Foundation for a structure and method of installing the same

Abstract

A foundation (1) for a structure (7) comprises a main body (8) having a distal end (10) and a lateral surface (11) for insertion into soil (2). At least one area of ​​the lateral surface (11) forms a first electrode. One or more second electrodes (9) are provided on the main body (8) and are coplanar with or protrude from the lateral surface (11). Each second electrode (9) extends laterally around the lateral surface (11) and is electrically insulated from it by an insulating strip (12) provided between each second electrode and the lateral surface. During installation, a voltage may be applied across the electrodes to induce an electroosmotic effect to reduce installation resistance.

Description

Technology Field

[0001] The present invention relates to foundations for structures and methods and systems for installing the same. In particular, the present invention relates to structural foundations that can be inserted into soil to support structures such as buildings, walls, sheet pile walls, coastal structures, and wind turbines, such as, for example, piles, tubular piles, closed-end piles, monopiles, bucket foundations, suction bucket foundations, suction pile foundations, suction submerged foundations, suction anchors, sheet piles, spud cans, shallow or gravity-based foundations, and other forms of temporary and permanent shallow or deep foundations. The foundations of the present invention are best suited for soils that typically have high clay or silt content and low hydropermeability, as is often associated with coastal, deep-sea, and seaside locations. Background Technology

[0002] Structural foundations are installed by driving the foundation into the ground using pile hammers to apply a series of axial impacts. As the piles are driven, the soil is displaced by the foundation piles, compressing the surrounding soil and increasing axial friction along the foundation body. Consequently, this increases the axial load-bearing capacity of the foundation. However, several problems arise because the shear forces that must be overcome while driving the foundation through the soil are very large. First, the high impact forces required to drive the piles impose significant mechanical requirements on the foundation itself to avoid failure during installation. Additionally, the noise generated by the impact can be very high. In the case of coastal installations, this poses a particularly significant environmental risk to marine life.

[0003] In this regard, the installation of foundations for coastal structures can cause physical and behavioral harmful effects on marine life. In recent years, significant efforts have been made to mitigate the noise generated during such installations. For example, bubble curtains or pile-in-pile systems are frequently required to reduce noise levels emitted from pile work sites. However, the use of these noise mitigation measures adds a significant cost to the installation of coastal structures. Furthermore, this is a particular problem for larger foundations, where increasing dimensions may render current noise mitigation options insufficient.

[0004] To address this, research is being conducted on reducing the resistance to driving piles in coastal installations by using electroosmosis to draw water from the soil toward the foundation body, which acts as a cathode. Porous hydrostatic pressure accumulates at the interface between the foundation body and the surrounding soil, lowering friction between soil grains and the foundation surface by reducing effective stress. This provides a lubricating effect by reducing the shear resistance required to drive the foundation into the ground. Consequently, this enables installation to be achieved using only ballast processing without a channel or hammer, or with lower impact / hammer energy. As a result, installation can be faster and noise disturbances can be easily reduced.

[0005] U.S. Patent No. 4,157,287 discloses such a system for driving piles using electro-osmosis. In U.S. Patent No. 4,157,287, an electrically conductive tubular pile is provided with an electrical insulation coating on its outer lateral surface, and its inner lateral surface is exposed to form a cathode. Then, one or more anodes are positioned on the seabed adjacent to the pile, and a direct current is applied to drive them through the soil beneath the outer side of the pile from the open end at the bottom toward the inside of the cathode. However, there are several problems with this arrangement. First, the system of U.S. Patent No. 4,157,287 requires the anodes to be installed on the seabed adjacent to the pile. This places a significant burden on installation time and cost. Second, very high voltages are required to generate sufficient electric field strength to achieve the electro-osmotic effect, which is dangerous in itself due to the long distance between the electrodes. Third, due to the high voltage, the integrity of the electrical insulation across the entire exterior of the pile is critical for avoiding short circuits. This forces the manufacturing of these files for use in this system to be much more expensive and nearly defect-free. Realistically, this means the technology is too risky to rely on commercially, and if the coating fails during installation, bubble curtains and larger hammers will still be required on-site as emergency measures. As such, all potential cost savings are nullified.

[0006] Faced with these problems, the applicant's own development in the field led to the invention disclosed in WO2018 / 115176. In this case, an anode is provided as a strip fixed to the main body of the foundation, and a recess or protrusion is used as a gap-forming part to form a gap between the surface of the anode and the soil when the foundation is installed. When in use, the main body acts as a cathode, and since both electrodes are effectively integrated into the foundation itself, this eliminates the need to provide and install a separate corresponding electrode on the seabed. At the same time, even if the soil around the anode is dehydrated, the gap-forming part acts to prevent adhesion with the dehydrated soil.

[0007] Although the concept taught in WO2018 / 115176 has proven effective, there have been some practical difficulties with commercial adoption. First, the gap-forming element has proven difficult to implement. Some embodiments have proposed seating the anode within a recess to provide a gap with the soil, but machining a recess of sufficient depth into the monopile body to create the required gap is relatively costly. Other embodiments involve using a drive shoe as a gap protrusion attached to the main lateral surface of the monopile body. However, these protrusions are prone to damage, and under many soil conditions, they have been shown to be ineffective in sufficiently separating the soil from the anode. Prior art literature

[0008] U.S. Registered Patent No. 4,157,287 International Published Patent WO2018 / 115176 The problem to be solved

[0009] Accordingly, the present invention aims to solve the above problems of the prior art and provides a foundation for a structure and a method for installing the same. means of solving the problem

[0010] According to a first aspect of the present invention, a foundation for a structure is provided, comprising: a main body having a lateral surface and a distal end for insertion into soil (at least one region of the lateral surface forms a first electrode); and one or more second electrodes provided on the main body and coplanar with or protruding from the lateral surface (each of the second electrodes extends transversely around the lateral surface and is electrically insulated from thereby by an insulating strip provided between each of the second electrodes and the lateral surface).

[0011] In this way, the present invention provides an arrangement in which the base assembly itself includes both the first and second electrodes, thereby eliminating the need to provide and install a separate corresponding electrode on the seabed. At the same time, because the second electrode is located coplanar with the lateral surface or provides a circumferential band protruding from the lateral surface, a relatively large electrode surface area can be provided without deformation of the base body or with minimal deformation. This contrasts with previous solutions that required machining a deep recess into the body or employing a smaller vertical electrode hidden behind a drive shoe protrusion. Thus, embodiments of the present invention can be implemented simply and cost-effectively.

[0012] When in use, an electrical potential difference is generated between different areas of soil surrounding the foundation itself, thereby inducing electroosmotic pressure and thus affecting the pumping of water through the soil. At the same time, because a potential difference can be established between different areas of the foundation, the distance between the electrodes can be relatively shorter, thereby allowing the use of lower voltages while still generating a sufficiently strong electric field to induce electroosmotic flow. During foundation installation where the second electrode is the anode and the main body is the cathode, water from the surrounding soil is drawn toward the main body, softening the soil and forming a lubricating film over its lateral surface. This makes the foundation easier to drive. While adhesion of dehydrated soil around the second electrode corresponds to this, the net advantage is a significant overall reduction in installation resistance. Additionally, multiple electrodes may be provided to be distributed axially along the main body to establish an electroosmotic effect across an expanded area of ​​the main body.

[0013] In an embodiment, one or more second electrodes comprise a plurality of second electrodes provided as a band across the main body. Thus, each second electrode may be formed from a continuous sheet of metal, and then the continuous sheet of metal is wrapped around all or part of the main body or around the circumference to conform to a lateral surface. Accordingly, this can simplify manufacturing.

[0014] In an embodiment, each insulating strip is provided as a band across the body. This simplifies manufacturing because each insulating strip can be formed from a narrow piece of insulating material, such as an extruded polymer or fiber-reinforced plastic sheet, and then adhered to a lateral surface. Alternatively, the insulating strip can be formed, for example, by painting insulating paint directly onto the lateral surface of the body. In this case, the insulating paint can also provide an adhesive for securing the second electrode.

[0015] In an embodiment, each insulating strip is wider than each second electrode. In this way, the exposed areas of the insulating strips above and below the second electrodes assist in regulating the electric field between them by providing an insulating buffer at the boundary between the electrodes. That is, the width of the insulator is designed to limit the current density. For example, this assists in maintaining a safe temperature level that could otherwise soften the adhesive.

[0016] In an embodiment, the main body is electrically conductive to function as a first electrode. In this way, the bulk material of the base main body can form a conventional first electrode. For example, the main body can be grounded to a 0 V potential to minimize safety issues with objects coming into contact with the main body.

[0017] In an embodiment, an insulating strip is provided on a lateral surface of the main body, and each second electrode is provided on each insulating strip. In this way, the insulating strip can be applied directly to the main body with the second electrode mounted on the insulating material.

[0018] In an embodiment, the second electrode defines the outer boundary of the foundation in a transverse plane. In this way, the second electrode can be fixed to the outer surface of the standard foundation without requiring additional customization of the foundation body.

[0019] In an embodiment, the base further comprises a wedge element provided at the boundary between the insulating strip and its respective second electrode, and each wedge element tapers radially outward from the insulating strip to each second electrode. In this way, the exposed edge of the second electrode can be protected to prevent delamination of the second electrode fixture during the base installation process.

[0020] In an embodiment, the main body is terminated at a distal end and includes an insertion region for insertion into soil, and a plurality of second electrodes are distributed axially along the insertion region.

[0021] In an embodiment, one or more of the plurality of second electrodes can be connected to a power supply independently of one or more other second electrodes. As such, the second electrodes can be selectively activated to limit their operation until each second electrode is below the soil surface. In some embodiments, the plurality of second electrodes are configured to have different potentials when in use. For example, if electrodes are provided on the inner and outer sides of a hollow base, the electrode potential can be adjusted to provide different levels of lubrication between the surfaces. For example, the inner and outer sides of the bucket base can be controlled to address the problem of plug lift. During the installation phase of the suction aid, if the suction force is sufficiently high to lift the clay layer covering the sand layer from inside the bucket, plug lift occurs. To address this, lubrication on the outer side of the bucket can be maximized by using a higher potential to reduce the suction pressure required. At the same time, lubrication on the inner side of the bucket can be set to a lower level or even reversed so that there is sufficient friction between the inner side of the bucket base and the plug to prevent the plug from sliding upward.

[0022] In an embodiment, each insulating strip includes a resistive tapered region in which one side of each of the second electrodes extends axially to control the spatial distribution of the electric field strength between the first and second electrodes.

[0023] In an embodiment, the foundation further comprises a plurality of fluid ports for supplying fluid to the surface of one or more of the plurality of second electrodes. In this manner, when the second electrode functions as an anode during installation, fluid is supplied to the second electrode, allowing electrolytic conductivity to be maintained while water is pumped away from the electrode into the soil. When the second electrode functions as a cathode during stabilization, fluid can also be drawn from the second electrode area and pumped elsewhere through an outlet. This can prevent excessive softening of the soil around the second electrode. Preferably, to provide fluid communication between the fluid port and the fluid pump, the fluid port is connected to a fluid pipe system. Preferably, the fluid pipe system extends to the proximal end of the foundation. Preferably, the fluid pipe system includes an electrically insulated bore to prevent short circuits. After installation, the fluid port and the piping system can be sealed with a containment or resin to prevent water from entering this area while the foundation undergoes periodic loading.

[0024] Additionally, in an embodiment, a second fluid port and a second piping system may be provided so that a fluid can be circulated. This may be used to circulate an electrolyte to optimize the electro-osmotic effect or electrochemical soil cement injection method.

[0025] In an embodiment, the body is tubular. For example, the foundation may be a monopile and may have an elongated tubular body with a length exceeding 10 m or 20 m. In another embodiment, the foundation may be a bucket foundation having a circular footprint, and the bucket foundation may have a diameter of 4-16 m and a vertical length of 2-30 m, and preferably a penetration depth of 7-12 m and 2-9 m. In an embodiment where the body has a hollow cavity, the body may include an internal lateral surface.

[0026] According to a further embodiment of the present invention, a wind turbine is provided comprising: a generator assembly for generating electricity from wind power; and a foundation according to any of the above for supporting said generator assembly. In this manner, the foundation may provide a base of the wind turbine, and the nacelle and rotor of the wind turbine generator assembly are supported on said foundation. The wind turbine may be installed, for example, offshore.

[0027] According to a further embodiment of the present invention, a method for installing a foundation according to any of the above is provided, the method comprising: connecting one or more of the plurality of second electrodes to the positive terminal of a power supply unit so that the second electrode functions as an anode; connecting the first electrode to the negative terminal of the power supply unit so that the first electrode functions as a cathode; inserting the distal end of the main body into the soil; and applying a potential difference to both ends of at least one of the first and second electrodes to create an electro-osmotic effect for easily inserting the main body into the soil by drawing water in the soil to the first electrode. In this manner, the foundation can be pushed more easily into the soil.

[0028] According to a further embodiment of the present invention, a method for stopping the installation process of a foundation according to the above is provided, the method comprising: connecting the second electrode to the negative terminal of a power supply unit so that the second electrode functions as a cathode; connecting the first electrode to the positive terminal of the power supply unit so that the first electrode functions as an anode; and applying a potential difference across the first and second electrodes to create an electro-osmotic effect that drives water in the soil away from the first electrode. In this regard, when the foundation is installed using ballast, the installation speed is mainly controlled by the provided downward force. At the same time, the faster the installation speed, the greater the resistance, and vice versa. As such, because too much ballast is often present on the foundation, it may sometimes be difficult to completely stop the installation process as soon as the target infiltration depth is achieved. For example, ballast is often applied to the foundation using a number of liftable ballast units, such as 1000 tons. Therefore, once the target installation depth is achieved, it may be difficult to rapidly remove sufficient units to reduce the downward force to a level low enough to completely stop the foundation from penetrating. In other words, even if some ballast units are removed, the foundation will continue to penetrate, albeit at a significantly reduced rate. As such, the stopping method acts to rapidly halt the lubrication effect by reversing the polarity. Although the previous anode electrode may now be partially lubricated, it is now advantageous to increase the installation resistance in the area ratio. Furthermore, under some soil conditions, soil baked into the second electrode during installation may not allow lubrication in this area if the polarity is reversed.

[0029] According to a further embodiment of the present invention, a method for stabilizing a foundation according to the above is provided, the method comprising the steps of: connecting the second electrode to the negative terminal of a power supply so that the second electrode functions as a cathode; connecting the first electrode to the positive terminal of the power supply so that the first electrode functions as an anode; and applying a potential difference across the first and second electrodes to create an electroosmotic effect that drives water in the soil away from the first electrode. In this manner, the soil surrounding the body of the foundation can be hardened to strengthen the shear resistance between the body of the foundation and the soil. This stabilizes the foundation. In practice, not only can the interfacial strength between the soil and the foundation be restored to a normal level, but the effect of additional soil hardening can potentially cause the interfacial strength to improve beyond this level. Furthermore, this effect can also extend beyond the vicinity near the foundation. Additionally, the stabilization process may also help to at least partially neutralize acidification that may have occurred in the soil during the installation process. That is, with the second electrode acting as a cathode, OH - Ions are generated from the pore water in the surrounding soil, and this is H remaining from the installation process. + It can neutralize.

[0030] According to a further embodiment of the present invention, a method for controlling a foundation inserted into soil according to the above is provided, the method comprising: connecting the second electrode to the positive terminal of a power supply so that the second electrode functions as an anode; connecting the first electrode to the negative terminal of the power supply so that the first electrode functions as a cathode; applying a potential difference across the first and second electrodes to create an electro-osmotic effect that draws water in the soil to the first electrode; and moving the body within the soil. In this manner, the foundation can be controlled more easily, for example, by retracting the foundation from the soil. This method may also be used to control the position of the foundation, for example, by resetting a foundation that has moved due to extreme loads. This may be particularly relevant to bucket foundations, as it involves reducing friction to re-level the bucket to straighten the structure. Conventional releveling methods for bucket foundations in highly clayey soils can be very difficult because the hydraulic pressure required to remove the bucket foundation risks causing the underlying soil to crack. This often means that sloped bucket foundations cannot be reused, and the buckets must instead be cut off and removed at the mud line. Accordingly, an embodiment of the present invention provides for the elevation of a single bucket that must be corrected after the structure has sloped beyond acceptable limits. Brief explanation of the drawing

[0031] An exemplary embodiment of the present invention will now be described with reference to the attached drawings. FIG. 1 shows a schematic cross-sectional view of a foundation during installation according to a first embodiment of the present invention. Figure 2 shows an enlarged view of the insertion area of ​​the base body shown in Figure 1. FIG. 3 shows a cross-sectional view through the second electrode according to the first embodiment. Figure 4 shows an isometric cross-sectional view through the second electrode shown in Figure 3. FIGS. 5a to 5c show schematic diagrams of an offshore wind turbine being installed using a foundation, system, and method according to an embodiment of the present invention. FIG. 6 shows a schematic diagram of a foundation according to the first embodiment of the present invention being installed, and electric field lines are shown. FIG. 7 shows a cross-sectional view through the second electrode according to the second embodiment. Figure 8 shows an isometric cross-sectional view through the second electrode shown in Figure 7. FIG. 9 shows a cross-sectional view through the second electrode according to the third embodiment. Figure 10 shows an isometric cross-sectional view through the second electrode shown in Figure 9. Specific details for implementing the invention

[0032] FIG. 1 shows a schematic cross-sectional view of a foundation during installation according to a first embodiment of the present invention. In this embodiment, the foundation (1) is a monopile for an offshore wind turbine (7). The foundation (1) comprises a hollow tubular body (8) having a proximal end portion for supporting a wind turbine (7) above sea level (3) and a distal end portion (10) inserted into soil (2). The body (8) is electrically conductive so that its outer lateral surface (11) functions as a first electrode. In this embodiment, although other configurations are possible, the body (8) is formed of metal to provide electrical conductivity throughout the material. For example, other materials may be used and / or a conductive area may be formed by applying a conductive coating to the exposed surface. A first terminal (4) is provided at the proximal end of the body (8) to electrically connect the terminal (4) to a power supply (not shown).

[0033] As described in more detail below, a plurality of second electrodes (9) are formed on the insertion area of ​​the main body toward its lower distal end. The second electrodes (9) are formed as circumferential bands that extend around the outer lateral surface (11) and are individually switchably connected to the second terminal array (5) at the proximal end of the main body (8) by wiring (not shown). In this way, each of the second electrodes (9) can be activated as part of an electroosmotic circuit.

[0034] FIG. 2 shows an enlarged view of the insertion area of ​​the main body (8). As shown, the second electrode (9) extends transversely across the outer lateral surface (11) of the main body (8) as a plurality of circumferential bands. The second electrode is fixed to a transverse insulating strip (12) of insulating material provided on the lateral surface (11) of the main body to electrically insulate the second electrode (9) from the main body (8). As shown, the insulating strip (11) is wider than the band of the second electrode (9) so that the insulating material extends vertically on both sides of the upper and lower boundaries of the second electrode (9). When in use, the second electrode (9) is electrically connected to a power supply unit through a terminal in the second terminal array (5) so that a potential difference can be established between the main body (8) acting as the first electrode and the respective activated second electrode (9). In this regard, the generated electric field will decrease as the axial distance from the activated second electrode increases. Accordingly, when two identical and adjacent second electrodes (9) are activated with the same voltage, a voltage gradient is formed between them with the lowest electric field strength around the midpoint between the electrodes, depending on the homogeneity of the soil. Accordingly, the distance between the second electrodes (9) as well as the width of the insulating strip (12) can be configured to optimize the voltage gradient to achieve sufficient electric field strength along the length of the insertion area, as well as limit current density spikes that could cause excessive heating of the soil.

[0035] FIGS. 3 and 4 show a cross-sectional and isometric cross-sectional view through the second electrode (9). In this embodiment, the insulating strip (12) is provided as a glass-reinforced plastic sheet applied as a transverse band around the lateral surface (11) of the main body (8) using epoxy glue. The glass-reinforced plastic sheet is preferably 1-2 mm thick, and 1.3 mm thick in this embodiment. In other embodiments, insulating paint may be applied to the lateral surface (11) to form the insulating strip.

[0036] Two wedge-shaped portions (14) of epoxy glue are provided at the upper and lower boundaries of the insulating strip (12) to provide a tapered joint between the surfaces, thereby mitigating the risk of delamination during use. The second electrode (9) is provided as an aluminum sheet that is bonded to the insulating strip (12) and conforms around the lateral surface (11) of the main body. In this way, the second electrode (9) protrudes from the lateral surface. Two additional wedge-shaped portions (13) of epoxy glue are provided at the upper and lower boundaries of the second electrode (9) to provide a tapered joint between the surface of the insulating strip (12) and the second electrode (9) to mitigate the risk of delamination during use. In this embodiment, the second electrode (9) is 200 mm wide from its bottom to the top boundary, while the insulating strip (12) is 500 mm wide from its bottom to the top boundary. In this way, the insulating strip (12) extends axially both above and below the second electrode (12), forming two insulating bands between the lateral surface (11) and the second electrode (9). In this way, when a potential difference is applied to both ends of the electrode, the exposed area of ​​the insulating material acts as a buffer area to induce an electric field and limit the current density.

[0037] FIGS. 5a through 5c schematically illustrate the foundation of FIGS. 1 and FIG. 2 being installed. As shown in FIG. 5a, the main body (8) of the foundation (1) is positioned by a crane (15) on the installation line (16), and the distal end (10) is slightly submerged in the soil (2). As described in detail below, once the first and second electrodes (9) are covered with soil, a DC power supply on the installation line (16) can be used to apply a potential difference through the first and second terminals (4, 5) to establish an electro-osmotic effect. Then, the main body (8) can penetrate deeper into the soil (2) as the shear resistance between the soil and the lateral surface of the main body (8) is reduced. Penetration can be facilitated under the weight of the foundation itself, or by applying additional ballast or pile-driven hammer impact. Advantageously, according to an embodiment of the present intent, the installation resistance can be sufficiently reduced so that installation can be achieved without the need to apply a hammer impact.

[0038] As shown in FIG. 5b, when the distal end (5) of the base reaches the required depth, the power supply can be turned off to restore the shear resistance between the soil (2) and the main body (8). This stops the electroosmotic effect and reduces its lubrication, thereby stabilizing the base. However, this stabilization may take time. This is because clay has very low permeability, and therefore it may take time for the excessive pore pressure near the base to dissipate back into the soil. Therefore, stabilization can be selectively further enhanced by temporarily reversing the polarity of the power supply so that the main body (8) acts as the anode and the second electrode (9) acts as the cathode. This improves the adhesion strength of the interface between the main body (8) and the soil (2) by reversing the electric field so that the number of pores is driven away from the lateral surface (11) of the main body (8). As shown in FIG. 5c, the wind turbine (7) can then be installed on top of the base (1). It will also be understood that the stabilization effect can be used to remove excessive pore pressure around the axial or single-pile foundation that may have accumulated during periodic loading. Alternatively, stabilization maintenance can be implemented using one or more remote anodes.

[0039] FIG. 6 shows a schematic diagram of a section of the base (1) during the installation process. As such, an electric field line (24) appears between the second electrode (9) and the lateral surface (11).

[0040] As described above, during the installation process, the main body (8) is lifted into place by a crane (15), and ballast (17) is applied to its proximal end to facilitate penetration into the soil (2). When the distal end of the main body (8) is pressed, the second electrode (9) is sequentially activated to become an anode when buried in the soil (2). To this end, a potential difference is provided on the installation line and applied by a DC power unit (19) supplied by an AC generator (20). The sequential activation of the second electrode (9) helps to avoid drawing excessive current through seawater during the initial installation phase while the electrode (9) is still on the soil (2). In this way, the second electrode (9) can remain uncharged until it is safely below the soil line, after which it can be connected to the DC power unit (19) to generate an electro-osmotic effect in that area.

[0041] In this regard, specifically, the DC power unit (19) is used to ground the main body (8) through the first power cable (23) so that it has a potential of 0 V and thus can function as a cathode. Since the main body (8) itself has a potential of zero, it does not provide a safety risk factor from contact with other main bodies during installation. At the same time, a positive voltage, preferably about +40 V to +400 V, most preferably about +200 V, is applied to each activated second electrode (9) through the second power cable (22). At a voltage of about +80 V or less, the voltage is ideally below a dangerous level. Additionally, as a result of the selective activation of the second electrode (9), the charged area of ​​the base is isolated from the installed area of ​​the main body that is buried under the soil (2). The application of a potential difference between each activated second electrode (9) and the main body (8) generates an electric field (24) through the soil between them.

[0042] An irrigation pump (18) may also be provided on the installation line to supply fluid into the second electrode (9) or to a port adjacent thereto through a fluid channel (21). This fluid may be, for example, seawater, and its delivery may help reduce surface friction and soil aggregation at the second electrode (9).

[0043] The electric field effect shown in FIG. 6 is that an electro-osmotic effect is induced by the electric field (24) in the soil surrounding the base. Specifically, negatively charged soil particles within the soil are surrounded by a porous water fluid located within the unbound water zone between the particles and / or within the double layer. When the electric field (24) is applied, a portion of this porous water is moved toward the negatively charged cathode provided by the lateral surface (11) of the main body (8). This has the effect of lubricating the interface between the main body (8) and the soil (2) by increasing soil moisture in the soil adjacent to the lateral surface (11).

[0044] As described above, simultaneously, the positively charged anode provided by the second electrode (9) serves to drive away the pore water. This results in a consequent reduction in soil moisture in the surrounding soil, and the dehydrated area adheres to the surface of the second electrode (9) and ultimately bakes itself there. However, while this increased soil adhesion increases the axial resistance to the installation of the body (8), unexpectedly, the total reduction in interfacial resistance across the bulk of the lateral surface (11) was found to be greater than what compensates for it. That is, while the soil may adhere to the second electrode (9), tests by the applicant showed that lubrication across the rest of the insertion area of ​​the base body provides a significant net reduction in installation resistance. Adhesion is limited, for example, to a horizontal annularity of soil surrounding each second electrode (9).

[0045] Advantageously, since the second electrode does not need to be separated from the soil and can be on or protrude from the main lateral surface (11) of the base body (8), there is no need to customize the base to provide a recess or a gap protrusion. In this way, not only is reliability improved, but the cost of the base can also be reduced. For example, a conventional monopile can be easily deformed by using an adhesive to fix the insulating strip (12) and the second electrode (9) to its surface (11).

[0046] It will be understood that alternative configurations may be used for the second electrode (9), and that these function in substantially the same manner as described above in relation to the first embodiment. FIGS. 7 and 8 show, for example, a cross-sectional and isometric cross-sectional view through the second electrode according to the second embodiment of the present invention. In this case, the insulating strip (12) is applied as a 1.5 mm layer of insulating paint, and the second electrode (9) is seated within a recess provided on the lateral surface. Thus, the second electrode (9) is seated substantially coplanar with the main lateral surface (11) of the base body (8). This provision of a shallow recess, which may be only 3-5 mm deep, can serve to prevent the second electrode (9) from peeling off from the body (8) without requiring a much deeper recess that might otherwise be needed to create a gap with the adjacent soil.

[0047] FIGS. 9 and 10 show a cross-sectional and isometric cross-sectional view through the second electrode according to a third embodiment of the present invention. In this embodiment, the second electrode (26) is formed from a machined aluminum piece comprising an inner opposing cavity (27) and a plurality of slits to the outer surface. The cover (25) is fitted across the outer surface of the second electrode (26) and comprises non-woven aramid fibers covered by a woven Kevlar (aramid fiber) top sheet. In this embodiment, the second electrode (26) is adhered to an insulating paint layer forming an insulating strip (12) applied to the main lateral surface (11). In another embodiment, the electrode may alternatively be seated within a recess. In use, fluid may be supplied to the cavity (27) using an irrigation pump (18), which is then sucked through the slot. The cover (25) acts to wick the fluid, thereby releasing the fluid over the exposed surface. In this way, the Kevlar top acts to prevent soil baking onto the second electrode (26). At the same time, the delivery of fluid acts to rehydrate the soil adjacent to each second electrode (26), which assists in maintaining the electrolytic fluid connection between the anode and the cathode. In some embodiments, additives may be additionally introduced into the fluid pumped from the irrigation pump (18) to, for example, improve its conductivity or provide chemical stabilization. In other embodiments, the fluid port(s) may also be used to seal the piping system and to supply containment or similar material to complete the installation, to transfer any residue trapped in the cavity (27).

[0048] In this connection, fluid delivery at the second electrode (26) can be used to neutralize or dilute the acidity generated at the anode. That is, 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 which ionic species are available or present, and thus the introduction of customized conditioning agents can serve to enhance or inhibit specific reactions. For example, H2 gas and OH in pure water with an inert electrode - Anions are generated at the cathode, and O2 Gas and H + Cations are generated at the anode. As a result of the electric field, cations and anions move toward the cathode and anode, respectively. H + Because cations have high mobility, the associated acidic front sweeps a larger volume of soil compared to the amount swept by hydroxide anions. This soil acidity can have various adverse effects, including reducing biological activity, lowering the soil's electroosmotic permeability, and accelerating the erosion of the base itself. To overcome these effects, chemical conditioning fluids are pumped from the port and positively charged H + It can be neutralized or diluted. Additionally, the conditioning fluid may be selected to modify the surface chemistry of clay particles or to precipitate cement within the pore spaces. These changes can increase the strength and stiffness of the soil. For example, during the normal polarity phase, limestone or calcium chloride solution may be introduced through the pot as a modifier, and when the polarity is reversed, these conditioners may contain sodium silicate, which precipitates in the cementitious bonding reaction.

[0049] The arrangement shown in FIGS. 9 and 10 may also be used without active perfusion. In this regard, during installation, the foundation is first lowered with water before it penetrates into the soil. This step serves to partially fill the cavity (27) within the second electrode (26) with seawater. At the same time, the air remaining in the cavity (27) is compressed. Thus, when seawater is drawn out of the cavity (27) during electroosmosis, the compressed air expands again, thereby preventing a vacuum from immediately forming within the cavity (27).

[0050] As can be understood, the arrangement of the invention disclosed herein enables the foundation to be pushed more easily into the soil without significantly extending the set-time required at the foundation site. This can reduce costs, provide a more stable foundation, and mitigate installation noise in the case of pile foundations, which are particularly important for coastal applications. At the same time, embodiments of the invention can be easily implemented without requiring substantial modifications to existing foundation designs.

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

[0052] Additionally, in some of the exemplary embodiments above, the foundation was a hollow body such as a monopile, but the present invention can be applied to other foundations, such as bucket foundations, axial piles and sheet piles, spud cans, and other gravity-based foundations.

[0053] In addition to wind turbines, the present invention can also be used in other structures such as coastal platforms, sheet walls, or dolphin piles.

[0054] Additionally, in the exemplary embodiment above, the system was described using a power supply provided on the installation line, but it will be understood that other arrangements are possible. For example, a battery or generator located in the foundation or the structure itself may be used as the power supply.

[0055] Furthermore, although the present invention has been described with reference to coastal locations, it will be understood that the invention may be used in other locations having sufficiently high moisture content for electroosmotic pressure. These may include, for example, fine-grained cohesive clay deposits, low-permeability problem soils, expansive soils, dispersible soils, highly compressible clays, marine clays, sensitive clays, acute clays, saline / sodium soils, and soft peats. Such soft clay soils are often associated not only with coastal soils but also with estuary, river, and lake locations.

[0056] It will also be understood that the present invention periodically re-reinforces the soil around the foundation by reactivating the electro-osmotic effect to expel water from the main body and draining the water collected at the second electrode. Likewise, the present invention can allow for simplified retreat of the foundation during dismantling by facilitating extraction from the soil by reactivating the electro-osmotic effect to form a fluid lubricating film on the main body.

[0057] In this regard, by applying a DC voltage across different regions of the foundation according to the present invention, two electroosmotic effects occur in the surrounding soil. First, electroosmotic pressure causes the movement of water that acts to weaken or strengthen the soil along the direction of flow at closed boundaries. As such, excess soil pore pressure can be generated to lubricate the soil / foundation interface with a water film during installation or removal. Alternatively, negative pore pressure can be used to restore or improve soil structure and interfacial friction to stabilize the foundation. For example, soft clay or other cohesive soils can be incorporated around the foundation for strength by pushing water out of the soil through electroosmotic pressure. The second effect of electroosmotic pressure is to move ions within the soil toward the foundation. This ionic effect can be particularly useful for granular soils, as it allows cementing electrolytes to infiltrate and cement the foundation in place.

[0058] The insulating strip may also additionally include a tapered resistivity region extending vertically on both sides of the second electrode. The tapered resistivity region may function to control the distribution of electric field strength in the soil generated between the main body and the second electrode. That is, when a potential difference is applied across the electrodes, the tapered resistivity region may function to reduce or mitigate the electric field strength to avoid an excessively high electric field strength in the region immediately adjacent to the junction between the insulating strip and the main body due to the relatively small distance between the electrodes. In some embodiments, the insulating material forming the insulating strip may be gradually gradiented as the distance from the second electrode increases to reduce the resistive effect. In this way, a resistance taper may be used to gradually offset the increased electric field strength due to the proximity for achieving a more uniform electric field extending from the second electrode.

[0059] Finally, while the exemplary embodiment illustrates an embodiment of the present invention having a second electrode provided on an external lateral surface, it will be understood that in the case of a hollow base, the second electrode may be provided on an internal lateral surface.

Claims

Claim 1 A foundation for a structure comprising: a body for insertion into soil having at least one region forming a first electrode, a lateral surface and a distal end; and one or more second electrodes provided on the body and coplanar with respect to the lateral surface or protruding from the lateral surface, wherein each of the second electrodes extends transversely around the lateral surface and is electrically insulated from thereby by an insulating strip provided between each of the second electrodes and the lateral surface, the body is electrically conductive to function as the first electrode, the insulating strip is provided on the lateral surface of the body, and one or more second electrodes are provided on each insulating strip, each second electrode and the insulating strip corresponding to each second electrode form a second electrode region, and one or more second electrodes define the outer boundary of the foundation in the transverse plane traversing each second electrode region. Claim 2 In claim 1, the one or more second electrodes comprise a plurality of second electrodes provided as a band across the main body. Claim 3 In paragraph 1 or 2, each insulating strip is provided as a band across the main body, a base. Claim 4 In paragraph 1, each insulating strip is wider than its respective second electrode, and is a base. Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 A base according to claim 1, further comprising a wedge element provided at the boundary between the insulating strip and each of its second electrodes, wherein each wedge element tapers radially outward from the insulating strip to each of its second electrodes. Claim 9 In paragraph 2, the main body comprises an insertion region terminated at a distal end for insertion into the soil, and the plurality of second electrodes are distributed axially along the insertion region, the base. Claim 10 In paragraph 2, a base further comprising a terminal for connecting the first and second electrodes to a power supply unit. Claim 11 In paragraph 10, one or more of the plurality of second electrodes are a base that can be connected to the power supply unit independently of one or more other second electrodes. Claim 12 A basis according to claim 1, wherein each insulating strip comprises a resistive tapered region extending axially on one side of each of its second electrodes to control the spatial distribution of the electric field strength between the first and second electrodes. Claim 13 A basis according to paragraph 2, further comprising a plurality of fluid ports for supplying fluid to the surface of one or more of the plurality of second electrodes. Claim 14 A wind turbine comprising: a generator assembly for generating electricity from wind; and a foundation according to claim 1 for supporting the generator assembly. Claim 15 A method for installing a foundation according to paragraph 2, the method comprising: connecting one or more of the plurality of second electrodes to the positive terminal of a power supply unit so that the second electrode functions as an anode; connecting the first electrode to the negative terminal of the power supply unit so that the first electrode functions as a cathode; inserting the distal end of the main body into the soil; and applying a potential difference to both ends of at least one of the first and second electrodes to create an electroosmotic effect for easily inserting the main body into the soil by drawing water in the soil to the first electrode.

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