FIELD OF THE INVENTION

The invention relates to a pile assembly comprising a concrete pile and a pile member, such as a second pile or a rock shoe , connected to each other by a connecting arrangement .

BACKGROUND OF THE INVENTION

When the soil is so soft that its load bearing capacity does not allow to construct directly on the soil and the soft soil layer is so thick that it is not economically possible to remove it , soil piling is one way to provide foundation support for buildings and other structures .

Displacement piles are driven into the soil using a pile-driver . One type of pile driver comprises a weight , i . e . a pile hammer, placed between guides so that it can slide vertically . The pile hammer is placed above a pile and raised . When the pile hammer is released, it hits the pile and drives it into the ground . Driven piles are constructed of wood, reinforced concrete or steel . Concrete piles are typically available in square , rectangular and round cross-sections . The concrete piles are reinforced with reinforcement bars and may be prestressed .

Reinforced concrete piles are produced by casting concrete in a mould in which a reinforcement structure made of steel has been placed . The reinforcement structure comprises longitudinal reinforcement bars at the corners of the pile and a transverse stirrup reinforcement surrounding the reinforcement bars . When deeper piling is required, longer piles may be formed by connecting piles to together by means of a connecting arrangement that comprises pile j oints cast into the ends of the piles to be j oined .

Displacement piles work in two di f ferent ways . In Scandinavia piles are driven into bedrock or load carrying soil layers and the pile end trans fers all loads . The harder the final hits are , the more compressive load the pi le can carry . When hitting the pile , the compressive load will reflect from the bedrock as a tension load and the j oint must be able to carry this load without deformation . The curvature of the pile will cause a bending load from the compressive load . In service limit state the pile j oint cross section is designed to carry only compression loads , the shear loads are transferred via friction . The rock shoe is usually designed for 100 years and a corrosion reduction 2 mm/ side .

In the rest of Europe piles are usually designed to trans fer loads to the soil via cohesion or friction . The load capacity depends on the pile side area and the structural design is based on both compression and tension piles . These pi les are usually driven into ground by using as little force as possible , since the cohesion force will drastically weaken if the soil is disturbed . The tension j oint will open up because of elongation in the locking member and corrosion, and shear load transfer must be considered .

Document WO 2020/ 094923 Al discloses a connecting arrangement in which pile j oints at the ends of the piles comprise lock hous ings and lock spindles that are connected to each other by means of locking pins . The drawback of this solution is that the lock spindles protrude from the end of the pile and therefore a separate drive plate must be placed on the pile j oint to protect the spindles from the driving impacts . Further, the locking pin i s installed by striking with a sledgehammer or by using a hydraulic clamping machine . Both ways are timeconsuming and di f ficult in site conditions .

In fig 6 represents a pile-rock shoe connection . Two lock housing-lock spindle j oints are situated below the bottom plate of the rock shoe , and the locking structure wi ll make it more di f f icult to penetrate the compacted soil above bedrock . The locking parts are unprotected and may be damaged during installation . The locking parts are further unprotected against corrosion . In tension this j oint with carbon steel must be designed with corrosion reduction, the pin diameter will decrease and the hole diameter will increase . In ultimate limit state it can be shown that pile ends do not separate but in service limit state the corrosion caused gap is a big problem, the deformation at the j oint will increase and cause extra loads that are hard to define . It is possible to manufacture these j oint parts of stainless steel , but it requires a lot of machining which will take time and cost money .

Document WO 2016/ 171566 Al discloses a pile connector that is locked by means of energy applied to the pile when rammed or vibrated into the ground . The fastening unit comprises a tubular expansion element and wedge elements with neck portions . Both ends of the fastening unit are inserted into locking spaces . The neck portions or a special metal core portion prevent the deformation of the central tubular section during ramming or vibrating . The wedge head portions will expand the ends of the tubular expansion element and lock the fastening unit to the lock space . The given structure in the document with entrance of the lock space at maximum 20 mm cannot trans fer the heavy loads caused by piling into bedrock . The tolerance of a pile j oint comprises manufacturing tolerances for steel part , manufacturing tolerances for concrete part and placing of steel part into the concrete part . Given space between various units 0 and 1 mm is not poss ible by using today' s production technology . On site parts may get dirty, e . g . by dropping the connector to the ground, and without needed tolerances the steel parts must be cleaned very carefully . The plastic deformation of the tubular section produces stress levels above the material yield strength . When the space between various units increases , the load eccentricity grows , and the applied dynamic load can lead to bending or buckling of the tubular section before the wedge elements enter the ends of the tubular section .

The obj ect of the present invention is to provide in improved pile assembly .

SUMMARY

The obj ect of the invention can be achieved by a pile assembly according to claim 1 .

The pile assembly according to the invention comprises a concrete pile , a pile member and a connecting arrangement for connecting an end of the pile and the pile member together . The connecting arrangement comprises a pile j oint at the end of the concrete pile . The pile j oint comprises at least one locking member placed in the concrete at the end of the pile, the locking member comprising an inlet part comprising an inlet hole having a first end at the end of the pile , a locking chamber extending from a second end of the inlet hole and having an inner diameter or inner width larger than that of the inlet hole . The connecting arrangement comprises at least one connecting member having a first end inserted through the inlet hole into the locking chamber and a second end connected to the pile member . A bending member is arranged in the locking chamber . The bending member is configured to bend and/or expand the connecting member against a surface of the inlet hole and/or against an inner surface of the locking chamber when the connecting member and the bending member are pressed against each other .

Signi ficant benefits can be achieved by the means of the invention . The pile assembly according to the invention does not comprise separate locking pins to connect the pile j oints at the ends of the piles to each other . This simpli fies and speeds up the installation work at the building site . The pile j oint placed at the end of the pile does not comprise parts that protrude from the end of the pile . Thus , no separate drive plate is needed to protect the pile end during the pile-driving . Further, the pile j oint of the pile assembly may have a simple structure that can be produced ef ficiently and economically . The pile j oint can also be easily made of stainless steel or non-corroding materials . The connecting arrangement of the pile assembly is sel f-locking when the weight of 12-meter standard pile and the pile hammer is put on the connecting arrangement . I f the pile member is a rock shoe , it can easily be mounted to the end of the standard pile kept in a stock . The connecting arrangement of the pile assembly can be used with all above-described displacement concrete piles , and all manufacturing and installing tolerances have been considered . When filling the locking chamber and the inlet hole with hardening sealant , the pile j oint deformations can be kept small , which will give a smaller design curvature and a better load bearing capacity .

The pile assembly according to the invention is very flexible i f pile manufacturing tolerances have been exceeded . Specially made thinner connecting members may be fixed in required positions and the assembly may continue as usual . The j oint load bearing capacity will be reduced because of the smal ler connecting member cross-section but the piles can still be j oined together . The foundation design is then checked, and i f needed, a pile or more will be added .

According to an embodiment of the invention the concrete pile comprises reinforcement bars placed in the concrete of the pile , which reinforcement bars extend in the lengthwise direction of the pile , and the combined tensile strength of the connecting members is at least equal to the combined tensile strength of the reinforcement bars . When hitting the pile , the compressive load reflects from the bedrock as a tension load and the connecting members must be able to carry this load without deformation . Since the combined tensile strength of the connecting members is equal to or greater than that of the reinforcement bars , tensile forces acting on the pile during the driving do not cause deformation to the connecting members .

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in detail by means of examples with reference to the accompanying drawings , in which

Fig . 1 shows a pile assembly according to an embodiment of the invention,

Fig . 2 shows a pile of the pile assembly of fig . 1 without an end plate , viewed from an end of the pile ,

Fig . 3 is a side view of the pile of fig . 2 , Fig. 4 is a side view of a locking member of a pile joint shown in fig. 2,

Fig. 5 is a front view the locking member of fig. 4,

Fig. 6 is a bottom view of the locking member of fig. 4,

Fig. 7 shows as a side view a connecting member insertable into the locking member of fig. 4,

Fig. 8 is a front view of the connecting member of fig. 7,

Figs. 9 and 10 show how an end of a second pile is connected to the end of the pile of fig. 2,

Fig. 11 and 12 show a second embodiment of locking member and connecting member that can be used in the pile assembly according to the invention,

Fig. 13 shows a third embodiment of locking member and connecting member that can be used in the pile assembly according to the invention, and

Fig. 14 shows a rock shoe that can be used in the pile assembly according to the invention.

DETAILED DESCRIPTION

Fig. 1 shows a pile assembly 1 according to an embodiment of the invention. The pile assembly 1 comprises a concrete pile 2, pile member 3, such as a second concrete pile or a rock shoe, and a connecting arrangement 4 for connecting the pile member 3, such as an end of the second pile or rock shoe, to an end 5 of the pile 2. The connecting arrangement 4 comprises a pile joint 6 placed at the end 5 of the pile 2. If the pile member 3 is the second pile, also the end of the second pile is provided with the pile joint 6. The pile joint 6 is cast into the end 5 of the pile.

Fig. 2 shows an end 5 of a driven pile 2 without an end plate 17 and fig. 3 the pile 2 end as a side view. The pile 2 can be used in the pile assembly 1 shown in fig. 1. The pile 2 is constructed of reinforced concrete. The pile 2 has a square cross-section. Alternatively, the pile 2 may have a rectangular or round cross-section. A reinforcement bar 9 is arranged at each corner of the pile 2. The reinforcement bars 9 extend in a longitudinal direction of the pile 2. Instead of a single reinforcement bar, a bundle of reinforcement bars may be used. The concrete pile 2 also comprises a transverse reinforcement 10, such as single stirrups or continuous helical reinforcement, that surrounds the reinforcement bars 9 or reinforcement bar bundles. The diameter of the reinforcement bar 9 is typically at most 28 mm or 32 mm.

The pile 2 typically has a length L of 3 to 15 meters. The dimensions of the square cross-section of the pile 2 are typically between 200 mm x 200 mm to 350 mm x 350 mm.

The pile joint 6 comprises at least one locking member 7 or locking members 7 placed in the concrete at the end 5 of the pile 2. Typically, each corner of the pile 2 is provided with the locking member 7, as shown in fig. 2. Larger piles, typically piles having cross-sectional dimension of 450 mm X 450 mm or more, may comprise eight locking members 7 at the end of the pile 2. In that case each corner and the midpoint of each side of the pile is provided with locking member 7. In the cross-section of the pile 2, the locking members 7 are arranged inside the loop formed by the transverse reinforcement 10. The locking member 7 comprises an inlet part 8 having an inlet hole 11. The inlet hole 11 has a first end 12 and a second end 13 (shown e.g. in figs. 4 and 5) . The first end 12 of the inlet hole is located on the end surface of the pile 2. The inlet hole 11 extends in the lengthwise direction of the pile 2.

The locking member 7 shown in figs. 4 to 6 has an inlet part 8 that may comprise two locking plates 14 arranged at a distance from each other in the transverse direction of the pile 2. The locking plates 14 are parallel. The inlet hole 11 is between the locking plates 14. The inlet hole 11 may be defined by said locking plates 14. The end edges of the locking plates 14 are located on the end surface of the pile 2. The length of the inlet hole 11, i.e. the distance between the first end 12 and the second end 13 of the inlet hole, is 30 to 70 mm, typically 40 to 60 mm. The locking plates 14 may be made of steel.

The locking member 7 may further comprise reinforcing bars 15, typically two reinforcing bars 15, by means of which the locking member 7 is attached to the concrete of the pile 2. The reinforcing bars 15 extend in the longitudinal direction of the pile 2. The reinforcing bars 15 are arranged at a distance from each other. The reinforcing bars 15 may be placed between the locking plates 14. The locking plates 14 are attached to the reinforcing bars 15 e.g. by welding. The reinforcing bars 15 close the sides between the locking plates 14. The inlet part 8 is anchored to the concrete of the pile 2 with reinforcing bars 15. The inlet hole 11 may be defined by locking plates 14 and the reinforcing bars 15 and/or welded seams. A rectangular profile may be placed between the locking plates 14. The locking plates 14 are attached to the rectangular profile e.g. by gluing, and the reinforcing bars 15 welded to the locking plates 14. The rectangular profile prevents concrete from entering the inlet hole 11. The rectangular profile may be made of plastic or steel.

The locking member 7 further comprises a locking chamber 16 extending from the second end 13 of the inlet hole 11 toward a second end of the pile 2. The locking chamber 16 may be formed of plastic or sheet metal. The locking chamber 16 is attached to the inlet part 8 e.g. by gluing or welding. The inner diameter or inner width Wi _c of the locking chamber 16 in the transverse direction of the pile 2 is larger than the inner diameter or width W±h of the inlet hole 11, typically larger than the diameter or width of the second end 13 of the inlet hole 11. In the embodiment shown in figs. 4 to 6 the width of the inlet hole 11 corresponds to the distance between the locking plates 14. Typically, the inner diameter or inner width Wi _c of the locking chamber 16 is 1.2-1.8 times the diameter or width Wih of the inlet hole 11, e.g. the second end 13 of the inlet hole 11. The locking chamber 16 may be conical in shape, for example in the case where the locking chamber 16 is filled with hardening agent. The inner diameter or inner width Wi _c of a bottom of the locking chamber 16 is 1.2-1.8 times the diameter or width Wih of the inlet hole 11. The length of the locking chamber 16 is 30 - 100 mm, typically 50-80 mm.

The pile joint 6 may further comprise an end plate 17 (best shown in fig. 3) placed against the end 5 of the pile 2. The end of the inlet part 8 is attached to the end plate 17. The end plate 17 comprises an opening that is aligned with the first end 12 of the inlet hole 11. If the pile joint 6 comprises more than one locking member 7, the end plate 17 comprises a corresponding number of openings that are aligned with the first ends 12 of the inlet holes 11 . The ends of the inlet parts 8 are attached to the end plate 17 .

The pile j oint 6 may comprise a collar 18 attached to the end plate 17 . The collar 18 extends from the end 5 of the pile 2 towards the second end of the pile 2 . The collar 18 encloses the first end of the pile 2 . The collar 18 protects the end of the pile 2 from the splitting forces caused by pile driving impacts . As can be seen from fig . 3 , the end 5 of the pile 2 does not have any protruding parts . Thus , no separate drive plate i s needed to protect the pi le end 5 during the pile-driving .

The connecting arrangement 4 comprises at least one connecting member 19 having a first end 20 and a second end 21 . The first end 20 is inserted through the inlet hole 11 into the locking chamber 16 . The second end 21 is connected to the pile member 3 , such as the rock shoe or a pile j oint 6 at the end of the second pile . The edge of the first end 12 of the inlet hole 11 may be chamfered . Further, the edges of the first end 20 and/or the second end 21 of the connecting member 19 may be chamfered to facilitate the insertion of the connecting member 19 into the inlet hole 11 .

In a case where the pile member 3 is the second pile , the connecting arrangement 4 comprises the second pile j oint 6 at the end of the second pile . The second pile j oint may be similar to the pile j oint 6 at end 5 of the pile 2 . The pile j oint 6 and the second pile j oint have equal number of locking members 7 . The second pile j oint 6 may comprise a similar end plate 17 and the collar 18 as the pile j oint 6 .

The connecting member 19 has a slit 22 at the end that is inserted into the locking chamber 16 . The slit 22 extends from the end towards the other end o f the connecting member 19 . When the end of connecting member 19 is against the bottom of the locking chamber 16 , the slit 22 extends at least to the middle of the inlet hole 11 in the lengthwise direction of the connecting member 19 . The slit 22 extends through the connecting member 19 in a transverse direction .

In case where the pile member 3 is the second pile , the connecting member 19 has a slit 22 at both ends . I f the pile member 3 is a rock shoe , the connecting member 17 may have a slit 22 only at the first end 20 that is inserted into the locking chamber 16 of the locking member 7 . The connecting member 19 may comprise two interconnected plate parts . The plate parts may be interconnected by spot welding, gluing, or wrapping plastic fi lm around the plate parts . The connecting member 19 may be made of structural steel , stainless steel , plastic, nylon or carbon fiber . The connecting member 19 is made of ductile and bendable material .

The pile j oint 8 comprises a bending member 23 arranged in each locking chamber 16 . Typically, the bending member 23 is attached to the first end 20 and/or to the second end 21 of the connecting member 19 . Alternatively, the bending member 23 may be attached to the bottom plate of the locking chamber 16 . The bending member 23 is configured to bend and/or expand the connecting member 19 against the inner surface of the locking chamber 16 and/or the surface of the inlet hole 11 , for example against the edge of the second end 13 of the inlet hole 11 , when the first end 20 of the connecting member 19 is inserted into the locking chamber 16 and pressed against the bending member 23 . The bending member 23 expands the connecting member 19 to a diameter larger than that of the inlet hole 11 , typically the end of the inlet hole 11. Thus, the connecting member 19 is attached to the locking member 7.

In the embodiment shown in figs. 2-10 the bending member 23 enters the slit 22, forces the slit 22 to open and thus bends and expands the connecting member 19, as shown in figs. 9 and 10. The bending member 23 may be wedge-shaped. The bending member 23 is shaped so that the connecting member 19 bends and/or expands at a desired point.

Figs. 11 and 12 show a second embodiment of the invention. The pile assembly 1 is similar to that shown in figs. 2 to 10, except the locking member 7, the connecting member 19 and the bending member 23 have different structures. The locking member 7 is tubular, for example a stepped pipe having two different inner diameters. The locking member 7 comprises the inlet part 8 with the inlet hole 11. The locking chamber 16 extends from the second end 13 of the inlet hole 11. The inner width or diameter of the locking chamber 16 is larger than that of the inlet hole 11, typically 1.2-1.8 times larger than that of the inlet hole 11. The inlet hole 11 and the connecting chamber 16 have round cross-sections. The end of the locking chamber 16 is closed with a plate.

The bending member 23 is placed in the locking chamber

16. The bending member 23 may be conical in shape.

The connecting member 19 is a round bar with an end bore 25. Depending on the type of the pile member 3, the first end (rock shoe) or both ends (second pile) of the connecting member 19 are provided with cuts 24, typically with four cuts 24. The cuts 24 extend from the end towards the other end of the connecting member 19. The cuts 24 may be equally spaced along the circumference of the connecting member 19. The bore at the first end or both ends of the connecting member 19 may be conical. Thus, the diameter of the through hole at the end(s) is larger than that at the middle portion. The connecting member 19 may be made of cold-drawn steel.

In the embodiment shown in figs. 11 and 12 the bending member 23 enters the hole at the end of the connecting member 19 and thus bends and expands the connecting member 19 against the inner surface of the locking chamber 16 and/or the surface of the inlet hole 11, as shown in fig. 12. The bending member 23 expands the connecting member 19 to a diameter larger than that of the inlet hole 11, typically the end of the inlet hole. The bending member 23 is shaped so that the connecting member 19 bends and/or expands at a desired point.

Fig 13 shows a third embodiment of the invention. The pile assembly 1 is similar to that shown in figs. 11 and 12, except the locking member 7, the connecting member 19 and the bending member 23 have different structures.

The locking member 7 is tubular. The locking member 7 comprises the inlet part 8 with the inlet hole 11. The locking chamber 16 extends from the second end 13 of the inlet hole 11. The inner width or inner diameter of the locking chamber 16 bottom is larger than the diame- ter/width of inlet hole (11) , typically 1.2-1.8 times larger. The inlet hole 11 and the locking chamber 16 may have round cross-sections. The end of the locking chamber 16 is closed with a plate.

The connecting member 19 may be a round bar, such as a solid axle. The connecting member 19 comprises a bore 25 extending from the first end at least to the middle of the inlet hole 11 in the lengthwise direction of the connecting member 19. In case where the pile member 3 is the second pile , the connecting member 19 has a bore 25 at both ends . The bore 25 is conical . The bending member 23 may be cylindrical in shape . The bending member 23 may be attached to the end of the connecting member 19 e . g . by gluing . Alternatively, the bending member 23 may be attached to the end of the connecting member 19 using a seal , such as a plastic seal . The space between the bore 25 end and the bending member 23 may be filled with void sealer or grout . The locking chamber 16 may be conical in shape .

In the embodiment shown in fig . 13 the bending member enters the bore 25 of the connecting member 19 and thus bends and expands the connecting member 19 against the surface of the inlet hole 11 and/or the conical inner surface of the locking chamber 16 . The bending member 23 expands the connecting member 19 to a diameter larger than that of the inlet hole 11 , typically the end of the inlet hole 11 . The bending member 23 and/or the bore 25 is shaped so that the connecting member 19 bends and/or expands at a desired point .

In the second and third embodiments the locking member 7 may comprise reinforcement bar ( s ) for attaching the locking member 7 to the concrete of the pile 2 and/or second pile . The reinforcement bars are attached to the outer surface of the locking member 7 . The reinforcement bars extend in the longitudinal direction of the pile 2 and/or second pile .

In all the above embodiments , the combined tensile strength of the connecting members 19 inserted into locking members 7 of the pile j oint 8 is at least equal to the combined tensile strength of the longitudinal reinforcement bars 9 of the pile 2 . In all the above embodiments the locking chamber 16 may be filled with a void sealer or grout , which fills gaps between the connecting member 19 and the inlet hole 11 during the mounting of the connecting member 7 and thus prevents water from entering the locking member 7 . Hardening agent may be applied to outer surfaces of the connecting member 19 . The hardening agent hardens the void sealer or grout after the mounting of the connecting member 19 .

In all the above embodiments there is a clearance between the inner surface of the inlet hole 11 and the outer surface of connecting member 19 . The clearance is 1 to 5 mm, typically 1 . 5 to 3 mm. Thus , the connecting member 19 is in the upright position during the installation . A slight inclination of the connecting member 19 is possible because the edges of the first end of the inlet hole 11 and the first and second ends of the connecting member 19 are chamfered .

The pile assembly 1 according to the invention may be formed as follows . The pile j oint 6 , i . e . the locking member ( s ) 7 , end plate 17 and/or the collar 18 , are installed in a pile mould before casting with concrete . After casting and curing of the concrete , the pile j oint 8 is connected to the end of the pile 2 .

In case the pile member 3 is the second concrete pile , the end of the second pile is also provided with a similar pile j oint 8 as the end of the pile 2 . The pile 2 is first driven into soil using a pile driver . When the pile 2 is at a desired depth, the ends of the pile and the second pile are connected to each other . The connecting members 19 are first inserted into the locking chambers 16 at the end of the pile 2 . Thereafter, the end of the second pile is lowered towards the end of the pile 2 so that the second ends of connecting members 19 enter the locking chambers of the pile j oint at the end of the second pile . The bending members 23 bend and expand the connecting members 19 . This is achieved by applying the weight of the second pile and/or the weight of the pile hammer to the connecting members 19 . When the end plates 17 of the pi le and the second pile are against each other, the connecting members 19 are bent and/or expanded against the surfaces of the inlet holes 11 and/or inner surfaces of the locking chambers 16 of both pile j oints 6 . Thus , the pile ends cannot be separated from each other . The second pile may have a similar cross-sectional shape and reinforcing structure as the pile 2 .

Before as sembly of concrete pi le 2 to the second pile , the length of the connecting member 19 plus two bending members 23 is 14-24 mm longer than the sum of two inlet hole 11 lengths and two locking chamber 16 lengths .

As shown in fig . 14 , the rock shoe 26 comprises a bottom plate 27 and a tip part 28 attached to the bottom plate 27 . The rock shoe 26 may further comprise support plates

29 configured to support the tip part 28 . The support plates 29 are attached to the bottom plate 27 . The rock shoe 26 may further comprise a frame collar 30 attached to the bottom plate 27 .

I f the pile member 3 is a rock shoe 26 , the second ends of connecting members 19 are attached to the bottom plate 27 of the rock shoe e . g . by welding . The connecting member 19 and the tip part 28 are attached to the opposite surfaces of the bottom plate 27 . The frame collar

30 encloses the connecting members 19 . The end of the pi le 2 is inserted into the frame collar 30 . The frame collar 30 comprises guide openings 31 through which the connecting members 19 can be guided and/or monitored . The rock shoe 26 is placed in a vertical position so that the connecting members 19 extend upwards from the bottom plate 27. The pile 2 is lowered toward the bottom plate 27 so that the ends of connecting members 19 enter the locking chambers 16 of the pile joint 6 at the end 5 of the pile 2. When the end plate 17 and the bottom plate 27 are against each other, the connecting members 19 are bent and/or expanded against the surfaces of the inlet holes 11 and/or inner surfaces of the locking chambers 16 of the pile joint 6. Alternatively, the rock shoe 26 may be attached to the end of horizontal pile using a stopper and a pressing machine.

As shown in fig. 14, the bottom plate 27 may comprise two plate parts, i.e. a lower bottom plate 27.1 and an upper bottom plate 27.2 placed against each other. The connecting members 19 are attached to the lower bottom plate 27.1 and an upper bottom plate 27.2 is placed against the lower bottom plate 27.1 so that the upper bottom plate 27.2 covers weld seams of the connecting members 19. The upper bottom plate 27.2 comprises holes through which the connecting members 19 extend. The edges of the holes of the upper bottom plate 27.2 may be chamfered. The upper bottom plate 27.2 is made of steel, nylon or any other suitable material having a sufficient compression strength.

If the bottom plate 27 comprises only one plate part, the connecting members 19 may be attached to the bottom plate 27 by full penetration butt welding.

Before assembly of concrete pile 2 to the rock shoe 3, the length of the part of the connecting member 19 above the bottom plate 27 plus the length of one bending member 23 is 7-12 mm longer than the sum of one inlet hole 11 length and one locking chamber 16 length. It is obvious to a person ski lled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways . The invention and its embodiments are thus not limited to the examples described above , instead they may vary within the scope of the claims .