The invention relates to the field of piles for foundations, wherein the piles are vibratorily driven into the ground e.g. by a vibratory pile hammer. Such piles may be called displacement piles, as when the piles are driven into the ground, the soil they are driven through is displaced.

The piles may form a foundation, or may be part of a foundation. As such the piles are designed to carry a load (and/or weight) of the structure that is to be supported. These loads may also be lateral forces and/or moments of the forces the pile is required to withstand. Yet, in practice the pile’s ability to correctly carry the load depends on the condition of the soil and the surrounding layers. This is because the soil and the surrounding layers determine the stability of the pile in its installed position. The soil conditions and/or the load to be supported are however rarely the same. Thus, this may require a newly designed and manufactured pile for each situation. This is not cost effective from a manufacturing point of view. Furthermore, the condition of the soil and the layers may e.g. be uncertain prior to installation of the piles and/or not be uniform across the foundation area. Disadvantageously, current displacement piles to be vibratorily driven into the ground - such as shown in KR102115707 - do not offer the flexibility to deal with such issues.

It is an object of the invention to provide a pile assembly which can be used in a wide range of conditions.

It is a further object of the invention to provide an alternative pile assembly.

This object is achieved with a pile assembly which is to be vibratorily driven into soil for a foundation, the pile assembly comprising: a pile shaft, a pile tip mountable to a bottom end of the pile shaft, the pile tip having at least one pair of radial tip fins, the tip fins being arranged along a length of the pile tip, a mounting member provided on a top end of the pile shaft and/or the pile sleeve, a pile sleeve adapted to be arranged coaxially with the pile shaft, wherein the pile shaft extends through the pile sleeve, such that the pile sleeve and pile shaft are axially movable with respect to each other, the pile sleeve being adapted to be coupled with the pile shaft in an installed state of the pile assembly, wherein the pile assembly has been driven into the soil to a predetermined depth, wherein the sleeve has at least a pair of radial sleeve fins, the sleeve fins being predominantly extending along a length of the sleeve, wherein at least the pile shaft, the pile tip and the pile sleeve are independently exchangeable.

The pile assembly is to be vibratorily driven into soil for a foundation. Typically that means the assembly is vibrated into the ground by means of a vibration device. This vibration device may be a vibratory hammer, e.g. a so-called variable moment vibratory hammer. Such a variable moment vibratory hammer is first accelerated to a certain frequency, e.g. 2000-2500 rpm, before the pile assembly to be driven by the vibratory hammer assembly is made to vibrate. This is achieved by adjusting eccentrically rotating weights.

Due to the high frequencies with which the variable moment vibratory hammer - and thus the driven pile assembly - vibrate, the soil around the pile assembly will become plastic. The resistance that the pile assembly has to overcome in order to be installed in the subsoil is thus significantly lower and the vibrations generated in the soil are also greatly reduced.

The pile shaft of the pile assembly is to be driven into the soil in a predominantly vertical manner. Then, the pile shaft forms a vertical structural component to carry vertical loads. With the pile shaft being an independently exchangeable component of the assembly, the dimensioning - e.g. length, diameter, thickness - and/or materials of the pile shaft can be chosen according to the application at hand and/or the conditions encountered in the field.

For example, the length of the pile shaft can be such that the pile tip mounted thereon is installed in a load-bearing layer of the soil.

The pile tip being mountable to the bottom end of the shaft, it is driven into the soil as an extension of the shaft. The radial tip fins arranged along the length of the pile tip provide lateral stability to the pile tip in that in the installed state more surface area - in a lateral direction - is in contact with the soil. By extension it provides lateral stability to the pile shaft and/or the structure to be supported thereby. With the pile tip being an independently exchangeable component of the assembly, the dimensioning and/or materials of the pile tip can be chosen according to the application at hand and/or the conditions as encountered in the field. For example, when installing the pile assembly in soil having a strong soil structure, the tip fins may be relatively small. Alternatively, when the pile assembly is to be installed into soil of a relatively weak structure, the tip fins may be relatively large. The pile sleeve is adapted to be arranged around the pile shaft. The radial sleeve fins arranged along the length of the pile sleeve provide lateral stability to the pile assembly in that in the installed state more surface area - in a lateral direction - is in contact with the soil. With the pile sleeve being an independently exchangeable component of the assembly, the dimensioning and/or materials of the pile sleeve can be chosen according to the application at hand and/or the conditions as encountered in the field. For example, when installing the pile assembly in soil having a strong soil structure, the sleeve fins may be relatively small. Alternatively, when the pile assembly is to be installed into soil of a relatively weak structure, the sleeve fins may be relatively large.

Should the soil layers in which the pile assembly is to be installed for example be non-uniform in terms of ‘structural strength’ then the dimensioning of the tip fins and sleeve fins can be arranged accordingly by independently selecting the appropriate tip fins and/or sleeve fins for the soil layer they are to be installed in.

As such it is an advantage of the pile shaft, the pile tip and the pile sleeve being independently exchangeable that the pile assembly according to the invention allows for constructing a pile assembly that befits a wide range of conditions. This constructing of the pile assembly can be done by changing components of the pile assembly, rather than manufacturing a new complete pile. This makes the pile assembly, and a foundation system based thereon, highly adaptable. As a result the pile assembly is more cost effective in use and manufacturing.

The wide range of conditions may relate to the soil conditions, and/or lateral loads and/or moments to be borne by the pile assembly. In a pile assembly according to the invention these requirements can be met by selecting the appropriate pile shaft, pile tip and/or pile sleeve. This means that by matching local conditions the use of materials can be optimised. This leads to a cheaper and/or more sustainable pile assembly.

To facilitate matching these local conditions, at an installation site for a pile assembly a range may be provided for the pile shafts, pile sleeves and/or pile tips. Then, an appropriate pile assembly can be constructed on-site, for example if the on-site local conditions turn out differently than anticipated.

It is an advantage of the sleeve being arranged around the pile shaft such that the pile sleeve and pile shaft are axially movable with respect to each other that then the pile shaft may be driven into the soil prior to driving the pile sleeve into the soil. This makes it easier to drive the pile assembly into the soil. Furthermore, this allows for positioning of the pile assembly with a high level of precision.

When the pile assembly has been driven into the soil to a predetermined depth, the pile sleeve is adapted to be coupled with the pile shaft in the installed state of the pile assembly. This can e.g. be done by connecting a top end of the pile sleeve to the top end of the pile shaft.

As the pile sleeve and pile shaft are coupled in the installed state, loads can be transferred from the pile tip and/or shaft into the pile sleeve, or vice versa.

In the installed state the pile assembly provides ‘ground anchoring’. That is, the pile assembly can transmit loads of the structure that is to be installed thereon - e.g. loads of a tensile nature - to deeper, stable areas within the ground.

In an embodiment, the sleeve fin at the trailing edge thereof branches off into two edges, both edges extending in opposite - at least partially - circumferential directions so as to define a Y- shaped cross-section. These edges increase the cross-section of the pile assembly that is to ‘cut’ the soil so as to be lowered into said soil. As such the two edges increase the resistance encountered by the pile assembly when it is being driven. Firstly, this provides further stability to the pile assembly in the circumferential direction. Secondly, this increased resistance may aid in slowing down the pile assembly when it is being driven into the soil, e.g. so as not the drive the pile assembly beyond a predetermined depth.

In a further embodiment, the sleeve fins have a slanting leading edge extending under an angle a with respect to the longitudinal axis of the sleeve, for example with an angle of 30°£ a £ 90°. This slanting leading edge aids in installing the pile assembly into the soil, in that the bottom of the leading edge defines the smallest cross-section to come in contact with the soil. After the leading edge has cut an initial path through the soil, the fins’ increasing cross- section can be driven into the ground with less resistance.

In another embodiment, the sleeve fins have a slanting trailing edge extending under an angle b with respect to the longitudinal axis of the sleeve.

In another embodiment, the sleeve fins are uniformly distributed along the circumference of the sleeve. ln a practical embodiment, the sleeve fins extend in diametrically opposite radial directions.

In a further embodiment, the pile sleeve has multiple pairs, preferably two pairs, of radial sleeve fins, wherein the fins of each of the pairs extend in diametrically opposite radial directions.

In yet another practical embodiment, the tip fins have a slanting leading edge.

In a further embodiment, the tip fins are uniformly distributed along the circumference of the sleeve.

In another practical embodiment, the tip fins extend in diametrically opposite radial directions.

In a further embodiment, the pile tip has multiple pairs, preferably two pairs, of radial tip fins wherein the fins of each of the pairs extend in diametrically opposite radial directions.

In yet a further embodiment, the assembly comprises at least one guiding element for centring the pile shaft within the sleeve.

In an embodiment, the guiding element comprises a ring mounted to an inner side of the sleeve. The pile shaft can then be arranged coaxially with the ring. Such a ring may be provided with ribs to increase stiffness thereof. The ring being mounted to the inner side of the sleeve and being arranged coaxially with the pile shaft, it may aid in transferring loads and moments from the pile shaft to the pile sleeve, and vice versa.

In another embodiment, the guiding element is provided with a friction preventive measure. Should the guiding element be embodied as a ring mounted to the inner side of the sleeve, then said ring may be provided with a friction preventive measure on an inner side thereof. This may for example be an inner ring to be mounted in the ring, e.g. a Teflon ring.

In yet another embodiment, the guiding element comprises two axially spaced rings.

In a further embodiment, the pile shaft is provided with a dedicated connection element adapted to be engaged by a vibratory device used for driving the pile assembly.

In a further embodiment, the pile sleeve is provided with a dedicated connection element adapted to be engaged by a vibratory device used for driving the pile assembly. ln a further embodiment, in a driving state, wherein the pile shaft and the pile sleeve are both driven into soil by means of a vibratory device, the connection element of the pile shaft and the connection element of the sleeve form a mutual connection element engageable by the vibratory device.

In embodiments, the pile shaft and pile sleeve are axially movable with respect to each other in a pre-installation state wherein the pile shaft is arranged coaxially in the pile sleeve and positioned such that the tip member engages the ground surface,

- the pile shaft and pile sleeve are axially movable with respect to each other in in a first driving state wherein the pile shaft is being driven into the soil by means of a vibratory device and the pile shaft is arranged coaxially in the pile sleeve,

- the pile shaft and the pile sleeve are coupled in a second driving state, wherein the pile shaft and the pile sleeve are driven together into soil by means of a vibratory device,

- the pile shaft is fixed to the pile sleeve, such that they form a unit, in an installed state wherein the pile assembly has been driven into the soil to a predetermined depth.

The invention also relates to a gripping member for a vibratory hammer assembly for driving a pile assembly according to the invention, the gripping member comprising a main body having dedicated pile shaft grippers and dedicated pile sleeve grippers.

In an embodiment, the pile shaft grippers and/or the pile sleeve grippers are hooks that are pivotably arranged in or on said main body.

The invention also relates to a method for driving a pile assembly according to the invention into the ground. The method comprises the steps of: arranging the pile shaft coaxially in the pile sleeve, positioning the pile shaft such that the tip member engages the ground surface, gripping the pile shaft with one or more grippers of a vibratory hammer assembly to drive the pile shaft into the soil in a first stroke, gripping the sleeve with one or more grippers of the vibratory hammer assembly to drive the sleeve and the shaft together into the soil in a second stroke, fixing the pile shaft to the pile sleeve such that they form a unit. ln embodiments, the method comprises the steps of: gripping the pile shaft with grippers of the vibratory hammer assembly to drive the pile shaft into the soil until the top end of the pile shaft is near to or aligned with a top end of the sleeve, gripping the sleeve with the vibratory hammer assembly in addition to the gripping of the pile shaft, so as to drive the pile shaft and the sleeve into the soil as a unit.

In embodiments, the gripping of the pile shaft is done using dedicated pile shaft grippers of the vibratory hammer assembly and/or wherein gripping of the pile sleeve is done using dedicated pile sleeve grippers of the vibratory hammer assembly.

In embodiments, the method comprises the steps of: providing a range for at least one of the pile shaft, pile tip and pile sleeve determining soil conditions at an installation site for the pile assembly selecting from at least one of the provided ranges the respective pile shaft, pile tip and/or pile sleeve that match the soil conditions constructing the pile assembly with the selected pile shaft, pile tip and/or pile

The method may further involve determining design requirements for the pile assembly, these may e.g. be design requirements relating to the structural loads, lateral forces and/or moments to be carried by the pile assembly and/or requirements relating to the soil conditions, and/or requirements as a result of interaction between the structural loads and the soil conditions.

The invention will now be described with reference to the figures, in which like reference symbols designate like parts. In these figures:

Figs. 1 A-1 B schematically show a frontal view and side view, respectively, of a pile assembly according to the invention in an installed state in the soil,

Fig. 2A-2B schematically show a frontal view and side view of a pile sleeve for the pile assembly of Figs. 1A-1B,

Fig. 2C schematically shows the pile shaft for the pile assembly of Fig.1 , Fig. 3 schematically shows in perspective the pile assembly of Figs. 1A-1B in a first driving state,

Fig. 4 schematically shows in perspective the pile assembly of Figs. 1A-1B in a second driving state,

Fig. 5 schematically shows in perspective the pile assembly of Figs. 1A-1B in an advanced second driving state,

Fig. 6A-6B schematically show side-by-side the pile assembly of Figs. 1A-1B in the installed state in perspective and in a frontal view another pile assembly according to the invention in the installed state;

Fig. 7A-7B schematically show in perspective the pile sleeve of Figs. 1A-1B,

Fig. 8 schematically shows in perspective a pile tip for a pile assembly according to the invention,

Fig. 9A schematically shows a detail of the pile assembly of Figs. 3-5,

Fig. 9B schematically shows in perspective the guiding mechanism of Fig. 9A,

Fig. 9C schematically shows in perspective a friction preventive measure for a pile assembly according to the invention,

Fig. 10 schematically shows in perspective a gripping member for a vibratory hammer assembly in the first driving state,

Fig. 11 schematically shows in perspective a gripping member for a vibratory hammer assembly in the second driving state,

Fig. 12A schematically shows in perspective a main body for the gripping member of Fig. 11

Fig. 12B schematically shows in perspective a hook for the gripping member of Fig. 11 , and

Fig. 13 schematically shows in perspective a structure mounted on a pile assembly according to the invention. In Figs. 1A-1B is shown a frontal view and side view, respectively, of a pile assembly 1 according to the invention. The assembly 1 in Figs. 1A-1B is in an installed state in the soil. That is the assembly is installed in the soil in a position below ground level 2. To achieve this position, the pile assembly 1 has been driven into the soil to a predetermined depth.

The pile assembly 1 comprises a pile shaft 10, a pile tip 30 and a pile sleeve 20. As at least the pile shaft, the pile tip and the pile sleeve are independently exchangeable, the shaft 10, tip 30 and sleeve 20 shown in Figs. 1A-1B and Figs. 2A-2C may have been selected so as to optimise the pile assembly 1 for use in the installation site of Figs. 1A-1B.

The pile tip 30 in Figs. 1A-1B comprises a tip shaft 32. This tip shaft 32 is mounted to a bottom end 11 of the pile shaft 10 by means of fastening means 33. The pile tip 30 has at least one pair of radial tip fins 31, 33 the tip fins 31,33 being arranged along a length LT1,

LT2 of the pile tip 30.

The pile assembly 1 further comprises a mounting member 40 provided on a top end 3 of the pile assembly 1. This mounting member 40 may be used for installing a structure on the pile assembly 1. The mounting member 40 may form an integral part of the pile sleeve 20 (as shown in Figs. 2A, 2B).

The pile sleeve 20 shown in Figs. 1A-1B is arranged coaxially with the pile shaft 10, wherein the pile shaft 10 extends through the pile sleeve 20. In the installed state as shown the pile sleeve 20 is coupled to the pile shaft 10 by means of a top plate 50 and fastening means 51. Thus, the pile sleeve 20 and pile shaft 10 are fixed to one another and may be used to support, hold and/or restrain a structure installed thereupon as a unit. It should be appreciated that the pile sleeve 20 and pile shaft 10 may equally be coupled in different ways for which a structure installed thereupon can be supported, held or restrained as a unit.

The pile sleeve 20 has a pair of radial sleeve fins 21 , with each of the sleeve fins 21 extending outwardly from the sleeve 20 in diametrically opposite radial directions.

The sleeve fins 21 have a slanting leading edge 22. The leading edge 22 extends under an angle a with respect to the longitudinal axis A of the sleeve 20. This angle may for example be in the range of 30°£ a < 80°.

The sleeve fins 21 have a slanting trailing edge 23 extending under an angle b with respect to the longitudinal axis of the sleeve 20. It can be seen in the side view of Fig. 1 B that the sleeve fins 21 predominantly extend along a length LS of the sleeve 20. The sleeve fins 21 - at the trailing edge 23 thereof branch off into two edges 25, 26. The edges 25,26 extend in opposite - at least partially - circumferential directions so as to define a Y-shaped cross-section (see the side view of Fig 1B). The pile sleeve 20 and the edges 25, 26 can also be seen in Figs. 7A-7B, in respectively a predominantly frontal view and a perspective side view.

The assembly 1 comprises guiding elements 60, 65. These guiding elements can be used for centring the pile shaft 10 within the sleeve 20. In Figs. 1A-1B there are two guiding elements 60, 65 which are axially spaced. That is, the guiding element 60 is provided near the top end 3 of the pile sleeve 20, and the guiding element 65 is provided near the bottom end 4 of the sleeve 20.

In Fig. 3 is schematically shown in perspective the pile assembly 1 in a first driving state. In this state, the pile shaft 10 and pile sleeve 20 are axially movable with respect to each other and the pile shaft 10 is being driven into the soil 6 by means of a vibratory device. The pile shaft 10 is arranged coaxially in the pile sleeve 20. In Fig. 3 the pile shaft has been gripped by a gripping member 100 of a vibratory hammer assembly - e.g. by means of grippers on or in the gripping member 100 - and the pile shaft 10 has been positioned so as to engage the ground surface 2 with the pile tip 30. Vibrations induced by the vibratory hammer assembly are transferred from the gripping member 100 to the pile shaft 10, as a result of which the pile shaft 10 and the pile tip 30 will provide pressure onto the soil so as to displace the soil and to be lowered underground.

The state shown in Fig. 3 prior to any driving of the vibratory hammer assembly may be called a pre-installation state.

In a first stroke the pile shaft is driven into the soil. The result of this stroke can be seen in Fig. 4, where the pile shaft 10, and the pile tip 30 mounted thereto, have been driven into the ground. Yet, the pile sleeve 20 is still positioned above ground.

In Fig. 4 in a second driving state, the pile shaft 10 and the pile sleeve 20 are to be driven together into soil 6 in a second stroke by means of the vibratory hammer assembly. To effect this second stroke the gripping member 100 grips the sleeve 20 with one or more grippers. This can be done in the current embodiment, as the pile shaft has been driven into the ground until the top end of the pile shaft 10 is near to or aligned with the top end of the sleeve 20. As the pile shaft 10 and sleeve 20 are driven together, they - at least temporarily - form a unit due to the mutual gripping of the shaft 10 and sleeve 20 by the gripping member 100. That is, the sleeve 20 and shaft 10 are coupled due to the mutual gripping. The sleeve 20 has been gripped by gripping member 100 in addition to retaining the grip on to pile shaft 10. The result of the second stroke can be seen in Fig. 5, where the pile shaft 10 and pile sleeve 20 are both positioned underground after having been driven into the soil as a unit.

Gripping of the pile shaft 20 can be done using dedicated pile shaft grippers of the vibratory hammer assembly and/or gripping of the pile sleeve can be done using dedicated pile sleeve grippers of the vibratory hammer assembly. Such dedicated grippers can be seen in Figs. 10- 11.

In Figs. 6A-6B the installed state of the pile assemblies 1 and 101 is shown. Here, the pile shaft 10 has been fixed to the pile sleeve 20 by a top plate 50 such that they form a unit. The difference between the pile assemblies 1 and 101 being that assembly 101 has a pile tip 130 with tip fins 131 that are smaller than the tip fins 31 of assembly 1. The tip fins 131 may e.g. more suited to soil layers of a stronger structure and/or for a structure for which smaller moments and/or loads are to be borne. Whereas the tip fins 31 may be more suited to soil layers of a weaker structure and/or for a structure for which larger moments and/or loads are to be borne. This underlines the independent exchangeability of the pile tips 30, 130. A similar principle may apply to the pile sleeve 20 with its sleeve fins 21 and/or the pile shaft 10.

To construct, or assemble, a pile assembly such as pile assemblies 1 or 101 a range may be provided for at least one of the pile shaft, pile tip and pile sleeve. Then, for certain soil conditions at an installation site for the pile assembly and/or design requirements for the pile assembly in those soil conditions the appropriate pile shaft, pile tip and/or pile sleeve may be selected. That is, these components can be selected such that the pile assembly is appropriate for use in the installation site and for carrying the loads of the structure to be mounted thereupon.

In Fig. 8 is schematically shown in perspective a pile tip 230 for a pile assembly according to the invention. The pile tip 230 comprises a tip shaft 234 which is adapted to be mounted to a pile shaft. The tip shaft 234 being mounted on a ring 235.

The pile tip 230 is shown to have radial tip fins 231, 232, 233 for which the fins 232 and 321 can be seen to be formed as a diametrically opposed pair of fins. The fin 233 may also be one of a pair of fins, e.g. a diametrically opposed pair. Then, the fins of pile tip 230 are uniformly distributed along the circumference thereof.

The fins at a top end 235, 236 of the pile 230 extend along the tip shaft 234. At a lower end 237 of the pile tip 230 the fins 231, 232, 233 form a pointed end.

In Fig. 9A is schematically shown a detail of the pile assembly 1 of Figs. 3-5. The pile shaft 10 of the assembly 1 is coaxially arranged in the pile sleeve 20 and has a pile tip 30 mounted thereto. The detail of Fig. 9A shows that the pile shaft 10 is arranged coaxially in a guiding mechanism 150. This guiding mechanism is shown in perspective in Fig. 9B.

Fig. 9B schematically shows in perspective the guiding mechanism 150 of Fig. 9A. The guiding mechanism 150 is embodied as a ring 151 having ribs 152, which ring is mounted on an inner side of the pile sleeve 20. The ring may be provided with a friction preventive measure. An example of such a measure is shown in Fig. 9C . There a ring 180 of low friction material, e.g. of Teflon, is shown which can be mounted in the ring 150. This ring 180 is also used in the assembly of Fig. 9A. There it can be seen that the lower end 181 of ring 180 protrudes out of the guiding mechanism 150.

In Fig. 10 is schematically shown in perspective a gripping member 200 for a vibratory hammer assembly in the first driving state. That is, the gripping member has gripped the pile shaft 310. It can be seen that pile shaft 310 is provided with a dedicated connection element 330 adapted to be engaged by the vibratory hammer assembly used for driving the pile assembly, i.e. in this case by means of the gripping member 200.

The gripping member 200 is embodied as comprising a main body 220 having dedicated pile shaft grippers 250 and dedicated pile sleeve grippers 270. In Fig. 10 these pile shaft grippers 250 and the pile sleeve grippers 270 are hooks that are pivotably arranged in or on said main body 220. The pile shaft grippers 250 of Fig. 10 pivot so as to hook their lower end 251 over protruding edge of the dedicated connection element 330. An example of an embodiment of the hooks 250, 270 can be seen in more detail in Fig. 12B. Provisions 255, 275 for arranging the hooks in the main body 220 can be seen in Fig. 12A.

In Fig. 11 is schematically shown in perspective the gripping member 200 for a vibratory hammer assembly in the first driving state. That is, the pile shaft 310 and the pile sleeve 320 are both driven into soil by means of the vibratory hammer assembly. In Fig. 11 the pile sleeve 320 is provided with a dedicated connection element 350 adapted to be engaged by the gripping member 200 of the vibratory hammer assembly used for driving the pile assembly. The pile sleeve grippers 270 have now pivoted with respect to their position of Fig. 10 so as to hook their lower end 271 over a protruding edge of the dedicated connection element 350 of the pile sleeve 320. In the state shown in Fig. 11 the connection element 330 of the pile shaft and the connection element 350 of the sleeve 320 form a mutual connection element engageable by the vibratory hammer assembly. Then, the pile sleeve 320 and pile shaft 310 can be driven into the soil as a unit.

In Fig. 13 is schematically shown in perspective a structure 400 mounted on a pile assembly 500 according to the invention. A pile shaft (not shown) arranged in the pile sleeve 520 is coupled therewith via fastening 550. A mounting member 450 of the structure 400 is fixed to a mounting member 525 of the pile assembly 500 by means of fasteners 600.