Monopile and method for inserting the monopile

Abstract

The invention relates to a monopile for an offshore foundation, wherein the monopile is configured for insertion into a subsoil in a vertical insert direction, wherein the monopile has a circumferential wall defining an internal monopile chamber therein, and a driving shoe having a distal end that forms an entry towards the internal monopile chamber, wherein the distal end of the monopile enters the subsoil first, wherein the monopile comprises a soil resistance compensator that is configured to distribute soil resistance on the monopile during insertion thereof into the subsoil, wherein the soil resistance compensator comprises a soil resistor that is arranged on the circumferential wall at a predetermined height from the distal end in the insert direction.

Description

[0001] Monopile and method for inserting the monopile

[0002] BACKGROUND

[0003] The invention relates to a monopile and a method for inserting the monopile into a subsoil .

[0004] A monopile is known in the prior art . For example, a conventional monopile is used for building a foundation for supporting an of fshore wind turbine . The monopile is inserted in a subsoil , for example a seabed, and at a later stage the wind turbine is installed thereon .

[0005] Insertion of the monopile into the subsoil is performed from a vessel . The monopile is li fted with a crane and positioned vertically above its insert location . The monopile is then lowered by the crane into the subsoil . Thereafter the monopile is inserted into an end layer by pile driving .

[0006] Due to the high demand for wind energy, more and larger offshore wind turbines are being produced . Larger wind turbines also require larger monopiles for their fixed foundation in the subsoil .

[0007] SUMMARY OF THE INVENTION

[0008] A disadvantage of the known monopiles is that their increased dimensions lead to additional challenges for the vessels and cranes that insert the monopiles into the subsoil .

[0009] During insertion into the subsoil the monopile may pass several subsoil layers with di fferent bearing capacities . At or near the transition of the monopile into a subsoil layer with a lower bearing capacity, for example a softer clay layer, the monopile will encounter a drop in soil resistance . In case the bearing capacity is smaller than the weight of the monopile and for example the attached hoisting tool or pile driver that is transferred to the subsoil , this causes so called 'punch through' and this has unfavorable effects to the vessel and the crane .

[0010] It is an obj ect of the present invention to ameliorate or to eliminate one or more disadvantages of the known prior art, or to at least provide an alternative to the known prior art .

[0011] According to a first aspect , the invention provides a monopile for an of fshore foundation, wherein the monopile is configured for insertion into a subsoil in a vertical insert direction, wherein the monopile has a circumferential wall defining an internal monopile chamber therein, and a driving shoe having a bottom end that forms an entry towards the internal monopile chamber, wherein the bottom end has a bottom end outer diameter and the bottom end enters the subsoil first, wherein the monopile comprises a soil resistance compensator that is configured to increase a soil resistance on the monopile during insertion thereof into the subsoil , wherein the soil resistance compensator comprises a soil resistor that is arranged on the circumferential wall , wherein the soil resistor comprises a soil resistance part having a soil engagement surface that faces the bottom end to engage the subsoil during insertion of the monopile therein, wherein the soil engagement surface is arranged at a predetermined height from the bottom end in the insert direction, wherein the predetermined height is at least 10% of the bottom end outer diameter, with a minimum of 1 meter .

[0012] During insertion of the monopile the soil engagement surface of the soil resistance part contacts the subsoil into which the monopile is inserted, and thereby provides an increased insertion resistance . This causes the monopile to enter the subsoil more gradually, since the drop in soil resistance is at least in part compensated by the increased insertion resistance and spread out over a larger depth interval . This allows for controlled and safe insertion of the monopile into the subsoil .

[0013] In an embodiment the soil engagement surface is arranged above the driving shoe .

[0014] In an embodiment the soil resistor is configured to break away the soil resistance part from the circumferential wall when a load exerted on the soil engagement surface exceeds a predetermined load threshold . During insertion of the monopile into the subsoil , a load exerted by soil of the subsoil acts on the soil resistance part . The soil resistance part breaks away from the circumferential wall when the load exerted on the soil resistance part exceeds a predetermined load threshold . Since the soil resistance part first acts as an increased surface for the monopile, it does not yet break when the soil resistance part is still performing its initiated compensation function . When the soil resistance part is no longer needed for providing the increased surface, it can be broken away so that is does not result in unnecessary resistance during further insertion, during pile driving of the monopile . The soil resistance part breaks for example due to impact from the pile driver .

[0015] In an embodiment the circumferential wall has a wall thickness at the predetermined height , wherein the soil resistance surface has a radial width, wherein the soil resistor is configured to act as a breakaway part when the radial width is at least the same as the wall thickness , preferably at least two times higher, more preferably at least three times higher than the wall thickness .

[0016] In an embodiment the soil resistor comprises a support that connects the soil resistance part to the circumferential wall . In an embodiment thereof the support has a connecting part that is connected to the circumferential wall and a break part between the connecting part and the soil resistance part .

[0017] In an embodiment thereof the break part is configured to break the soil resistance part from the connecting part when a load exerted on the soil engagement surface exceeds a predetermined load threshold . By breaking away from the support at the break part, the soil resistance part reduces damage of the circumferential wall .

[0018] In an embodiment thereof the connecting part has a connecting side along which the connecting part is connected to the circumferential wall .

[0019] In an embodiment thereof the break part is spaced apart from the circumferential wall to define a clearance at the connecting side between the break part and the circumferential wall .

[0020] In an embodiment thereof the break part comprises a notch that is configured to initiate a target break line through the break part . The notch that is configured to initiate the target break line , causes the soil resistance part to break away from the support via this target break line . This allows for a controlled break of the soil resistance part away from the support . Also, the target break line makes it possible to set the predetermined load threshold .

[0021] In an embodiment thereof the connecting part has a connecting side along which the connecting part is connected to the circumferential wall , wherein the break part is spaced apart from the circumferential wall to define a clearance at the connecting side between the break part and the circumferential wall , wherein the break part comprises a notch that is configured to initiate a target break line through the break part, and wherein the notch debouches in the clearance .

[0022] As the notch faces the circumferential wall , the target break line extends away from the circumferential wall . This causes the soil resistance part to break away from the connecting part in a direction away from the circumferential wall , thereby preventing the soil resistance part to hit and damage the circumferential wall after breaking away .

[0023] In an embodiment the soil resistance part extends spaced apart from the circumferential wall .

[0024] In an embodiment the soil resistor is provided in the internal monopile chamber . By arranging the soil resistor inside the monopile, the outer circumference of the monopile is not increased . This makes it easier to handle to monopile .

[0025] In an embodiment the soil resistance part extends along and follows the curvature of the circumferential wall , wherein the soil resistance part extends along at least a portion of the circumferential wall .

[0026] In an embodiment thereof the soil resistance compensator comprises a plurality of soil resistors , wherein each soil resistance part thereof extends along a different portion of the circumferential wall .

[0027] In an embodiment thereof each soil resistance part extends along a dif ferent circumferential portion of the circumferential wall when seen in a proj ection along the insert direction . The soil resistance parts disrupt and remolds the subsoil as the monopile passes through it . By arranging the soil resistance parts at di fferent circumferential portions of the circumferential wall , the soil resistance parts that are arranged at dif ferent predetermined heights each pass through an undisturbed part of the subsoil .

[0028] In an embodiment thereof a plurality of soil resistors is arranged at a same first predetermined height . By providing multiple soil resistors at the same predetermined height .

[0029] In an embodiment thereof a plurality of soil resistors is arranged at a same second predetermined height that dif fers from the first predetermined height . Multiple soil resistors that are arranged at dif ferent predetermined height allow the monopile to be compensated for the decrease or drop in subsoil resistance at dif ferent depths in the subsoil . This is useful when the subsoil has multiple softer layers or layers with a decreased bearing capacity into which layers the monopile needs to be controlled during insertion therein .

[0030] In an embodiment the monopile is made of steel .

[0031] According to a second aspect, the invention provides a method for inserting a monopile for an offshore foundation, wherein the monopile is configured for insertion into a subsoil in a vertical insert direction, wherein the monopile has a circumferential wall defining an internal monopile chamber therein, and a driving shoe having a bottom end that forms an entry towards the internal monopile chamber, wherein the bottom end has a bottom end outer diameter and the bottom end enters the subsoil first, wherein the monopile comprises a soil resistance compensator that is configured to increase a soil resistance on the monopile during insertion thereof into the subsoil , wherein the soil resistance compensator comprises a soil resistor that is arranged on the circumferential wall , wherein the soil resistor comprises a soil resistance part having a soil engagement surface that faces the bottom end to engage the subsoil during insertion of the monopile therein, wherein the soil engagement surface is arranged at a predetermined height from the bottom end in the insert direction, wherein the subsoil comprises at least one first subsoil layer with a first bearing capacity, at least one second subsoil layer below the first subsoil layer with a second bearing capacity, and an end layer below the second subsoil layer with an end bearing capacity, wherein the second bearing capacity is lower than the first bearing capacity and wherein the end bearing capacity is higher than the second bearing capacity, wherein the method comprises the steps of : by a crane , lifting the monopile into a vertical position above the subsoil , wherein the bottom end faces the subsoil , by the crane, lowering the monopile such that the bottom end enters the subsoil , lowering the monopile through the at least one first subsoil layer, and through the at least one second subsoil layer, whereby soil of the subsoil enters the internal monopile chamber via the bottom end, wherein the bottom end follows a first traj ectory in the subsoil that ends inside the first subsoil layer at a first resistance transition depth, wherein the subsoil provides a first subsoil resistance during the first tra ectory, wherein the bottom end follows a second traj ectory in the subsoil after the first traj ectory, wherein the subsoil provides a second subsoil resistance during the second traj ectory, which second subsoil resistance is lower than the first subsoil resistance , wherein the second traj ectory starts at the first resistance transition depth, wherein the predetermined height is such that soil of a first subsoil layer engages the soil engagement surface of the soil resistance part when the bottom end starts with the second traj ectory, by a pile driver, driving the monopile into the end layer .

[0032] In an embodiment thereof the predetermined height is at least 10% of the bottom end outer diameter, with a minimum of 1 meter .

[0033] In an embodiment thereof the soil resistance part breaks away from the circumferential wall when a load exerted on the soil engagement surface exceeds a predetermined load threshold .

[0034] The various aspects and features described and shown in the speci fication can be applied, individually, wherever possible . These individual aspects , in particular the aspects and features described in the attached dependent claims , can be made subj ect of divisional patent applications .

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings , in which :

[0037] Figures 1A and IB respectively are a straight side view and a straight rear view of a vessel , a guiding structure and a crane to which a monopile according to the invention is suspended;

[0038] Figure 2 shows an isometric cross-section of a bottom part of the monopile of figure 1 , wherein a soil resistance compensator with soil resistors of the monopile is shown;

[0039] Figure 3 is an isometric view of one of the soil resistors of figure 2 ;

[0040] Figure 4 is a straight side view of the soil resistor of figure 2 ;

[0041] Figure 5 is a straight side view of the soil resistor after a soil resistance part of the soil resistor has broken away from the monopile ;

[0042] Figures 6A- 6D are cross-sections of a subsoil into which the monopile of figure 1 is inserted in four di fferent positions during insertion, and figure 6E is a cone penetration test diagram of the subsoil as shown in figures 6A- 6D .

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] Figures 1A and IB show an assembly 1 of a crane 2 on a vessel 3 , a monopile guiding structure 5 on the vessel 3 , and a monopile 4 that is suspended from the crane 2 . The assembly 1 is configured for inserting the monopile 4 in a downwards vertical insert direction J into a subsoil 51 , in this example a seabed of a sea 50 . After insertion into the seabed 51 , the monopile 4 can be used as a support structure to install , for example, an of fshore wind turbine thereon . In that case the monopile 4 has to provide sideward stability to withstand the radial forces acting on the monopile 4 .

[0045] The vessel 3 comprises a hull 7 with a bow 8 , a stern 9, a main cabin 10 at the bow 8 , and a deck 11 between the main cabin 10 and the stern 9 . The crane 2 has a crane pedestal 12 on the deck 11 , a crane body 13 that is slewable with respect to the crane pedestal 12 around a vertical slewing axis , a crane boom 14 that is hingeable with respect to the crane body 13 around a horizontal hinge axis , and a crane hook 15 that is suspended from the crane boom 14 by a hoisting cable 16 to move the crane hook 15 in a vertical lifting direction L . The crane 2 is used to erect and to lift the monopile 4 from the deck 11 into a vertical position alongside the vessel 3 using a pile hoisting tool 6 on the crane 2 .

[0046] The monopile guiding structure 5 is arranged at the deck 11 of the vessel 3 and is configured to guide the monopile 4 during insertion into the subsoil 51 . The guiding structure 5 comprises a guiding section 17 that proj ects aside from the vessel 3 and that is located directly above the sea 50 . The guiding section 17 has a guide channel 18 for receiving the monopile 4 , and in this example a plurality of guide wheels 19 to guide the monopile 4 through the guide channel 18 .

[0047] The monopile 4 is finally driven into the subsoil 51 by a non-shown pile driver that is , in a later stage , hoisted and installed onto the monopile 4 in the same way as the pile hoisting tool 6 . The pile driver is in this example a hydraulic pile driver that is clamped onto the monopile 4 and that uses hydraulic rams or vibrators to drive the monopile 4 into the subsoil 51 . The pile driver has a typical dead weight of 600- 1000 tons .

[0048] As best shown in figures 2 and 6 , the monopile 4 is a hollow cylindrical steel pile with a central axis M . The monopile 4 comprises a bottom part 61 that has in this example a constant outer diameter of approximately 10 meters over its entire height, and a bottom part wall thickness W1 . The monopile 4 comprises a top part 62 that has a constant outer diameter of approximately 7-8 meters over its entire height, a conical part 63 between the bottom part 61 and the top part 62 , and a driving shoe 64 that forms the lower side of the bottom part 61 . The monopile 4 has in this example a length of approximately 90-100 meters . The monopile 4 has a typical deadweight of 1500-2000 tons .

[0049] The monopile 4 has a circumferential wall 20 defining an internal cylindrical monopile chamber 21 therein . The monopile 4 has an open bottom end 25 at the driving shoe 64 , and a top end 26 at the top part 62 . The bottom end 25 is inserted into the subsoil 51 , whereby sea water of the sea 50 and soil of the subsoil 51 can enter the monopile 4 during insertion . The driving shoe 64 may be optimi zed to withstand the penetrating forces that act on the bottom side of the monopile 4 during the insertion into the subsoil 51 . The driving shoe 64 has for example a larger circumferential wall thickness or has a higher material strength . The driving shoe 64 can for example be arranged to the remainder of the monopile 4 by a weld 65. At the bottom end 25 the monopile 4 has a bottom end outer diameter DI . The top part 62 is the load-carrying part onto which for example the wind turbine is installed . The top part 62 of the monopile 4 extends above the sea level at a predefined installation height, whereby the conical part 63 and the top part 62 have a fixed length . The bottom part 61 of the monopile 4 is inserted into the subsoil 51 to a predefined depth . For each individual monopile 4 this predefined depth is such that the monopile 4 stands on a stable and load carrying subsoil . The bottom part 61 has a predefined length that depends on the water depth of the sea 50 and a composition of soil layers of the subsoil 51 .

[0050] As best shown in figure 2 , the bottom part 61 of the monopile 4 comprises a soil resistance compensator 27 . The soil resistance compensator 27 comprises in this example multiple soil resistors 60 that are arranged at the circumferential wall 20 of the monopile 4 . As best shown in figures 3 and 4 , the soil resistor 60 comprises a soil resistance part 28 and a support 29. In this example the soil resistor 60 comprises two supports 29. The soil resistance part 28 and the supports 29 are made of straight steel plates . The soil resistance part 28 has a soil engagement surface 41 at the underside of the soil resistance part 28 that faces the bottom end 25 of the monopile 4 . Each soil resistor 60 extends in the internal monopile chamber 21 , and is arranged with its soil engagement surface 41 at a predetermined height Hl from the bottom end 25 in the insert direction J of the monopile 4 . The predetermined height Hl is at least 10% of the bottom end outer diameter DI of the monopile 4 with a minimum of 1 meter . Further, each soil resistor 60 is arranged above the driving shoe 64 in the insert direction J of the monopile 4 when seen from the bottom end 25 .

[0051] The soil engagement surface 41 is configured to engage soil of the subsoil 51 during insertion of the monopile 4 therein . The soil resistance part 28 is configured to locally increase the surface of the monopile 4 at the predetermined height Hl when seen in the insert direction J of the monopile 4 . The soil resistance part 28 and the circumferential wall 20 of the monopile 4 are connected to each other by the supports 29. The support 29 has a first side 35, a second side 36 opposite the first side 35, a front edge 34 , a back edge 30 opposite the front edge 34 , a top edge 37 , and a bottom edge 31 opposite the top edge 37 . The circumferential wall 20 of the monopile 4 has an inner side 22 that faces the internal monopile chamber 21 and the center axis M, and an outer side 23 opposite the inner side 22 . The back edge 30 of the support 29 is connected to the inner side 22 of the circumferential wall 20 by welding . The front edge 34 of the support 29 faces the center axis M of the monopile 4 . The bottom edge 31 slopes downwards from the front edge 34 towards the back edge 30 . At the top edge 37 the support 29 is welded to the soil resistance part 28 at the soil engagement surface 41 thereof .

[0052] The support 29 has a connecting part 42 and a break part 43 . The connecting part 42 extends along the back edge 30 . The break part 43 connects the connecting part 42 with the soil resistance part 28 . Near the top edge 37 , the break part 43 is narrowed so that a break part clearance 32 is present between the inner side 22 of the circumferential wall 20 and the break part 43 of the support 29. The break part 43 comprises in this example a notch 33 that debouches towards the break part clearance 32 and near the top edge 37 . A soil resistance part clearance 38 extends between the soil resistance part 28 and the inner side 22 of the circumferential wall 20 above the break part clearance 32 , such that the soil resistance part 28 and the circumferential wall 20 are spaced apart from each other .

[0053] As best shown in figure 5 , the notch 33 is provided to establish a target break line 40 that originates at the notch 33 and extends towards the front edge 34 of the support 29. The soil resistance part 28 is configured to break away from the support 29 along the target break line 40 at a predefined load threshold onto the soil engagement surface 41 . The soil resistance part 28 breaks away from the circumferential wall 20 towards the central axis M . This is in order to prevent that the soil resistance part 28 damages the circumferential wall 20 . Other configurations of the support 29 are possible to arrange that the soil resistance part 28 breaks away from the circumferential wall 20 above the predefined load threshold .

[0054] The soil resistance surface 41 has a radial width W2 , wherein the soil resistance part 28 is configured to act as a breakaway part when the radial width W2 is at least the same as the bottom part wall thickness Wl , preferably at least two times higher, more preferably at least three times higher than the bottom part wall thickness Wl .

[0055] The soil resistance part 28 extends along and follows the curvature of the circumferential wall 20 . Such that the soil resistance part 28 extends along at least a portion of the circumferential wall 20 .

[0056] The soil resistance compensator 27 comprises in this example a plurality of soil resistors 60 , wherein one or more soil resistors 60 can be arranged at the same first predetermined height Hl and wherein one or more soil resistors 60 can be arranged at a same second predetermined that is dif ferent than the first predetermined height Hl . Multiple soil resistors 60 may also on average be arranged at the same first predetermined height Hl with a small spread around the first predetermined height Hl . When seen in a proj ection along the insert direction J, the soil resistance parts 28 of the plurality of soil resistors 60 that are arranged at dif ferent predetermined heights Hl are each distributed to extend along a dif ferent circumferential portion of the circumferential wall 20 . When seen in the proj ection along the insert direction J, the soil resistance parts 28 of the plurality of soil resistors 60 that are arranged at dif ferent predetermined heights Hl may also partly or entirely overlap each other . Soil resistors 60 that are arranged at the same predetermined height Hl may be evenly distributed along the circumference of the circumferential wall 20 .

[0057] Figure 6 shows an example of the subsoil 51 into which the monopile 4 is inserted in the vertical insert direction J . The subsoil 51 is build up from di fferent subsoil layers . Examples of subsoil layers are a layer of mainly clay or a layer of mainly sand . These subsoil layers each have dif ferent bearing capacities . In this assumption a layer of mainly sand has a higher bearing capacity than a layer of mainly clay . Insertion of the monopile 4 through a layer of mainly clay requires therefore less downward force than insertion of the monopile 4 through a layer of mainly sand . In this example the subsoil 51 comprises a first subsoil layer 53 that has a first thickness T1 and a first bearing capacity, a second subsoil layer 54 below the first subsoil layer 53 that has a second thickness T2 and a second bearing capacity, and an end subsoil layer 55 below the second subsoil layer 54 that has an end bearing capacity . The first bearing capacity is higher than the second bearing capacity, and the end bearing capacity is higher than the second bearing capacity . The end subsoil layer 55 is the subsoil layer into which the bottom end 25 of the monopile 4 is located when the monopile 4 is no longer inserted under its own weight and optionally the weight of the attached pile hoisting tool 6. The monopile 4 is in the end layer 55 finally pile driven to its predetermined depth . In this example the subsoil 51 has one first subsoil layer 53 , one second subsoil layer 54 , and an end subsoil layer 55. However, the monopile 4 according to the invention can also be inserted into a subsoil with a plurality of combinations of a first subsoil layer 53 and second subsoil layer 54 below a first subsoil layer 53 , as long as the subsoil has an end subsoil layer 55 below the first subsoil layers 53 and the second subsoil layers 54 into which the monopile 4 is finally pile driven to its predetermined depth .

[0058] During insertion of the monopile 4 , the bottom end 25 is directed downwards such that the bottom end 25 enters the subsoil 51 first . The top end 26 is directed upwards and is connected to the pile hoisting tool 6. When the monopile 4 is inserted into the subsoil 51 , the monopile 4 is lowered by the crane 2 such that the bottom end 25 enters the subsoil 51 . The monopile 4 is inserted through the first subsoil layer 53 and the second subsoil layer 54 under its own weight . Soil of the subsoil 51 then enters the internal monopile chamber 21 via the bottom end 25 .

[0059] During insertion the bottom end 25 follows a first traj ectory TRI during which the subsoil 51 provides a first subsoil resistance . The first traj ectory TRI ends inside the first subsoil layer 53 at a first resistance transition depth TD1 near the second subsoil layer 54 .

[0060] After the first traj ectory TRI , the bottom end 25 follows a second traj ectory TR2 during which the subsoil 51 provides a second subsoil resistance that is lower than the first subsoil resistance . The second traj ectory TR2 starts at the first resistance transition depth TD1 .

[0061] During insertion the monopile 4 encounters a sudden, but gradual drop in subsoil resistance at the transition from the first traj ectory TRI into the second traj ectory TR2 . This is near the transition of the bottom end 25 from the first subsoil layer 53 into the second subsoil layer 54 . The decrease starts at the first resistance transition depth TD1 and is caused by breaking through a final portion 56 of the stronger first subsoil layer 53 before reaching the weaker second subsoil layer 54 .

[0062] The predetermined height Hl at which the soil engagement surface 41 is arranged, is such that soil of a first subsoil layer 53 engages the soil engagement surface 41 of the soil resistance part 28 when the bottom end 25 starts with the second traj ectory TR2 . Therefore , the predetermined height Hl is related to the first resistance transition depth TD1 . This is when the soil resistance compensator 27 starts functioning . The soil engagement surfaces 41 of the soil resistance parts 28 of the soil resistors 60 provide a locally increased surface of the monopile 4 at the predetermined height Hl when seen in the insert direction J of the monopile 4 . This causes a compensation for the decrease in soil resistance at the transition from the first traj ectory TRI to the second traj ectory TR2 , and thereby prevents or minimi zes the ef fects of punch through when the monopile 4 is inserted through the second subsoil layer 54 .

[0063] When the bottom end 25 is transited through the second subsoil layer 54 in a controlled manner, and the monopile 4 does not sink into the subsoil 51 anymore by its own weight or by a combined weight of the monopile 4 and for example the pile driver, the monopile 4 is pile driven into the subsoil 51 by the pile driver . When the soil resistors 60 have passed the second subsoil layer 54 , the soil resistance surfaces 41 provides unnecessary resistance for the insertion . Therefore , the soil resistance parts 28 of the soil resistors 60 are configured to break away from the supports 29 when the predetermined load threshold onto the soil engagement surface 41 is reached . The soil resistance parts 28 break away from the supports 29 at the break parts 43 along the target break lines 40 , for example by powering the pile driver 6 to that extend . Finally, the bottom end 25 of the monopile 4 is pile driven into the end layer 55, such that the monopile 4 stands on a stable and load carrying soil layer .

[0064] In figure 6E a typical cone penetration test (CPT ) diagram 100 is shown of the subsoil 51 , wherein the subsoil 51 has a penetration resistance of 10-30 MPa during the first traj ectory TRI , a penetration resistance of <10 MPa during the second traj ectory TR2 , and a penetration resistance of >30 MPA in the end layer 55 .

[0065] The monopile 4 can comprise multiple soil resistors 60 that are arranged at di fferent predetermined heights Hl , such that the monopile 4 can be inserted controlled into a subsoil that comprises multiple subsoil layers with a lower bearing capacity below layers with a higher bearing capacity . Due to the multiple subsoil layers , the monopile 4 will encounter multiple decreases in soil resistance during insertion . These multiple decreases in soil resistance , at dif ferent soil resistance transition depths can be compensated by multiple soil resistors 60 that are arranged at different predetermined heights Hl to engage a soil layer with the higher bearing capacity than the soil layer that is actually penetrated .

[0066] Further, the monopile can comprise multiple soil resistors 60 that are arranged at dif ferent predetermined heights Hl , such that the monopile 4 can be inserted controlled into a subsoil 51 wherein the first thickness T1 of the first subsoil layer 53 is relatively small compared to the second thickness T2 of the second subsoil layer 54 .

[0067] It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention . From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention .

Claims

C L A I M S1 . Monopile for an of fshore foundation, wherein the monopile is configured for insertion into a subsoil in a vertical insert direction, wherein the monopile has a circumferential wall defining an internal monopile chamber therein, and a driving shoe having a bottom end that forms an entry towards the internal monopile chamber, wherein the bottom end has a bottom end outer diameter and the bottom end enters the subsoil first, wherein the monopile comprises a soil resistance compensator that is configured to increase a soil resistance on the monopile during insertion thereof into the subsoil , wherein the soil resistance compensator comprises a soil resistor that is arranged on the circumferential wall , wherein the soil resistor comprises a soil resistance part having a soil engagement surface that faces the bottom end to engage the subsoil during insertion of the monopile therein, wherein the soil engagement surface is arranged at a predetermined height from the bottom end in the insert direction, wherein the predetermined height is at least 10% of the bottom end outer diameter, with a minimum of 1 meter .2 . Monopile according to claim 1 , wherein the soil engagement surface is arranged above the driving shoe .3 . Monopile according to any one of the preceding claims , wherein the soil resistor is configured to break away the soil resistance part from the circumferential wall when a load exerted on the soil engagement surface exceeds a predetermined load threshold .4 . Monopile according to any one of the preceding claims , wherein the circumferential wall has a wall thickness at the predetermined height , wherein the soil resistance surface has a radial width, wherein the soil resistor is configured to act as a breakaway part when the radial widthis at least the same as the wall thickness , preferably at least two times higher, more preferably at least three times higher than the wall thickness .

5. Monopile according to any one of the preceding claims , wherein the soil resistor comprises a support that connects the soil resistance part to the circumferential wall .

6. Monopile according to claim 5 , wherein the support has a connecting part that is connected to the circumferential wall and a break part between the connecting part and the soil resistance part .7 . Monopile according to claim 6 , wherein the break part is configured to break the soil resistance part from the connecting part when a load exerted on the soil engagement surface exceeds a predetermined load threshold .8 . Monopile according to claim 6 or 7 , wherein the connecting part has a connecting side along which the connecting part is connected to the circumferential wall .

9. Monopile according to claim 8 , wherein the break part is spaced apart from the circumferential wall to define a clearance at the connecting side between the break part and the circumferential wall .10 . Monopile according to any one of the claims 6-9, wherein the break part comprises a notch that is configured to initiate a target break line through the break part .11 . Monopile according to any one of the claims 6-10 , wherein the connecting part has a connecting side along which the connecting part is connected to the circumferential wall , wherein the break part is spaced apart from the circumferential wall to define a clearance at the connecting side between the break part and the circumferential wall , wherein the break part comprises a notch that is configured to initiate a target break line through the break part, and wherein the notch debouches in the clearance .12 . Monopile according to any one of the preceding claims , wherein the soil resistance part extends spaced apart from the circumferential wall .13 . Monopile according to any one of the preceding claims , wherein the soil resistor is provided in the internal monopile chamber .14 . Monopile according to any one of the preceding claims , wherein the soil resistance part extends along and follows the curvature of the circumferential wall , wherein the soil resistance part extends along at least a portion of the circumferential wall .

15. Monopile according to claim 14 , wherein the soil resistance compensator comprises a plurality of soil resistors , wherein each soil resistance part thereof extends along a dif ferent portion of the circumferential wall .

16. Monopile according to claim 15, wherein each soil resistance part extends along a dif ferent circumferential portion of the circumferential wall when seen in a proj ection along the insert direction .17 . Monopile according to claim 16 , wherein a plurality of soil resistors is arranged at a same first predetermined height .18 . Monopile according to claim 17 , wherein a plurality of soil resistors is arranged at a same second predetermined height that differs from the first predetermined height .

19. Monopile according to any one of the preceding claims , wherein the monopile is made of steel .20 . Method for inserting a monopile for an of fshore foundation, wherein the monopile is configured for insertion into a subsoil in a vertical insert direction, wherein the monopile has a circumferential wall defining an internal monopile chamber therein, and a driving shoe having a bottom end that forms an entry towards the internal monopile chamber, wherein the bottom end has a bottom end outer diameter and the bottom end enters the subsoil first, wherein the monopile comprises a soil resistance compensator that is configured to increase a soil resistance on the monopile during insertion thereof into the subsoil ,wherein the soil resistance compensator comprises a soil resistor that is arranged on the circumferential wall , wherein the soil resistor comprises a soil resistance part having a soil engagement surface that faces the bottom end to engage the subsoil during insertion of the monopile therein, wherein the soil engagement surface is arranged at a predetermined height from the bottom end in the insert direction, wherein the subsoil comprises at least one first subsoil layer with a first bearing capacity, at least one second subsoil layer below the first subsoil layer with a second bearing capacity, and an end layer below the second subsoil layer with an end bearing capacity, wherein the second bearing capacity is lower than the first bearing capacity and wherein the end bearing capacity is higher than the second bearing capacity, wherein the method comprises the steps of : by a crane , lifting the monopile into a vertical position above the subsoil , wherein the bottom end faces the subsoil , by the crane, lowering the monopile such that the bottom end enters the subsoil , lowering the monopile through the at least one first subsoil layer, and through the at least one second subsoil layer, whereby soil of the subsoil enters the internal monopile chamber via the bottom end, wherein the bottom end follows a first traj ectory in the subsoil that ends inside the first subsoil layer at a first resistance transition depth, wherein the subsoil provides a first subsoil resistance during the first tra ectory, wherein the bottom end follows a second traj ectory in the subsoil after the first traj ectory, wherein the subsoil provides a second subsoil resistance during the second traj ectory, which second subsoil resistance is lower than the first subsoil resistance , wherein the second traj ectorystarts at the first resistance transition depth, wherein the predetermined height is such that soil of a first subsoil layer engages the soil engagement surface of the soil resistance part when the bottom end starts with the second traj ectory, by a pile driver, driving the monopile into the end layer .21 . Method according to claim 20 , wherein the predetermined height is at least 10% of the bottom end outer diameter, with a minimum of 1 meter .22 . Method according to claim 20 or 21 , wherein the soil resistance part breaks away from the circumferential wall when a load exerted on the soil engagement surface exceeds a predetermined load threshold .-o- o-o-o-o- o-o-o-LO / FG

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