Pile driving assembly and a follower

Abstract

A pile driving assembly for installing a pile in an underwater bottom comprises a tubular pile and a hammer for driving the pile into an underwater bottom. The assembly is provided with a soil remover for removing soil inside the pile. The soil remover is located below the hammer and remote from a lower end of the pile in assembled operating condition.

Claims

1. A pile driving assembly for installing a pile in an underwater bottom, comprising, a hammer configured to drive the pile into the underwater bottom, a soil remover configured to remove soil from inside the pile, wherein the soil remover is located below the hammer and remote from a lower end of the pile in an assembled operating condition, a follower having a tubular transmission portion configured to transmit hammering energy from the hammer to the pile, wherein the follower supports the weight of the soil remover in the pile, and wherein the soil remover is displaceable with respect to the transmission portion in at least a longitudinal direction of the pile.

2. The pile driving assembly according to claim 1, wherein the soil remover is located at an upper end portion of the pile.

3. The pile driving assembly according to claim 2, wherein the upper end portion of the pile has a length of less than 50% of the length of the pile.

4. The pile driving assembly according to claim 2, wherein the soil remover has a centring element fitting to the pile.

5. The pile driving assembly according to claim 2, wherein the upper end portion of the pile has a length of less than 25% of the length of the pile.

6. The pile driving assembly according to claim 1, wherein the soil remover comprises a fluid jet.

7. The pile driving assembly according to claim 1, wherein the assembly further comprises a soil discharger configured to discharge removed soil from the inner side of the pile to the outer side thereof.

8. The pile driving assembly according to claim 7, wherein the soil discharger comprises a through-hole in the follower through which removed soil is discharged.

9. The pile driving assembly according to claim 1, wherein the follower slidably fits into the pile and the fluid jet is located such that the fluid is pressed between an outer circumference of the follower and an inner wall of the pile.

10. A follower for transmitting hammering energy from an anvil of a pile driver to a tubular pile to be inserted into a bottom, comprising: a tubular transmission portion removably coupled to the tubular pile, the tubular transmission portion including an anvil contact surface configured to receive hammering energy from the anvils and a soil remover configured to remove sediment inside the pile, wherein the tubular transmission portion supports the weight of the soil remover from above and the soil remover is displaceable with respect to the transmission portion in at least a longitudinal direction thereof, and wherein soil remover is located below the anvil contact surface.

11. The follower according to claim 10, wherein the soil remover comprises a centring element to be fit to a pile for positioning the soil remover to the pile.

12. The follower according to claim 11, wherein the centring element is slidable with respect to the transmission portion in longitudinal direction thereof.

13. The follower according to claim 12, wherein the centring element has such a circumference that it slidably fits in a tubular pile.

14. The follower of claim 13 wherein the centring includes a bush.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Aspects of the invention will hereafter be elucidated with reference to very schematic drawings showing embodiments of the invention by way of example.

(2) FIG. 1 is a side view and a partly sectional view of an embodiment of a pile driving assembly, showing the assembly in assembled operating condition at the beginning of driving a pile into the bottom.

(3) FIG. 2 is a similar view as FIG. 1, but showing the assembly at the end of driving the pile into the bottom.

(4) FIG. 3 is a similar view as FIG. 2, but showing a disassembled condition.

(5) FIG. 4 is a perspective view of a part of the embodiment as shown in FIG. 1 on a larger scale.

(6) FIG. 5 is a plan view of the embodiment as shown in FIG. 4.

(7) FIG. 6 is an enlarged sectional view along the line VI-VI in FIG. 5.

(8) FIG. 7 is an enlarged sectional view along the line VII-VII in FIG. 5.

(9) FIG. 8 is an enlarged sectional view along the line VIII-VIII in FIG. 4.

(10) FIG. 9 is a similar view as FIG. 6, but showing the follower as a separate unit.

(11) FIG. 10 is a similar view as FIG. 9, but showing an alternative embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT

(12) FIG. 1 shows an embodiment of a pile driving assembly 1. The pile driving assembly 1 is shown in assembled operating condition in a situation at a site where a tubular pile 2 must be installed in an underwater bottom B. The water level is indicated by reference sign S in FIG. 1. In this case the pile 2 has a circular cross-section. Its diameter may be 2.5 m and its length may be 40 m, for example, but numerous alternative dimensions are conceivable.

(13) The embodiment of the pile driving assembly 1 as shown in FIGS. 1-8 comprises the pile 2, a hammer in the form of a hydraulic driver 3 for driving the pile 2 into the bottom B and a soil remover 4 for removing sediment within an upper portion of the pile 2 during a final period of driving the pile 2 into the bottom B. The hydraulic driver 3 is connectable to a power pack on board of a surface vessel (not shown). The hydraulic driver 3 can be hoisted by a hoisting device such as a crane (not shown), which is for example placed on the surface vessel. During a first period of driving, the sediment within the pile 2 substantially remains at its initial level with respect to the rest of the bottom B as shown in FIG. 1. When the upper portion of the pile 2 approaches the bottom B the soil remover 4 will start to remove bottom material within the pile 2 as illustrated in FIG. 2.

(14) In the final position of the pile 2 its upper end is still at a distance above the bottom B. However, due to the relative position of the soil remover 4 in the pile 2 the level of the bottom material inside the pile 2 has become lower than outside the pile 2, which is illustrated in the disassembled condition according to FIG. 3.

(15) The pile 2 is driven into the bottom B by the hydraulic driver 3. FIGS. 2 and 3 show a final stage of driving the pile 2 into the bottom B. In a next step (not shown) a leg of a jacket, for example for a wind turbine, can be placed within the upper portion of the pile 2, after which grout may be added to the pile 2 in order to secure the jacket leg to the pile 2. Other applications are conceivable for using the pile 2 of which the upper portion is free from bottom material.

(16) FIGS. 4-8 show the pile driving assembly 1 in more detail. FIGS. 6 and 7 show an anvil 5 at the lower part of the hydraulic driver 3. The anvil 5 rests on an upper side of a follower 6. The follower is depicted in FIG. 9 as a separate unit. The follower 6 has a tubular transmission portion 6A which rests on the upper end of the pile 2. The upper side of the transmission portion 6A constitutes an anvil contact surface for receiving hammering energy from the anvil 5. Under operating conditions the transmission portion 6A transmits hammering energy from the anvil 5 to the pile 2. The lower part of the hydraulic driver 3 is provided with a tubular sleeve 7 which surrounds the anvil 5 and a part of the follower 6. The sleeve 7 comprises a number of pins 8 at its circumference which protrude at its inner wall for supporting a circumferential protrusion 8A of the transmission portion 6A upon lifting the follower 6 by the sleeve 7, for example in case of removing the hydraulic driver 3 from the pile 2 after finishing the driving action. During driving the pile 2 into the bottom B there is a vertical distance between the pins 8 and the protrusion 8A in order to avoid transmission of hammering energy directly to the sleeve 7 via the pins 8.

(17) The follower 6 comprises a centring element 9 which fits closely in the pile 2. The centring element 9 has a fixed position with respect to the transmission portion 6A of the follower 6 in radial direction and serves to position the transmission portion 6A easily onto the pile 2 before hammering, on the one hand, and to position the soil remover 4 at the correct position, on the other hand. The centring element 9 has radial plates 10 surrounded by a bush which fits slidably in the pile 2. The centring element 9 suspends from a horizontal pipe 11 at the top of the follower 6 via cables 12. Lower sections of the plates 10 which are located inside the surrounding bush are fixed to the bush at their radial outer ends, whereas upper sections of the plates 10 which protrude above the bush can slide along the inner wall of the transmission portion 6A in longitudinal direction thereof. As a consequence, the bush has a substantially fixed position with respect to the transmission portion 6A in radial direction thereof, but it is displaceable with respect to the transmission portion 6A in vertical direction due to its suspension by means of the cables 12.

(18) In the embodiment as shown in the figures, the soil remover 4 of the pile driving assembly 1 is integrated in the follower 6. The soil remover 4 comprises a fluid jet having high pressure jet nozzles 13 for electing a fluid into the bottom material inside the pile 2. This cuts and dislodges the bottom material. The jet nozzles 13 and their fluid supply lines are mounted to the radial plates 10. The fluid can be supplied from outside via the pipe 11 extending through holes in the sleeve 7 and the transmission portion 6A as shown by arrows in FIG. 6. Since the centring element 9 is vertically displaceable with respect to the transmission portion 6A of the follower 6 there is a flexible coupling 14 to absorb movements between the fluid supply lines to the jet nozzles 13 and the pipe 11.

(19) The jet nozzles 13 project below the bottom side of the surrounding bush of the centring element 9 and are positioned in a conical arrangement. This creates a conical shape in the bottom material inside the pile 2 as shown in FIG. 3. The soil remover 4 can be operated during pile driving and started when the upper portion of the pile 2 approaches the bottom B.

(20) The embodiment of the pile drying assembly 1 as shown in the figures is also provided with a soil discharger for discharging removed soil from the inner side of the pile 2 to the outer side thereof. The soil discharger comprises a discharge tube 15 extending upwardly at the centre of the follower 6 from its entrance at the bottom side of the follower 6. At the transmission portion 6A of the follower 6 the discharge tube 15 bends towards the circumferential outer side of the sleeve 7 and runs through respective holes in the transmission portion 6A and the sleeve 7 to a suction device (not shown). Alternatively, a pump at its inlet at the follower 6 may be applied. Similar to the fluid supply lines, the flexible coupling 14 also allows movements between the horizontal pipe 11 and the vertical discharge tube 15.

(21) FIG. 10 shows an alternative embodiment of the follower 6, in which the jet nozzles 13 of the soil remover 4 are located at the surrounding bush of the centring element 9. The jet nozzles 13 are directed such that during pile driving fluid is pressed between the bush of the centring element 9 and the pile 2. This avoids accumulation of soil material between the follower 6 and the pile 2 which simplifies removal of the follower 6 from a pile 2 after the pile 2 has been installed. It is noted that the fluid jet nozzles 13 at the circumference of the follower 6 can be applied independently from the presence of jet nozzles 13 at the bottom of the follower 6 and of the discharge tube 15, such as described in the embodiment of the pile driving assembly and the follower as shown in FIGS. 1-9.

(22) From the foregoing, it will be clear that the invention provides an efficient pile driving assembly because of the possibility of removing sediment from the upper portion of the pile during driving that portion into the bottom.

(23) The invention is not limited to the embodiments shown in the drawings and described hereinbefore, which may be varied in different manners within the scope of the claims and their technical equivalents.