Pile device and method for vibration driving

Abstract

A pile device for vibratory driving includes a stem extending longitudinally between a first end and a second end, the first end being arranged to underlie the second end during driving of the pile device, and a base structure disposed at or adjacent the first end. The base structure includes a plurality of longitudinally open cells, the cells being symmetrically arranged around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls. Each cell has a height-to-width ratio calculated as the longitudinal length of the shortest cell wall defining the cell divided by the effective distance of the cross-section of the cell. The height-to-width ratio is between 1 and 30, the effective distance being, for cells having a non-triangular cross-section, the shortest distance between two non-adjacent sides of the cross-section, and for cells having a triangular cross-section, the shortest of the base and height of the cross-sectional triangle.

Description

[Technical field]

[0001] The present disclosure relates generally to the field of pile driving, and more particularly to vibratory driving of piles into the ground or seabed. In particular, the present disclosure provides a pile apparatus and method for such vibratory pile driving. [Background technology]

[0002] Piling is frequently used in construction engineering to increase the load-bearing capacity of foundations or anchors embedded in the ground or seabed. Typically, piling is used in situations where the ground or seabed material at or near the surface of the earth is not sufficiently rigid to support the loads applied by shallow soil anchors. To provide secure anchoring to offshore structures such as platforms, floating wind turbines, or wave energy conversion buoys, the piles may be driven into the seabed until they reach a burial depth at which the end bearing and friction forces acting between the surrounding soil material and the pile, accumulated along the buried length of the pile, are high enough to maintain the pile in its buried position when a downward or upward load to be supported is applied to the pile.

[0003] The prior art proposes various techniques for driving piles into the ground or seabed and providing the required load capacity. Examples of such driving methods are screw piling, suction piling, push piling and impact piling. Another method of driving piles is the so-called vibratory driving, sometimes called vibro driving or vibro hammer. In such vibratory driving, the pile to be driven is subjected to a vibration force that typically vibrates the pile in a longitudinal, vertical direction, while gravity acting on the pile and an additional bias mass from the vibro hammer allow the pile to be displaced vertically downwards into the ground or seabed. Typically, the vibratory motion applied to the pile can have an amplitude of 5-35 mm and a frequency of 20-50 Hz. In such vibratory piling, the vibratory motion of the pile interacts with the surrounding material, greatly reducing the static friction forces acting between the material and the exposed surface of the pile, so that the weight of the pile and the vibro hammer overcomes the resistance and drives the pile downwards into the ground or seabed. Such reduction in resistance occurs only while the vibratory motion is maintained, and when the pile has reached the intended depth, the vibration is stopped, whereby the resistance forces between the surrounding material and the pile come into play, acting to maintain the pile in the position reached.

[0004] Typically, in such vibratory driving, the pile may be suspended from a crane, piling rig, or the like, and a vibration inducer may be attached to the top end of the pile, often acting as a combined vibro hammer and lifting tool for the pile. Thus, during the driving operation, gravity may act on the accumulated mass of the pile and the vibration inducer. By controlling the lifting force applied by the crane or rig, the resulting downward force acting on the pile may be controlled, and in combination with setting the frequency and / or eccentric moment of the vibro hammer, the downward driving speed of the pile may be controlled.

[0005] It has been suggested in the prior art that such vibratory driven piles may be strengthened by placing a structure of longitudinally open cells at the lower end of the pile to be driven. US Pat. Nos. 5,393,633, 5,496,923 and 5,523,663 show such known pile apparatus.

[0006] US Pat. No. 5,399,433 also discloses such a pile device for vibratory driving. The device comprises a pile, a tube concentrically arranged around the bottom of the pile, and a number of radial ribs extending between the pile and the tube. The pile, the tube and the ribs thereby form walls defining a number of downwardly and upwardly open cells. According to US Pat. No. 5,399,433, the upper diameter of the tube must be smaller than its lower diameter so that the cells taper upwardly. In addition, US Pat. No. 5,399,433 specifies that the vertical height of each cell must be at least as large as the diameter or maximum diagonal of the bottom region of the cell. US Pat. No. 5,399,433 further asserts that the device exhibits low envelope resistance during vibratory driving, but high load-bearing capacity under static load after driving. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Pat. No. 3,683,633 [Patent Document 2] International Publication No. 2021 / 045626 [Patent Document 3] JP 2013-256791 A [Patent Document 4] WO 95 / 35416 Summary of the Invention

[0008] It is an object of the present disclosure to provide an improved pile device for vibratory driving, which exhibits a high load capacity in the longitudinal direction. Another object is to provide such a pile device which allows for fast and reliable driving during driving and provides a high load capacity of the pile after it has been driven to the intended embedment depth.

[0009] It is a further object of the present invention to provide such a pile arrangement which is simple in construction and which can be manufactured at relatively low cost using relatively little material in relation to its load carrying capacity in the soil.

[0010] Yet another object is to provide such a pile apparatus that has a relatively low mass and small size for its load capacity in the soil and has a structural design that allows it to be lifted and handled by relatively small, low-cost equipment such as trucks, cranes and ships.

[0011] Another object is to provide such a pile device which achieves the required holding capacity at a relatively low penetration depth into the soil, allowing reliable anchoring in locations with limited soil depth.

[0012] Yet another object is to provide such a piling device that can be extracted at low cost during the demolition phase of the project. A further object is to provide a pile arrangement which is resistant to the effects of cyclic loads typical of floating structures such as wind turbines or wave energy devices, where the ratio of average load to peak dynamic load is much lower than in typical uses of piles in offshore structures and which act mainly, if not entirely, in the longitudinal direction of the pile.

[0013] Yet another object is to provide such a pile device capable of resisting a combination of static loads, wave frequency loads (within the load cycle time range of 5 to 25 second period, sometimes referred to as quasi-static loads), and dynamic loads which may occur over time periods of 5 seconds or less but longer than the 0.05 second load cycle time period typical of vibratory hammers, which are likely to occur when anchoring certain marine structures such as buoyant wind, tidal or wave energy conversion devices.

[0014] A further object is to provide such a piling apparatus which allows efficient transmission of vibration energy from an upper end, where the vibro hammer is attached, to a lower end, where a base structure may be located.

[0015] A further object of certain embodiments is to increase the horizontal (radial) load capacity of such pile devices. In general, all terms used in the claims should be interpreted according to their ordinary meaning in the art, unless expressly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." should be interpreted broadly as referring to at least one example of the element, apparatus, component, means, step, etc., unless expressly defined otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless expressly stated.

[0016] According to a first aspect, the present disclosure provides a piling device as set forth in claim 1 attached hereto. The piling device is intended for vibratory driving. The piling device comprises a stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the piling device. A base structure is arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being symmetrically arranged around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls. Each cell has a height-to-width ratio calculated as the longitudinal length of the shortest cell wall defining the cell divided by the effective distance of the cross-section of the cell, the height-to-width ratio being in the range of 1 to 30, preferably 2 to 18, most preferably 3 to 12, wherein the effective distance is - for cells with a non-triangular cross section, it is constituted by the shortest distance between two non-adjacent sides of the cross section, For cells with a triangular cross section, it is formed by the shortest of the base and height of the cross-sectional triangle.

[0017] Thus, a first aspect relates to a vibratory driveable pile having a base structure with a number of longitudinally open cells arranged at the bottom of the stem. Such an open cell structure has been proven to significantly increase the load-bearing capacity of the pile, especially for upward and downward load forces along the longitudinal direction of the stem, compared to conventional piles without such an open cell structure. When such a pile is accurately driven into the ground or seabed to the intended burial depth and the vibration of the pile is stopped, the fine or granular material received in the cells tends to form a solid plug in each cell. The base structure with a number of filled cells distributed over the cross section of the base structure thereby forms the equivalent of a solid plate buried in the ground or seabed.

[0018] A plate with a cross-sectional area equal to that of the base structure is theoretically described in a simple form to drive two mechanisms of load-bearing capacity: first, along a shear plane in the form of an inverted truncated cone (frustum), the truncated base of which is defined by the area of ​​the plate, the top of which is placed on the surface of the ground or seabed, and second, within that theoretical cone, the mass of soil is accommodated. The fact that the plate-like device resists the applied load by two combined mechanisms thus allows the pile to support significantly higher upward loads than conventional piles without such an open-cell base structure, which rely mainly only on the interfacial friction between the soil and the walls of the stem.

[0019] Piles provided with a base structure with longitudinally open cells are particularly suitable for applications where the pile is subjected to large upward or downward loads along the longitudinal direction of the stem. Some examples of such applications requiring large vertical load capacity are anchoring devices for offshore and marine-based installations such as floating wind turbines, wave energy converters, platforms, etc., as well as various land-based applications.

[0020] The increased bearing area defined by the underside of the infilled base structure also increases the downward load capacity compared to piles without such a base structure. Under downward load, the upward vertical force exerted by the granular material below the pile acts on the increased downward surface defined by the infilled open-cell base structure. Thus, such piles also support significantly higher downward loads compared to piles without a base structure, which have a downward bearing surface limited to the cross-sectional area of ​​the stems.

[0021] An important aspect when vibrating such open-cell piling devices is to create a balance between the driving capacity during driving and the load capacity after driving. Driving capacity is increased by the ability of the piling device to reduce friction between the surrounding material and the exposed surface of the device during vibration. On the other hand, the load capacity after driving is increased by the ability of the device to form and maintain a rigid plug of the received material in the open cells after the vibrating action is stopped. In the literature, the ability of the surrounding material to move smoothly against the piling device, including the stem and base structure, during driving is sometimes referred to as coring. Correspondingly, the ability of the piling device to form a rigid plug of material in the stem and originally open cells is often referred to as coring.

[0022] The prior art recognizes that both of these opposing capabilities of coring and infilling depend on the geometry of the open cell base structure. US Pat. No. 5,399,433 discloses that the relationship between the cell wall height and a particular length in the cell's cross-sectional area, as well as the vertical orientation of the cell walls, are important in finding a favorable balance between driveability and load capacity, i.e., between coring and infilling. According to US Pat. No. 5,399,433, it is the relationship between the cell wall height and the maximum diagonal or diameter of the cell's cross-sectional area that is important, and US Pat. No. 5,399,433 asserts that the wall height should be at least as large as this maximum diagonal. In addition, US Pat. No. 5,399,433 asserts that the cell walls should be inclined relative to the stem so that the cells taper upwards.

[0023] In stark contrast to what is proposed by US Pat. No. 5,999,633, the piling device according to the first aspect of the present disclosure has cell-defining walls extending in the longitudinal direction of the stem, so that the cross-sectional area of ​​the open cells is essentially constant throughout the height of each cell. In addition, according to the present disclosure, it is the relationship between the height of the cell walls and the shortest effective distance in the cross-sectional area of ​​the cells that is important in finding the optimum balance between driving ability and load capacity.

[0024] It has been found that when seeking an optimal balance between coring and filling, it is not primarily the relationship between the cell height and the cross-sectional area of ​​the cell as represented by the largest diagonal that is important. Instead, it has been found that what is important is the relationship between the cell height and the distance between the two cell walls that form the narrowest or most restricted passage in the cross-sectional area of ​​the cell. This distance between the two walls that define the narrowest passage in the cross-section of the cell is referred to herein as the effective distance. For simplicity, the appropriate relationship between cell height and effective distance is referred to herein as the height-to-width ratio, which is calculated by dividing the longitudinal height of the shortest wall that defines the cell by the effective distance of the cell.

[0025] The base structure can have many different cross-sectional shapes, as will be further described below. If the cross-section of the cell is polygonal, or is formed by a combination of curves or curves and straight lines, the effective distance can be expressed as the shortest distance between two non-adjacent cell walls. If the cross-section of the cell is triangular, the effective distance is constituted by the shortest of the height and base of the triangle.

[0026] It has been found that by finding the correct relationship between cell height and this effective distance, the pile device provides good coring during vibration driving and also reliable filling after the pile device reaches the driving or embedment depth and vibration is stopped. Thus, the correct relationship between cell height and effective distance provides a pile device that combines good driveability with good load capacity to resist both static and cyclic loads.

[0027] If the cell height is too large relative to the working distance, the pile machine will result in insufficient coring due to high resistance to vibro driving (early filling), thereby resulting in poor driveability, whereas if the cell height is too small relative to the working distance, the pile machine will result in insufficient filling after driving, thereby resulting in low load capacity.

[0028] In general, it has been found that an advantageous balance between coring and filling capacity can be achieved when the height to width ratio is from 1:1 to 30:1, preferably from 2:1 to 18:1, and most preferably from 3:1 to 12:1.

[0029] However, the optimum height to width ratio will depend on the type of soil into which the pile device is driven. If the soil is primarily made up of loose sand, the ratio may preferably be in the higher range, for example 10:1 to 30:1. If the soil is primarily made up of medium density sand and similar materials, the ratio may preferably be in the approximate intermediate range, such as 3:1 and 12:1. If the soil is primarily made up of a mixture of high density sand, clay or other similar materials, the ratio may preferably be in the lower range, such as 1:1 to 6:1.

[0030] In laboratory and field tests, the disclosed pile device has demonstrated at least 4-5 times higher retention capacity in the longitudinal direction compared to a plain pile of the same dimensions. Additionally, the specific height to width ratio has been shown to result in improved stiffness, improved cyclic load resistance, and improved static retention capacity compared to previously known pile structures with a base structure having longitudinally open cells.

[0031] In an embodiment of the first aspect, the base structure may comprise at least two tubular walls extending longitudinally and arranged concentrically with the longitudinal axis of the stem, and at least two radial walls extending radially and longitudinally, each cell being defined by two adjacent tubular walls and two adjacent radial walls, and the effective distance being the shortest of the shortest radial distance between the tubular walls and the shortest circumferential distance between the radial walls.

[0032] In such an embodiment, for each cell, the effective distance may be the shortest radial distance between the tubular walls. In some embodiments, the tubular wall is cylindrical.

[0033] The cylindrical and radial walls may be configured such that the cross-sectional area is essentially equal for all cells. It has further been found that an advantageous balance between coring and filling can also be achieved by designing the base structure so that other geometric relationships between the base structure and the cells fall within specific ranges.

[0034] Thus, according to a second aspect, there is provided a pile device for vibratory driving, comprising a stem extending longitudinally between a first end and a second end, the first end being arranged such that it is located under the second end during driving of the pile device, and a base structure arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, the pile device exhibiting a closed area ratio calculated by dividing the cumulative closed cross-sectional area perpendicular to the longitudinal direction of the stem and the cell walls defining all the cells by the cumulative open cross-sectional area of ​​the stem and all the cells, the closed area ratio being in the range of 0.01-0.4, preferably 0.015-0.3, most preferably 0.02-0.1.

[0035] The term "closed cross-sectional area" is used herein to mean that portion of the cross-sectional area of ​​the pile device that is occupied by material that forms part of the pile device, such as a cell wall, a tubular wall of a hollow stem, or the entire cross section of a solid stem. The term "open cross-sectional area" means that portion of the cross-sectional area that is not occupied by material that forms part of the pile device, i.e., that portion of the cross-sectional area of ​​the pile device that allows longitudinal flow of soil through the base structure and hollow stem during driving.

[0036] Base structures with higher cumulative cross-sectional cell wall area relative to open cross-sectional cell area exhibit higher driving resistance due to a combination of two suitable mechanisms. First, the higher the percentage of the total cross-section of the base structure that is made up of cell walls, the more soil compaction must take place to move the soil through the remaining open areas as the base structure is penetrated downward through the soil, thus increasing the lateral stress in the soil within the cells. Second, the soil mass moved through the cells is constant. Thus, an increase in the closed or non-open end surface of the base structure leads to a higher compressibility of the soil moved through the open cells. This results in a higher so-called tip resistance. Thus, the greater the wall thickness relative to the open cell area, the more difficult it is to core the soil under vibration action and the greater the chance of premature rejection during driving due to either tip resistance or infilling. Too high a ratio will result in premature infilling and rejection during driving, while too low a ratio may result in more difficulty remaining infilled under static, wave frequency, or dynamic loads. On the other hand, from an economic point of view, it is advantageous to keep the wall thickness as thin as possible, which reduces the use of material for the base structure and also reduces the driving resistance, making it possible to use smaller and cheaper vibrating hammers with less energy consumption. The above ratio ranges have been found to be particularly advantageous in many different applications.

[0037] According to a third aspect, there is provided a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged such that the stem is located under the second end during driving of the pile device; and a base structure arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, the ratio of the longitudinal length of the shortest cell wall to the square root of the open cross-sectional area of ​​the cell being in the range of 1 to 40, preferably 2 to 20, most preferably 3 to 12.

[0038] According to a fourth aspect there is provided a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged such that the stem is located under the second end during driving of the pile device; and a base structure arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, and for each cell a ratio of a cumulative internal area of ​​the cell walls defining the cell to an open cross-sectional area of ​​the cell is in the range of 4-100, preferably 10-40, most preferably 15-35.

[0039] The pile devices according to the third and fourth aspects have also been shown to exhibit an improved balance between coring during vibratory driving and reliable filling after driving, compared to previously known pile devices with longitudinally open cells arranged at the lower end of the stem.

[0040] According to a fifth aspect there is provided a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to underlie the second end during driving of the pile device; and a base structure arranged at or adjacent the first end, the base structure comprising a plurality of longitudinally open cells, the cells being arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, the ratio of maximum to minimum cell cross-sectional area for all cells being equal to or less than 5:1, preferably equal to or less than 2.5:1 and most preferably equal to or less than 1.2:1.

[0041] The advantage of having cells of approximately equal cross-sectional area is that for a concentrically arranged base structure, it provides unequal widths in the radially outward direction, which provides beneficial stress distribution under load that may prevent premature coring of the cells closest to the stem.

[0042] According to a sixth aspect, there is provided a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the pile device; and a base structure arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, the base structure being cylindrical and comprising cell walls arranged concentrically around the stem, the ratio of the longitudinal length to the diameter of the radially outermost cylindrical wall being in the range of 0.1 to 4, preferably 0.2 to 1.2, most preferably 0.25 to 0.7.

[0043] When the pile device is driven by vibratory driving so that the cells are fully filled and the pile device is subjected to cyclic vertical loads, the soil particles tend to move not only through the cells but also outside the base structure between the upper and lower regions of the base structure. With upward cyclic loads, the particles tend to move from the upper region towards the lower region, and with downward cyclic loads, the particles tend to move from the lower region towards the upper region. Such soil particle movement may, over time, cause the pile device to slip out of its intended driving depth, thereby reducing the vertical load capacity of the pile device. It has been found that by configuring the base structure with a ratio between the base structure's outer height and outer diameter defined within the above ranges, the pile device exhibits advantageous coring and driving capabilities while still minimizing soil particle movement with cyclic loads applied after driving. It has also been proven that with the above-mentioned base structure height to outer diameter ratio, the base structure may be designed in a structurally efficient manner in which the thickness of the cell walls relative to the open cell area may be kept low, thereby facilitating coring. In addition, the specified range makes it possible to design a base structure having a relatively high stiffness, such that vibrations induced at the upper second end of the stem during vibration driving are efficiently transmitted radially outward throughout the base structure to the outer wall of the base structure.

[0044] According to a seventh aspect, there is provided a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to underlie the second end during driving of the pile device; and a base structure arranged at or adjacent the first end, the base structure comprising a plurality of longitudinally open cells, the cells being arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, the first end of the stem protruding longitudinally beyond the base structure.

[0045] The protruding portion of the stem thereby forms a pile guide or ground spike that penetrates the soil before or during vibration before the base structure reaches the soil surface. The protruding portion of the stem thereby guides the stem and base structure vertically downward during the successive driving procedure and prevents the pile device from deviating from the intended vertical or other intended driving direction. This can eliminate or reduce complex and time-consuming tilt adjustments achieved by moving the support crane in a horizontal plane during driving. It can also enable driving procedures without the use of an external pile guide frame on the seabed or ground.

[0046] In an embodiment of the seventh aspect, the protruding portion of the stem may be sharpened to reduce driving resistance during casting. If the stem is tubular, such sharpening may be achieved by chamfering the protruding edge of the annular wall of the stem or tapering it towards the protruding end of the stem.

[0047] According to an eighth aspect, the present disclosure provides a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the pile device; and a base structure arranged at or proximate to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being defined by at least two tubular walls arranged concentrically with the pile, each tubular wall comprising a first edge proximal to the first end and a second edge distal to the first end, and a plurality of radial walls; the first edges of at least two tubular walls are located at different longitudinal distances from the first end, and / or the second edges of at least two of the tubular walls are arranged at different longitudinal distances from the first end.

[0048] When the pile device is oriented with its longitudinal axis vertical during and after vibratory driving, the first lower edge of the concentrically arranged tubular walls defines a downwardly facing bottom surface of the base structure, and the second upper edge defines an upwardly facing top surface of the base structure. By locating the first lower edge at different longitudinal distances (i.e., at different vertical heights) from the first lower end of the stem, the bottom surface can be configured to be generally inclined relative to the longitudinal direction. Correspondingly, by locating the second upper edge at different longitudinal distances from the first lower end of the stem, the top surface can be configured to be generally inclined relative to the longitudinal direction. Such inclined bottom and upper base structure surfaces increase the load capacity for downward and upward vertical loads, respectively.

[0049] Advantageously, the concentrically arranged tubular walls should be configured such that the vertical height of the walls decreases from the radially innermost wall to the radially outermost wall, In such a device, the bottom surface forms a downwardly facing surface, the radial centre of which is located longitudinally closer to the lower first end of the stem than the radial periphery of the bottom surface, and / or the top surface forms an upwardly facing surface, the radial centre of which is located longitudinally closer to the upper second end of the stem than the radial periphery of the top surface.

[0050] In such a pile device having a sloped bottom surface, a force applied downward to the pile device creates a double shear plane in the soil below the base structure. Such double shear plane results in loads being distributed from the base structure to the soil below the base structure in a manner that provides increased capacity for downward loads. Correspondingly, in a pile device having a sloped top surface, a force applied upward to the pile device creates a double shear plane in the soil above the base structure. Such double shear plane results in loads being distributed from the base structure to the soil above the base structure in a manner that provides increased capacity for upward loads.

[0051] The configuration of the inclined bottom or top surface of the base structure can be said to increase the apex angle of the truncated cones located below and above the base structure, respectively, which contain the soil to which the vertical load applied to the pile device is transferred during use after driving.

[0052] The generally sloped bottom and / or top surface arrangement of the base structure also results in a more gradual rate of change of the structural impedance at the transition from the stem to the base structure. This improves the ability of the base structure to transmit vibrations from the stem to all parts of the base structure, including the radially outermost parts, during vibration driving, since rapid changes in structural impedance are known to reduce the ability of stress waves to pass through the structure and thus hinder driving capabilities. Furthermore, such generally sloped bottom and / or top surfaces of the base structure improve the overall structural efficiency of the base structure. The sloped bottom and / or top surfaces allow the vertical length of the radial walls connecting the concentrically arranged tubular walls to the stem to decrease in a radially outward direction from the central stem. This increases the ability of the radial walls to support the cumulative load from the concentrically arranged tubular walls in a radially inward direction toward the stem. As a result, the thickness of the radial walls, and therefore the cross-sectional area of ​​the radial walls, can be kept relatively small, thereby reducing the overall driving resistance caused by the base structure as well as the overall weight and cost of the pile apparatus.

[0053] Providing the base structure with a generally inclined bottom surface provides the additional advantage that the downwardly facing base structure so formed can act as a step-wise guide means for the pile device during initial penetration into the soil. With such a device, the initial penetration resistance provided by the soil as the pile device contacts and begins to penetrate the soil is reduced, and the downward driving force can be reduced accordingly. This in turn makes it easier to maintain the vertical or other intended orientation of the pile device during initial penetration into the soil, since lower forces are required. In addition, any differences in soil stiffness distributed spatially over the area where the base contacts the soil will result in lower force imbalances, which can result in overturning moments that can destabilize the pile from its intended vertical path.

[0054] Laboratory and field testing of the disclosed pile device has shown that the sloped top and bottom surfaces of the base structure provide significant improvements in stiffness, cyclic load resistance, and ultimate static holding capacity compared to the same device having flat top and bottom surfaces. Additionally, the sloped surfaces have been shown to improve driving capabilities.

[0055] In an embodiment of the eighth aspect of the present invention, the bottom surface of the base structure is generally sloped. The first edge of each tubular wall may be disposed a smaller longitudinal distance from the first end than the first edge of an adjacent radially outwardly disposed tubular wall.

[0056] In such embodiments, the first edge of the tubular wall may define a first conical shape tapering toward the first end. Alternatively, the first edge may define a first rotationally symmetric surface that is concave or convex.

[0057] The overall inclination of the first conical shape or the first rotationally symmetric concave or convex surface may be defined by a base inclination angle, which is defined as the angle between the longitudinal direction and a straight line extending in the longitudinal plane of the piling device and connecting the first edge of the innermost tubular wall with the first edge of the outermost tubular wall, the base inclination angle being in the range of 20 to 80°, preferably 40 to 70°, most preferably 50 to 65°.

[0058] In another embodiment of the eighth aspect of the present invention, the top surface of the base structure is generally sloped. The second edge of each tubular wall may be disposed a greater longitudinal distance from the first end than the second edge of an adjacent radially outwardly disposed tubular wall.

[0059] In such embodiments, the second edge of the tubular wall may define a second conical shape tapering toward the second end. Alternatively, the second edge may define a second rotationally symmetric surface that is concave or convex.

[0060] The overall inclination of the second conical shape or the second rotationally symmetric concave or convex surface may be defined by a top surface inclination angle, which is defined as the angle between the longitudinal direction and a straight line extending in the longitudinal plane of the piling device and connecting the second edge of the innermost tubular wall with the second edge of the outermost tubular wall, and a bottom surface inclination angle in the range of 20 to 80°, preferably 40 to 70°, most preferably 50 to 65°.

[0061] According to a ninth aspect, the present disclosure provides a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the pile device; and a base structure arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being defined by at least two tubular walls arranged concentrically with the stem and a plurality of radial walls, the radial cross-sectional area of ​​the radial walls decreasing radially outward.

[0062] Such an arrangement of the radial walls with a decreasing cross-sectional area towards the outside improves the transmission of vibrations from the vibration inducing device fixed to the stem to all parts of the base structure during vibration driving. During vibration driving, stress waves are transmitted through the radial walls of the stem and the base structure to the concentrically arranged tubular walls. Such transmission of stress waves through the structure may be hindered by an abrupt change in the structural impedance along the transmission path. At such an abrupt change in the structural impedance, the wave may be reflected back through the structure towards the location of the wave's origin. The structural impedance is a function of the cross-sectional area of ​​the structure through which the wave is transmitted. By arranging the radial walls of the base structure with a gradually decreasing radial cross-sectional area, such abrupt change in the radial structural impedance along the radial walls may be effectively eliminated or reduced. This improves the transmission rate of the stress waves transmitted from the stem to the outer tubular walls, whereby the driving of the pile device may be achieved with a higher efficiency.

[0063] Furthermore, by arranging the radial walls with an outwardly decreasing radial cross-sectional area, the structural efficiency of the base structure is also improved. The cumulative loads experienced by the concentrically arranged tubular walls, both during and after casting, are transferred to the central stem via the radial walls. This causes the radially inner portions of the radial walls to be subjected to higher loads than the outer portions. By arranging the radial walls with an outwardly decreasing cross-sectional area, the load-bearing capacity of the radial walls increases inwardly corresponding to the cumulative loads carried by each portion of the radial walls. Thus, the outwardly decreasing cross-sectional area of ​​the radial walls allows the overall material required to form the radial walls to be kept to a minimum while still establishing a sufficient load capacity of the radial walls. As a result, the overall weight and cost of the base structure can also be reduced.

[0064] In one embodiment of the pile device according to the ninth aspect, the radial cross-sectional thickness (in the circumferential direction of the base structure) of the radial wall gradually decreases in the radially outward direction from the central stem. This allows the longitudinal cross-sectional area of ​​the radial wall to be kept to a minimum while still establishing sufficient load-bearing capacity of the radial wall. As a result, the driving resistance caused by the radial wall during vibration driving is kept small, thereby improving the driving efficiency.

[0065] In another embodiment, the radial section height, i.e. the length of the radial wall in the longitudinal direction of the stem, gradually decreases in a radially outward direction from the stem. In a further embodiment, both the radial cross-sectional thickness and the radial cross-sectional height of the radial wall gradually decrease in a radially outward direction from the stem.

[0066] According to a tenth aspect, the present disclosure provides a pile device for vibratory driving, the pile device comprising: a cylindrical stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the pile device; and a base structure arranged at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being defined by at least two cylindrical walls arranged concentrically with the pile, each cylindrical wall extending parallel to the longitudinal direction of the stem, and a plurality of radial walls, the ratio of the diameter of the radially outermost cylindrical wall to the outer diameter of the stem being in the range of 1.1 to 8, preferably 1.5 to 5, most preferably 2 to 4.

[0067] Such an arrangement of the outer diameter of the base structure relative to the outer diameter of the stem provides optimal development of the plate-type soil mechanism described above. If the diameters are very similar (low ratio), the soil mechanism typical of plate-type anchors will not move and essentially the pile device will behave like a conventional tubular pile. If the diameter ratio is too large, the base structure will have higher resistance during driving and the relative accumulation of load across the surface of the base will result in higher stresses at the joint between the base and the stem. The spacings described above have proven to provide an advantageous balance in many applications.

[0068] According to an eleventh aspect, the present disclosure provides a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the pile device; and a base structure arranged at or proximate to the first end, the base structure having a plurality of longitudinally open cells, the cells being defined by at least two cylindrical walls arranged concentrically with the stem, each cylindrical wall extending parallel to the longitudinal direction of the stem, each tubular wall having a first edge proximate to the first end and a second edge proximate to the second end. and a base structure comprising cells and a plurality of radial walls, the cells having a first edge defining a first end face of the base structure and a second edge defining a second end face of the base structure, the stems at or adjacent the second end defining an effective top which is located at a level with the surface of the ground or seabed when the pile device is driven to a predetermined burial depth, the pile device exhibiting an burial depth ratio defined as the average longitudinal distance between the effective top and the second end face of the base structure divided by the outer diameter of the outermost cylindrical wall, the burial depth ratio being 1 or greater, preferably 2 or greater, and most preferably 5 or greater.

[0069] When the second end face of the base structure is flat and perpendicular to the longitudinal direction, the average longitudinal distance between the effective apex and the second surface is equal to the longitudinal distance from the effective apex to each second edge of the tubular wall. However, in some embodiments, the base structure may exhibit an inclined second surface, which is defined by second edges located at different longitudinal heights. In such embodiments, the average longitudinal distance is constituted by the average value of the longitudinal distance between the effective apex and each second edge.

[0070] After driving the pile device, the volume of the inverted truncated cone located above the base structure contains the soil material that acts on the filled base structure under the influence of gravity and is proportional to the embedment depth and the diameter of the base structure. Configuring the pile device with the above mentioned embedment depth ratio ranges has been proven to provide sufficient upward vertical load capacity of the pile device while optimizing driving ability and structural efficiency at various embedment depths and various soil qualities. Assuming sufficient soil depth is available, the deeper the base structure of the pile device is embedded, the higher the capacity will be provided by a given base structure, and therefore the most preferred devices have an embedment length (L) to diameter (L / D ratio) of 5 or more.

[0071] According to a twelfth aspect, the present disclosure provides a pile device for vibratory driving, the pile device comprising: a stem extending longitudinally between a first end and a second end, the first end being arranged to be located under the second end during driving of the pile device; and a base structure arranged at or adjacent to the first end, the base structure including a plurality of longitudinally open cells extending parallel to the longitudinal direction of the stem, the pile device further comprising an upper structure projecting radially outward from the stem at or adjacent the second end.

[0072] A pile device provided with such a superstructure provides an improved horizontal load capacity. The superstructure is located at a longitudinal distance from the first end of the stem such that the superstructure is at least partially embedded in the soil when the pile device reaches its final burial depth. The radially protruding superstructure thus acts on the surrounding soil such that horizontal load components are transferred to and absorbed by the surrounding soil.

[0073] By providing the pile device with such a superstructure, the horizontal load capacity can be increased even when the stem has a relatively small outer diameter and wall thickness. In addition to the advantages provided by the increased horizontal load capacity, such elongated pile devices may also use thin-walled stems due to the reduced stresses in the stem walls, since the bending moment that needs to be resisted by the stem can be significantly reduced by such a superstructure, which bears most of the horizontal load. Such elongated thin-walled pile devices exhibit excellent driveability, which reduces driving costs, allows for a low mass design, and can be manufactured at a relatively low cost.

[0074] In an embodiment of the piling device according to the twelfth aspect, the upper structure may comprise a plurality of fins extending radially from the stem. The fins may be symmetrically distributed around the circumference of the stem.

[0075] The fins may extend essentially parallel to the longitudinal axis of the stem. In some embodiments, the superstructure comprises at least one tubular wall concentrically disposed about the stem and secured to the stem by a plurality of radial fins.

[0076] In such an embodiment, the one or more tubular walls and the radial fins together may form a longitudinally open superstructure cell. Such superstructure cells may be configured to allow vibration-induced coring through the cells during vibratory driving of the piling device. They may also be configured to allow filling of the superstructure cells when the piling device reaches the intended burial depth and vibratory driving is stopped.

[0077] The superstructure may be applied to a piling machine having a base structure with longitudinal open base structure cells having different cross-sectional shapes, examples of such open base structure cell shapes are described in the detailed description below.

[0078] According to a thirteenth aspect, the present disclosure provides a pile device for vibratory driving, comprising a plurality of stems extending parallel to each other in a longitudinal direction between respective first ends and respective second ends, the first ends being arranged to be located vertically below the respective second ends during driving of the pile device, and a base structure fixed to the stems at or adjacent to their respective first ends, the base structure comprising a plurality of longitudinally open cells extending parallel to the longitudinal direction of the stems.

[0079] In such pile devices having multiple stem configurations, the improved vertical load capacity provided by the open cell base structure is distributed among the stems. The second upper ends of the stems may function as individual load bearing or anchoring points, whereby the entire load applied to the stems is supported by the base structure. Such multiple stem devices may provide improved structural efficiency in certain anchoring applications, since the connection between the base structure, which provides the majority of the load capacity in the direction of the stems, and the upper ends, which act as anchor connection points to the external device, may be connected by multiple stem structures, which require less material and lower manufacturing costs, compared to single stem devices.

[0080] In an embodiment of the pile device according to the thirteenth aspect, the second upper ends of the stems are interconnected to each other by a connecting member fixed to each second end. The piling device may be positioned so that when the piling device reaches the intended burial depth, the connecting members lie slightly above or slightly below the ground or seabed surface.

[0081] The connecting members may be provided with fins which protrude transversely to the longitudinal direction and act on the surrounding soil when the pile device reaches the intended burial depth, thereby increasing the horizontal load capacity of the pile device.

[0082] Alternatively, or in combination, the connecting member may comprise at least one tubular wall extending parallel to the longitudinal direction, the tubular wall being arranged to be embedded in the surrounding soil when the pile device reaches the intended burial depth, thereby increasing the horizontal load capacity of the pile device.

[0083] The connecting member is fixed to the connecting member for transmitting vibrations from a vibration inducing device attached to the connecting member to the stem during vibration driving of the pile device, and can be releasably fixed to the second upper end of the stem so that the connecting member can be removed after completion of vibration driving.

[0084] According to a fourteenth aspect, the present disclosure provides a method for vibratory driving of a piling apparatus according to the first aspect into the ground or seabed, the method comprising the steps of: - mounting a vibration-induced oscillator at or adjacent to the second end of the stem; - suspending a pile device comprising an oscillation device from a load support device; - orienting the piling device so that the first end is positioned below the second end in essentially vertical alignment with the second end and lowering the piling device until the first end contacts the ground or seabed; - achieving an initial gravity drive penetration of the first end into the ground or seabed without activating the vibration inducing device; - actuating an oscillator to vibrate the piling device in a predetermined vibration frequency range; - lowering the pile device while the oscillator is still operating, thereby driving the pile device further into the ground or seabed; - monitoring the inclination of the stem, the vertical load suspended from the load-bearing device, the vibration frequency of the pile device and the penetration depth of the first end of the stem into the ground or seabed during further driving of the pile device; - repeating during further driving of the piling device and adjusting the inclination of the stem, the vertical load suspended from the load-bearing device and the vibration frequency when the monitored values ​​deviate from the respective predefined nominal ranges; - stopping the oscillator when the first end of the stem reaches a predetermined penetration depth in the ground or seabed; Includes.

[0085] Such a method of driving a pile device provides adequate control and continuous regulation of the vibratory driving process, which allows driving to be carried out in ground or seabeds exhibiting widely differing and unknown properties, while still minimizing the risk that unforeseen soil properties will adversely affect the vibratory driving or cause interruptions to the vibratory driving.

[0086] Additionally, the method provides a further advantage in that precise control of vibration frequency allows the piling device to be driven into the soil whilst maintaining coring of the soil through the cells of the base structure, providing high driving rates, typically of several millimetres per second.

[0087] In one embodiment of the method according to the fourteenth aspect, the method further comprises: - determining a first system natural frequency of the pile-soil-oscillator-system when the penetration depth of the first end reaches a predetermined value; - vibrating the piling device at a first system natural frequency for a first predetermined period of time by an oscillator; - determining a second system natural frequency of the pile-soil-oscillator-system after the first period of time; - vibrating the piling device at a second system natural frequency for a second predetermined time period; Further includes.

[0088] By carrying out the additional method steps of this embodiment, the load-bearing capacity of the driven pile device can be significantly increased. Vibrating the pile device at least at the first system natural frequency and then at the second system natural frequency caused by the pile-soil-oscillator-system efficiently provides soil densification in many soil types, which contributes to increased stiffness. It can also reduce the so-called arching effect that occurs in the soil after the initial vibration driving at a given vibration frequency. Thereby, the frictional forces acting between the soil after completion of the vibration driving and the stem of the pile device and the base structure are increased, so that the load capacity of the driven pile device is increased by making the soil filling of the cells more resistant to external loads. In particular, the additional vibration of the pile device at the first, second and possibly any further system natural frequencies of the pile-soil-oscillator-system efficiently reduces or eliminates such arching effect occurring inside the open cells of the base structure. This facilitates advantageous filling of the cells in a relatively easy and cost-effective manner. The term pile-soil-oscillating machine-system is used herein to mean a system comprising a pile machine, an oscillator and soil, with mass movement when the oscillator operates to vibrate the pile machine. During such vibration of the pile machine, not only do the oscillator and the pile machine vibrate, but the vibration motion is also transferred to the soil around the pile machine. Thus, the pile-soil-oscillating machine-system also includes the soil that moves during the vibration of the pile machine.

[0089] The system natural frequency of the pile-soil-oscillator-system may be determined by various different methods known per se to those skilled in the art. One such method of determining the system natural frequency of the system is to determine the response of the soil vertical velocity at the surface of the soil surrounding the pile device as a result of the excitation energy input into the system by a vibrating hammer. This response amplitude can be measured, for example, by placing a geophone on the surface of the soil in close proximity to the pile device. When the response of the soil vertical velocity reaches its maximum value in relation to the frequency of the excitation energy, the pile device is vibrating at the natural frequency of the pile-soil-oscillator-system. Thus, the first natural frequency, the second natural frequency and any further natural frequencies of the pile-soil-oscillator-system can be determined by vibrating the pile device at different vibration frequencies, such as from 50 Hz to 1 Hz, continuously monitoring the vertical velocity of the soil surface in close proximity to the pile device and recording at which input frequency the response amplitude reaches its maximum value. Other signals, such as the vibration amplitude and acceleration measured on the oscillatory device, can also be used to identify the natural frequency or resonant period of the system.

[0090] In a further embodiment of the method according to the fourteenth aspect, the method comprises the steps of: - repeating the above steps until no significant change in the system natural frequency is detected from one cycle to the next; Includes.

[0091] According to a fifteenth aspect, the present disclosure provides a method of driving a piling device into the ground or seabed, the piling device comprising a stem extending longitudinally between a first end and a second end, and a base structure disposed at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being symmetrically arranged around the stem in a cross-section of the base structure, the method comprising: - vibrating the pile device into the ground or seabed to a predetermined burial depth by means of an oscillator device attached to or adjacent to the second end of the stem while maintaining the longitudinal direction of the pile device essentially vertical; - reorienting the pile device by applying a lateral force to the second end of the stem such that the longitudinal direction of the pile device is out of the vertical direction, thereby pivoting the pile device about a horizontal pivot axis extending through the stem; Includes.

[0092] The method may be advantageously used in driving where the external load to be supported by the pile device is not oriented vertically. In such driving, it may be advantageous to reorient the pile device so that its longitudinal direction essentially coincides with the direction of the external load applied to the pile device during use. This coincidence of the longitudinal direction of the pile device with the load direction optimally exploits the advantageous load-bearing-increasing properties of the filled open-cell base structure. This is achieved because the load-bearing capacity of the filled open-cell base structure is greatest in the longitudinal direction of the pile device. In particular, the method may be advantageously used in offshore mooring applications where the load to be supported by the pile device is transmitted to the pile device by mooring lines extending transversely from the sea surface to a second end of the stem located at or close to the surface of the seabed. In such applications, the longitudinal direction of the pile device may be advantageously aligned with the predominantly occurring longitudinal orientation of the mooring lines.

[0093] In one embodiment of the method according to the fifteenth aspect, the vibration of the piling equipment induced by the oscillatory device is maintained during the reorientation step of the method, whereby the coring achieved by the maintained oscillatory motion of the piling equipment reduces the magnitude of the lateral force components required to achieve the desired reorientation.

[0094] In other embodiments, the lateral force may be applied to the second end without simultaneous oscillation of the piling device. In such embodiments, the oscillator may be removed from the piling device prior to application of the reorienting non-normal force to facilitate reorientation.

[0095] In some embodiments, the lateral reorientation force may be applied by an external manipulator, such as a crane, vehicle, or vessel, connected to the second end by a wire, rod, or corresponding force transmission device. Such embodiments allow for precise control of the direction and magnitude of the applied non-vertical reorientation force. In addition, such embodiments allow for the reoriented angle of the piling device to be verified and verified prior to connecting the external manipulating load to the piling device.

[0096] In other embodiments, a lateral reorientation force may be applied to the second end of the stem by the actual structure to be anchored, a load which is intended to be continuously maintained after completion of the driving of the pile device. For example, a floating wave energy conversion buoy or a floating wind turbine may be connected to the second end of the stem by a mooring line when the pile device is still oriented vertically after completion of the vibratory driving to the intended burial depth. Lateral forces applied to the second end via the mooring line and resulting from ocean waves acting on the floating buoy or wind turbine can then reorient the stem so that its longitudinal direction is aligned with the predominantly occurring longitudinal direction of the mooring line. Such an embodiment presents the advantage of not requiring any additional manipulators or additional specific reorientation steps after the vibratory driving to the intended burial depth has been achieved.

[0097] According to a sixteenth aspect, the present disclosure provides a further method of driving a piling device into the ground or seabed, the piling device comprising a stem extending longitudinally between a first end and a second end, and a base structure disposed at or adjacent to the first end, the base structure comprising a plurality of longitudinally open cells, the cells being symmetrically arranged around the stem in a cross-section of the base structure. The method comprises: - placing a pile guide device on the ground or seabed, the pile guide device presenting a guide structure configured to support a stem such that the longitudinal direction of the stem coincides with the intended off-vertical driving direction; - positioning the pile device on the pile guide device such that the stem is supported by the guide structure; - vibrating the piling device by means of an oscillator device attached to or adjacent to a second end of the stem while allowing the stem to slide along the support structure to the ground or seabed; - maintaining the vibration of the pile device until the pile device reaches a predetermined embedment length in the ground or seabed; - thereafter, terminating the vibration of the piling device and removing the guide device; Includes.

[0098] The method according to the sixteenth aspect may advantageously be used in applications similar to those of the method according to the fifteenth aspect, where the longitudinal direction of the piling device should be non-vertical after driving is completed. The method offers the advantage of allowing very precise control of the final longitudinal orientation of the piling device reached after driving is completed.

[0099] According to a seventeenth aspect, the present disclosure provides a method of removing a piling device comprising a stem extending longitudinally between a first end and a second end, and a base structure, the base structure comprising a plurality of longitudinally open cells arranged symmetrically around the stem in a cross-section of the base structure, each cell being defined by a plurality of longitudinally extending cell walls, the piling device being vibratory driven into the ground or seabed with the first end located below the second end. The method comprises: - mounting a vibration-induced oscillator at or adjacent to the second end of the stem; - connecting a pile device with an oscillation device to a load-bearing device; - activating an oscillator to vibrate the pile device in a predetermined vibration frequency range; - lifting the piling device by means of the load-bearing device while the oscillator is in operation, thereby extracting the piling device from the ground or seabed; Includes.

[0100] In fact, the method for removing the piling device can be considered as a reversal of some of the steps of the above-described method for driving the piling device by vibratory driving. The method for removing provides a reliable, fast and cost-effective way to extract a previously driven piling device from the ground or seabed.

[0101] In one embodiment, the method of removing further comprises: - determining the system natural frequency of the pile-soil-oscillator-system; - setting a predetermined vibration frequency range higher than the determined system natural frequency of the pile-soil-oscillator-system, preferably at least 1.5 times higher; Includes.

[0102] By vibrating the pile equipment during extraction at a frequency sufficiently higher than the natural frequency of the pile-soil-oscillator-system, for example 1.5 times the natural frequency, a higher relative movement between the pile equipment and the soil is possible, which allows the pile equipment to be extracted at a higher speed and at reduced cost.

[0103] In various aspects and embodiments, the outer surface of the stem may form a cell wall of the base structure, such as an innermost tubular or cylindrical wall of the base structure. The pile apparatus and methods according to various embodiments have proven useful in a variety of soil types, including, but not limited to, silt, clay, sand, and mixtures thereof.

[0104] Further objects and advantages of various aspects will become apparent from the following detailed description and the appended claims. Aspects and embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0105] [Figure 1] FIG. 1 is a side view showing diagrammatically the vibratory driving of a piling device according to a first embodiment into the seabed; [Figure 2A] FIG. 2 is a perspective view showing the pile device shown in FIG. 1. [Figure 2B] FIG. 2 is a side view showing the pile device shown in FIG. 1. [Figure 2C] FIG. 2 is a top view showing the pile device shown in FIG. 1. [Figure 3A] FIG. 13 is a perspective view showing a schematic representation of an alternative embodiment of the piling device; [Figure 3B] FIG. 13 is a side view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 3C] FIG. 13 is a top view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 4A] FIG. 13 is a perspective view showing a schematic representation of an alternative embodiment of the piling device; [Figure 4B]FIG. 13 is a side view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 4C] FIG. 13 is a top view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 5A] FIG. 13 is a perspective view showing a schematic representation of an alternative embodiment of the piling device; [Figure 5B] FIG. 13 is a side view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 5C] FIG. 13 is a top view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 6A] FIG. 13 is a perspective view showing a schematic representation of an alternative embodiment of the piling device; [Figure 6B] FIG. 13 is a side view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 6C] FIG. 13 is a top view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 7A] FIG. 13 is a perspective view showing a schematic representation of an alternative embodiment of the piling device; [Figure 7B] FIG. 13 is a side view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 7C] FIG. 13 is a top view diagrammatically illustrating an alternative embodiment of the piling device; [Figure 8A] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 8B] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 8C] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 8D] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 8E] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 8F] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 8G] FIG. 4 is a cross-sectional view showing a schematic diagram of a further embodiment of a piling device; [Figure 9A] 3A and 3B show schematic side and top views of a further embodiment of a piling device; [Figure 9B] 3A and 3B show schematic side and top views of a further embodiment of a piling device; [Figure 10A] 1 is a schematic side view illustrating an embodiment of a method according to the present disclosure. [Figure 10B] 1 is a schematic side view illustrating an embodiment of a method according to the present disclosure. [Figure 11A] 1 is a schematic side view illustrating another embodiment of a method according to the present disclosure. [Figure 11B] 1 is a schematic side view illustrating another embodiment of a method according to the present disclosure. [Figure 12] 1 is a schematic side view illustrating a further embodiment of a method according to the present disclosure. [Figure 13A] FIG. 4 is a perspective view showing a schematic diagram of a pile device according to a further embodiment; [Figure 13B] 4 is a top view diagrammatically illustrating a pile device according to a further embodiment; FIG. [Figure 14] FIG. 2 is a perspective view showing a schematic diagram of a further embodiment of a piling device; [Figure 15A] FIG. 4 is a side view showing a schematic view of the lower part of a pile device according to a further embodiment; [Figure 15B] FIG. 4 is a side view showing a schematic view of the lower part of a pile device according to a further embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0106] Aspects of the present disclosure are described more fully hereinafter with reference to the accompanying drawings, in which specific embodiments are shown. However, these aspects may be embodied in many different forms and should not be construed as limiting. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the scope of all aspects of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0107] Figure 1 shows diagrammatically the driving of a piling apparatus 1 according to a first embodiment into the seabed by vibratory driving. The piling apparatus 1 is shown in more detail in Figures 2A-2C. The piling apparatus 1 comprises an elongated cylindrical stem 2 having a first end 2a and a second end 2b. During vibratory driving, the first end 2a is positioned downwards and vertically aligned with the second end 2b. The piling apparatus further comprises a base structure 3 arranged concentrically around the stem 2 close to the first end 2a.

[0108] FIG. 1 further shows diagrammatically a driving device used when driving a piling device on the seabed. The driving device comprises a vessel 20 with a crane 21 and a hydraulic power unit 22. A vibration-inducing oscillator 23 is suspended on the crane 21 by a wire 24. The oscillator is fixed to the second end 2b of the stem 2 by a hydraulic clamp (not shown) and is connected to the hydraulic power unit 22 by a hydraulic hose 25. Oscillating devices that can be used for vibratory driving of piling devices are known per se. Such oscillators are sometimes called vibratory hammers or vibro hammers. They may have one or several rotating eccentric masses driven by a hydraulic motor. For vibratory driving of piling devices disclosed herein, the oscillator must be able to induce a vibratory movement in the stem 2, which is mainly directed in the longitudinal direction of the stem and has a frequency range of 20-50 Hz and an amplitude range of 5-35 mm. The output power may be in the range of 200 kW to 2000 kW.

[0109] When the piling device is suspended from the crane 21 via the oscillator 23 and wire 24, the piling device is oriented so that the longitudinal direction of the stem 2 becomes vertical under the influence of gravity. The dimensions of the piling device can vary greatly depending on the application. In the example shown in Figures 1 and 2a-2c, the stem 2 is tubular and has a longitudinal length of about 22 m, an outer diameter of about 1.6 m and a wall thickness of about 0.03 m.

[0110] 3A-3C show the lower part of the piling apparatus shown in FIGS. 1 and 2A-2C. As best seen in FIGS. 3A-3C, the base structure 3 comprises five cylindrical walls 4 extending longitudinally (vertically as seen in the figures) and arranged concentrically around the stem 2 proximate to the lower first end 2a of the stem 2. The cylindrical walls 4 are formed of steel plates having equal plate thickness. The longitudinal height of the cylindrical walls linearly decreases radially outward such that the innermost cylindrical wall 4 has a maximum height and the outermost cylindrical wall 4 has a minimum height. The cylindrical walls 4 are horizontally aligned such that their vertical centers lie in a common horizontal plane.

[0111] The base structure 3 further comprises twelve radial walls 5, each of which is formed from a steel plate having an equal thickness and which extend radially from the stem 2 to the outermost cylindrical wall 4 in a respective vertical plane. The radial walls 5 are uniformly distributed around the circumference of the stem 2. The vertical height of each radial wall decreases from its radially innermost edge fixed to the stem to its outermost edge fixed to the outermost cylindrical wall 4. The radial walls 5 are also horizontally aligned such that their vertical centers are located in a common horizontal plane. The radial walls 5 are further horizontally aligned with the cylindrical walls 4 such that the vertical centers of all the cylindrical walls 4 and all the radial walls 5 are located in a common horizontal plane.

[0112] As will be explained in more detail below, the cylindrical and radial walls may actually be formed and manufactured in a number of different ways. The cylindrical wall 4 and the radial walls 5 together with the outer surface of the stem 2 form a number of longitudinally (i.e. vertically as shown in the figures) open cells 6. In the example shown in Figures 1-3, where the base structure 3 comprises five cylindrical walls and twelve radial walls, a total of 5 x 12 = 60 longitudinally open cells 6 are formed. The longitudinal cross section of each cell 6 is defined by two mutually opposing straight lines forming the radial cross section of the respective radial wall 5 and two mutually opposing circular segments forming the circumferential segment of the respective circular wall 4.

[0113] In this example, the radial distance between adjacent cylindrical walls 4 decreases radially outward, so that the cross-sectional area of ​​all cells 6 is essentially equal. As explained in more detail in the overview above, it has been shown that certain geometrical ratios of the cells are very important to achieve an advantageous balance between coring and filling during and after the vibratory driving of the pile device. According to the first embodiment, it is important to keep the height-to-width ratio within certain limits. As mentioned above, the height-to-width ratio is defined as the ratio of the height of the cell to the effective distance between the walls defining the cross-section of the cell. In general, the effective distance is constituted by the shortest distance between two non-adjacent walls defining the cross-section of the cell. In the example shown in Figs. 1 to 3, the shortest distance for each cell is the radial distance between two adjacent cylindrical walls defining the cell. Thus, for the base device 3 shown in Figs. 1 to 3, the height-to-width ratio according to the first embodiment is, for each cell, the vertical height of the outer lower cylindrical wall defining the cell divided by the radial length of the cell. In the example shown, this ratio is close to 10 for all cells.

[0114] This ratio is well within the range of 3 to 12, which has been proven to provide a good balance between coring and filling during and after vibratory driving of the pile equipment, especially when used with soil types having similar properties to medium density sand.

[0115] The circular walls 4 present a respective lower first edge 4a proximal to the lower first end 2a of the stem 2 and an upper second edge 4b ​​proximal to the upper second end 2b, i.e. distal to the first end 2a of the stem 2. As mentioned above, the height of the horizontally aligned circular walls 4 decreases radially outwardly such that the innermost lower first edge 4a is located vertically closer to the first end 2a than the outermost lower first edge 4a. The lower first edge 4a of the intermediate portion is located on a straight line connecting the innermost lower first edge 4a and the outermost lower first edge 4a. Correspondingly, the innermost upper second edge 4b ​​is located vertically closer to the second end 2a than the outermost upper second edge 4b. In addition, the upper second edge 4a of the middle portion is disposed on a straight line connecting the innermost upper second edge 4b ​​and the outermost upper second edge 4b. As a result, the lower first edge 4a and the upper second edge 4b ​​define their respective conical surfaces. The lower first edge 4a defines the downward conical bottom surface of the base structure 3, and the upper second edge 4b ​​defines the upward top surface of the base structure 3.

[0116] As explained in the "Summary of the Invention" above in relation to the eighth aspect, such sloping bottom and top surfaces of the base structure 3 significantly increase the load capacity of the pile device, especially for loads applied in the longitudinal direction of the pile device. In the examples shown in Figures 1-3, the top and bottom surfaces are conical. In some examples, such as the embodiment shown in Figures 4A-4C, the sloping bottom and / or top surfaces of the base structure may be hyperbolic instead of conical. In other non-illustrated embodiments, the lower first edge and / or the upper second edge may be arranged on a convex line, such that the bottom and / or top surfaces, respectively, are parabolic.

[0117] 15A-15B show schematic diagrams of such conical and hyperbolic top and bottom surfaces. In the embodiment shown in FIG. 15A, the piling device comprises a cylindrical stem 1702 and a base structure 1703. The base structure 1703 comprises a number of concentrically arranged cylindrical walls, including an innermost cylindrical wall 1704', an outermost cylindrical wall 1704'' and three intermediate cylindrical walls. For better clarity, the radial walls are not shown in FIG. 15A and FIG. 15B. Each cylindrical wall has a lower first edge 1704a', 1704a'' and an upper second edge 1704b', 1704b''. Here, the lower first edges 1704a', 1704a'' of all cylindrical walls, including the intermediate cylindrical walls, lie on a common straight line L1 extending in the longitudinal plane of the piling device. The bottom surface is therefore conical in this example. A general bottom surface inclination angle Ab is defined as the angle between this line L1 and the longitudinal direction Ld of the piling device. In the example shown in FIG. 17A, the bottom surface inclination angle Ab is about 45°.

[0118] Correspondingly, all upper second edges 1704b', 1704b'', including the upper second edge of the middle portion, are disposed on a common straight line L2 extending in the longitudinal plane of the pile device. The upper surface is therefore also conical, with an upper surface inclination angle At of about 60° in this example.

[0119] FIG. 15B shows a schematic example in which the top and bottom surfaces of the base structure are hyperbolic. Here, the piling device comprises a stem 1802 and a base structure 1803 with an innermost cylindrical wall 1804', an outermost cylindrical wall 1804'' and several intermediate cylindrical walls. In this example, the upper second edges 1804b', 1804b'' of all cylindrical walls are not arranged on a straight line but on a concave line Lc, so that the top surface of the base structure 1803 is hyperbolic. The overall inclination of the top surface is defined as the angle At between the longitudinal direction Ld and a line L3, which extends in the longitudinal plane and connects the upper second edge 1804b' of the innermost cylindrical wall 1804' with the upper second edge 1804b'' of the outermost cylindrical wall 1804'', but not the upper second edges of the intermediate cylindrical walls. In the example shown in Figure 17B, the top surface inclination angle At is about 45 degrees. As shown in the figure, although not indicated by a line, the bottom surface is also hyperbolic with a bottom surface inclination angle of about 45 degrees.

[0120] Referring again to FIGS. 1-3, the pile device shown in FIGS. 1-3 also exhibits the following preferred geometric proportions in accordance with the various aspects described above: According to a second embodiment, the pile device exhibits a closed area ratio in the range of 0.051.

[0121] According to a third embodiment, the ratio between the longitudinal length of the shortest cell wall and the square root of the cross-sectional area of ​​the cell 6 lies between 4.1 and 6.7 for all cells 6 shown in FIG. 3c. According to a fourth embodiment, the ratio between the cumulative internal area of ​​the cell walls 4, 5 defining the cell 6 and the cross-sectional area of ​​the cell 6 is between 21 and 29 for all cells shown in FIG. 3c.

[0122] According to a fifth aspect, the base structure 3 of this embodiment is designed with essentially equal cell cross-sectional areas for all cells 6, so that the variation in the cross-sectional area of ​​the cells 6 is less than 3% for all cells.

[0123] According to the sixth embodiment, the ratio of the longitudinal length to the diameter of the outermost cylindrical wall 4 is 0.41. According to the seventh embodiment, the first end 2a of the stem 2 projects longitudinally beyond the base structure 3, thereby forming a ground spike which facilitates initial driving into the seabed as described above.

[0124] According to the tenth embodiment, the ratio of the diameter of the radially outermost cylindrical wall 4 to the outside diameter of the stem 2 is 2.19. By exhibiting the geometrical proportions listed above, the pile apparatus 1 shown in Figures 1-3C has been proven to exhibit an advantageous balance between coring during vibratory driving and filling of the cells 6 after completion of vibratory driving. This results in excellent driving capabilities combined with high load capacity during driving.

[0125] Figures 4A-4C show a second embodiment of a piling device 101. This piling device 101 comprises a stem 102 and a base structure 103 arranged concentrically around the stem 102 at its first end 102a. The base structure 103 comprises five concentric cylindrical walls 104 supported by twelve radial walls. The cross-sectional shape is similar to that shown in Figure 3a and comprises 60 longitudinally open cells 106 presenting essentially equal cross-sectional areas.

[0126] The pile device 106 differs from the one shown in Figures 1 to 3C in that the base structure 103 is arranged at the first end 102a of the stem 102. As a result, the pile device 106 does not present any ground spike formed by a downwardly projecting portion of the stem. However, also in this embodiment, the vertical height of the cylindrical wall 104 and the radial wall 105 decreases radially outward. As a result, the lower first edge 104a of the cylindrical wall 104 defines a sloping bottom surface of the base structure 103. In this embodiment, the lower first edge 104 lies on a concave line connecting the innermost lower first edge 104a and the outermost lower first edge 104a. As a result, the bottom surface defined by the lower first edge 104 presents a hyperbolic shape. Correspondingly, an upper second edge 104 b of the cylindrical wall 104 defines a hyperbolic upper surface of the base structure 103 .

[0127] Similar to the conical top and bottom surfaces of the piling device 1 shown in Figures 1 to 3C, the hyperbolic top and bottom surfaces of the base structure 103 significantly increase the load capacity of the piling device 101 after driving, especially for vertical loads.

[0128] The hyperbolic bottom surface of the base structure 103, with the bottom surface located proximate the first end 102, further acts as a ground spike during initial penetration into the ground or seabed. The sloping bottom surface results in a gradually increasing driving resistance experienced by the pile device 101 during initial penetration into the ground or seabed. This facilitates maintaining a vertical orientation of the pile device during the initial stages of vibratory driving.

[0129] The embodiment of the piling device 201 shown in Figures 5A-5C comprises a stem 202 and a base structure 203 disposed proximate a first end 202a of the stem 202. The base structure 203 comprises three cylindrical walls 204 arranged concentrically around the base structure 203 and a plurality of radial walls 205. In this embodiment, the radial distance between the cylindrical walls 204 is equal throughout the base structure 203, and the plurality of radial walls 205 are circumferentially distributed such that all longitudinally open cells 206 defined by the cylindrical walls 204 and the radial walls 205 present essentially equal cross-sectional areas.

[0130] Furthermore, in this embodiment, all cylindrical walls 204 and vertical walls 205 present equal longitudinal heights such that the base structure 203 presents a flat bottom surface and a flat top surface, both surfaces being disposed in a horizontal plane perpendicular to the longitudinal direction of the stem 202. The first end 202a protrudes somewhat beyond the bottom surface of the base structure 203, thereby forming a relatively short ground spike.

[0131] In the embodiment shown in Figures 6A-6C, the piling device 301 comprises a stem 302 and a base structure 303 disposed at a first end 302a of the stem 302. Similar to the embodiment shown in Figures 3A-3C and 4A-4C, the base structure 303 comprises five concentrically arranged cylindrical walls 304 and twelve radial walls 305 separated by an outwardly decreasing radial distance between each pair of adjacent cylindrical walls. The cylindrical walls 304 and the radial walls 305 define longitudinally open cells 306 having equal cross-sectional areas. In this embodiment, all cylindrical walls 304 are of the same height, so that the bottom and top surfaces defined by the lower first edge and upper second edge 304b of the cylindrical walls are flat and oriented horizontally.

[0132] However, in this embodiment, the vertical height of the radial walls 305 decreases radially outwardly, such that the radial cross-sectional area of ​​the radial walls 305 also decreases radially outwardly from the stem 302. Such an arrangement of the radial walls 305 provides advantages associated with the continuous change in structural impedance and structural efficiency discussed above in relation to the ninth aspect.

[0133] In the embodiment shown in Figures 7A-7C, the piling device 401 comprises a stem 402 and a base structure 403. The base structure comprises five concentrically arranged cylindrical walls 404 and twelve radial walls 405 separated by equal radial distances, which together with the stem 402 define 60 longitudinally open cells 406. In this embodiment, the cross-sectional area of ​​the cells increases radially outward. The cylindrical walls 404 and the radial walls 405 have equal and constant heights such that the bottom and top surfaces defined by a lower first edge and an upper second edge 404b of the cylindrical wall 404 are flat and horizontally disposed.

[0134] It should be noted that for all of the embodiments shown in Figures 1-7C, the shortest distance between two non-adjacent walls defining each cell is the radial distance between the two cylindrical walls defining the cell. Thus, for each cell, the effective distance is constituted by the radial distance between the two cylindrical walls defining the cell. Thus, when calculating the height-to-width ratio of a cell in these embodiments, the height of the shortest wall defining the cell is divided by the radial distance between the two cylindrical walls defining the cell.

[0135] 8A to 8G show alternative cross-sectional shapes of a base structure in a pile device according to a further embodiment, in which the effective distance of some exemplary cells is given the reference Sd.

[0136] The piling device shown in FIG. 8A comprises a cylindrical stem 502 and a base structure 503 arranged concentrically around the stem 502. The base structure comprises five cylindrical walls 504 arranged concentrically and twelve radial walls 505 which together with the stem 502 define sixty longitudinally open cells 506. The radial distance between the cylindrical walls 504 decreases radially outward. The effective distance Sd1-Sd5 of each cell 506 is constituted by the radial distance between the two cylindrical walls 504 which define the cell 506. The circumferential thickness of the radial walls 505 gradually decreases radially outward. In addition, the radial thickness of the cylindrical walls 504 decreases wall by wall radially outward. Such a reduction in the thickness, and therefore the cross-sectional area, of the walls 504, 505 is advantageous in terms of structural impedance and structural efficiency, as described above with reference to the ninth embodiment.

[0137] The piling device shown in FIG. 8B comprises a cylindrical stem 602 and a base structure 603 arranged concentrically around the stem 602. The base structure 603 comprises three cylindrical walls 604 arranged concentrically, separated by equal radial distances. The radial thickness of the cylindrical walls 604 decreases from wall to wall in the radially outward direction. The base structure 603 further comprises a plurality of radial walls 605. The circumferential thickness of each radial wall 605 decreases radially outward. The cylindrical walls 604 and the radial walls 605 together with the stem 602 define a plurality of longitudinally open cells 606. The effective distances Sd1-Sd3 of each cell 606 are here constituted by the circumferential distance between the two radial walls 605 defining the cell 506. According to the fifth embodiment, the cross-sectional area of ​​the cells 606 varies by less than 10% between all the cells 606 in the base structure 603.

[0138] The pile device shown in Fig. 8C comprises a cylindrical stem 702 and a base structure 703, the cross section of which generally forms a hexagon arranged symmetrically around the stem 702. The base structure 703 comprises a plurality of longitudinally open cells 706 symmetrically distributed around the stem 702. Each cell 706 is defined by six walls having equal lengths in the cross-sectional plane such that each cell 706 presents a regular hexagonal cross section. In this embodiment, the cross-sectional area is equal for all cells 706, and the effective distance Sd of each cell 706 is the shortest distance between two non-adjacent walls, which in this case is equal to the length of a side of the hexagonal cross section of the cell.

[0139] The pile device, as shown diagrammatically in FIG. 8D, comprises a tubular stem 802 with a square cross section and a base structure 803. The base structure comprises two tubular walls 804 with a square cross section, which are arranged concentrically around the stem 802. The tubular walls 804 are connected by a laterally extending partition wall 805. The tubular walls 804 and the partition wall 805 together with the tubular stem 802 define a number of longitudinally open cells 806a, 806b, whereby some of the cells 806a have a substantially L-shaped cross section and other cells 806b have a rectangular cross section. In this embodiment, the effective distance Sd of each cell 806a, 806b is constituted by the shortest distance between the two tubular walls 805 or between the stem 802 and the innermost tubular wall 805, which in this case is equal to the length of the partition wall 805 in the cross-sectional plane.

[0140] The pile device, as shown diagrammatically in FIG. 8E, comprises a tubular stem 902 having a cross section forming an equilateral triangle, and a base structure 903. The base structure comprises one tubular wall 904 having a cross section forming an equilateral triangle, arranged concentrically outside the tubular stem 902. The base structure also comprises a number of partition walls 905 arranged to form a number of longitudinally open cells 906 together with the tubular wall 904 and the stem 802. Each cell 806 presents a cross section having the shape of an equilateral triangle. In this embodiment, the effective distance is constituted by the shortest of the base and height of the cell 806 of triangular cross section. Since the cross section of the cell 906 in this embodiment is equilateral, the effective distance Sd is constituted by the height of the cross-sectional triangle.

[0141] The pile device, as shown diagrammatically in FIG. 8F, comprises a tubular stem 1002 having an octagonal cross section and a base structure 1003. The base structure 1003 comprises two tubular walls 1004 having an octagonal cross section and arranged concentrically around the stem 1002. The base structure 1003 further comprises a number of radial walls 1005 extending from the stem 1002 to the outermost tubular wall 1004. The tubular walls 1004 and the radial walls 1005 together with the stem 1002 define a number of longitudinally open cells 1006 having an inclined cross section. In this embodiment, the effective distance Sd is equal for all cells 1006 and is constituted by the radial distance between the stem 1002 and the inner tubular wall and the radial distance between the inner tubular wall and the outer tubular wall, respectively.

[0142] The pile device, as shown diagrammatically in FIG. 8G, comprises a cylindrical stem 1102 and a base structure 1103. The base structure 1103 comprises an inner tubular wall 1104a and an outer tubular wall 1104b. Both tubular walls 1104a, 1104b have a square cross section and are arranged concentrically around the stem 1102. The base structure further comprises a number of partition walls 1105, all of which have equal length in the cross-sectional plane. The inner tubular wall 1104a is connected to the stem by four inner partition walls 1105a evenly distributed around the stem 1102. The inner tubular wall 1104a and the inner partition walls 1105a thereby define, together with the stem 1102, four inner longitudinally open cells 1106a. Furthermore, the inner tubular wall 1104a and the outer tubular wall 1104b together with the outer partition wall 1105b define a plurality of outer longitudinally open cells 1106b, some of which have rectangular cross sections and some of which have angled cross sections. In this embodiment, the effective distances Sd1, Sd2 for each of the inner cells 1106a and the outer cells 1106b are constituted by the length of the inner partition wall 1105a and the outer partition wall 1105b, respectively. Since the inner partition wall 1105a and the outer partition wall 1105b have equal lengths in cross section, the effective distances Sd1, Sd2 are equal for all cells 1106a, 1106b.

[0143] Figures 9A and 9B show diagrammatically the respective piling devices 1301, 1401 according to the twelfth embodiment described above. Both Figures 9A and 9B show the respective piling devices 1301, 1401 in a side view and in a cross section taken from line AA after they have been driven into the seabed.

[0144] Both pile devices comprise a cylindrical stem 1302, 1402 and a base structure 1303, 1403 concentrically disposed about the stem 1302, 1402 proximate a first end 1302a, 1402a of the stem 1302, 1402. The stem 1302, 1402 and base structure 1303, 1402 are essentially identical to the stem 2 and base structure 3 shown in Figures 1-3C and will not be described further here.

[0145] However, the pile devices 1301, 1401 differ from the previously described pile devices in that they each include an upper structure 1310, 1410 disposed adjacent the upper second ends 1302b, 1402b of the stems 1302, 1402, respectively.

[0146] In the embodiment shown in FIG. 9A, the superstructure 1310 comprises four fins 1311a-1311d fixed to the top of the stem 1302, i.e. adjacent to the upper second end 1302b of the stem 1302. Each fin 1311a-1311c comprises a rectangular steel plate arranged to extend parallel to the longitudinal direction of the stem 1302 and to project radially from the stem 1302. The fins 1311a-1311c are further symmetrically distributed along the periphery of the stem 1302. During driving of the piling device 1301 into the seabed, the piling device is vibratory driven to a burial depth where the fins 1311a-1311d are at least partially embedded in the seabed. The fins thereby transfer horizontal loads to the surrounding soil, thereby significantly improving the horizontal load capacity of the piling device 1301, as explained in more detail in the Summary of the Invention above with reference to the twelfth aspect.

[0147] In the embodiment shown in Fig. 9B, the superstructure 1410 also comprises four fins 1411a-1411d shaped and arranged essentially like the fins 1311a-1311d shown in Fig. 9a. In addition to the fins 1411a-1411d, the superstructure 1410 further comprises a cylindrical wall 1412 arranged concentrically around the stem 14012 and secured to the radially outer edges of the fins 1411a-1411d. The fins 1411a-1411c and the cylindrical wall 1412, together with the stem 1402, thereby define four longitudinally open cells 1413a-1413d. The superstructure 1401 may preferably be designed such that the open cells 1413a-1413d facilitate coring during vibratory driving of the pile device 1401 and facilitate filling of the cells 1413a-1413d after driving. Also, the advantages of the upper structure 1410 shown in FIG. 9b are further explained in the Summary of the Invention above with reference to the twelfth embodiment.

[0148] 13A-14 show diagrammatically a piling device according to a sixteenth aspect. In these embodiments, the piling device comprises a base structure 1503, 1603 with longitudinally open cells as described above. These embodiments generally differ from the above-mentioned embodiments in that the piling device comprises a plurality of stems 1502a-1502c, 1602a-1602c. Each stem extends between a first end intended to be placed under a second end during casting, as in the previous embodiment. However, here each stem 1502a-1502c, 1602a-1602c is thinner than the above-mentioned stems. The base structure 1503, 1603 is arranged at the first ends of the stems 1502a-1502c, 1602a-1602c.

[0149] In the embodiment shown in Figures 13A-13B, the second ends of the stems 1502a-1502c are not interconnected and form independent anchoring points to which mooring lines or the like can be anchored when the piling device is driven.

[0150] In the embodiment shown in Fig. 14, the second upper ends of the stems 1602a-1602c are interconnected to form a single anchoring structure of the piling device. In the embodiment shown in Fig. 14, the second ends of the stems 1602a-1602c are interconnected by a cylindrical sleeve 1616 disposed between the second upper ends of the stems 1602a-1602c such that the second ends are fixed to the outer circumference of the cylindrical sleeve 1616. In general, the stems and / or base structures of the piling devices according to the various embodiments described above may preferably be manufactured from structurally rigid materials such as, for example, steel or fiber-reinforced composites, or other materials that exhibit sufficient strength and fatigue resistance to the loads experienced during driving and operation.

[0151] The base structure and / or stem can be manufactured by rolling sheet metal and welding the longitudinal edges of the sheet together to form a straight hollow pipe or cylinder. Such a hollow pipe or cylinder may be used to form the cylindrical wall of the base structure. To form the stem, several so-formed hollow pipes can be joined together longitudinally, for example by butt welding, to form the longitudinal sections of the finished stem. Another method of forming the stem in particular is by helical welding an elongated rectangular metal sheet, which is helically rolled and helically welded along its longitudinal edges.

[0152] Alternatively, the base structure and / or stems may be manufactured from fiber reinforced plastic using a filament winding process or other automated additive manufacturing process for fiber reinforced pipe sections. The walls of the pipe section may be constructed layer by layer by mixing fibers and resins / prepregs to form a composite matrix with multiple fiber directions combined in stacked layers to form a pipe section that can resist normal tension and compression loads as well as bending and torsional loads using a minimum amount of layers and wall thickness.

[0153] The base structure may also be formed by bending segments of sheet metal and welding the segments to the open cell configuration of the base structure. The base structure may also be formed by welding radial segments onto a stem, followed by bending the sheet into circular segments that are welded or otherwise rigidly joined to the radial segments to form a ring, and adding concentric ring segments thereto. Each segment may also be generally L-shaped in the cross-sectional plane of the base structure. One leg of the L-shaped segment may be straight to form the radial wall of the cell, and the other leg may be curved to form a circular segment that forms the outer circular wall segment of the same cell. A number of such L-shaped segments may then be circumferentially welded to the periphery of the stem to form a radially innermost ring of cells, with the curved legs of the segments together forming the innermost circular wall of the base structure. By adding additional similar segments in turn outside the innermost circular wall thus formed, the base structure may be completed to include any desired number of concentrically arranged circular walls radially separated by the straight legs of the L-shaped segments.

[0154] The base structure may also be manufactured by first forming a number of sheet metal cylinders with different diameters and a number of straight rectangular sheet metal walls. Slits extending in the longitudinal direction of the completed base structure may then be cut in the cylindrical and straight walls. Preferably, the slits may extend over about half the vertical height and may be cut from opposite edges of the cylindrical and straight walls, respectively. The base structure is then formed by arranging the cylindrical walls concentrically around the stem and the straight walls radially outward from the stem, where the walls intersect, the cylindrical walls are received in the slits of the radial walls and vice versa. Finally, the intersections may be secured by welding.

[0155] The base structure may be attached to the stem either as part of the process in which the base structure is manufactured or thereafter by joining the completed base structure to the stem and welding at least one radial wall of the base structure onto an outer wall surface of the stem.

[0156] Alternatively, the base structure may be formed by 3D printing, casting, and / or pouring resin into a mold that holds the fiber material. If the base structure is formed by any of these methods, e.g., casting, a portion of the stem within the height of the base structure can be cast in the same process, and then such base structure with the stem portion can be joined with a second part of the stem to form the entire stem to form the pile device.

[0157] Referring again to Figure 1, an exemplary method of vibratory driving of a piling device 1 into a seabed will now be described. As mentioned above, the piling device comprises a stem 2 extending longitudinally between a first end 2a and a second end 2b, and a base structure 3 arranged at or adjacent to the first end 2a, the base structure 3 comprising a plurality of longitudinally open cells 6 (see Figures 2a-c), the cells being symmetrically arranged around the stem 2 in a cross-section of the base structure 3, each cell being defined by a plurality of longitudinally extending cell walls 4, 5. The method comprises the following steps:

[0158] - mounting a vibration-inducing oscillator 23 on or close to the second end 2b of the stem 2; The oscillator 23 may, for example, comprise a vibro hammer and may be attached to the second end of the stem 2 by a hydraulic clamp (not shown) that grips the upper edge of the cylindrical wall of the stem 2 .

[0159] - suspending the pile device 1 equipped with the oscillation device 23 from the load support device 21. In the illustrated example, the piling device 1 equipped with the oscillation device 23 is suspended from a three-axis crane 21 via a wire 24 .

[0160] - orienting the piling device 1 so that the first end 2a is positioned below the second end 2b in essentially vertical alignment with the second end 2b and lowering the piling device 1 until the first end 2a contacts the ground or seabed.

[0161] In the illustrated example, the piling device 1 equipped with the oscillation device 23 orients itself vertically under the effect of gravity acting on the piling device 1 . - achieving an initial gravity drive penetration of the first end into the ground or seabed without activating the vibration inducing device.

[0162] In the illustrated example, the first end 2a of the stem 2 projects vertically below the bottom surface of the base structure 3. This facilitates the initial portion of penetration as the downwardly projecting portion of the stem 2 forms a ground spike that guides the first end 2a vertically downward.

[0163] - activating the oscillation device 23 to vibrate the piling device 1 in a predetermined vibration frequency range. The predetermined frequency range varies depending on many factors such as the weight of the piling device and the oscillator, as well as the density and other properties of the soil into which the piling device is driven. Usually, the vibration frequency should be kept about 1.5 times the natural frequency of the piling device-soil-oscillator-system. Typically, the predetermined vibration frequency range may be around 20-50 Hz.

[0164] - Lowering the pile device 1 while the oscillator 23 is still operating, thereby driving it further into the ground or seabed. Typically, during this phase, the downward driving speed is regulated by controlling the load suspended from the crane 21 so that gravity does not act on the entire mass of the piling device 1 and the oscillator device for pulling the piling device 1 downwards.

[0165] - monitoring the inclination of the stem, the vertical load suspended from the load support device, the vibration frequency of the pile device and the penetration depth of the first end of the stem into the ground or seabed during further driving of the pile device.

[0166] The inclination of the stem 1 may be monitored by using a combination of visual (human eye, camera) and inclinometer measuring devices. The hanging load may be monitored by using a load cell or equivalent load sensor. The maximum hanging load used may be equivalent to the wet mass (for subsea casting) or dry mass (on land) of the system. Applying this maximum hanging load with the mass suspended on the wire effectively prevents the base structure 3 from penetrating further. On the other hand, keeping the hanging load at zero effectively leaves the full weight of the system as a downward force acting on the bottom surface of the base structure 3.

[0167] - Repeatedly during further driving of the pile device, adjusting the inclination of the stem, the vertical load suspended from the load support device and the vibration frequency when the monitored values ​​deviate from the respective predefined nominal ranges.

[0168] Such repeated adjustment of critical implantation parameters allows implantation to be easily completed without unintended interruptions or failures, even in ground or seabeds with highly unknown properties.

[0169] - stopping the oscillator when the first end of the stem reaches a predetermined penetration depth in the ground or seabed. In some applications, it may be advantageous for the pile device after driving to be oriented such that the longitudinal direction of the stem deviates from the vertical. An example of such an application is when the pile device is used as a subsea mooring for a floating structure such as a wave energy converter buoy. In such applications, the load to be supported by the pile device is typically applied to the upper second end of the stem as a non-vertical tensile force that is transferred to the stem by the mooring wires. To increase the ability of the pile device to withstand such non-vertical loads, it may be advantageous to orient the stem such that it is generally aligned with the direction in which the mooring wires extend when transferring forces to the pile device.

[0170] Figures 10A-12 show, in schematic form, three different methods for achieving such a reorientation of the pile device. The exemplary pile device 1 used in these methods is essentially identical to the pile device 1 shown in Figures 1-3c and will not be described in detail again here.

[0171] In the method shown in Figures 10A-10B, the piling device 1 is first vibration driven vertically by the oscillator 23 to a predetermined burial depth. This initial driving can be achieved by the method described above with reference to Figure 1. After such initial driving, the piling device 1 reaches the position and vertical orientation shown in Figure 10A. After the initial driving, the wire 26 is fixed to the oscillator 23 and the vessel 27. Reorientation of the piling device 1 is then achieved by keeping the oscillator 23 in operation, thereby vibrating the piling device continuously at a predetermined frequency during the reorientation phase. As shown in Figure 10B, the actual reorientation is achieved by driving the vessel 27 horizontally away from the piling device such that a non-vertical pulling force is transferred via the wire 26 to the top of the piling device 1. This causes the piling device to pivot about a horizontal pivot axis extending through the stem 2 such that the piling device assumes the non-vertical orientation shown in Figure 10b. After the reorientation is completed, the oscillator device 23 is detached from the pile device 1. In the above-described reorientation method, the continuous vibration of the pile device 1 during the reorientation phase reduces the friction between the pile device and the surrounding soil, so that the pulling force applied by the vessel through the wires can be further significantly reduced compared to the corresponding reorientation operation without simultaneous vibration of the pile device. The above-described reorientation method can be advantageously applied to pile devices whose stem and base structures have relatively large diameters.

[0172] In the reorientation method shown in Figures 11A-11B, the piling device is also first vibrated vertically to a predetermined burial depth as shown in Figure 11A. The oscillator is then removed and a vessel is connected to the second end 2a of the stem 2 of the piling device 1 via a wire 26. Once the wire is connected to the vessel 27 and the piling device 1, a reorientation operation is performed in a similar manner to that described above by driving the vessel 27 away from the piling device 1 so that a non-vertical pulling force is applied to the second end 2b of the stem 2. This causes the piling device to be pivoted about a horizontal pivot axis extending through the stem until the piling device reaches the orientation shown in Figure 11B. However, the reorientation method shown in Figures 11A-11B differs from that shown in Figures 10A-10B in that no vibration is applied to the piling device during the reorientation phase. This non-vibration reorientation method presents the advantage of not requiring any operation of the oscillator during the reorientation. This latter redirection method may be used to advantage with elongated pile devices in which the diameter of the stem and base structures is relatively small.

[0173] Further details of the orientation change method described above with reference to Figures 10A-11B are described in the summary above with reference to the fifteenth embodiment. Figure 12 shows a schematic diagram of a method for driving the piling apparatus 1 into the seabed in a non-vertical direction. The exemplary piling apparatus 1 is essentially identical to the piling apparatus 1 shown in Figures 1 to 3C and will not be described in detail again here.

[0174] As shown in Figure 12, the method utilizes a pile guide device 30 comprising a base 31 and a guide structure 32 pivotable relative to the base 31 and arranged to support the stem 2 of the pile device 1 to be driven. By adjusting the pivot angle between the base 31 and the guide structure 32, the non-perpendicular driving angle can be set to any desired value.

[0175] The method is carried out by first placing the pile guide device at a desired position on the seabed or ground and adjusting the pivot angle so that the guide structure assumes a desired driving angle. Afterwards or before, the pile device 1 is placed on the pile guide device 30 so that the stem 2 is supported by the guide structure 32. Then, the oscillator device 23 attached to the second end 2b of the stem is activated to vibrate the pile device at a predetermined frequency. While maintaining the vibration in an activated state, the pile device is allowed to slide along the guide structure 32 to the ground or seabed. In some applications, such sliding may be achieved simply by the effect of gravity acting on the pile device 1 and the oscillator device 23. In other applications, it may be necessary to apply additional driving force in the longitudinal direction of the stem by a driving force device (not shown). The vibration is maintained until the pile device 1 reaches a predetermined embedment depth in the ground or seabed, after which the vibration is stopped and the pile guide device 30 is removed from the driving site.

[0176] The above described method is advantageous in that it allows, for example, the casting angle to be controlled with high precision. The method described above with reference to Figure 12 is further explained in the summary above with reference to the sixteenth aspect.

[0177] Aspects of the present disclosure have been described above primarily with reference to certain embodiments and examples thereof. However, as will be readily understood by those skilled in the art, embodiments other than those disclosed above are equally possible within the scope of the appended claims.

Claims

1. A pile device (1) for vibratory driving, comprising: a stem (2) extending longitudinally between a first end (2a) and a second end (2b), the first end (2a) being positioned to be located below the second end (2b) during driving of the pile device (1); a base structure (3) disposed at or adjacent to the first end (2a), the base structure (3) comprising a plurality of longitudinally open cells (6) arranged symmetrically around the stem (2) in a cross section of the base structure (3), each cell (6) being defined by a plurality of longitudinally extending cell walls (4, 5); each cell (6) has a height-to-width ratio calculated as the longitudinal length of the shortest cell wall (4, 5) defining said cell (6) divided by the effective cross-sectional distance (Sd) of said cell (6), said height-to-width ratio being in the range of 1 to 30, preferably 2 to 18, most preferably 3 to 12; The effective distance (Sd) is - for cells (6) with a non-triangular cross section, constituted by the shortest distance between two non-adjacent sides of said cross section, - for cells (806) with a triangular cross section, a pile device (1) constituted by the shortest of the base and height of the cross-sectional triangle.

2. 2. The pile device according to claim 1, wherein the base structure (3) comprises at least two tubular walls (4) extending in the longitudinal direction and arranged concentrically with the longitudinal axis of the stem (2), and at least two radial walls (5) extending radially and in the longitudinal direction, each cell (6) being defined by two adjacent tubular walls (4) and two adjacent radial walls (5), and the effective distance (Sd) is the shortest of the shortest radial distance between the tubular walls (4) and the shortest circumferential distance between the radial walls (5).

3. 3. A piling device according to claim 2, wherein for each cell (6), the effective distance (Sd) is the shortest radial distance between the tubular walls (4).

4. 3. A piling device according to claim 2, wherein said tubular wall (4) is cylindrical.

5. 5. A piling device according to claim 4, wherein the cylindrical wall (4) and the radial walls (5) are arranged so that the cross-sectional area is essentially equal for all cells (6).

6. 2. The pile device according to claim 1, wherein the pile device exhibits a closed area ratio calculated by dividing the cumulative closed cross-sectional area perpendicular to the longitudinal direction of the cell walls defining the stems and all cells by the cumulative open cross-sectional area of ​​the stems and all cells, the closed area ratio being in the range of 0.01 to 0.4, preferably 0.015 to 0.3, and most preferably 0.02 to 0.

1.

7. 2. The pile device according to claim 1, wherein the ratio of the longitudinal length of the shortest cell wall to the square root of the open cross-sectional area of ​​the cell is in the range of 1 to 40, preferably 2 to 20, most preferably 3 to 12.

8. 2. The pile device according to claim 1, wherein for each cell (6), the ratio of the cumulative internal area of ​​the cell walls (4, 5) defining the cell (6) to the open cross-sectional area of ​​the cell (6) is in the range of 4 to 100, preferably 10 to 40, and most preferably 15 to 35.

9. 2. A piling device according to claim 1, wherein for all cells (6), the ratio of the maximum cell cross-sectional area to the minimum cell cross-sectional area is not more than 5:1, preferably not more than 2.5:1, most preferably not more than 1.2:

1.

10. 5. The pile device according to claim 4, wherein the ratio of the longitudinal length to the diameter of the radially outermost cylindrical wall (4) is in the range of 0.1 to 4, preferably 0.2 to 1.2, most preferably 0.25 to 0.

7.

11. 2. A piling device according to claim 1, wherein the first end (2a) of the stem (2) projects longitudinally beyond the base structure (3).

12. Each tubular wall (4) comprises a first edge (4a) proximal to said first end (2a) and a second edge (4b) distal to said first end (2a); the first edges (4a) of at least two tubular walls (4) are located at different distances from the first end (2a), and / or - A piling device according to claim 1, wherein the second edges (4b) of at least two tubular walls (4) are arranged at different distances from the first end (2a).

13. 5. A pile device according to claim 4, wherein the stem (2) at or close to the second end defines an effective top which is located at a level with the surface of the ground or seabed when the pile device is driven to a predetermined burial depth, the pile device exhibiting an burial depth ratio defined as the longitudinal distance between the effective top and a proximal part of the base structure (3) divided by the outer diameter of the outermost cylindrical wall (4), the burial depth ratio being 1 or more, preferably 2 or more, most preferably 5 or more.

14. A method for vibratory driving of a pile device (1) according to any one of claims 1 to 13 into the ground or seabed, comprising: - attaching a vibration-inducing oscillator (23) to or adjacent to the second end (2b) of the stem (2); - suspending said pile device (1) equipped with said oscillation device (23) from a load-bearing device (21); - orienting the piling device (1) so that the first end (2a) is positioned below the second end (2b) in essentially vertical alignment with the second end (2b), and lowering the piling device (1) until the first end (2a) contacts the ground or seabed; - achieving an initial gravity driving penetration of said first end (2a) into said ground or seabed without activating said vibration inducing device (23); - activating the oscillation device (23) to vibrate the pile device (1) in a predetermined vibration frequency range; - lowering the pile device (1) while the oscillator device (23) is still operating, thereby driving the pile device (1) further into the ground or seabed; - monitoring the tilt of the stem (2), the vertical load suspended from the load-bearing device (21), the vibration frequency of the piling device (1) and the penetration depth of the first end (2a) of the stem into the ground or seabed during the further driving of the piling device (1); - repeatedly during the further driving of the pile device (1), adjusting the inclination of the stem (2), the vertical load suspended from the load-bearing device (21) and the vibration frequency when the monitored values ​​deviate from their respective predetermined nominal ranges; - stopping the oscillator (23) when the first end (2a) of the stem (2) reaches a predetermined penetration depth in the ground or seabed; A method comprising:

15. - determining a first system natural frequency of the pile-soil-oscillator-system when the penetration depth of the first end (2a) reaches the predetermined value; - vibrating the pile device (1) by means of the oscillator device (23) at the first system natural frequency for a first predetermined period of time; - determining a second system natural frequency of the pile-soil-oscillator system after said first period of time; vibrating said piling device (1) at said second system natural frequency for a second predetermined period of time; The method of claim 14 further comprising:

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