Foundation pile

Abstract

The invention relates to a foundation pile (10) for installation into the ground, comprising an elongate body extending in a longitudinal direction having a first end and a second, and a screw thread element (12) extending helically at least along part of the outer surface of said elongated body. The elongated body comprising a hollow cavity (14) defined by an inner wall extending in the longitudinal direction of the body, wherein the inner wall having a longitudinal groove (16) comprising a bottom (22, 24) and two sidewalls (18, 20), wherein a first of said side walls (18, 20) extending in a direction having an oblique angle compared to said longitudinal direction.

Description

[0001] Foundation pile

[0002] TECHNICAL FIELD

[0003] The present invention relates to the technical field of foundation, and specifically relates to a foundation pile having a screw thread.

[0004] BACKGROUND OF THE INVENTION

[0005] The invention relates to a foundation pile of concrete comprising an elongated body having a screw thread extending helically at least along part of the outer surface of the body, and a cavity extending at least over a considerable part of the length of the body and coaxially therewith.

[0006] The known foundation piles are driven into the ground by a rotatably driven equipment called a drive rod, which is arranged in the cavity of the piles and engages an inner part of the pile for transferring the rotational forces to the pile.

[0007] The foundation piles are inside the inner cavity arranged with a longitudinal groove, preferably two internal longitudinal grooves, which cooperate with corresponding longitudinal projections on the drive rod, such that the rotational forces of the drive rod can be transferred to both the piles.

[0008] The individual piles may be manufactured in different lengths according to the depth required at a construction site.

[0009] In the past it was therefore generally necessary to produce such prefabricated pillars in many different lengths in order to have pillars of the necessary length available for a particular application. In more recent years, it is known to join a number of concrete piles in order to achieve a necessary desired length.

[0010] The concrete piles are typically manufactured as reinforced concrete piles and cast in standardized lengths, such as approx. 6-8 meters, but may as well be longer or shorter.

[0011] When such screw-threaded piles are to be installed into the ground, the pile is, as described, driven into the ground by a drive rod in a known manner.

[0012] However, when driving the piles into the ground by use of the driving equipment, the forces from the ground acting upon the pile are transferred into the driving equipment. The driving equipment (drive rod), made from a steel, is commonly made up from an elongated main body having two longitudinal projections arranged on opposite sides of the main body, which projections engage the elongated grooves arranged inside the foundation pile.

[0013] When the driving equipment drives the pile into the ground and the forces from the ground are transferred into the driving equipment, the driving equipment main body including projections will, due to the material properties of the steel, twist over the length of the main body. Thus, the longitudinal projections will be deformed from being linear elongated projections to having a more spiral-shaped configuration from the lower end of the pile to the upper end.

[0014] As the elongated grooves inside the foundation pile are arranged as linear grooves, the deformation of the driving equipment will cause the foundation pile to crack.

[0015] It is therefore an object of the present invention to overcome the above-defined problems and provide a foundation pile where the risk of cracking the pile when being driven into the ground is eliminated.

[0016] The above object and advantages, together with numerous other objects and advantages, which will be evident from the description of the present invention, are according to a first aspect of the present invention obtained by:

[0017] A foundation pile for installation into the ground, comprising an elongate body extending in a longitudinal direction having a first end and a second end, and a screw thread element extending helically at least along part of the outer surface of the elongated body, the elongated body comprising a hollow cavity defined by an inner wall extending in the longitudinal direction of the body, the inner wall having a longitudinal groove comprising a bottom and two sidewalls, a first of the side walls extending in a direction having an oblique angle compared to the longitudinal direction.

[0018] The foundation pile manufactured from a concrete may be manufactured in various lengths and may comprise couplings, such as the one described in EP4223936A1 for interconnecting multiple piles if such is required. Arranging a groove with a bottom and two side walls, where a first of the side walls extends in the longitudinal direction of the pile at an oblique angle compared to the longitudinal direction of the pile, has the technical effect that a deformation of the driving means, when driving the pile into the ground, is compensated for within the groove, such that the pressure from the driving means is evenly distributed over the length of the pile, hereby minimizing the risk of cracking the concrete pile.

[0019] According to a further embodiment of the first aspect of the invention, the sidewall extends in a direction having an oblique angle compared to the longitudinal direction over a main part of the length of the pile.

[0020] Tests have shown that the extent of the side wall having the oblique angle is of great importance. When the driving in of the pile into the ground has started, the pressure from the driving means is largest at the upper end of the pile, whereby cracks in the pile begin to form at the upper end thereof. The forces from the driving means into the pile start at the upper end of the pile and propagate downwards towards the bottom end. Arranging the side wall with the oblique angle over a main part, and preferably the entire length of the pile, compensates for a deformation of the driving means over the most part and preferably the entire length of the pile.

[0021] According to a further embodiment of the first aspect of the invention, the groove has a width that increases over the length of said groove.

[0022] The groove may be arranged as an internal screw thread, but is in a preferred embodiment arranged with an increasing width, such that the driving means before driving the pile into the ground is inserted into the pile in the longitudinal direction, and when the driving in of the pile begins, the driving means deforms and distributes the forces onto the oblique side wall.

[0023] According to a further embodiment of the first aspect of the invention, a second of the side walls extends in a direction being parallel with the longitudinal direction.

[0024] The second of the sidewalls preferably extends in a direction parallel with the longitudinal direction of the pile, which minimises the removal of concrete compared to a configuration where the second of the side walls extends in a direction having an opposite oblique angle, compared to the first of the side walls, which renders the groove cone shaped. “Removing” too much concrete may weaken the structural strength of the pile.

[0025] According to a further embodiment of the first aspect of the invention, the second of the side walls extends in a direction having an oblique angle compared to the longitudinal direction.

[0026] In an alternative embodiment, the second of the side walls extends in a direction having an opposite oblique angle in relation to the longitudinal direction of the pile and compared to the direction of the first side wall. Such configuration renders the groove cone shaped and provides the technical effect as previously disclosed in relation to driving the pile into the ground, but also a similar effect when driving the pile out from the ground. After installation, it may be desired to remove the pile, and frictional forces between the ground and the pile will be transferred to the driving means, and depending on the structure of the ground, such as the soil composition, these frictional forces may cause the driving means to deform with the possibility of cracking the pile.

[0027] According to a further embodiment of the first aspect of the invention, the oblique angle at one of the ends of said pile is between 5-15 degrees, preferably between 6-12 degrees, most preferred 8-10 degrees.

[0028] It has shown that arranging the first of the side walls with a direction having an oblique angle in relation to the longitudinal direction of the pile, within the above ranges, the pile has a groove configuration suitable for most types of soil compositions, where the most preferred range provides a groove configuration suitable for most types of soil and with a minimum of tapered shape, which avoids a minimum removal of concrete when casting the pile. Further, piles having a length shorter than e.g. 8 meters will have an oblique angle in the lower range, whereas piles of 8 meter or more will have an oblique angle in the upper range.

[0029] According to a further embodiment of the first aspect of the invention, the groove has a width which at one of the ends is between 10-30% wider, compared to the width at the opposite end, preferably 15-25%, most preferred 18-23% wider.

[0030] The width of the groove at one end of the pile, which end, arranged to be the lower end of the pile when installed into the ground, has a width corresponding to the width of standard grooves known from prior art piles, but the width of the groove arranged at the opposite end of the pile is between 10-30% larger compared to the width at the lower end in a situation where the pile has a length of between 6-8 meters. These features establish the possibility of both having a groove configuration where the first of the wall surfaces has substantial the same oblique angle over the length of the groove, and a configuration where the oblique angle is graduated over the length of the pile.

[0031] According to a further embodiment of the first aspect of the invention, the longitudinal groove comprises a longitudinal bottom main surface and two bottom side surfaces, each bottom side surface being arranged on opposite sides of the bottom main surface, one of the bottom side surfaces having a width which increases towards one of the ends of the pile.

[0032] The above-defined configuration of the bottom of the groove provides at dove tail groove having a less acute angle between the two bottom side surfaces and the respective side wall surfaces. This feature has the technical effect that when casting the pile, a minimum of concrete is “removed” at the bottom corners of the groove which increases the strength of the pile.

[0033] According to a further embodiment of the first aspect of the invention, the first and second side surfaces of said groove each has a plane, said planes having a radial direction in relation to a cross section of the pile (10)..

[0034] In a preferred embodiment, the side surfaces of the groove each has a plane which is arranged radially in relation the cross section of the pile, which ensures that the contact surface between the side surfaces and the drive rod is radial in relation to the cross section of the pile. This feature has the technical effect that the force from the drive rod onto the pile has a direction which is substantial perpendicular to the radial direction, which ensures optimal transfer of the forces from the drive rod to the pile.

[0035] According to a further embodiment of the first aspect of the invention, the first and second side surfaces have a mutual angle a defined by the following: a= 2-sin-1- ± 0.1*2-sin-1-, a a where d is the internal diameter of the pile and w is the width of the opening of the groove. Individual piles may vary in diameters and lengths, which requires individual dimensions of the groove cooperating with driving means, and by defining the mutual angles between the side walls by the above defined function, it is ensured that the direction of the force from the drive rod to the pile is in the most optimal direction of the pile, namely in a direction which is substantially perpendicular to the radial direction of the pile. Hereby the forces are effectively absorbed by the pile with a minimum risk of cracking the pile.

[0036] The range of ± 0.1*2-sin-1ensures that the pile may be cast with tolerances while maintaining the optimal transfer of ferees from the drive rod to the pile.

[0037] It should be noted that though the above-defined mutual angle between the first and second side walls in the circumferential directions of the pile, together with the oblique angle of the first side wall in relation to the longitudinal direction of the pile, has the synergistic effect of further minimizing the risk of cracking the pile, the mutual angle defined by a= 2-sin-1 ± 0.1*2-sin-1may also be incorporated in relation to a prior art piles, where the side walls of the groove are parallel in relation to the longitudinal direction of the pile.

[0038] According to a further embodiment of the first aspect of the invention, the pile comprises two longitudinal grooves.

[0039] In a most basic embodiment the pile may comprise only one groove, but in a preferred embodiment the pile comprises two grooves arranged at opposites of the pile for engaging two longitudinal projections on the driving means in order to evenly distribute the forces from the driving means to the pile.

[0040] According to a further embodiment of the first aspect of the invention, a width of the grooves increases uniformly from one end of the pile towards the opposite end of the pile with between 1.25-3.75% per meter of the pile, preferably 1.87-3.12%, most preferred 2.25-2.87%.

[0041] Though the width of the groove may increase gradually over the length of the pile, it is preferred that the width increases uniformly between the two ends of the pile, as the pile in most situations during installation is stressed uniformly throughout the pile. According to a further embodiment of the first aspect of the invention, the first of the side walls twists partly around a longitudinal centerline of the pile, over the length of the pile, in the same direction as the screw thread.

[0042] The first of the side walls preferably twists in the same direction as the screw thread of the pile. As previously described, a prior art pile may crack during installation and during removal of the pile, but as the forces between the ground and pile are the highest during installation, it is preferred that the first of the side walls twists in the same direction as the screw thread on the outer surface of the pile.

[0043] Fig. 1 A and 1 B shows a prior art concrete pile and a cross section of a prior art concrete pile.

[0044] Fig. 2 shows a cross section of a concrete pile.

[0045] Fig. 3A shows a cross section of a concrete pile to be driven into the ground.

[0046] Fig. 3B and 3C show cross sections of the pile in fig. 3A.

[0047] Fig. 4A shows a cross section of a concrete pile driven into the ground.

[0048] Fig. 4B and 4C show cross sections of the pile in fig. 4A.

[0049] Fig. 5A shows a cross section of the pile and fig 5B shows an enhanced view of the cross section.

[0050] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Like elements will thus not be described in detail with respect to the description of each figure.

[0051] Fig. 1A and 1 B shows a prior art concrete pile 10 and a cross section of a prior art concrete pile 10. The pile 10 is manufactured from concrete and comprises a screw thread element 12 extending helically along and around the pile 10.

[0052] Figure 1 B shows that the elongated pile 10 comprises a hollow cavity 14 extending all the way through the pile, the cavity being configured for receiving a driving element for driving / screwing the concrete pile 10 into the ground. It should be understood that the pile 10 may be connected to one or more similar piles in order to establish a desired long pile foundation.

[0053] It should also be understood that the illustrated pile 10 may be arranged with a pointy end 40 (shown with broken lines), for being the lower end of the pile 10, in order for the pile 10 to easier penetrate the ground. The pointy end 40 may either be inte- grated / cast together with the elongated pile 10 or may be a separate element to be manually connected to the illustrated pile 10.

[0054] Further, the hollow cavity 14 of the pile comprises two grooves (only one is shown) arranged on opposite sides of the pile 10 within the cavity 14.

[0055] The grooves 16 of these known concrete piles are arranged as linear grooves 16 having a bottom and two parallel side walls and configured for receiving corresponding elongate projections arranged on the driving means, such that a rotation movement of the driving means is transferred to the pile 10 which will hereby be screwed into the ground.

[0056] Typically, the projecting elements of the driving means has a play, e.g. 5 mm inside the grooves to compensate for manufacturing tolerances.

[0057] Fig. 2 shows a cross section of a concrete pile 10 in a possible embodiment according to the invention.

[0058] The outer configuration of the pile 10 may be similar to the configuration shown in figure 1A where the pile 10 comprises a screw thread 12.

[0059] The pile comprises a cavity 14 with a groove 16, preferably two grooves (only one groove is shown). As shown, the groove 16 comprises a tapered shape, having a narrow end arranged at one end of the pile, which end is intended to be the lower end of the pile 10, and the groove 16 comprises a wider end arranged at the opposite end, which opposite end is intended to be the upper end of the pile 10.

[0060] The groove 16 comprises a bottom and two side walls 18, 20, where the first side wall 18 has a wall surface arranged with and oblique angle 34 in relation to the longitudinal direction of the pile. The second side wall 18 is arranged with a wall surface substantially parallel to the longitudinal direction of the pile 10.

[0061] It is important to note that the drawing is schematic, and that the shown oblique angle 34 is illustrated much larger than the claimed angles, which is for visual purpose only, in order for the viewer / reader to better understand / visualize the function of the groove. The same aspect applies to figures 4A-4C. Fig. 3A shows a cross section of a concrete pile 10 to be driven into the ground 36. The shown pile 10 corresponds to the pile shown in fig. 2, but is shown in a situation before the pile 10 is driven deep into the ground 36 by driving means 38, such as a drive rod, which known in the art. Such driving means typically comprises an elongated main body 30 with two longitudinal projections 32 extending in the longitudinal direction of the main body 30 and configured for interacting with the grooves 16, as also described in the introductory part of the description.

[0062] In the shown embodiment, the driving means main body 30 is illustrated with broken lines, in order to see the interaction between the groove 16 and the projecting means 32.

[0063] In the figure, the driving in of the pile 10 into the ground has just begun.

[0064] The driving means 28 is inserted into the pile 10 from the upper end and rotated by suitable machinery, such that the rotation (see arrow) of the driving means 28 is transferred to the pile 10 which hereby is screwed into the ground 36. At the beginning of driving the pile 10 into the ground, the counteracting forces from the ground 36 onto the pile are relatively low, compared to when the pile 10 is driven deeper into the ground.

[0065] The projecting element 32 which is arranged as a linear element engages the groove 16, and in this embodiment, the projecting element 32 the lower end of the groove 16 only.

[0066] Fig. 3B and 3C show cross sections of the pilei 0 in fig. 3A.

[0067] The two cross sections show the width of the groove 16 at the upper end and the lower end of the pile 10. As shown, the projecting element 32 engages the first side wall 18 at the lower end of the pile 10, as the driving means 28 begins to drive the pile 10 into the ground 36. At the upper end of the pile 10 there is a gap between the projecting element 32 and the first side wall 18, as the projecting element 32 is a linear element parallel to the longitudinal direction of the pile, and the first side wall 18 has a wall surface arranged with an oblique angle in relation to longitudinal direction of the pile 10.

[0068] Fig. 4A shows a cross section of a concrete pile 10 being driven deep into the ground 36.

[0069] The figure shows a next step of driving the pile into the ground 36 compared to the embodiment in figures 3A-3B. It is in figure 4A shown how the pile 10 is driven deeper into the ground 36 which results in the counter forces from the ground 36 and onto the pile 10 being increased. This increasing of the counter forces from the ground 36 to the pile 10, causes the driving means 28 to twist / deform, such that the projecting element begins to twist like a spiral partly around the driving means 28. Note that the shown embodiment exaggerates the deformation of the driving means, in order for the viewer / reader to understand the effect. If a prior art pile 10 with a known groove would have been used, this twisting of the driving means 28 could cause the prior art pile 10 to crack.

[0070] In the shown illustration, as the groove 16 comprises a first side wall with a wall surface which has an oblique angle in relation to the longitudinal direction of the pile 10, the groove compensates for the deformation of the driving means 28, as the driving means will only deform to a certain extend due to the material characteristics of the driving means material, which preferably is steel.

[0071] Fig. 4B and 4C show cross sections of the pile 10 in fig. 4A. As can be seen in figure 4B and 4C the projecting element 32 has due to the counter forces from the ground 36 deformed, such that the projecting means 32 interacts against the first of the side walls 18 from one end of the pile 10 to the other end of the pile.

[0072] Fig. 5A shows a cross section of the pile 10 and fig 5B shows an enhanced view of the cross section.

[0073] As explained earlier, the mutual angle between the two side surfaces of the groove is important in order to effectively transfer the forces from the drive rod to the pile.

[0074] Figures 5A and 5B show the groove having a bottom surface which comprises a main bottom surface 22 and two bottom side surfaces 24. This feature has the technical effect that when casting the pile 10, a minimum of concrete is “removed” at the bottom corners of the groove, which increases the strength of the pile. Removing too much concrete in the formation of the grooves during casting also decreases the strength of the pile 10.

[0075] Further, in order to maintain optimal strength of the pile and arranging the first of the side walls with the described oblique angle in relation to the longitudinal direction of the pile, the width of the bottom side surface 24 adjacent the first of the side walls has a width which decreases from one end of the pile toward the other end.

[0076] Figure 5B further illustrates that the first and second side walls are arranged with a mutual angle 26, which angle (a) is defined by the function: a= 2-sin-1- a ± 0.1*2-sin-1- a , where d is the internal diameter of the pile and w is the width of the opening of the groove.

[0077] As explained earlier, individual piles may vary in diameters and lengths, which requires individual dimensions of the grooves cooperating with driving means, and by defining the mutual angles between the side walls by the above defined function, it is ensured that the direction of the force from the drive rod to the pile is in the most optimal direction of the pile, namely in a direction which is substantially perpendicular to the radial direction of the pile. Hereby the forces are effectively absorbed by the pile with a mini- mum risk of cracking the pile.

[0078] In the following is given a list of reference signs that are used in the detailed description of the invention and the drawings referred to in the detailed description of the invention.

[0079] 10 Pile

[0080] 12 Screw thread

[0081] 14 Hollow cavity

[0082] 16 Groove

[0083] 18 First side wall

[0084] 20 Second side wall

[0085] 22 Bottom main surface

[0086] 24 Bottom side surface

[0087] 26 Bottom side surface angle

[0088] 28 Driving means

[0089] 30 Driving means main body

[0090] 32 Driving means projection

[0091] 40 Pointy end

Claims

CLAIMS1. A foundation pile (10) for installation into the ground, comprising an elongate body extending in a longitudinal direction having a first end and a second, and a screw thread (12) element extending helically at least along part of the outer surface of said elongated body, said elongated body comprising a hollow cavity (14) defined by an inner wall extending in the longitudinal direction of said body, said inner wall having a longitudinal groove (16) comprising a bottom (22, 24) and two sidewalls (18, 20), a first of said side walls (18) extending in a direction having an oblique angle compared to said longitudinal direction.

2. A foundation pile (10) according to claim 1 , said first sidewall (18) extending in a direction having an oblique angle compared to said longitudinal direction over a main part of the length of said pile (10).

3. A foundation pile (10) according to claim 1 or 2, said groove having a width that increases over said length of said groove.

4. A foundation pile (10) according to claim 3, a second of said side walls (20) extending in a direction being parallel with said longitudinal direction.

5. A foundation pile (10) according to claim 3, a second of said side walls (20) extending in a direction having an oblique angle compared to said longitudinal direction.

6. A foundation pile (10) according to any of the previous claims, wherein said oblique angle at one of said ends of said pile (10) is between 5-15 degrees, preferably between 6-12 degrees, most preferred 8-10 degrees.

7. A foundation pile (10) according to any of the previous claims, said groove (16) having a width, which at one of said ends is between 10-30% wider compared to said width at said opposite end, preferably 15-25%, most preferred 18-23% wider.

8. A foundation pile (10) according to any of the previous claims, said longitudinal groove (16) comprising a longitudinal bottom main surface (22) and two bottom sidesurfaces (24), each bottom side surface being arranged on opposite sides of said bottom main surface (22), one of said bottom side surfaces (24) having a width that increases toward one of said ends of said pile (10).

9. A foundation pile (10) according to claim 8, said first and second side surface (18, 20) of said groove (16) each having a plane, said planes having a radial direction in relation to a cross section of the pile (10).

10. A foundation pile (10) according to claim 8 or 9, said first and second side surface (18, 20) having a mutual angle a defined by the following: a= 2-sm1- ± 0.1*2-sm1- , a a where d is the internal diameter of the pile and w is the width of the opening of the groove.

11. A foundation pile (10) according to any of the previous claims, said pile (10) comprising two longitudinal grooves (16).

12. A foundation pile (10) according to any of the previous claims, wherein a width of said grooves (16) increases uniformly from one end of the pile (10) towards the opposite end of the pile (10) with between 1.25-3.75% per meter of the pile (10), preferably 1.87-3.12%, most preferred 2.25-2.87%.

13. A foundation pile (10) according to any of the previous claims, wherein said first of said side walls (18) twists partly around a longitudinal centerline of the pile (10), over the length of the pile (10), in the same direction as the screw thread (12).

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