Electrode and method of installing a foundation

Abstract

Electrode (10) for use during electro-osmosis installation of a foundation (100) into soil. The electrode (10) comprising an electrode body (12) for insertion into the soil. The electrode body (12) comprising an insertion end (14) and one or more electrically conductive regions (18) for forming a second electrode to a first electrode on the foundation. An internal fluid channel is formed in the electrode body (12) for supplying fluid. The electrode (10) further comprises a nozzle (28) for jetting the supplied fluid ahead of the insertion end (14) of the electrode body (12) for facilitating the insertion of the electrode body (12) into the soil (200).

Description

[0001] The present invention concerns an electrode for foundation installation and a method of installing a foundation using said electrode. In particular, the present invention concerns using the electrode to aid in the installation of structural foundations using electro-osmosis. For example, structural foundations may be piles, tubular piles, closed ended piles, monopiles, bucket foundations, suction bucket foundations, suction pile foundations, suction caisson foundations, suction anchors, sheet piles, spudcans, shallow or gravity base foundations, and other types of temporary and permanent shallow or deep foundations, that may be inserted into a soil for supporting structures such as buildings, walls, sheet pile walls, offshore structures, and wind turbines. The electrode structure of embodiments of the present invention are most suited to soils of low hydraulic permeability, typically with a high clay or silt content, as are often associated with offshore, deep sea, and coastal locations. The disclosure is also relevant to methods of installing foundations using the electrode structure.

[0002] Structural foundations are often installed by driving the foundation into the ground using a pile hammer to apply a series of axial impacts to drive the foundation down into the soil. As it is driven, soil is displaced by the foundation pile, thereby compressing the surrounding soil and increasing the axial friction forces along the foundation's body. This thereby increases the foundation's axial load-bearing capacity. However, as the shear forces to overcome, while driving the foundation through the soil, are very high, several issues arise. Firstly, the high impact forces that are required for pile driving impose significant mechanical requirements on the foundation itself to avoid its failure during installation. Furthermore, the noise generated by the impacts can be extremely high. In the case of offshore installations, this poses a particularly significant environmental hazard to marine life.

[0003] In this respect, the installation of foundations for offshore structures can cause detrimental physical and behavioural effects to marine wildlife. In recent years, significant efforts have been made to mitigate the noise generated during such installations. For instance, bubble curtains or pile-in-pile systems are often required to reduce the level of noise emitted from the piling location. However, the use of such noise mitigating measures adds considerable expense to the installation of offshore structures. Furthermore, this is a particular issue for larger foundations where the increased dimensions can render current noise mitigation options insufficient.

[0004] To address the above, research has been made into using electro-osmosis to reduce the pile driving resistance in offshore installations by attracting water in the soil towards the foundation body surface, with this surface acting as a cathode. The pore water pressure at the interface between the foundation body and surrounding soil builds up, reducing the effective stresses, and thereby lowering the friction between the soil grains and the foundation surface. This has a lubricating effect by reducing the shear resistance required to drive the foundation down into the ground. This in turn allows installation to be achieved with a lower number of impacts / hammer energy or even by using ballasting only, without requiring a hammer. This may thereby facilitate quicker installation and less noise disturbance.

[0005] US 4,157,287 discloses one such pile driving system using electro-osmosis. In US 4,157,287, an electro-conductive tubular pile is provided with an electrically insulating coating on its exterior lateral surface and its interior lateral surface is left exposed to form a cathode. One or more anodes are then placed on the seabed adjacent to the pile and a direct current is applied to cause water to migrate through the soil down the outside of the pile towards the cathodic interior at its open end at the bottom. However, there are several issues with this arrangement. Firstly, to generate sufficient field strength to achieve an electro-osmotic effect, very high voltages are required because of the long distance between the electrodes, which itself is hazardous. Secondly, because of the high voltages, the integrity of the electrical insulation over the entire exterior of the pile is crucial to avoid short circuiting. This makes the manufacture of such piles for use in this system much more expensive and less tolerant to defects. In practical terms, this means that the technique is too risky commercially to rely on; a bubble curtain and larger hammer would still be required at the location as a contingency if the coating was to fail during installation. As such, any potential cost savings are negated.

[0006] Faced with these issues, the Applicant's own developments in this field led to the invention disclosed in WO2018 / 115176. In this case, an anode was provided as a strip secured to the body of the foundation, with a recess or projection being used as a spacing formation to form a gap between the anode surface and the soil when the foundation was installed. In use, the body acts as the cathode and, since both electrodes were effectively integrated into the foundation itself, this avoided the need to provide and install a separate counter-electrode on the seabed. At the same time, although the soil around the anode would dehydrate, the spacing formation acted to prevent adhesion with the dehydrated soil.

[0007] Although the concepts taught in WO2018 / 115176 have proven to be effective, the spacing formation may increase the complexity and cost of manufacturing the monopile foundation. For example, whilst some embodiments proposed seating the anode in a recess to provide a gap with the soil, it is relatively expensive to machine a recess of sufficient depth into the monopole body to create the necessary spacing.

[0008] The present invention therefore seeks to address the above issues with the prior art.

[0009] According to a first aspect of the present invention, there is provided an electrode for use during electro-osmosis installation of a foundation into soil, the electrode comprising: an electrode body for insertion into the soil, the electrode body comprising an insertion end and one or more electrically conductive regions for forming a second electrode to a first electrode on the foundation; an internal fluid channel formed in the electrode body for supplying fluid; and a nozzle for jetting the supplied fluid ahead of the insertion end of the electrode body for facilitating the insertion of the electrode body into the soil.

[0010] In this way, a remote electrode is provided for enabling electro-osmosis for easing foundation installation by reducing soil resistance. As such, the electrode may be provided as a part of an electro-osmosis system which works in combination with a conductive surface provided on the body of the foundation to form an electro-osmosis circuit for attracting water to the foundation. This thereby lowers the forces required for installation, allowing a foundation to be installed with less noise. As the electrode is provided as a separate structure to the foundation, it can be pre-installed at the installation location before the foundation is inserted. Furthermore, by integrating jetting into the electrode, the electrode may be installed more easily by eroding the soil ahead of the insertion end of the electrode body as it is inserted. Once used during the installation of a foundation, the electrode can also be withdrawn and re-used or partially re-used for multiple foundation installations, thereby helping to reduce costs. In addition, the jetting fluid may also act to maintain the electro-osmotic effect, thereby preventing undue dehydration of the soil, and lubricating the foundation body.

[0011] In embodiments, the nozzle is provided at or adjacent an insertion end of the electrode body for jetting fluid in an insertion direction.

[0012] In embodiments, the electrode further comprises an inlet for receiving high pressured fluid for feeding the internal fluid channel.

[0013] In embodiments, the electrode further comprises irrigation holes for supplying fluid to the one or more electrically conductive regions.

[0014] In embodiments, the electrode further comprises a secondary fluid supply for supplying fluid to the irrigation holes.

[0015] In embodiments, the electrode further comprises a plurality of electrode bodies, as described above, for insertion into the soil. In this way, a plurality of electrode bodies may be provided in the soil around the foundation or within the foundation's interior for enabling electro-osmosis for easing foundation installation by reducing soil resistance over the exterior and / or interior lateral surfaces.

[0016] In embodiments, the electrode further comprises a frame for connecting the plurality of electrode bodies. In this way, the plurality of electrode bodies can be supported around or within the interior of the foundation. At the same time, because the electrode provides a plurality of electrode bodies on the frame, as each electrode body comprises at least one electrically conductive region, a large electric field area can be created with the body of the foundation. This can also be provided without modification to the foundation body. As such, embodiments of the invention may be implemented straightforwardly and cost-effectively.

[0017] In embodiments, the frame comprises a manifold in fluid communication with the internal fluid channels in the plurality of electrode bodies. In this way, the frame may be formed as a manifold for feeding fluid to the internal fluid channels in the electrode bodies. This may thereby allow fluid to be supplied from a single to be distributed and jetted out through a plurality of nozzles.

[0018] In embodiments, the frame comprises two or more sections separably connected together. In this way, the electrode structure can be separated into sections for transport and, once the foundation has been installed, can be separated for easier removal from the foundation body.

[0019] In embodiments, the electrode body comprises two or more sections connected by joints, such that the electrode body is foldable. In this way, the electrode body can be folded during storage on an installation vessel or in a warehouse and during transportation to an installation location on the vessel. As such, the electrode can occupy a much smaller area when stored or transported, thereby reducing the space required for the electrode.

[0020] In embodiments, the plurality of electrode bodies are evenly distributed on the frame. In this way, the electro-osmosis effect can take place evenly around or within the foundation.

[0021] In embodiments, the electrode further comprises a pressurised fluid supply for supplying pressurised fluid to the internal fluid channel.

[0022] In embodiments, the first electrode is configured to connect to a negative terminal of a power supply to form a cathode, and the second electrode is configured to connect to a positive terminal to the power supply to form an anode. In this way, an electro-osmotic effect can be generated to attract water in the soil to the body of the foundation to thereby reduce the force required to insert the body.

[0023] In embodiments, the electrode body comprises a plurality of electrically conductive regions, wherein each region is selectively activatable for forming a second electrode to a first electrode on the foundation. In embodiments, the electrode further comprises a controller for controlling the activation of the plurality of electrically conductive regions. In this way, the plurality of electrically conductive regions can be selectively controlled, for instance, based on soil conditions. For example, the conductive regions may be selectively activated only down to a depth corresponding to the thickness of an upper clay layer for concentrating the electro-osmosis effect in this region.

[0024] In embodiments, the foundation is a monopile comprising a hollow interior and an exterior surface, and wherein the electrode is configured to be inserted into the soil within the hollow interior or facing the exterior surface. In this way, the electro-osmotic effect can be provided over the interior surface of the foundation or around the external surface of the foundation.

[0025] According to a second aspect of the present invention, there is provided a method of installing a foundation using an electrode according to any one of the above, the method comprising: inserting the electrode into the soil; supplying fluid through the internal fluid channel of each electrode body for jetting the supplied fluid from its nozzle; connecting the first electrode to a negative terminal of a power supply; connecting the second electrode to a positive terminal of the power supply; inserting the foundation into the soil, such that the electrode is located within an interior of the foundation or facing an exterior surface of the foundation; and applying a potential difference across the first and second electrodes to form a cathode and anode, respectively, for generating an electroosmotic effect for attracting water in the soil to the body of the foundation.

[0026] In embodiments, the electrode is pre-installed into the soil before inserting the foundation into the soil.

[0027] In embodiments, the method further comprises the step of removing the electrode or part of the electrode from the soil once the foundation has been inserted to a desired installation depth, wherein the step of removing comprises connecting the first electrode to a positive terminal of a power supply and connecting the second electrode to a negative terminal of the power supply.

[0028] Illustrative embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows an isometric view of an electrode according to a first illustrative embodiment; Figure 2 shows an isometric view of an electrode according to a second illustrative embodiment; Figure 3 shows an isometric view of the electrode of Figure 2 placed around a foundation; Figure 4 shows a partial cross-section of two electrodes; and Figure 5A-5C shows the process of foundation installation according to an illustrative embodiment.

[0029] Figure 1 shows an isometric view of an electrode 10 according to a first embodiment of the invention. The electrode 10 is suitable for use during electro-osmosis installation of a foundation into soil. The electrode 10 comprises an electrode body 12 for insertion into the soil. The electrode body 12 comprises an insertion end 14 at a distal end of the foundation, for insertion into the soil.

[0030] The electrode body 12 is electrically conductive for allowing its external lateral surface 16 to function as a second electrode in an electro-osmosis system. In some embodiments, the electrode body 12 is formed of metal for providing the electrical conductivity throughout the material, although other configurations are possible. For instance, other materials may be used. In some embodiments, such as is described in further detail below in relation to Figure 1, discontinuous electrically conductive regions 18 are provided down a length of the electrode body 12. In embodiments this may be achieved, for instance, by applying a conductive coating to an exposed insulating surface provided on or forming the electrode body 12. In such arrangements, the electrically conductive regions 18 may function as activatable segments which are activatable individually or in groups for selectively enabling the electroosmosis effect at different depths.

[0031] As shown in Figure 1, the electrode body 12 comprises one or more electrically conductive regions 18 provided down the length of the electrode body 12, such that each electrically conductive region 20 functions as a respective second electrode to the first electrode on the foundation. In embodiments, a controller 22 is provided for controlling the activation of each one of the electrically conductive regions 18 the electrode body 12. For example, in embodiments, each conductive region 20 may be switched on or off independently, and / or different voltage levels may be applied to different regions. This may allow different electric resistivities in different soil layers to be accommodated, as well as allow regional reactivity to be controlled during installation to mitigate risks of electric currents exceeding safe limits.

[0032] In an embodiment, a terminal 24 is provided on the electrode body 12 for electrically connecting the one or more electrically conductive regions 18 to a power supply (not shown). The one or more electrically conductive regions 18 can be individually connected to the first terminal 24 by wiring (not shown). As such, the one or more electrically conductive regions 18 can each be activated by a controller 22 as part of the electroosmosis circuit.

[0033] The body 102 of the foundation comprises an electrically conductive surface for allowing its external lateral surface 104 to function as a first electrode. In some scenarios, the body 102 is formed of metal for providing the electrical conductivity throughout the material, although other configurations are possible. For instance, other materials may be used, and / or conductive regions may be formed by applying a conductive coating to an exposed lateral surface 104 of a non-conductive body 102. In this connection, for example, the body of the foundation may comprise an insulating material, such as concrete, with electrically conductive regions formed on the interior and / or exterior exposed lateral surface(s) of its body. In this way, the body of the foundation, or the electrically conductive regions on the body, can be electrically connected to the same power supply as the electrode body. In this way, once the electrode 10 is inserted into the soil it may form a second electrode to a first electrode on the foundation.

[0034] The electrode body 12 comprises an internal fluid channel 26 for supplying a fluid. At the insertion end 14 of the body 12, the body 12 comprises a nozzle 28 for jetting the supplied fluid ahead of the insertion end 14. In use, the jetted fluid may penetrate, break-up and displace soil ahead of the insertion end 14 for facilitating the insertion of the electrode body 12 into the soil. A pressurised fluid flow may be delivered to the internal fluid channel 26 by a feed pipe supplied from an installation vessel, or a secondary vessel.

[0035] During installation of the electrode, the electrode 10 in inserted into the soil 200, with the electrode body 12 being forced down under its own weight, by using a ballast, vibro-hammer or by using a jack. At the same time, insertion may be facilitated using jetting, with the nozzle 28 increasing the fluid velocity of the supplied fluid through the internal fluid channel 26. The jetted fluid can be used to erode the soil 200 immediately ahead of the insertion end 14 of the electrode body 12, thereby reducing the installation resistance required to insert the electrode 10 into the soil.

[0036] Figure 2 shows an isometric view of an electrode 10 according to a second embodiment of the invention. In this embodiment, the electrode 10 comprises a plurality of electrode bodies 12, as described above, and further comprises a frame 30 for connecting the plurality of electrode bodies 12, forming an electrode structure. The plurality of electrode bodies 12 extend from the frame 30 in a perpendicular direction. Preferably, the plurality of electrode bodies 12 are configured to extend substantially parallel to the interior or exterior lateral surface 104 of the foundation. As described above, each of the plurality of electrode bodies 12 comprise a nozzle 28 and in this embodiment are evenly distributed around the frame 30. In this way, the electrode 10 is suitable for positioning around a structural foundation 100, such as a monopile, as shown in Figure 3. However, it will be understood that whilst the electrode 10 in this embodiment is shown provided around the exterior of the foundation 100, in other embodiments the electrode 10 may be sized to fit within the interior bore of the foundation 100.

[0037] The electrode 10 may be inserted into the soil before the foundation 100. That is, the electrode 10 may be preinstalled at the installation location for the foundation. In other embodiments, the electrode 10 may be inserted with the foundation 100.

[0038] In this embodiment, the frame 30 has a circular shape, although other configurations are possible depending on the foundation shape the electrode is being used with. The frame 30 may be formed of sections 34 for allowing the frame 30 to be split for easier transport and assembly and disassembly. The sections 34 of the frame 30 may be coupled together using a coupling, such as bolts or a mechanical locking mechanism. While Figure 2 shows the frame 30 formed of two sections 34, it is to be understood that any number of sections 34 can be provided.

[0039] The frame 30 comprises a fluid channel within the frame 30 forming a manifold for feeding the internal fluid channels 26 of the plurality of electrode bodies 12, as is described in further detail below in relation to Figure 4. The manifold 36 is configured to receive the fluid from the pressurised fluid flow and distribute the fluid to each of the internal fluid channels 26 in the plurality of electrode bodies 12.

[0040] In an embodiment, the first terminal 24 is provided on the frame 30 for electrically connecting the one or more electrically conductive regions 18 of the electrode bodies 12 to a power supply (not shown). The one or more electrically conductive regions 18 are individually connected to the first terminal 24 on the frame 30 by wiring (not shown). As such, each of the one or more electrically conductive regions 18 of the electrode bodies 12 can each be activated by a controller 22 as part of the electroosmosis circuit.

[0041] Figure 3 shows an isometric view of the electrode 10 of Figure 2 placed around a portion of a foundation 100. The electrode 10 is sized and shaped according to the foundation 100, such that the electrode 10 can be placed around the body 102 of the foundation 100. The foundation 100 comprises a hollow tubular body 102 having a proximal end 106 for supporting, for example, a wind turbine and a distal end 108 that has been inserted into the soil. The region of the distal end 108 that penetrates the soil is referred to as the insertion region 110 and may vary depending on the required installation depth of the foundation 100.

[0042] When the first terminal 24 on the frame 30 is connected to a positive terminal of the power supply, and the body 102 is connected to a negative terminal of a power supply, the plurality of electrode bodies 12 form anodes. Accordingly, when the body 102 of the foundation 100 is connected to a negative terminal of the power supply, the body 102 of the foundation 100 forms a cathode. During foundation installation, where the plurality of electrode bodies 12 are the anode and the body 102 is the cathode, water in the surrounding soil is attracted to the body 102, softening the soil at an interface between the foundation 100 and the soil, and forming a lubricating film over the exterior and / or interior lateral surfaces 104 of the body 102.

[0043] During foundation installation, the distal end 108 of the foundation 100 is inserted into the soil 200 in an insertion direction. Penetration may be facilitated under the weight of the foundation 100 itself, by applying additional ballast 302, by pile driving hammer impacts, or using a vibro-hammer for vibratory driving. The distal end 108 of the foundation 100 is inserted into the soil until a required installation depth has been reached. The installation depth varies depending on the soil composition and the size / weight of the foundation 100 itself and corresponds to the insertion region 110 of the foundation 100.

[0044] Each of the plurality of electrode bodies 12 have a length for projecting into the soil a sufficient distance for establishing the electro-osmosis effect with the conductive surface regions provided on the foundation. For instance, in soil structures comprising a thick upper clay layer with an underlying region of sand, the length may be selected to penetrate only the clay layer for establishing the electro-osmosis in this moist soil structure, without needing to penetrate into the dryer sand layer below. Consequently, in some embodiments, the electrode bodies 12 may have relatively long lengths corresponding to the installation depth of the foundation, whereas in other embodiments the electrode bodies 12 may be shorter depending on the soil compositions. In one example, the electrode body or bodies 12 may have a length of 6-12 meters for, for example, projecting into a clay top layer. In other embodiments, the length of the electrode body or bodies 12 may be longer such that electrode 10 is suitable for various soil compositions. In this case, the controller 22 may be configured to only activate electrically conductive regions 20 that are within soil layers where the electro-osmosis effect can be established.

[0045] Figure 4 shows a cross-sectional view through the electrode 10 at an intersection between the frame 30 and two electrode bodies 12. In this embodiment, the frame 30 is a circular, hollow ring with an internal cavity forming a manifold 36, suitable for allowing a fluid to flow through the internal cavity 36. The internal fluid channels 26 of the plurality of electrode bodies 12 are in fluid communication with the manifold 36 of the frame 12. In an embodiment, the frame 12 comprises an inlet 38 for receiving the pressurised fluid flow and the plurality of electrode bodies 12 each comprise a nozzle 28 for jetting the supplied fluid in a direction substantially parallel with the insertion direction of the foundation 100 and ahead of the insertion end 14 of the electrode body 12 for facilitating the insertion of the electrode body 12 into the soil 200.

[0046] As described above, before or during foundation 100 installation, the plurality of electrode bodies 12 are each forced into the soil 200. At the same time, high-pressure liquid is supplied via the manifold 36 to be jetted from the nozzles 28. The nozzles 28 act to further increase the fluid velocity of the jetted liquid, such that the supplied fluid can be used to erode the soil immediately head of the insertion end 14 of the plurality of electrode bodies 12. In this way, the force required to insert the electrode 10 into the soil can be minimised.

[0047] Each of the plurality of electrode bodies 12 have a small surface area, when compared to the body 102 of the foundation 100. As such, when each of the plurality of electrode bodies 12 are connected to the power supply, there is a high current density in each of the plurality of electrode bodies 12. As a result, the temperature of the plurality of electrode bodies 12 increases, which decreases the life of the plurality of electrode bodies 12. In addition, when the plurality of electrode bodies 12 form anodes, water is pushed away from the anodes causing the soil to dry and bake in the vicinity of the anodes. The delivery of fluid through the nozzles 28 may therefore function to cool and hydrate the plurality of electrode bodies 12 during installation of the foundation 100.

[0048] As mentioned above, the plurality of electrode bodies 12 in this embodiment comprise a plurality of electrically conductive regions 18. The controller 28 may selectively activate each of the plurality of electrically conductive regions. For example, this could be used during installation of the electrode 10 to generate a self-electro-osmosis effect over the electrode body to aid its insertion. For example, different conductive regions can be used to create a potential difference across areas of the electrode itself, to attract water during installation. Once the electrode 10 installed, all the conductive regions 18 may be activated to become the anode.

[0049] In addition to the electro-osmotic effect, electrolysis results in chemical oxidation and reduction reactions at the anode and cathode respectively. The range of possible reactions depends on what ionic species are available or present and thus the introduction of tailored conditioning agents can serve to enhance or suppress particular reactions. As an example, in pure water with inert electrodes H 2 gas and OH- anions are generated at the cathode and 0 2 gas and H +< cations are generated at the anode. As a result of the electric field, the cations and anions migrate towards the cathode and anode, respectively. Due to the higher mobility of H +< cations, the associated acid front generally sweeps across a larger volume of soil 200 compared to that swept by hydroxide anions. This acidity in the soil 200 can have several unwelcome effects including reducing biological activity, lowering the electroosmotic permeability of the soil 200 and accelerating corrosion of the foundation 100 itself.

[0050] To counter the above effects, chemical conditioning fluid may be pumped through the electrode 10 to neutralise or dilute the positively charged H +< ions. In an embodiment, the plurality of electrode bodies 12 may further comprise irrigation holes for dispersing the fluid along the length of the electrode bodies 12. In some embodiments, these irrigation holes may be used to supply the chemical conditioning fluid delivered via a secondary fluid supply, separate to the pressurised fluid flow used for jetting. In addition, conditioning fluids may be selected to modify the surface chemistry of clay particles, or to precipitate cements in pore spaces. Such changes can increase the strength and stiffness of the soil 200. For instance, during phases of normal polarity, lime or calcium chloride solutions may be introduced through the electrode 10 as modifying agents, upon reverse polarity such conditioners could include sodium silicate to participate in cementation reactions. In addition, the internal fluid channel 26 of each, or some, electrodes bodies 12 may comprise a granular material, such as those described above, to prevent baking of the soil 200. During installation of the of the electrode or the foundation 100, finest particles may be dispersed first by the pressurised fluid, leaving coarse material in the jetted annulus. This may help to promote further soil erosion as coarse particle are driven by the fluid flows.

[0051] Figures 5A-5C show schematic illustrations of the electrode 10 of Figures 2 and 3 being used during the installation of foundation 100. As shown in Figure 5A, the body 102 of the foundation 100 is lowered by a crane 304 on an installation vessel 300 towards the soil 200. The electrode 10 is also lowered by the crane 304 on the installation vessel 300, or by another crane located on the installation vessel 300 or a secondary vessel. The electrode structure 10 can be lowered down around the foundation 100. Alternatively, the electrode 10 may be first located onto the seabed at the beginning of the installation process, with the electrode bodies 12 inserted into the soil 200. As such, the foundation 100 can then be lowered through, or around, the frame 30 of the electrode 10.

[0052] As the electrode 10 is inserted into the soil 200, pressurised fluid is supplied through its nozzles 28 at the insertion end 14 of the electrode bodies 12 for eroding the soil 200 below. The pressurised fluid can be supplied by the installation vessel 300 or by a secondary vessel.

[0053] Once the electrode 10 is inserted into the soil and the conductive regions are covered, they can be activated such that a DC power supply on the installation vessel or support vessel applies a potential difference through the terminal 24 to establish the electro-osmosis effect between the electrode 10 and the body 102 of the foundation 100. The electro-osmosis effect may then facilitate the insertion of the body 102 deeper into the soil 200 as the shear resistance between the soil 200 and the buried lateral surfaces 104 of the body 102 of the foundation 100 may be reduced.

[0054] Penetration of the foundation 100 may be facilitated under the weight of the foundation 100 itself, by applying additional ballast 302, using pile driving hammer impacts, or by vibratory driving. Advantageously, with embodiments of the present intention, the installation resistance may be sufficiently reduced that installation can be achieved without the need to apply hammer impacts or with much lighter hammer forces.

[0055] Once the distal end 108 of the foundation 100 has reached the required depth, as shown in Figure 5B, the shear resistance between the soil 200 and the body 102 of the foundation 100 can be restored by turning off the power supply. This stops the electro-osmosis effect and stabilises the foundation 100 by reducing its lubrication. However, as clay has a low permeability, excess pore pressure next to the foundation 100 can take time to dissipate back into the soil 200. Therefore, stabilisation may optionally be further enhanced by temporarily reversing the polarity of the power supply so that the body 102 of the foundation 100 acts as the anode and at least one of the electrodes bodies 12 act as a cathode. This reverses the electric field so that pore water is driven away from the lateral surface 104 of the body 104, thereby enhancing the adhesion strength of the interface between the body 104 and the soil 200. Moreover, reversing the polarity of the power supply may also be used during the removal stage discussed below to ease the removal of the electrode 10 by attracting water thereto and lubricating its lateral surfaces as it is withdrawn from the soil.

[0056] As shown in Figure 5C, once the installation of the body 102 of the foundation 100 is complete, the electrode 10 may then be removed from the body 102 of the foundation 100. For example, the frame 30 may be split into sections allowing the electrode 10 to be more easily removed from the body 102 of the foundation 100. For this, the electrode 10 may be initially raised by the crane 304 and then split into sections 34 closer to the installation vessel 300, or a secondary vessel, where it is easier to retrieve the sections of the electrode. Alternatively, in other embodiments, the electrode 10 may be left in place following installation, or it may be partially left in place. For instance, the electrode bodies 12 may be detached from the frame 30, allowing the main fluid manifold 36 and electrical connections to be reused, but leaving electrode bodies 12 to avoid further disturbing the soil 200.

[0057] 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.

[0058] For example, although in the above illustrative embodiments, the foundation 100 has been a hollow body 102 such as a monopile, the invention may be applied to other foundations 100, such as bucket foundations, axial piles and sheet piles, spudcans, and other gravity base foundations.

[0059] Furthermore, although the frame has been described as surrounding the body of the foundation, it will be understood that the frame may not completely surround the body and may for instance be provided as a section following the profile of the body. In such arrangements, a plurality of sections may be used in combination.

[0060] In addition, although in the above illustrative embodiments, the electrode 10 has been described using a power supply provided on the installation vessel 300, it will be understood that other arrangements are possible. For example, a battery or generator located on the foundation 100 or electrode 10 itself may be used as a power supply.

[0061] Moreover, although the present invention has been described in reference to offshore locations, it will be understood that the invention may be used in other locations where the soil 200 has a sufficiently high moisture content for electro-osmosis. This may include, for example, fine-grained, cohesive clay sediments, low permeable problem soils, expansive soils, dispersive soils, high compressible clays, marine clays, sensitive clays, quick clays, saline / sodic soils, and soft peat. Such soft clay soils are often associated with coastal soils, as well as estuaries, river and lake-side locations.

[0062] In this respect, with the invention, by applying a DC voltage across between the electrode 10 and the body 102 of the foundation 100, two electro-osmosis effects can be generated in the surrounding soil 200. Firstly, the electro-osmosis causes the movement of water which acts to weaken or strengthen the soil 200 at a closed boundary depending on the direction of flow. As such, an excess of soil pore pressure may be generated to lubricate the soil / foundation interface with a water film during installation or removal. Alternatively, by reversing the polarity, a negative pore pressure may be used to restore or improve soil structure and interface friction for stabilising the foundation 200. For instance, soft clay or other cohesive soils may be consolidated around the foundation for strength by electro-osmotically pushing water out of the soil 200. A second effect of electro-osmosis is that it acts to move ions within the soil 200, relative to the foundation. The ion effect may allow infiltration of cementing electrolytes to cement the foundation in place, which may be particularly useful with granular soils.

Claims

1. An electrode for use during electro-osmosis installation of a foundation into soil, the electrode comprising: an electrode body for insertion into the soil, the electrode body comprising an insertion end and one or more electrically conductive regions for forming a second electrode to a first electrode on the foundation; an internal fluid channel formed in the electrode body for supplying fluid; and a nozzle for jetting the supplied fluid ahead of the insertion end of the electrode body for facilitating the insertion of the electrode body into the soil.

2. The electrode according to claim 1, wherein the nozzle is provided at or adjacent an insertion end of the electrode body for jetting fluid in an insertion direction.

3. The electrode according to claim 1 or 2, further comprising an inlet for receiving high pressured fluid for feeding the internal fluid channel.

4. The electrode according to any preceding claim, further comprising irrigation holes for supplying fluid to the one or more electrically conductive regions.

5. The electrode according to claim 3, further comprising a secondary fluid supply for supplying fluid to the irrigation holes.

6. The electrode according to any preceding claim, further comprising a plurality of electrode bodies for insertion into the soil.

7. The electrode according to claim 6, further comprising a frame for connecting the plurality of electrode bodies.

8. The electrode according to claim 7, wherein the frame comprises a manifold in fluid communication with the internal fluid channels in the plurality of electrode bodies.

9. The electrode according to any preceding claim, further comprising a pressurised fluid supply for supplying pressurised fluid to the internal fluid channel.

10. The electrode according to any preceding claim, wherein the first electrode is configured to connect to a negative terminal of a power supply to form a cathode, and the second electrode is configured to connect to a positive terminal to the power supply to form an anode.

11. The electrode according to any preceding claim, wherein the electrode body comprises a plurality of electrically conductive regions, wherein each region is selectively activatable for forming a second electrode to a first electrode on the foundation.

12. The electrode according to claim 11, further comprising a controller for controlling the activation of the plurality of electrically conductive regions.

13. The electrode according to any preceding claim, wherein the foundation is a monopile comprising a hollow interior and an exterior surface, and wherein the electrode body is configured to be inserted into the soil within the hollow interior or facing the exterior surface of the foundation.

14. A method of installing a foundation using an electrode according to any one of claims 1-13, the method comprising: inserting the electrode into the soil; supplying fluid through the internal fluid channel of each electrode body for jetting the supplied fluid from its nozzle; connecting the first electrode to a negative terminal of a power supply; connecting the second electrode to a positive terminal of the power supply; inserting the foundation into the soil, such that the electrode is located within an interior of the foundation or facing an exterior surface of the foundation; and applying a potential difference across the first and second electrodes to form a cathode and anode, respectively, for generating an electroosmotic effect for attracting water in the soil to the body of the foundation.

15. The method according to claim 14, further comprising the step of removing the electrode or part of the electrode from the soil once the foundation has been inserted to a desired installation depth, wherein the step of removing comprises connecting the first electrode to a positive terminal of a power supply and connecting the second electrode to a negative terminal of the power supply.

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