Pile-driver and method for application thereof

Abstract

The present invention relates to a pile-driver, comprising a support member arranged or arrangeable in transverse direction at or on a pile, a liquid chamber which is bounded on the underside by the support member and which further comprises one or more side walls and is configured to receive a liquid therein, one or more pressure build-up chambers, an ignition mechanism configured to ignite a fuel present in the combustion space, and wherein the combustion space is configured to expand fuel present therein during combustion such that a pressure build-up takes place above the support member and the liquid present above the support member in the liquid chamber is displaced at least in upward direction away from the support member, whereby a downward force is exerted on the pile via the support member. The invention further relates to a method for driving a pile downward into the ground using such a pile-driver.

Claims

1. A pile-driver, comprising: a support member arranged or arrangeable in transverse direction at or on a pile; a liquid chamber which is bounded on the underside by the support member and which further comprises one or more side walls and is configured to receive a liquid therein; one or more pressure build-up chambers, comprising: an upper part enclosing a combustion space; a lower part provided with one or more passage openings which are in fluid connection with the liquid chamber; an ignition mechanism configured to ignite a fuel present in the combustion space; and wherein the combustion space is configured to expand fuel present therein during combustion such that a pressure build-up takes place above the support member and the liquid present above the support member in the liquid chamber is displaced at least in upward direction away from the support member, and a downward force is exerted on the pile via the support member.

2. The pile-driver as claimed in claim 1, wherein the pressure build-up chamber forms a rigid housing.

3. The pile-driver as claimed in claim 1, wherein the one or more pressure build-up chambers are attached inside the liquid chamber to the support member.

4. The pile-driver as claimed in claim 1, wherein the one or more side walls of the liquid chamber separate the liquid from the surrounding area.

5. The pile-driver as claimed in claim 1, wherein the liquid present above the support member in the liquid chamber is water.

6. The pile-driver as claimed in claim 1, further comprising: a fuel supply channel for carrying fuel into the combustion space; and a combustion product discharge channel for discharging combustion products after combustion.

7. The pile-driver as claimed in claim 1, wherein: at least a closure is provided which, together with the support member and the one or more side walls, forms a liquid chamber with a volume closed in substantially gas-tight manner; and supply means are provided for the purpose of thereby carrying a fluid into and/or out of the substantially gas-tight liquid chamber.

8. The pile-driver as claimed in claim 7, wherein the fluid is air and/or water.

9. The pile-driver as claimed in claim 1, wherein a plurality of pressure build-up chambers are provided which each comprise an ignition mechanism, and wherein control means are further provided which are configured to ignite the fuel in the one or more pressure build-up chambers in a predetermined sequence and/or at predetermined intervals.

10. The pile-driver as claimed in claim 1, wherein control means are provided which are configured to inject extra fuel into a combustion space during the combustion of the fuel to vary the moment of ignition.

11. The pile-driver as claimed in claim 1, wherein at least one opening, with a pressure-relief valve, is provided in or under the support member.

12. The pile-driver as claimed in claim 11, wherein the opening is variable and control means are provided with which the size of the opening can be controlled.

13. The pile-driver as claimed in claim 1, wherein the combustion space is in gas connection with an underpressure space which is configured to suction combustion products released during combustion out of the combustion space.

14. The pile-driver as claimed in claim 1, wherein the pile-driver is integrated into the pile which forms with its side wall a side wall of the liquid chamber.

15. A method for driving a pile downward into the ground, comprising the steps of: arranging a support member in transverse direction at or on a pile; receiving a liquid in a liquid chamber which is bounded on the underside by the support member; supplying a fuel to a pressure build-up chamber, wherein the pressure build-up chamber comprises: an upper part enclosing a combustion space; and a lower part provided with one or more passage openings which are in fluid connection with the liquid chamber; wherein a quantity of gas builds up in the upper part of the pressure build-up chamber when fuel is supplied to the pressure build-up chamber and thereby presses the liquid away downward in the pressure build-up chamber; bringing the fuel located above the liquid level in the pressure build-up chamber to combustion using an ignition mechanism, whereby an expansion takes place; displacing by means of the expansion at least some of the liquid and/or combustion products present in the pressure build-up chamber from the pressure build-up chamber via the fluid connection to the liquid chamber; whereby a pressure build-up takes place above the support member and whereby the liquid located above the support member in the liquid chamber is also displaced at least in upward direction away from the support member; and driving the pile downward into the ground with the downward reaction force exerted on the pile.

16. The method as claimed in claim 15, further comprising the steps of: carrying fuel into the combustion space of the pressure build-up chamber through a fuel supply channel; combusting the fuel in the pressure build-up chamber using the ignition mechanism; discharging combustion products through a combustion product discharge channel after combustion; and repeating these steps in order to drive the pile stepwise into the ground.

17. The method as claimed in claim 16, further comprising the step of injecting extra fuel into the combustion space during combustion of the fuel.

18. The method as claimed in claim 15, wherein at least a closure is provided which, together with the support member and the one or more side walls, forms a liquid chamber with a volume closed in substantially gas-tight manner; and comprising the step of carrying a fluid into and/or out of the substantially gas-tight liquid chamber using a supply means.

19. The method as claimed in claim 18, wherein the fluid is air and brings about a pre-pressure.

20. The method as claimed in claim 18, wherein the fluid is water and provides a reaction mass.

21. The method as claimed in claim 15, wherein the combustion space is in gas connection with an underpressure space and the method comprises the step, almost immediately after a combustion, of suctioning out of the combustion space the combustion products formed therein by the combustion, so that these combustion products are at least substantially removed from the combustion space before the medium displaced in upward direction by the combustion drops back and collides once again with the support member.

22. The method as claimed in claim 15, wherein a pile-driver according to claim 1 is applied.

Description

(1) Preferred embodiments of the present invention are further elucidated in the following description with reference to the drawing, in which:

(2) FIG. 1 shows a view of an offshore wind turbine on a monopile construction;

(3) FIG. 2 shows a schematic view of the operating principle at three successive stages A, B and C;

(4) FIGS. 3A-3E are detailed cross-sectional views of the support member of the device shown in FIG. 2;

(5) FIG. 4 is a schematic view of the transmission of forces in a conventional pile-driver;

(6) FIG. 5 is a schematic view of the transmission of forces in a pile-driver according to the invention;

(7) FIG. 6 shows a graph in which a typical force curve of the pile-drivers of FIGS. 4 and 5 is plotted;

(8) FIG. 7 is a schematic view of three successive stages A, B and C when drilling-out is desired;

(9) FIG. 8 is a schematic view of an extra-powerful pressure build-up;

(10) FIG. 9 shows an alternative embodiment wherein the connections for the various conduits are arranged in a unit outside the liquid chamber of the pile-driver and are connected to the pressure build-up chamber via a feed channel;

(11) FIG. 10 shows an alternative embodiment wherein the pressure build-up chamber is arranged outside the liquid chamber of the pile-driver; and

(12) FIG. 11 shows a further alternative embodiment for deepwater pile-driving.

(13) The offshore wind turbine 36 shown in FIG. 1 is a so-called monopile construction and comprises a pile 2 which is driven fixedly into the ground 40, formed by the seabed, below water level 38.

(14) The operating principle of fixedly driving the wind turbine construction 36 of FIG. 1 is shown schematically in FIG. 2 using stages A, B and C. Arranged on pile 2 is a pile-driver 1 in the form of a pile hammer 3. This pile hammer 3 has a bottom plate part, which functions as support member 8, and a side wall 4. Support member 8 and side wall 4 together form a liquid chamber 5 in which a water column 42 is received (stage A). Bringing a fuel mixture 29 to combustion in a pressure build-up chamber 14 brings about an expansion which generates a homogenous pressure build-up above support member 8 which drives pile 2 downward into ground 40. Water column 42 is moreover displaced upward (stage B). According to Newton's third law the upward displacement of water column 42 is accompanied by an equal and opposite reaction force, which displaces pile 2 in downward direction. When it drops back this water column 42 will moreover come down onto support member 8 and thus exert a downward force on pile 2 which drives the pile further downward into the ground.

(15) It is noted that the operating principle in FIG. 2 is shown on enlarged scale. In stage C pile 2 has already been driven over some downward distance into ground 40.

(16) The different stages of the operating principle will now be elucidated in more detail with reference to FIGS. 3A-3E.

(17) FIG. 3A shows a starting situation in which a water column 42 is present in liquid chamber 5. Liquid chamber 5 is bounded by support member 8 and side wall 4 of pile-driver 1. Although other media are likewise suitable, use is preferably made of the medium water, which is available in abundance offshore. Reference is therefore made in this application to a water column 42.

(18) A fuel mixture is introduced via a fuel supply channel 30 and an oxygen supply channel 31 into the combustion space enclosed by the upper side of the pressure build-up chamber (FIG. 3B). This gas mixture presses the water present in the pressure build-up chamber 14 downward and, via passage openings 26 arranged in the lower part of the pressure build-up chamber 14, outward from the volume enclosed by the pressure build-up chamber 14 into water column 42. The water level of water column 42 will hereby rise to some extent.

(19) If desired, the fuel supply channel 30 supplies a fuel mixture, in which case the oxygen supply channel may be unnecessary. It is even possible to envisage there being a single channel which alternately fulfils the function of the fuel supply channel 30 and that of a combustion gas discharge channel 32 to be discussed below.

(20) When the fuel mixture 29 present in combustion space 22 is ignited with an ignition mechanism 28 (FIG. 3C), an expansion will take place in a very short time which will also displace a large part of the water still present in the pressure build-up chamber 14 via passage openings 26 to the water column 42 outside pressure build-up chamber 14. This results in an increased homogeneous pressure above support member 8, whereby a downward force is exerted on pile 2 which is driven further into ground 40. The effect of water column 42 displacing upward and dropping back again onto support member 8 already mentioned with reference to FIG. 2 will also occur. This will drive pile 2 further into ground 40.

(21) It is possible to envisage some of fuel mixture 29 being ignited outside the pressure build-up chamber 14 and displacing in burning state via the fuel supply channel 30 to the pressure build-up chamber 14, and bringing to combustion the fuel mixture 29 already present in combustion space 22.

(22) The water level inside the pressure build-up chamber 14 ideally remains slightly above passage openings 26 during the expansion phase so that only water is displaced from the pressure build-up chamber 14 via the passage openings to the space outside the pressure build-up chamber. This guarantees that pile-driver 1 will quickly be operational again for a subsequent combustion cycle, which will be further elucidated with reference to FIG. 8.

(23) Combustion products 33 are formed in combustion space 22 by the combustion process of fuel mixture 29 (FIG. 3D). These combustion products 33 are discharged using a combustion gas discharge channel 32 (FIG. 3E). The water level in pressure build-up chamber 14 will rise and, as soon as water flows into the combustion gas discharge channel 32, the combustion products 33 are fully discharged from upper part 24 of pressure build-up chamber 14. The system will then be in the situation of FIG. 3A and is ready for a subsequent combustion cycle.

(24) The combustion products can be removed from combustion space 22 before water column 42 displaced in upward direction by the expansion drops back and once again collides with support member 8. The falling water column 42 does not hereby come down onto a gas spring but collides with support member 8. The downward force exerted by the falling water column 42 on support member 8 can hereby be utilized almost wholly for the purpose of driving pile 2 downward into the ground.

(25) As a pile 2 is driven deeper into ground 40, pile 2 will obtain more stability and be able to bear more mass. The total pile-driving resistance encountered by pile 2 is the sum of the point resistance and the shaft friction resistance. The shaft friction resistance increases as a greater part of pile 2 is driven into ground 40. Since this situation is also associated with a pile 2 which has already obtained some stability, the height of water column 42 in liquid chamber 5 can be increased.

(26) The transmission of forces in a conventional pile-driver (FIG. 4) is much more concentrated than in the pile-driver 1 according to the invention (FIG. 5). In a conventional pile-driver steel-to-steel contact takes place, wherein a striker plate 7 is struck. This is accompanied by considerable noise production and high peak forces, whereby such as striker plate 7 must take a very heavy form. In pile-driver 1 according to the invention however, a homogenous pressure build-up takes place above support member 8. Because much less plastic deformation occurs according to the invention, a much thinner and lighter plate can be applied for support member 8.

(27) FIG. 6 shows a graph which plots a typical force curve of the conventional pile-driver shown in FIG. 4 (line 54) and the pile-driver 1 shown in FIG. 5 (line 56). Shown clearly here in the case of pile-driver 1 according to the invention is that the profile has a longer pulse duration, whereby the pile-driving process is quieter, more descent is achieved per stroke and lower tensile forces occur. Because there is more descent per stroke, fewer strokes are necessary, this placing the pile under less fatigue load during pile-driving. The build-up of force is moreover more gradual and, in the case of for instance a monopile, this allows components arranged thereon to be applied without the risk of them breaking off during driving. The longer pulse duration ensures that tensile stress waves occurring in the material are smaller, whereby it is even possible to drive concrete piles.

(28) Water column 42 is separated from the surrounding area by a separating wall 4. In the embodiment in which pile-driver 1 is integrated into pile 2, the inner wall of pile 2 forms this separating wall 4 (FIG. 7).

(29) If the pile-driver is integrated into pile 2, support member 8 preferably rests on protrusions or inner edge 6 which is arranged on inner wall 4 of pile 2 and which provides a local narrowing (stage A). Support member 8 is in this way temporarily removable from pile 2 (stage B), for instance by attaching a chain 46 to eye 34 and hoisting the whole. Pile 2 can then be drilled out using a drill 48, which may be necessary in the exceptional situation that the shaft resistance cannot be overcome with combustions according to the operating principle of the invention. After the soil has been drilled out of pile 2, support member 8 with the one or more pressure build-up chambers 14 can be re-placed (stage C).

(30) It is however noted that the above stated situation will probably be a rare occurrence, since pile-driver 1 according to the invention is also suitableif necessaryfor carrying out stronger combustions. The combustion space 22 enclosed by pressure build-up chamber 14 is for this purpose filled to the point that during expansion not only water but also combustion gases 33 are displaced via passage openings 26 out of the volume enclosed by pressure build-up chamber 14 to the space outside pressure build-up chamber 14 (FIG. 8). The combustion space is in this way temporarily made larger.

(31) A drawback is that combustion gases will get into the water column 42 of pile-driver 1, with the result that owing to the gas the driving mass will acquire some compressibility. The desired incompressibility of the water column is restored by allowing the gas time to rise through the water column. This takes time however, whereby these stronger combustions are preferably utilized only when necessitated by the shaft resistance.

(32) According to an alternative embodiment, the connections for the various supply channels 30, 31, 32 and ignition mechanism 28 are arranged in a unit 58 outside liquid chamber 5 of pile-driver 1. A feed channel 60 extending through wall 4 of pile-driver 1 provides the connection to pressure build-up chamber 14. Because unit 58 and all connections of supply channels 30, 31, 32 and ignition mechanism 28 are arranged outside liquid chamber 5, these components are easily accessible.

(33) It is also possible to envisage the pressure build-up chamber 14 being arranged outside liquid chamber 5 of pile-driver 1 (FIG. 10). One or more passage openings 26 in the wall of pressure build-up chamber 14 are in that case brought into fluid connection with liquid chamber 5 via a feed channel 50. In this embodiment support member 8 can itself be provided with an eye 10 so that it can be lifted from inner edge 6 using a chain should it be necessary to drill out pile 2.

(34) In a particularly advantageous embodiment in which pile 2 and pile-driver 1 are integrated, at least one opening (not shown) with a pressure-relief valve is provided in the support member 8 itself or, if desired, under support member 8 in the wall of pile 2. Overpressure occurring under support member 8 during pile-driving can escape through this opening from the space enclosed by support member 8, the inner wall of pile 2 and the ground 40. The opening provides a restrictive passage with which the outflow speed can be regulated. The descent speed of pile 2 as a result of an impact can hereby also be limited, whereby the opening reduces the chance of undesired shock load on the crane.

(35) FIG. 11 shows an alternative embodiment for deepwater pile-driving, wherein the shown tube segment 52 can be coupled to other similar tube segments in order to reach a great depth. The operating principle is identical to that described above, and will not therefore be further elucidated. It is however noted that reservoirs 52, 54 contain respectively oxygen and hydrogen. The chemical reaction during combustion produces water as end product, which can be added without problem to water column 42. If desired, the embodiment of FIG. 11 enables pile-driver 1 to comprise one or more fully closed tubes segments 52, which can result from tube segment parts 52 being coupled to each other. A self-driving, submersible pile-driver 1 can moreover be constructed in this way.

(36) Provided according to a further preferred embodiment (not shown) on the upper side of pile-driver 1 is a closure which, together with support member 8 and the inner wall 4 of pile-driver 1, encloses a volume closed in substantially gas-tight manner. With a pump air and/or water can be introduced into this closed volume, whereby the pressure build-up profile resulting from the combustion of the fuel mixture in combustion space 22 can be optimized for driving pile 2 downward into ground 40. The height of water column 42 can on the one hand be adjusted, and the desired pre-pressure resulting from the quantity of air present in the closed volume can on the other hand be adjusted so as to optimize the desired pressure build-up.

(37) Although they show preferred embodiments of the invention, the above described embodiments are intended solely to illustrate the present invention and not to limit the scope of the invention in any way. When measures in the claims are followed by reference numerals, such reference numerals serve only to contribute toward understanding of the claims, but are in no way limitative of the scope of protection. It is particularly noted that the skilled person can combine technical measures of the different embodiments. The described rights are defined by the following claims, within the scope of which many modifications can be envisaged.