Methods for installing foundations and foundations for structures

Abstract

A method for installing a foundation (1) for a structure is provided. The foundation body (2) has a distal end (7) defining an opening within an internal cavity (12) defined by an inner wall (8). Fluid is injected from a plurality of nozzles (9) to direct the fluid distally into the soil (5) forward of the distal end (7) during installation. A pump arrangement (13) controlled by a controller (16) is used to vary the amount of fluid at the proximal end, thereby varying the fluid suspension pressure adjacent the distal end (7) within a fluid communication channel (11) extending between the proximal end and the distal end (7). The controller (16) varies the fluid suspension pressure as the distal end (7) is inserted deeper into the soil (5) based on a target fluid suspension pressure that varies with tip depth.

Description

Technical Field

[0001] The present invention relates to a method of installing a foundation, a structural foundation, a controller for use during installation of the foundation, and software for controlling such a controller. In particular, the present invention relates to structural foundations such as piles, tubular piles, monopiles, jacket piles, suction bucket / caisson foundations and suction anchors, skirt foundations, etc. that can be inserted into the soil to support structures such as buildings, offshore structures, wind turbines, etc. It will be appreciated that suction bucket / caisson foundations are most suitable for shallow foundations with a jacket structure in water depths up to 100 m and strong soil. Suction anchors are optimal for anchor chains connecting deep-sea floating oil platforms in soft sediments. The present invention is particularly suitable for offshore foundations, and more specifically, for open ended tubular foundation types such as monopiles, jacket piles and suction buckets.

Background Art

[0002] Structural foundations are typically installed by using a pile hammer to drive the foundation into the ground and applying a series of axial impacts to drive the foundation into the soil in the insertion direction. Once installed, the foundation is axially supported by the friction exerted on the side surface of the foundation body, which is a resistance to further penetration at the toe of the foundation, although to a lesser extent.

[0003] During installation, the toe at the distal end of the foundation displaces the soil as it is driven down. This causes the soil in the surrounding area to be compressed. However, as the foundation is driven deeper and the pressure increases, the force required to continue displacing the soil at the toe of the foundation also increases. At the same time, the surface area of the foundation in contact with the soil increases, and the shear force required to overcome the frictional resistance to movement increases. As a result, the bearing resistance increases as the foundation is installed deeper into the soil.

[0004] In recent years, monopile-type and other foundations have been tending to become larger, and the problems in installation have been intensifying. For example, to drive a larger foundation, higher impact force and / or a larger number of hammer blows are required. This imposes significant fault tolerance requirements on the foundation. At the same time, the noise generated by the large impact also increases, posing a significant danger to the environment and safety.

[0005] In view of the above, various methods and systems for facilitating the installation of foundations have been proposed.

[0006] In this context, one solution involves the use of a liquid excavation technique where high-pressure nozzles are used to flood a large amount of soil with an injected liquid in order to excavate the space for the foundation. In this type of conventional method, the soil is removed in an uncontrollable manner, and the excavated location is effectively refilled with the recovered soil when the foundation is installed in its original location. However, since the soil for refilling the space is newly placed, the space has little developed structure. As a result, the space is essentially weak.

[0007] An alternative method is described in the applicant's own previous patent application published as WO2019 / 206690. In particular, WO2019 / 206690 aims to reduce the installation resistance of the tip by using nozzles inside the foundation to direct a fluid upward above the tip of the foundation, radially inward along the inner wall of the foundation, and laterally into the soil region. In this way, after the soil is displaced inward by the tip of the foundation, it can be transported away from the displaced soil region in the fluid. Also, a pump system is used to discharge the fluid from the internal cavity at the top of the foundation during installation. Therefore, the compression of the soil in the displaced soil region is reduced. This arrangement localizes the fluid delivered by the nozzles within the internal cavity and minimizes the disturbance of the external soil structure, providing a significant advantage over the above-described liquid excavation technique.

[0008] Notwithstanding this, as the understanding of the failure mechanisms at the tip of the foundation continues to evolve, there remains a need for new methods and systems for reducing the installation resistance during foundation installation.

[0009] Accordingly, the present invention seeks to address the above problems of the prior art.

Summary of the Invention

[0010] According to a first aspect of the present invention, there is provided a method of installing a foundation of a structure, the method comprising: inserting a body of the foundation in an insertion direction into soil, the body having a tip portion at a tip of the body that defines an opening within an internal cavity defined by an inner wall; injecting fluid from a plurality of nozzles provided in a tip region of the body to orient the fluid in a tip direction within the soil in front of the tip portion; varying the amount of fluid at a proximal end of the internal cavity using a pump arrangement; controlling the pump arrangement using a controller to vary a fluid suspension pressure adjacent to the tip portion within a fluid communication channel formed between the proximal end of the internal cavity, the inner wall, and the tip portion formed with the soil, wherein the controller varies the fluid suspension pressure as the tip portion is inserted deeper into the soil based on a target fluid suspension pressure that varies according to the tip depth.

[0011] In this way, during installation, the fluid ejected from the plurality of nozzles can cut through the soil region below the tip in the tip-side direction and form a suspension that extends in the fluid communication channel from the tip to the water table at the proximal end of the internal cavity. Thus, under the control of the controller, the pump arrangement can adjust the suspension pressure adjacent to the tip by changing the amount of fluid at the proximal end of the internal cavity using the pump arrangement. For example, the pump arrangement can lower or raise the water table by discharging water from the internal cavity or supplying water to the internal cavity. By this control, in a controlled manner, the active earth pressure in the soil region below and on the tip side of the tip is balanced by the fluid suspension pressure. That is, by changing the fluid suspension pressure to a target suspension pressure, the external soil can be relaxed into the soil suspension in this region. At the same time, the suspension pressure can be maintained high enough to minimize the risk of grounding or hydraulic failure that would otherwise compromise the stability of the foundation. Thus, by matching the suspension pressure to the target as the foundation is driven (inserted) deeper, the soil structure is essentially left intact while relaxation allows the lateral earth pressure applied to the outer wall of the foundation to be reduced. This reduces the frictional resistance against the outside of the pile. Importantly, the controller recited in the claims can vary the suspension pressure in response to changes in the active earth pressure with installation depth. For example, the active earth pressure generally increases with depth, but changes in soil properties between different soil layers can also decrease or increase the active earth pressure. As a result, the claimed invention can account for these changes and reduce the installation resistance throughout the installation process.

[0012] The above results can make the pile driving force required to drive (insert) the pile smaller, and in some cases, installation may be possible without the need to apply hammer blows. Once the foundation is installed to the required depth, the fluid injection system can then be turned off to allow the fluid to drain from the soil and the soil to re-stabilize.

[0013] In an embodiment, the method further includes controlling the flow rate of fluid ejected from a plurality of nozzles to vary the fluid suspension pressure within the fluid communication channel. Thus, the volume of fluid ejected from the nozzles can be increased or decreased to vary the suspension pressure. Typically, varying the inflow rate of the fluid is less desirable than varying the amount of fluid at the proximal end of the internal cavity because it responds relatively slowly when an increase in suspension pressure is required. For example, excess fluid may take time to dissipate, and the extent to which the flow rate can be decreased is limited by the need to maintain a sufficiently high injection pressure to cut into the soil. That said, control of the fluid inflow can provide a useful control parameter when it is necessary to rapidly decrease the suspension pressure or redundancy in the event of pump arrangement failure.

[0014] In an embodiment, the target fluid suspension pressure increases with the tip depth. In this way, the target fluid suspension pressure can compensate for the increase in active earth pressure as the base is inserted into the soil. It will be appreciated that the active earth pressure can increase linearly or non-linearly with depth and can further decrease over the period during which the tip is descending through a particular soil layer.

[0015] In an embodiment, the target fluid suspension pressure is determined based on soil characteristics. In this way, the target fluid suspension pressure can compensate for changes in active earth pressure between different soil types and different soil layers.

[0016] In an embodiment, the target fluid suspension pressure is determined based on an estimated active earth pressure coefficient.

[0017] In an embodiment, the method further includes, before the step of injecting fluid from a plurality of nozzles, a step of obtaining a target fluid suspension pressure according to the tip depth. In this way, the target parameters for implementation by the controller may be determined in advance before starting the basic physical installation. Next, the installation may proceed based on these predetermined parameters. For example, the controller may control the pump based on the parameters to maintain the target fluid suspension pressure as the installation progresses.

[0018] In an embodiment, the step of controlling the pump arrangement using a controller includes a step of controlling based on the received sensor input. In this way, the controller may provide feedback control during installation to maintain the target suspension pressure or a preferred installation speed.

[0019] In an embodiment, the received sensor input includes an input corresponding to the fluid suspension pressure adjacent to the tip. In this way, the fluid suspension pressure is directly measured, thereby enabling a rapid response using control parameters to maintain the target suspension pressure.

[0020] In an embodiment, the received sensor input includes an input corresponding to the installation resistance. In this way, the detected installation resistance may be compared with the predicted installation resistance. For example, if the installation resistance increases faster than expected, the suspension pressure may decrease in response.

[0021] In an embodiment, the step of changing the amount of fluid at the proximal end of the internal cavity includes the pump arrangement pumping water out of the internal cavity and / or supplying water to the internal cavity. In this way, the suspension pressure may change rapidly by changing the height of the water surface in the internal cavity.

[0022] In an embodiment, the method further includes maintaining an open fluid communication channel between a proximal end and a distal end of an internal cavity using means for separating an inner wall from soil. For example, the means for maintaining the open fluid communication channel may include a secondary array of nozzles distributed circumferentially and axially on an inner surface of a distal region of the foundation body. These separation nozzles may provide a distribution of jets for maintaining separation between the inner surface and the opposing soil vertically upward around the inner circumference of the body and along its axis. Preferably, these secondary nozzles may be oriented in a plane that is 90 to 180 degrees with respect to the insertion direction to enhance the upward movement of sediment.

[0023] According to a second aspect of the present invention, a foundation of a structure is provided. The foundation of the structure is a foundation body for insertion in a soil in an insertion direction, having a distal end portion defining an opening in an internal cavity defined by an inner wall at its distal end, a body, a plurality of nozzles provided in a distal region of the body for jetting a fluid in a distal direction into the soil in front of the distal end portion, a pump arrangement for changing an amount of fluid at a proximal end of the internal cavity, and a controller for controlling the pump arrangement to change a fluid suspension pressure adjacent to the distal end portion in a fluid communication channel between the proximal end of the internal cavity and the distal end portion formed between the inner wall and the soil. The controller changes the fluid suspension pressure as the distal end portion is inserted deeper into the soil based on a target fluid suspension pressure that changes according to the distal end depth.

[0024] In an embodiment, the foundation further includes a pressure sensor for determining the fluid suspension pressure and an installation resistance sensor for determining a resistance to insertion of the foundation body into the soil. The step of controlling the pump arrangement using the controller includes controlling based on sensor inputs received from the pressure sensor and the installation resistance sensor.

[0025] According to a third aspect of the present invention, a foundation of a structure is provided. The foundation of the structure is a body for insertion in a soil in an insertion direction during installation, the body having a tip portion at its tip, the tip portion defining an opening in an internal cavity defined by an inner wall, a body, one or more nozzles for orienting fluid injection in a tip direction into the soil in front of the tip portion, a pump for discharging fluid from a proximal end of the internal cavity, a proximal end of the internal cavity, and means for maintaining a fluid communication channel between the inner wall and a toe formed between the soil and the toe.

[0026] The fluid preferably includes water. The fluid can be, for example, seawater, or an aqueous solution or suspension.

[0027] According to a fourth aspect of the present invention, a controller for controlling the installation of a foundation of a structure is provided. The foundation includes a foundation body for insertion in a soil in an insertion direction, the body having a tip portion at its tip that defines an opening in an internal cavity defined by an inner wall, the controller including injection control for controlling the injection of fluid from a plurality of nozzles provided in a tip region of the body for orienting the fluid in a tip direction into the soil in front of the tip portion, and pump control for controlling the pump arrangement to vary the amount of fluid at the proximal end of the internal cavity, the controller changing the fluid suspension pressure adjacent to the tip portion in a fluid communication channel between the proximal end of the internal cavity and the tip portion formed between the inner wall and the soil, and the controller changing the fluid suspension pressure as the tip portion is inserted deeper into the soil based on a target fluid suspension pressure that varies according to the tip depth.

[0028] According to a fifth aspect of the present invention, software is provided for operating a controller for controlling the installation of a foundation structure. The foundation includes a foundation body for insertion in an insertion direction into the soil. The body has, at its tip, a tip portion that defines an opening within an internal cavity defined by an inner wall. The software includes instructions for controlling the injection of fluid from a plurality of nozzles provided in the tip region of the body for orienting the fluid in the soil in front of the tip portion in the tip direction, and instructions for controlling a pump arrangement for changing the amount of fluid at the proximal end of the internal cavity. The fluid suspension pressure varies adjacent to the tip portion within a fluid communication channel formed between the proximal end of the internal cavity, the inner wall, and the tip portion formed between the soil. The fluid suspension pressure changes based on a target fluid suspension pressure as a function of the tip portion depth and changes as the tip portion is inserted deeper into the soil.

Brief Description of the Drawings

[0029] Here, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0030] FIG. 1 shows a schematic cross-sectional view of a foundation 1 according to an embodiment of the present invention. In this embodiment, the foundation 2 is a monopile for installation at sea.

[0031] The foundation 1 includes a hollow tubular body 2 having an outer surface 4 and an inner surface 8 that defines a well (bore)-shaped internal cavity 12. In this example, the body 2 has a conical section towards its proximal end. The tip portion of the body 2 includes an insertion section 6 for insertion into the soil 5 under the sea 3. The tip of the insertion section 6 ends at a tip portion 7 that defines an opening within the internal cavity 12.

[0032] In this embodiment, the inner surface 8 includes a fluid injection system including a nozzle array. This array includes a plurality of cutting nozzles 9 that are located at or adjacent to the tip 7 and are oriented in the tip direction for injecting high-pressure fluid into the soil in front of the tip 7 of the foundation. In an embodiment, the cutting nozzles are located within 10 cm, more preferably within 2 cm, of the tip 7. In this embodiment, the cutting nozzles 9 can inject fluid at 200 - 400 bar and penetrate into the soil by 10 - 20 cm during use, depending on the soil properties. The injected fluid acts to cut and erode the soil in front of the tip 7 in its insertion direction 15. The plurality of cutting nozzles 9 are arranged around the perimeter of the tip opening and are supplied by a high-pressure supply pipe system (not shown).

[0033] Further inside the foundation, a pump arrangement 13 is provided that connects to the water surface inside the foundation during installation. The pump arrangement 13 is used to adjust the height of the water surface in the proximal section of the internal cavity 12 by supplying water to or discharging water from the cavity 13 using a pipe 14. In this embodiment, a single pump and pipe are shown, but it will be understood that the pump arrangement 13 may include separate multiple suction and discharge pipes driven by one or more pumps. In an embodiment, the suction inlet of the pump arrangement may alternatively be provided by a controllable valve and is activatable to allow seawater to be discharged into the internal cavity 12. In an embodiment, the pump arrangement may be provided within the cable hole of the foundation and thus be located 3 - 4 m above the seabed at the final installation depth. Thus, such an arrangement may not require a pipe 14.

[0034] In an embodiment where the foundation body 2 is a closed ended pile, the pump arrangement 13 may alternatively be provided above the water surface and operate to increase or decrease the air pressure within the internal cavity 12.

[0035] The controller 16 is provided to control the pump 13 to adjust the height of the water surface in the internal cavity. In this embodiment, the controller 16 may also vary the flow rate of the fluid ejected from the cutting nozzle 9. The controller 16 may be provided, for example, on a vessel or a jack-up barge used during the installation of the monopile.

[0036] During installation, the foundation body 2 descends through the seawater 3, the tip 8 moves in the insertion direction 15, and axially penetrates downward into the soil 5.

[0037] The foundation body 2 is pushed in the insertion direction 15 under its own weight. In some embodiments, additional ballast weight can be used to increase the driving weight of the foundation. In some situations, it may be necessary to apply a hammer impact to the proximal end of the body 2 to drive the foundation downward.

[0038] During installation, the cutting nozzle 9 is activated to direct a high-pressure jet of fluid into the soil in front of the tip 7. This action cuts the soil over a short distance and divides the soil in this area directly below and radially inward of the tip 7.

[0039] FIG. 2 shows a schematic enlarged cross-sectional view of the tip 7 when penetrating the soil 5. The fluid 19 ejected from the cutting nozzle 9 enters the soil and cuts, forming a suspension in the soil region adjacent to the tip 7, thereby separating the soil 5 adjacent to the inner surface 8 of the body 2 from the foundation body 2 itself. The fluid builds and forms a communication channel 11 that extends upward over the inner surface 8 of the body 2 to the proximal end of the internal cavity above the seabed (see FIG. 1). The establishment of this communication channel 11 means that a pressure change at the proximal end of the internal cavity can directly affect the suspension pressure of the fluid at the tip in the region adjacent to the tip 7.

[0040] In this context, when the foundation body 2 is pushed down, its inner and outer surfaces are subject to lateral earth pressure from the surrounding soil 5. This then appears as shaft resistance 18 that resists installation.

[0041] As described above, in this arrangement, the cutting nozzle 9 acts to cut and discharge a section of soil, thereby creating a fluid communication channel 11 that extends from the tip region below the tip 7 to the proximal end of the internal cavity 12. In this way, in particular, the lateral earth pressure applied by the soil 5 to the inner surface 8 of the main body 2 is removed. The outer surface 4 of the main body remains exposed to the lateral earth pressure 17 applied by the adjacent soil. However, in the cut-off region below the tip 7, the absence of the pile main body 2 means that this lateral pressure 17 is the active effective horizontal earth pressure. Thus, at the front surface 22 between the soil and the suspension, the sum of the soil pore pressure u and this active effective horizontal earth pressure is counteracted by the fluid suspension pressure (P_sus) 21 in the opposing region of the fluid communication channel 11. Therefore, by using the parameters set by the controller 16 to control the suspension pressure P_sus21 through the communication channel 11, P_sus21 can match the soil pore pressure and the lateral force of this active effective horizontal earth pressure as follows. P_sus >= soil pore pressure + active effective horizontal earth pressure

[0042] Therefore, the controller 16 can control the water level by using the flow rate of the fluid ejected by the pump 13 and / or the cutting nozzle 9 to control the suspension pressure in the region adjacent to the tip 7. Specifically, the controller can increase the flow of the fluid ejected by the cutting nozzle 9 to decrease the suspension pressure P_sus21. This can be counteracted by adding water from the water surface in the internal cavity 12 using the pump arrangement 13. Conversely, the suspension pressure can also be decreased by removing (discharging) water from the internal cavity 12 using the pump arrangement 13. Similarly, in the embodiment of the closed-end pile, the air pressure in the internal cavity 12 may be increased or decreased to change the suspension pressure.

[0043] The suspension pressure P_sus21 can be controlled to be high enough to prevent ground failure where the external soil collapses into the injection annulus. More importantly, it can also prevent hydraulic failures that would significantly damage the surrounding soil structure. Hydraulic failures are particularly devastating because the suspension pressure causes the inflow of interstitial water into the injection annulus, dropping below the adjacent interstitial pressure. This interstitial water inflow rapidly erodes the soil at the erosion front, which is already unstable because the suspension pressure is not high enough to counteract the active earth pressure. Thus, the erosion front is eaten away progressively outwards into the surrounding soil structure, severely compromising the static stability of the foundation.

[0044] At the same time, the suspension pressure P_sus21 can be controlled to be low enough to allow the soil 5 to relax radially inwards into the fluid at the front 22. This has the effect of releasing part of the lateral earth pressure 17 of the soil 5 that is radially adjacent to the front 22. As the tip 7 continues to move downwards, it moves into this region of relaxed soil 5. Thus, the advancing tip 7 fixes the external lateral pressure 17 of the soil 5 at a magnitude when it was counteracted by the suspension pressure 21. This significantly reduces the lateral earth pressure 17 applied to the outside 4 of the foundation, resulting in a reduction of the shaft resistance 18. There is also a reduction of the tip resistance as a by-product of the enhanced soil erosion at the tip 7, but this is a secondary factor in the overall installation resistance.

[0045] As the pile installation progresses and the tip 7 is driven deeper into the soil, the active effective horizontal earth pressure in the soil at the front 22 generally increases. In a homogeneous soil profile, this increase is substantially linear. However, in a layered soil profile, the increase is non-linear because the active effective horizontal earth pressure coefficient varies with soil type. Some soil layers may also exhibit a decrease in the active effective horizontal earth pressure. As a result, to maintain the reduction of the installation resistance while avoiding detrimental grounding or hydraulic failures, the controller 16 varies the suspension pressure as the tip 7 is driven deeper into the soil, with the overall tendency being to increase the suspension pressure with depth.

[0046] In this regard, in the present embodiment, the controller 16 controls the jet injection through the pump arrangement 13 and / or the nozzle 9 during the installation process to maintain a target suspension pressure that varies with the depth of the tip 7. This target suspension pressure may be based on the estimated properties of the soil. For example, prior to installation, modeling may be used to determine the target suspension pressure as a function of depth, taking into account factors such as the weight of the foundation, any additional ballast used, the jet configuration, and the specific soil conditions and properties at the installation location of the foundation. Based on this, the controller may then attempt to adjust the jet pressure and the height of the water surface to match the actual suspension pressure to the target for a given tip depth. To this end, the controller 16 may monitor the input from the feedback sensors. For example, the feedback sensors may include a cut-off nozzle flow sensor 25 and a pump flow sensor 26, respectively, for indicating the flow rate at the cut-off nozzle 9 and the pump 13. In an embodiment, the controller may directly monitor the suspension pressure using, for example, a pressure sensor 24 provided near the tip of the pile.

[0047] The controller 16 may also use an installation resistance sensor 23 to monitor the installation resistance and compare it with the predicted installation resistance calculated as part of the modeling stage. During installation, if the installation resistance increases faster than predicted, the controller may, for example, lower the suspension pressure to reduce the resistance. The controller 16 may also reduce the installation speed to increase the erosion of the soil by the cut-off jet 9.

[0048] Accordingly, in the above arrangement, an injection region is generated below the tip 7, and by controlling the suspension pressure in the communication channel 11, the outer wall friction 18 can be reduced, thereby reducing the downward force required to facilitate installation. In this way, the driving resistance of the pile can be reduced in some soils to the extent that the pile can be installed under its own weight or with minimal additional ballast. As a result, this can avoid or reduce the need to use an impact hammer to facilitate pile installation.

[0049] FIG. 3 shows a schematic cross-sectional view of a foundation according to a second embodiment of the present invention. This second embodiment operates in substantially the same manner as the first embodiment shown in FIGS. 1 and 2, except that it further includes a second nozzle array having a plurality of separation nozzles 10 distributed circumferentially and axially on the inner surface 8 of the insertion section 6. The separation nozzles 10 provide an injection distribution to help maintain separation between the soil 5 facing the inner surface 8, vertically upward around the inner circumference of the body, and along its axis. In this way, the separation nozzles 10 function as a means for maintaining the communication channel 11 in an open state by preventing the soil from the inner soil struts from relaxing again and contacting the pile 2. In this embodiment, the separation nozzles 10 are shown as being oriented in the proximal direction to inject fluid upward toward the inner cavity 12 of the foundation above the soil 5. This promotes an upward flow of fluid through the channel 11 for transporting sediment and generates a pressure that counteracts the downward hydrostatic pressure. In other embodiments, the separation nozzles 10 may be oriented radially inward or tangentially.

[0050] Therefore, it will be understood that with the above methods and arrangements, the foundation can be more easily installed in the soil. This can reduce costs and minimize noise during installation. After the foundation is installed to the required depth, the fluid injection system shuts off, and as the soil particles settle and compress over time due to the periodic vibration effect, excess water can be discharged from the area, thereby enabling the soil to be stabilized again.

[0051] It will be understood that the above embodiments are shown for illustrative purposes only of the application of the present invention. In practice, the present invention may be applied to many different configurations, and detailed embodiments are straightforward for those skilled in the art to implement.

[0052] For example, while the above embodiments use injection pressure and fluid discharge flow rate to control the suspension pressure, it will be understood that other control parameters may additionally be used.

[0053] In this regard, for example, additional ballast can be used to increase the total weight of the foundation and thus the downward driving force applied. In this way, the controller 16 can take into account the total weight of the foundation during installation by appropriately adjusting the injection and pump flow rates.

[0054] The controller may also include means for controlling the installation speed that can affect the flow rate at which the suspension pressure increases for a given injection flow rate. For example, if the installation speed is slow, the time for the soil to be eroded by the injection is longer. The controller 16 can vary the installation speed in combination with other parameters.

[0055] It will also be understood that additional mechanisms and systems can be used in combination with the fluid injection system to further reduce the driving resistance. For example, the foundation may further incorporate electrodes for electroosmosis. In this way, the fluid injection system can act synergistically with the electroosmosis system.

[0056] The means for maintaining the communication channel 11 in the second embodiment uses the separation nozzle 10, but it will also be understood that other means are also conceivable. For example, a drill mechanism provided adjacent to the inner wall 8 can be used to maintain the communication channel 11.

[0057] Finally, in the above exemplary embodiment, the foundation was monopile type, nevertheless, it will be understood that other foundations such as suction bucket foundations and jacket foundations are also possible. The present invention can also enable a simplified removal of the foundation during removal. In particular, the nozzle can be used to apply high-pressure fluid to reduce the friction on the surface of the foundation when being withdrawn.

Claims

1. A method for installing a foundation (1) for a structure, comprising the steps of: inserting a foundation body (2) into the soil (5) in an insertion direction, the foundation body (2) having at its tip a tip portion (7) defining an opening in an internal cavity (12) defined by an inner wall (8); injecting fluid from a number of nozzles (9) provided in a tip region of the foundation body (2) to direct the fluid in a tip direction into the soil (5) in front of the tip portion (7); Varying the amount of fluid at the proximal end of said internal cavity (12) using a pump arrangement (13); controlling the pump arrangement (13) using a controller (16) to vary the fluid suspension pressure adjacent the tip (7) in a fluid communication channel (11) between the base end of the internal cavity (12) and the tip (7) formed between the inner wall (8) and the soil (5); The method of claim 1, wherein the controller (16) varies the fluid suspension pressure as the tip (7) is inserted deeper into the soil (5) based on a target fluid suspension pressure that varies with tip depth.

2. 2. The method of claim 1, further comprising controlling a flow rate of the fluid ejected from the plurality of nozzles (9) to vary the fluid suspension pressure in the fluid communication channel (11).

3. The method of claim 1 or 2, wherein the target fluid suspension pressure increases with the tip depth.

4. The method according to any one of claims 1 to 3, wherein the target fluid suspension pressure is determined based on properties of the soil (5).

5. The method of claim 4 , wherein the target fluid suspension pressure varies with soil type for different soil layers.

6. The method of claim 1 , wherein the target fluid suspension pressure is determined based on an estimated active earth pressure coefficient.

7. 7. The method according to claim 1, further comprising the step of determining the target fluid suspension pressure, which varies as a function of the tip depth, prior to the step of ejecting the fluid from the plurality of nozzles (9).

8. said step of controlling said pump arrangement (13) using said controller (16) comprising the step of controlling based on received sensor input; The method of any of claims 1 to 7, wherein the received sensor input comprises an input corresponding to the fluid suspension pressure adjacent the tip (7) and / or an input corresponding to a ground resistance.

9. 9. The method according to any one of claims 1 to 8, wherein the step of varying the amount of fluid at the base end of the internal cavity (12) comprises the step of the pump arrangement (13) discharging water from the internal cavity (12) and / or supplying water to the internal cavity (12).

10. The method according to any of the preceding claims, further comprising the step of maintaining the fluid communication channel (11) open between the base end and the tip end (7) of the internal cavity (12) using a means for separating the inner wall (8) and the soil (5).

11. A structural foundation (1), a foundation body (2) for insertion in an insertion direction into soil (5), the foundation body (2) having at its tip a tip portion (7) defining an opening in an internal cavity (12) defined by an inner wall (8); a number of nozzles (9) provided in a tip region of the foundation body (2) for injecting fluid in a tip direction into the soil (5) in front of the tip portion (7); a pump arrangement (13) for varying the amount of fluid at the proximal end of said internal cavity (12); a controller (16) for controlling the pump arrangement (13) to vary a fluid suspension pressure adjacent the tip (7) in a fluid communication channel (11) between the base end of the internal cavity (12) and the tip (7) formed between the inner wall (8) and the soil (5); The controller (16) varies the fluid suspension pressure as the tip (7) is inserted deeper into the soil (5) based on a target fluid suspension pressure that varies with tip depth.

12. a pressure sensor (24) for determining the fluid suspension pressure; and a ground resistance sensor (23) for determining the resistance to insertion of the foundation body (2) into the soil (5), The method of claim 11, wherein controlling the pump arrangement (13) using the controller (16) includes controlling based on sensor inputs received from the pressure sensor (24) and the ground resistance sensor (23).

13. A structural foundation (1), a body (2) for insertion in an insertion direction into soil (5) during installation, the body (2) having a tip (7) at a distal end thereof, the tip (7) defining an opening in an internal cavity (12) defined by an inner wall (8); one or more nozzles (9) for directing a jet of fluid into the soil (5) forward of the tip (7) in a tip-directed manner; a pump (13) for discharging fluid from a proximal end of the internal cavity (12); and means (10) for maintaining a fluid communication channel (11) between the base end of the internal cavity (12) and the tip end (7) formed between the inner wall (8) and the soil (5).

14. A controller (16) for controlling the installation of a foundation (1) of a structure, comprising: The foundation (1) comprises a foundation body (2) for insertion in an insertion direction into soil (5), The body (2) has at its distal end a distal end portion (7) defining an opening into an internal cavity (12) defined by an inner wall (8); The controller (16) a jet control for controlling jetting of fluid from a number of nozzles (9) disposed in a tip region of the body (2) to direct fluid in a tip direction into the soil (5) forward of the tip portion (7); a pump control for controlling a pump arrangement (13) to vary the amount of fluid at the proximal end of the internal cavity (12); the controller (16) varying a fluid suspension pressure adjacent the tip (7) in a fluid communication channel (11) between the base end of the internal cavity (12) and the tip (7) formed between the inner wall (8) and the soil (5); The controller (16) varies the fluid suspension pressure as the tip (7) is inserted deeper into the soil (5) based on a target fluid suspension pressure that varies with tip depth.

15. 1. Software operating a controller (16) for controlling the installation of a foundation (1) of a structure, comprising: The foundation (1) comprises a foundation body (2) for insertion in an insertion direction into soil (5), The base body (2) has at its tip a tip portion (7) defining an opening in an internal cavity (12) defined by an inner wall (8); The software comprises: instructions for controlling the ejection of fluid from a number of nozzles (9) disposed in a tip region of said body (2) to direct fluid in a tip direction into said soil (5) forward of said tip portion (7); and instructions for controlling a pump arrangement (13) to vary the amount of fluid at the proximal end of said internal cavity (12), a fluid suspension pressure varies adjacent to the tip portion (7) within a fluid communication channel (11) between the base end of the internal cavity (12) and the tip portion (7) formed between the inner wall (8) and the soil (5); The fluid suspension pressure varies as the tip (7) is inserted deeper into the soil (5) based on a target fluid suspension pressure that varies with tip depth.

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