Liquid jetting device

Abstract

Liquid jetting device (10) for excavating soil during installation of a structure (100). The liquid jetting device (10) comprising a nozzle (20) and a first liquid channel (14) for feeding a primary liquid flow (18) to the nozzle (20) for forming a liquid jet (24) in a first direction. The first direction along a centreline (26) of the nozzle (20). The jetting device (10) further comprising one or more second liquid channels (16) for feeding a respective secondary liquid flow (28) into the liquid jet (24) for deflecting the liquid jet (24) at a deflection angle away from a centreline (26) of the nozzle (20).

Description

[0001] The present invention concerns a liquid jetting device, and particularly a liquid jetting device for excavating soil during installation of a foundation. The foundation can be any permanent or temporary structure that is buried into the ground for supporting a structure above. For example, the present disclosure is particularly relevant to foundations including: a pile, a tubular pile, a monopile, a jacket pile, a suction bucket / caisson foundation and suction anchor, a skirted foundation, a sheet wall, and a berthing dolphin. The present disclosure is also relevant to other foundation structures including other types of temporary and permanent shallow or deep structures, that may be inserted into a soil when installing an above ground structure such as a building, a wall, an onshore / offshore structure, and a wind turbine. The present invention is particularly suited to offshore foundations, and more particularly to open ended tubular foundation types, such as monopiles, jacket piles and suction buckets, and especially for offshore wind turbine foundations.

[0002] Offshore foundations are typically installed by forcing the body of the foundation into the ground using a pile hammer to apply a series of axial impacts for driving the foundation down into the soil in an insertion direction. Once installed, the foundation is axially supported by the friction applied to the lateral surfaces of the structure's body and the resistance to further penetration at the foundation structure's toe.

[0003] During installation, the toe at the distal end of the foundation displaces soil as it is driven down. This compresses the soil in the surrounding region. However, as the structure is driven deeper, and pressure increases, the forces required to continue displacing soil at the structure's toe also increase. At the same time, the surface area of the structure in contact with the soil increases, leading to an increase in the shear forces required to overcome the frictional resistance to driving. As a result, the bearing resistance increases as the foundation is installed deeper into the soil.

[0004] In recent years, there has been a trend towards having larger foundations, such as monopiles, and this has exacerbated the above challenges of their installation. For example, higher impact forces and / or a higher number of hammer strikes are required for pile driving larger structures. This in turn imposes significant failure resistance requirements on the foundation. At the same time, the noise generated by the larger impacts is also increased, which presents significant environmental and safety hazards.

[0005] In view of the above, various methods and systems have been proposed for making the installation of such foundations easier. For example, in a previous innovation by the applicant, foundations have been fitted with nozzles at their distal end for jetting into the soil ahead of the toe to create space and mitigate the compaction of soil as the foundation is driven. However, as soils are typically nonhomogeneous, the effectiveness of the jetting nozzles may be compromised as the foundation is driven through different soil layers. For example, when the toe of the foundation is driven down, it may pass through regions of soil comprising rocks or dense aggregates which restrain its advance and aren't effectively displaced by the jets. Equally, in softer soil layers, the jets may cause an unduly wide gully to be formed, which can compromise the eventual load bearing capacity of the foundation by disturbing too much of the adjacent soil structure.

[0006] The present invention therefore seeks to address the above issues.

[0007] According to a first aspect of the present invention, there is provided a liquid jetting device for excavating soil during installation of a structure as defined in claim 1 hereinafter. The liquid jetting device comprises: a nozzle; a first liquid channel for feeding a primary liquid flow to the nozzle for forming a liquid jet in a first direction, the first direction being along a centreline of the nozzle; and one or more second liquid channels for feeding a respective secondary liquid flow into the liquid jet for deflecting the liquid jet at a deflection angle away from the centreline of the nozzle.

[0008] In this way, a liquid jetting device is provided in which the direction of the liquid jet can be changed without movement of the liquid jetting device itself. That is, the liquid jet can be deflected by momentum transfer between each one of the one or more secondary liquid flows and the primary liquid flow. Accordingly, the liquid jet can be deflected away from the centreline of the nozzle. Advantageously, the liquid jet can be used to excavate soil during installation of a structure, such as a foundation. For example, the liquid jet can be deflected in response to changes in the soil type to vary the channel eroded by the jetting action. As such, the width of the cavity formed by the excavated soil directly below and around a toe of the structure can be varied in order to optimise installation.

[0009] In embodiments, the liquid jetting device further comprises a pressurised fluid supply for supplying pressurised fluid to the liquid jetting device. In this way, the flow rate of the primary and secondary liquid flow can be controlled to determine the overall flow rate of the liquid jet from the liquid jetting device.

[0010] In embodiments, the liquid jetting device further comprises a controller for controlling a fluid pressure of the pressurised fluid supplied to the liquid jetting device. In this way, the flow rate of the primary and secondary liquid flow can be controlled by the controller for adjusting the amount of deflection of the liquid jet.

[0011] In embodiments, respective pressurised fluid supplies are provided for each one of the first liquid channel and the one or more second liquid channels. In this way, the flow rate of the primary and secondary liquid flows can be controlled independently. As such, the controller can adjust the flow rate of the pressurised fluid supplies to the first and second liquid channels to control the amount of deflection of the liquid jet.

[0012] In embodiments, the controller is configured to control the fluid pressure of each one of the respective pressurised fluid supplies. In this way, the flow rate of the primary and secondary liquid flow can be controlled independently by the controller. That is, the controller can adjust the fluid pressure, and the flow rate as a result, of the pressurised fluid supplies to the first and second liquid channels to control the amount of deflection of the liquid jet.

[0013] In embodiments, each one of one or more second liquid channels comprises a respective valve. Each respective valve may be one of a hydraulic valve, an electronically controlled valve, a pneumatic valve, or a mechanically operated valve. In this way, when a pressurised liquid is supplied to the liquid jetting device, the valves can be used to vary the flow rate of the secondary liquid flows to control the amount and direction of deflection of the output liquid jet.

[0014] In embodiments, the controller is configured to regulate each respective valve to control the fluid pressure of each one of the respective pressurised fluid supplies. In this way, the controller can control the valves to vary the flow rate of the secondary liquid flows to control the amount of deflection of the liquid jet.

[0015] In embodiments, the deflection angle is up to 20 degrees. In this way, the liquid jet can be deflected away from the centreline of the nozzle by momentum transfer between the secondary liquid flows and the liquid jet.

[0016] In embodiments, the liquid jetting device comprises three second liquid channels. In this way, the liquid jet can be deflected away from the centreline of the nozzle by the momentum balance between the different secondary liquid flows and the liquid jet.

[0017] In embodiments, the three secondary liquid channels are provided circumferentially around the nozzle. In this way, the liquid jet can be deflected in all directions by the three second liquid channels. That is, secondary liquid flows may be directed radially into the primary flow in a circumferentially distributed arrangement to allow the lateral deflection of the liquid in all directions. As such, with this arrangement, the liquid jet can be controlled to be deflected following in a path around the centreline of the nozzle. For example, in embodiments a circular path may be adopted, or any other pattern. In embodiments, the liquid jet may be deflected from the centreline by up to 15 degrees. In embodiments, four or more liquid channels may be provided.

[0018] In embodiments, a centreline of an outlet of each second liquid channel is at a jetting angle relative to a centreline of an outlet of the nozzle. In this way, each one of the one or more secondary liquid flows will intersect with the liquid jet to deflect the liquid jet by momentum transfer.

[0019] In embodiments, the jetting angle is greater than 0 degrees and less than or equal to 90 degrees. In this way, momentum transfer between the each one of the one or more secondary liquid flows and the liquid jet is enhanced, thereby increasing the deflection of the liquid jet.

[0020] According to a second aspect of the present invention, there is provided a structure. The structure comprises a body for insertion into a soil in an insertion direction during installation, the body having a toe at its distal end. The structure further comprises an array of liquid jetting devices as described above. The array of liquid jetting devices provided towards the distal end for jetting a liquid jet in the insertion direction. The array of liquid jetting devices may be provided at the distal end of the body.

[0021] According to a third aspect of the present invention, there is provided a method of installing the above structure. The method comprises: inserting the toe into the soil; supplying a pressurised fluid to the array of nozzles to jet fluid for generating a liquid jet ahead of the toe which flows in the insertion direction; and controlling the pressurised fluid by a controller for deflecting the liquid jet away from the insertion direction.

[0022] Illustrative embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a cross sectional view of a liquid jetting device according to a first illustrative embodiment; Figure 2 shows a cross sectional view of a liquid jetting device according to a second illustrative embodiment having two second liquid channels; Figure 3a shows the liquid jetting device of Figure 2 provided at a toe of a foundation with an undeflected liquid jet; Figure 3b shows the liquid jetting device of Figure 2 provided at a toe of a foundation with an inwardly deflected liquid jet; Figure 3c shows the liquid jetting device of Figure 2 provided at a toe of a foundation with an outwardly deflected liquid jet.

[0023] Figure 1 shows a cross sectional view of a liquid jetting device 10 according to a first illustrative embodiment. Preferably, the liquid jetting device 10 is used while submerged. The liquid jetting device 10 comprises a body 12 with a first liquid channel 14 and a second liquid channel 16 (or a by-pass channel) formed within. In use, a primary liquid flow 18 is fed through the first liquid channel 14 to a nozzle 20. The diameter or cross-sectional area of the nozzle 20 gradually decreases towards the nozzle outlet 22, such that the pressure of the primary liquid flow 18 decreases and the velocity of the primary liquid flow 18 increases at the outlet 22 of the nozzle 20. As a result, the primary liquid flow 18 streams out of the nozzle 20 to form a liquid jet 24. The liquid jet 24 has a higher velocity than the velocity of the primary liquid flow 18 fed through the first liquid channel 14 and jets out of the nozzle 20 at a centreline 26. The centreline 26 corresponds to the axis of symmetry of the first liquid channel 14 and the nozzle 20.

[0024] The second liquid channel 16 is provided adjacent to the outlet 22 of the nozzle 20 for feeding a secondary liquid flow 28. The second liquid channel 16 can be shaped such that velocity of the secondary liquid flow 28 increases as it passes through the second liquid channel 16, functioning similarly to a nozzle. That is, the gauge, or cross sectional area, of the second liquid channel 16 decreases as it reaches an outlet 30 of the second liquid channel 16, thereby increasing the velocity of the secondary liquid flow 28 at the outlet 30. That is, the flow accelerates in the conical section due to flow rate continuity and the pressure drops accordingly (Bernoulli's principle). The primary liquid flow 18 and secondary liquid flow 28 are shown as streamlines in Figure 1.

[0025] The secondary liquid flow 28 jets out from the outlet 30 of the second liquid channel 16 into the stream of the liquid jet 24. The secondary liquid flow 28 jets out from the outlet 30 of the second liquid channel 16 at a centreline 32. The centreline of the outlet 30 of the second liquid channel 16 corresponds to the axis of symmetry of the outlet 30 of the second liquid channel 16.

[0026] The outlet 30 of the second liquid channel 16 is arranged such that the centreline 32 of the second liquid channel 16 intersects the centreline 26 of the outlet 20 of the first liquid channel 14. The intersection between the centreline 32 of the second liquid channel 16 and the centreline 26 of the liquid jet 24 defines a jetting angle, α. As shown in Figure 1, the jetting angle, α, is preferably 90 degrees. In alternative arrangements, the jetting angle, α, can be any angle that is less than or equal to 90 degrees, but greater than zero degrees. That is, if the jetting angle, α, is zero degrees, the secondary liquid flow 28 and the liquid jet 24 are jetted coaxially from their respective outlets 22,30, such that the secondary liquid flow 28 and the liquid jet 24 do not intersect. In a further arrangement, the jetting angle, α, may be greater than 90 degrees, such that the secondary liquid flow 28 is jetted against the stream of the liquid jet 24.

[0027] As the secondary liquid flow 28 and the liquid jet 24 intersect, the secondary liquid flow 28 exerts a force on the liquid jet 24 to deflect the liquid jet 24 away from the centreline 26 of the liquid jet by a deflection angle, β. This results in liquid jet 24 being deflected by the deflection angle, β.

[0028] In an exemplary embodiment, a controller 34 may be provided to control the fluid flow rate of the primary liquid flow 18 and the secondary liquid flow 28. For example, a separate pressurised liquid may be supplied to each of the first liquid channel 14 and the second liquid channel 16. Each of the separate pressurised liquids may have a different liquid flow rate. As such, each of the pressurised fluid supplies may be controlled by the controller 34 to increase or decrease the pressure, and / or flow rate, of the primary liquid flow 18 and the secondary liquid flow 28 independently. In this way, the controller 34 can control the degree to which the secondary liquid flow 28 deflects the liquid jet 24. That is, the controller 34 may control the pressure, and / or flow rate, of the primary liquid flow 18 and / or the secondary liquid flow 28 to adjust the deflection angle, β

[0029] As the liquid flow rate of the secondary liquid flow 28 (relative to the primary liquid flow 18) is increased by the controller 34, the amount that the liquid jet 24 is deflected is increased as there is a higher amount of momentum transfer between the secondary liquid flow 28 and the liquid jet 24. As such, the deflection angle, β, can be controlled by the controller 34 by varying the liquid flow rate of primary liquid flow 18 and the secondary liquid flow 28. While the flow rate of the secondary liquid flow 28 may be higher than the primary liquid flow 18 to achieve a larger deflection angle β, the momentum transfer from the secondary liquid flow 28 to the liquid jet 24 may cause the liquid jet 24 to diffuse, reducing the effectiveness of the liquid jet 24. Preferably, the flow rate of the secondary liquid flow 28 is lower than the primary liquid flow 18, such that there is momentum transfer between the secondary liquid flow 28 and the liquid jet 24, without causing the primary jet to diffuse. As a result, the controller 34 can vary the flow rate of the secondary liquid flow 28, such that the deflection angle, β, reaches a maximum of 20 degrees. In other words, the liquid jet 24 is deflected by up to 20 degrees from its normal, undisturbed direction of flow (i.e., along the centreline 26 of the nozzle 20). In other embodiments, deflection angles of up to 15 degrees, and more preferably up to 10 degrees are used in order to minimise diffusion and distortion of the primary flow jet.

[0030] In the exemplary embodiment shown in Figure 1, the same pressurised liquid is supplied to each of the first liquid channel 14 and the second liquid channel 16. In other words, a pressurised liquid is supplied to the liquid jetting device 10, which is then distributed between the first liquid channel 14 and the second liquid channel 16. In this embodiment, a valve 36 is provided in the second liquid channel 16 for controlling the passage of liquid through the second liquid channel 16. The controller 34 is connected to and configured for controlling the valve 36 to regulate the flow rate of the liquid through the second liquid channel 16. The valve 36 can be one of a hydraulic valve or an electronic valve, both being controllable by the controller 34 for regulating the flow rate of the secondary liquid flow 28.

[0031] Further embodiments may use the arrangements described above but comprise a plurality of second liquid channels 16 for deflecting the liquid jet 24 in different directions. For example, Figure 2 shows two second liquid channels 16. In such embodiments, each of the plurality of second liquid channels 16 is provided for feeding a respective secondary liquid flow 28. Each of the plurality of second liquid channels 16 may have the same internal cross-sectional area, such that each second liquid channels 16 has the same liquid flow rate. In addition, each of the plurality of second liquid channels 16 may be supplied with a respective pressurised liquid (i.e., different liquid supplies for each one of the second liquid channels 16). Alternatively, the pressurized liquid supplied to the first liquid channel 14 and to each of the plurality of second liquid channels 16 may be the same. In this respect, in embodiments the vale 36 will constrain the flow into the bypass channel to an extent that the pressure build up in the bypass caused by constrained outflow through the small nozzle 30 will be at a lower pressure (e.g. 50 bar) compared to the pressure applied from the main nozzle (e.g. 250bar). Alternatively, a pressure drop across the valve 36 can be avoided by having a narrower gap (e.g. 0.15mm). In such an arrangement, the bypass channel can be charged with the same pressure as the main nozzle (e.g. 250bar) .

[0032] In embodiments, the plurality of second liquid channels 16 are arranged radially around the centreline 26 of the nozzle 20, which can provide balanced and uniform distribution of the secondary liquid flow 28 into the liquid jet 24. Preferably, the centreline 32 of each outlet of the plurality second liquid channels 16 intersects the centreline 26 of the nozzle outlet 22. That is, while the direction of each of the respective secondary liquid flows 28 from each second liquid channel 16 is different, the jetting angle, α, for each respective secondary liquid flow 28 is the same. In other words, the plurality of second liquid channels 16 are arranged such that each secondary liquid flow 28 intersects the liquid jet 24 at a singular point, as shown in Figure 2. While each secondary liquid flow 28 and the liquid jet 24 are separate flows, once each secondary liquid flow 28 and the liquid jet 24 intersect they form a single, deflected liquid jet 24.

[0033] In embodiments where a plurality of second liquid channels 16 are provided, the controller 34 can independently control the flow rate of the pressurised liquid through each one of the second liquid channels 16, either by controlling the flow rate of the pressurised liquid supplied to each of the second liquid channels 16 or by regulating the valve 36 in each of the second liquid channels 16. For example, as shown in Figure 2, the controller 34 may increase the flow rate of one of the second liquid channels 16, while reducing the flow rate of the other second liquid channel 16. As such, momentum transfer in this scenario only occurs between one of the secondary liquid flows 28 and the liquid jet 24. Thus, the liquid jet 24 is deflected in a single direction. In this manner, the controller 34 can precisely control the deflection angle, β, of the liquid jet 24 by controlling each the flow rate through each one of the second liquid channels 16.

[0034] In one exemplary embodiment, the liquid jetting device 10 may comprise three second liquid channels 16. In this arrangement, the deflection angle, β, can be adjusted radially around the centreline 26 of the nozzle outlet 22. In other words, at least three second liquid channels 16 are required to deflect the liquid jet 24 in any direction relative to the centreline 26 of the nozzle outlet 22. For instance, the liquid jet 24 could be controlled to be deflected in a circular path around the centreline 26.

[0035] As shown in Figures 3a to 3c, the liquid jetting device 10 according to embodiments of the present invention can be used to excavate soil during installation of a foundation 100. Using a monopile foundation for illustrative purposes, the foundation comprises a tubular body 102 having an exterior lateral surface 104 that is driven into the soil 106 in an insertion direction. A distal end 108 of the body 102 forms a toe 110, which comprises a manifold 112 for feeding the pressurised liquid to the liquid jetting devices 10. It will be understood that a plurality of jetting devices 10 may be distributed around the toe of the foundation. For example, preferably, the liquid jetting devices 10 are arranged circumferentially around the toe 110 of the structure 100. In further arrangements, the plurality of liquid jetting devices 10 may be positioned at a distance away from the toe of the foundation. The manifold 112 is fed by a pressurised fluid supply which delivers pressurised liquid to the distal end of the structure 100, for example, from a pump provided on a nearby installation vessel. Typically, the liquid supplied through the manifold 112 is sea water.

[0036] The liquid jetting devices 10 can be supported on lateral extensions which extends out from the manifold 112. However, the liquid jetting devices 10 may be supported directly on the manifold 112. The manifold 112 includes an internal fluid pathway connecting between the interior of the manifold 112 and each liquid jetting device 10. As such, pressurised fluid from the manifold 112 is jetted out through the liquid jetting devices 10.

[0037] When pressurised fluid is supplied via the manifold 112, each liquid jetting device 10 produces a liquid jet 24 in the insertion direction when undeflected by the secondary liquid flow 28, as shown in Figure 3a. The water jets act to erode soil located directly below and around the toe 110 of the structure 100. The liquid jets form a fluid channel cavity 114 with high velocity flow streams that are loaded with abrasive soil grains in suspension and act to erode the walls of the fluid channels further. This thereby forms annuli either side of the foundation body 102, which separates the soil 106 from the structure's exterior surface 104. The excess soil suspension caused by the persistent fluid influx through the liquid jetting devices 10 also generates upward fluid flows through the gaps formed between the structure's exterior surface 104 and the soil 106. Soil is thereby transported up the body 102 of the structure 100. These combined effects result in much lower frictional resistance during installation of the foundation 100.

[0038] The controller 34 controls the deflection of the liquid jet 24, as described above, to vary the amount of erosion ahead of and around the toe 110 of the foundation 100. For example, the controller 34 can adjust the direction of liquid jet 24 to optimise the jetting direction depending on the soil type. That is, the deflection of the liquid jet 24 can be controlled such that the liquid jet 24 is directed inwardly towards the axis of the structure 100, as shown in Figure 3c. Advantageously, this can be used in gravel regions of the soil to create gravel pockets, which act as areas around the toe of the foundation 100 for displacing gravel into. As a result, the gravel can be broken up more quickly and displaced away from the toe of the structure, thereby making installation of the structure into the soil easier.

[0039] Additionally, the deflection of the liquid jet 24 can be controlled such that the liquid jet 24 is directed outwardly from the axis of the structure 100 to erode soil 106 directly below and around the toe 110 of the structure 100. This may reduce the disturbance of the soil structure in the lateral regions of soil 106, as shown in Figure 3b. This is particularly in areas of soil 106 that require more than one liquid jet to break up the soil 106. For example, the outward deflection of the liquid 24 may excavate clay in the soil directly below and around the toe 110 to reduce the installation resistance of toe. In addition, the outward deflection of the liquid 24 may excavate soil 106 around the toe 100 to reduce friction between the soil 106 and the exterior lateral surface 104 of the foundation 100.

[0040] Adjusting the deflection of the liquid jet 24 also allows for the width of the eroded area to be controlled so as to be increased or decreased. This thereby allows control based on soil conditions and may, for instance, allow a reduced number of liquid jetting devices 10 to be used to achieve installation of the foundation 100.

[0041] Accordingly, by varying the deflection of the liquid jet 24, the liquid jetting device 10 is suitable for eroding a variety of different soil types, thereby decreasing the time needed to install a structure 100. Additionally, as the direction of the liquid jet 24 is not adjusted mechanically, this avoids the disadvantages associated with such devices. Specifically, mechanically adjustable nozzles are not robust and prone to failure, such that they are unsuitable for the harsh conditions and pressures present during installation of a foundation. By providing a liquid jetting device 10 without any moveable parts, these drawbacks can be avoided.

[0042] It will be understood that the embodiments illustrated above show applications of the invention only for the purposes of illustration. In practice the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

[0043] For example, although the above example has been described with reference to a foundation, it will be understood that the invention may be equally applicable to other structures which are inserted into soil. In this connection, the liquid jetting device of the present disclosure may be used to install remote anodes into the soil, where the deflection of the liquid jet can be used to maintain the vertical orientation of the remote anodes. Further, the liquid jetting device may also be used to excavating soil during the installation of ground probes, such as those used for cone penetration tests (CPT). The deflection of the liquid jet can be used to excavate a larger area of soil when compared to a fixed jet. Furthermore, the liquid jetting device of the present disclosure may be used to excavate soil to create ducts in the soil for cables and pipes to pass through as they are installed.

Claims

1. A liquid jetting device for excavating soil during installation of a structure, the jetting device comprising: a nozzle; a first liquid channel for feeding a primary liquid flow to the nozzle for forming a liquid jet in a first direction, the first direction being along a centreline of the nozzle; and one or more second liquid channels for feeding a respective secondary liquid flow into the liquid jet for deflecting the liquid jet at a deflection angle away from the centreline of the nozzle.

2. The liquid jetting device according to claim 1, further comprising a pressurised fluid supply for supplying pressurised fluid to the liquid jetting device.

3. The liquid jetting device according to claim 2, further comprising a controller for controlling a fluid pressure of the pressurised fluid supplied to the liquid jetting device.

4. The liquid jetting device according to claim 3, wherein respective pressurised fluid supplies are provided for each one of the first liquid channel and the one or more second liquid channels.

5. The liquid jetting device according to claim 4, wherein the controller is configured to control the fluid pressure of each one of the respective pressurised fluid supplies.

6. The liquid jetting device according to claim 3, wherein each one of one or more second liquid channels comprises a respective valve.

7. The liquid jetting device according to claim 6, wherein each respective valve is one of a hydraulic valve , electronic valve, a pneumatic valve, or a mechanically operated valve.

8. The liquid jetting device according to claim 6 or 7, wherein the controller is configured to regulate each respective valve to control the fluid pressure of each one of the respective pressurised fluid supplies.

9. The liquid jetting device according to any preceding claim, wherein the deflection angle is up to 20 degrees.

10. The liquid jetting device according to any preceding claim, wherein the liquid jetting device comprises three second liquid channels.

11. The liquid jetting device according to claim 10, wherein the three second liquid channels are provided circumferentially around the nozzle.

12. The liquid jetting device according to any preceding claim, wherein a centreline of an outlet of each second liquid channel is at a jetting angle relative to a centreline of an outlet of the nozzle.

13. The liquid jetting device according to claim 12, wherein the jetting angle is greater than 0 degrees and less than or equal to 90 degrees.

14. A structure comprising: a body for insertion into a soil in an insertion direction during installation, the body having a toe at its distal end; an array of liquid jetting devices according to any one of claims 1 to 13, the array of liquid jetting devices provided towards the distal end for jetting a liquid jet in the insertion direction.

15. A method of installing a structure according to claim 14, the method comprising: inserting the toe into the soil; supplying a pressurised fluid to the array of nozzles to jet fluid for generating a liquid jet ahead of the toe which flows in the insertion direction; and controlling the pressurised fluid by a controller for deflecting the liquid jet away from the insertion direction.

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