is a control panel 62 which, in addition to an input field 64 for general working parameters, has an adjustment knob 66 for the pitch of the rib 16 and an adjustment knob 68 for the length of the concrete pile. The setting buttons 66 and 68 are drawn out separately only to highlight the assigned input size; It goes without saying that, if necessary, these quantities can also be entered via the general input field, which can include an alphanumeric keypad in addition to control keys. The general working parameters entered there include, in particular, the target speed selected with regard to the soil strength at which the concrete pile 10 is to be screwed into the ground 12.

The control unit 60 controls two 4/3 solenoid valves 70, 72, via which the hydraulic motor 42 or the working cylinder 48 for driving in both working directions with a pressure line 74 coming from a hydraulic pump (not shown) or one to one not shown Return line 76 leading pressure sump are connectable.

As can be seen from FIG. 2, an adjustable throttle 78, which is adjusted by a servomotor 80, is inserted into the supply line to the hydraulic motor 42. Similarly, an adjustable throttle 82, which is adjusted by a servo motor 84, is inserted into the supply line leading to the rear working space of the working cylinder 48.

The two servomotors 80 and 84 are excited by the control unit 60 in such a way that the helical movement impressed on the upper end of the concrete pile has the same pitch as the rib 16.

The control unit 60 preferably works in such a way that it first tries to set the feed speed corresponding to the target speed on the piston rod 46. The speed of rotation of the hydraulic motor 42, on the other hand, is regulated as a function of the actual travel of the piston rod 46 measured via the position transmitter 56.

This forced synchronization of the axial movement and rotary movement of the concrete pile 10 ensures that it is screwed into the ground 12 and that no free spaces are created around the concrete pile.

The tracking of the speed of the hydraulic motor 42 to the actual stroke of the piston rod 46 is preferably carried out at least until some gears of the rib 16 have gripped in the ground and by merely turning the concrete pile 10 due to the support of the ribs, the axial necessary to displace the soil Force can be provided. In this case, the operation of the control unit 60 can then be modified so that it first of all sets the rotational speed of the hydraulic motor 42 according to the desired feed speed for the concrete pile 10, while the working cylinder 48 ge rade as far as pressure medium is applied, as is necessary to produce any remnants of the axial feed force (according to the remaining position of the piston rod 46 compared to a target position, which results from the total angle of rotation of the concrete pile 10 taking into account the slope the rib 16 results).

For a pile foundation, the concrete pile and the device described above are first used in a factory to manufacture the concrete pile, the square drive 22, the reinforcement part 18, the reinforcement head 20 and other reinforcement components being prefabricated in a known manner and firmly connected to one another by welding. The unit obtained in this way is introduced into a mold with an inner contour which corresponds to the desired outer contour of the concrete pile 10. The concrete is then poured into this mold, and when the concrete has obtained sufficient inherent strength, the concrete pile 10 can be shaped. When using a split mold, this can be done by removing the mold cover and removing the finished pile; when using a one-piece mold, in which the inner surface of the mold is then covered with a release agent, also by unscrewing the finished concrete pile 10.

The concrete piles produced in this way can be solid piles, but hollow centrifugal concrete piles can also be produced using a circumferential shape. It is further understood that the reinforcement can also be put under tension when producing the concrete piles 10, so that prestressed concrete piles are obtained.

The concrete piles, which are between 10 and 20 meters long in practice, are transported to the construction site in a vehicle. There is then a pile with a hoist, as is usually provided on drilling devices for handling drill pipes, when the hoist is raised Drill head 32 placed under this and aligned substantially vertically. Then the drill head 32 is lowered so that the drive square 22 is inserted into the drive ring 26. Now the hoist can be released.

The hydraulic motor 42 and the working cylinder 48 are now set in motion, initially with a vertical pile orientation, until the pile tip has worked so far into the ground that it no longer deviates in the lateral direction. Now, by adjusting the struts 52, 54, the drilling mast 44 is inclined in the direction in which the concrete pile 10 is to be screwed into the ground. The hydraulic motor 42 and the working cylinder 48 are then again supplied with pressure medium in a controlled manner via the control unit 60, and the concrete pile 10 is quickly screwed into the ground 12 in the manner already described in more detail above. In practice, an approximately 12 meter long pile can be screwed into a medium-heavy subsoil in a total of 6 minutes (main time), so that pile foundations with closely adjacent piles achieve an output of around ten piles per hour.

Figure 3 shows a modified concrete pile 10, in which the helical rib 16 extends only over part of its axial length. Such a pile is used when the top layer of the soil is very hard and has to be overcome by ramming. However, the advantages associated with screwing a concrete pile into the ground are still obtained during the second phase of being brought into the ground, which still results in considerable time savings and a considerable reduction in noise pollution.

Conversely, it is also possible to provide only the lower pile section with a helical rib, the empty thread remaining in the upper pile section can be filled with liquid concrete in the subsurface if this should be necessary.

The concrete pile shown in FIG. 4 differs from the exemplary embodiments described above in that it has a cutting tip 86 which can work through hard layers of the subsurface.

In addition, there is a two-course rib arrangement consisting of two ribs 16a and 16b which are offset by 180 degrees in the circumferential direction, these ribs also being very wide and spherical. In the exemplary embodiment shown in FIG. 4, the width of the base of the ribs corresponds to half the spiral pitch, so that the two nested ribs 16a and 16b touch one another. The rib profile is circular. Such a circumferential contour concrete post is particularly suitable for use in resilient subsoil which can spring back into the recesses given by the ribs.

The concrete pile shown in FIG. 5 differs from the exemplary embodiments described above in that its main body is slightly conical and tapers towards the lower end. Thus, the upper sections of the rib 16 still perform a radial displacement work when they enter the recesses in the substrate that have already been cut by the lower rib sections.

In addition, the concrete pile 10 according to FIG. 5 has a tip, in which fold-out semi-conical cutting tools 88, 90 are provided. The latter can be placed on a frustoconical seat 92 formed on the lower end of the pile, so that they form the closed cone tip 94 shown in broken lines in FIG. In the folded-down state from the seat 92, which is shown in FIG. 5 by solid lines is given, the cutting tools 88, 90 create a free space 96 which, depending on the time at which the cutting tools are extended, extends over a smaller or larger part of the lower end of the concrete pile.

The free space 96 can be filled with liquid concrete via an axial through-channel 98 of the concrete pile and - if desired - can be expanded to form an enlarged onion by applying pressure.

The exemplary embodiments according to FIGS. 4 and 5 also differ from the previously described exemplary embodiments by the torque-transmitting connection between the upper end of the pile and the drill head 32.

The concrete pile according to FIG. 4 has a transverse passage 100 at the upper end, into which a steel bolt 102 is inserted. The latter works together with complementary grooves in the inner circumferential surface of a correspondingly modified drive ring. In the concrete pile shown in FIG. 5, a square 104 having a large edge length is molded onto the upper end of the pile itself.

It goes without saying that further modifications of the exemplary embodiments described above can be obtained by assembling the described pile main parts, tips and form-locking means in a different combination.

As can be seen from FIG. 6, the drive square 22 of adjacent concrete piles 10, which were screwed equally far into the ground 12, can be firmly connected by a common head plate 108 which has recesses 110, in each of which a drive square 22 is positively received.

As can be seen from FIG. 7, a reinforcement section 112 of the concrete pile 10 can be partially drawn into the rib 16 in order to increase the dynamic strength of the rib 16. In addition, a helical protective rail 114 can be fastened to the radially outer end of this reinforcement section 112, which is provided with an outer welded wear layer 116. Since the protective rail 114 is fastened to the reinforcement section 112 before the pile is poured, its outer surface merges flush with the outer surface of the concrete. The protective rail 114 facilitates the cutting of threads in the subsurface and generally only needs to be provided in the lower section of the concrete pile, since the part of the rib 16 located there has to do most of the cutting and displacement work and is the longest to engage with the underground.

As shown in FIG. 8 using the example of a substantially triangular cross section 16, the rib 16 can be interrupted. In the illustrated embodiment, two diametrically opposite openings 118 are provided for each course of the rib 16. These openings are important when screwing the concrete pile 10 into the ground 12 insofar as they represent additional cutting edges. However, material of the subsurface can also spring into the openings 118 after the screwing in has ended, so that the concrete pile 10 is additionally locked in the direction of rotation.

The concrete pile 10 shown in FIG. 8 has an internal axial passage 120, via which a lubricant can be pressed from the upper pile end to the pile tip and from there to the pile circumference. Such a central passage does not significantly reduce the area moment of inertia of the pile and thus its ability to transmit torque; the static load capacity in the axial direction is also only slightly reduced. The passage 120 is poured with concrete after the concrete pile 10 has been completely introduced into the subsurface.

The last-mentioned advantage is also obtained in the exemplary embodiment according to FIG. 9, in which the rib 16 has a corrugated edge 120 when viewed in axial view.

Claims (12)

1. Prefabricated concrete pile for introduction into the ground, which is reinforced by a reinforcement and is provided on at least part of its outer surface with a helical rib arrangement, characterized in that the reinforcement has a helical reinforcement part (18), the direction of rotation of which is that of the rib arrangement (16 ) is opposite. 2. Concrete pile according to claim 1, characterized in that the mechanical strength of the reinforcement decreases substantially continuously from the upper to the lower end of the pile. 3. Concrete pile according to claim 1 or 2, characterized in that at least a portion of the back of the rib arrangement (16) carries a wear-resistant protective rail (114). 4. Concrete pile according to claim 3, characterized in that the protective rail (114) with the reinforcement (112) is fixedly connected. 5. Concrete pile according to one of claims 1 to 4, characterized in that the rib arrangement (16) has interruptions (118). 6. Concrete pile according to one of claims 1 to 5, characterized in that the outer edge (120) of the rib arrangement (16) is corrugated in an axial view. 7. Concrete pile according to one of claims 1 to 16, characterized in that at its upper end positive engagement means are provided, via which a further pile segment can be coupled, which has complementary positive locking means at the lower end and preferably the same positive locking means at the upper end. 8. A method for screwing concrete piles according to claim 7 into the ground, characterized in that the positive locking parts of adjacent concrete piles introduced into the ground are rotationally fixed in a common head plate. 9. Device for screwing a concrete pile according to one of claims 1 to 7 into the ground, characterized by a rotary drive (26, 40, 42), the driven part (26) with a with the upper end of the pile (22) cooperating driving positive locking part (24) is; by a linear drive (48), the driven part (46) of which works directly or indirectly via the rotary drive on the upper end of the concrete pile (10); by an angle transmitter (58) assigned to the rotary drive (26, 40, 42) and a linear position transmitter (56) assigned to the linear drive (48); and by a control unit (60) which, depending on the output signals from the angle transmitter (58) and position transmitter (46), as well as from control signals which correspond to the pitch of the rib arrangement (16) and a desired insertion speed for the concrete pile (10) Rotary drive (26, 40, 42) and the linear drive (48) controls. 10. The apparatus of claim 9, characterized in that the rotary drive (26, 40, 42) and the linear drive (48) are hydraulic motors, and the control unit (60) works on servo throttles (78 to 84), which in one of the connecting lines of the drive under consideration are switched. 11. The device according to claim 9 or 10, characterized shows that it has a sensor for the torque required to screw in the concrete pile. 12. The apparatus according to claim 11, characterized in that the output signal of the torque sensor is used to specify the target insertion speed.

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