Excavation enclosure with floating structure and sheet pile wall

Abstract

Excavation shoring with • a floating body arrangement having a bottom and a central opening (25) and designed to be lowered with its bottom to the bottom of a body of water so that the bottom of the body of water is accessible through the opening, and • a ring-shaped sheet pile wall which is attached to the floating body arrangement, characterized in that • the sheet pile wall is arranged on an outside of the floating body arrangement and has a lateral distance from the opening (25).

Description

[0001] The invention relates to an excavation pit enclosure with the features of the preamble of claim 1.

[0002] As part of the energy transition, offshore wind farms must be connected to the energy distribution grid. Crossing the islands and bringing the cables ashore is of particular importance in this process. The cables cross the highly sensitive Wadden Sea areas, which are part of the Wadden Sea World Heritage Site and have national park status. The flood protection structures on the islands and along the mainland coasts that need to be crossed are generally traversed using horizontal directional drilling. The launch pits are usually located on the landward side. The exit points of the boreholes are in the tidal flats. Since the zero discharge principle applies in the Wadden Sea, the bentonite suspensions used in the drilling work must not be released into the environment under any circumstances. To ensure this, construction pits are also used in the tidal flats. Because the construction period must adhere to the requirements of the national park authority and storm surge protection measures, work is only permitted between the 15th and the 16th.Construction is permitted from July to September 30th. Conventional excavation pits cannot be created and dismantled within this short timeframe and are therefore not an option on the Wadden Sea side.

[0003] A trench enclosure with the features of the preamble of claim 1 is known from EP 3 653 795 A1. It is intended for use in the target area of ​​a horizontal borehole in the Wadden Sea to collect emerging drill cuttings and / or drilling fluid so that they can be pumped out and transported ashore. The known trench enclosure can be transported by floating and easily positioned and anchored on the seabed at the intended deployment site. A perimeter sheet pile wall is arranged in the center, and the floating body assembly extends outside the sheet pile wall.

[0004] The object of the invention is to improve the known excavation pit enclosure in such a way that impairment of the ecosystem is prevented even more reliably and reduced in its extent.

[0005] This problem is solved by the excavation enclosure with the features of claim 1. The excavation enclosure has the following features: • a floating arrangement having a bottom and a central opening and designed to be lowered to the bottom of a body of water with its bottom facing down, so that the bottom of the body of water is accessible through the opening, and • a ring-shaped sheet pile wall attached to the floating body arrangement, wherein • the sheet pile wall is located on an outside side of the floating body arrangement and has a lateral distance from the opening.

[0006] The opening forms a passage extending from the bottom of the floating structure to one of its upper ends. Such an opening is also known as a moonpool. The opening may be enclosed by a vertical wall. For example, the opening may have a rectangular cross-section. Overall, the opening forms a kind of shaft through which the bottom of the body of water is accessible when the floating structure has been lowered to the bottom.

[0007] This lowering of the floating assembly can be achieved by ballasting, in particular by flooding chambers of the floating assembly. In its unballasted state, the floating assembly, together with all other elements of the excavation shoring, is buoyant, allowing it to be easily transported to the desired location, for example, by a tugboat or workboat. When floating, the excavation shoring has a draft. The base of the floating assembly is submerged in the water to a depth dependent on the weight of the excavation shoring; water is present below the base. The opening is filled with water to a level corresponding to the water table.After positioning the floating structure at the desired location (for example, by surveying using DGPS), the structure can be fixed in place, for example, by lowering piles that are vertically adjustable and mounted on the floating structure. The piles can be positioned within the opening, for example, at two diagonally opposite corners. After the floating structure is lowered onto the bottom of the water body, the base rests on the bottom.

[0008] The sheet pile wall runs in a ring shape. Once it has been driven into the riverbed to a predetermined depth, it separates the area within the sheet pile wall from the surrounding water, and the water within the sheet pile wall can be pumped out. The height of the sheet pile wall is designed so that the expected water levels, including wave action, remain below the top edge of the sheet pile wall. Furthermore, the sheet pile wall is constructed to safely withstand the static and dynamic loads caused by the surrounding water.

[0009] The floating body assembly can be ring-shaped, completely enclosing the central opening on all sides. In any case, the sheet pile wall is positioned on one outer side of the floating body assembly and is set back laterally from the opening.

[0010] The area of ​​the riverbed accessible through the opening corresponds to a working area in which the borehole exit point is located. For example, the opening can have a length of 15 m to 40 m, preferably 20 m to 35 m, and a width of 3 m to 10 m, preferably 5 m to 7 m. Typically, the length is about 27 m and the width about 6 m. The area of ​​the riverbed enclosed by the sheet pile wall is significantly larger because the sheet pile wall is located on the outside of the floating assembly at a lateral distance from the opening. The lateral distance of the sheet pile wall from the opening depends on the dimensions of the floating assembly and can typically be in the range of 2 m to 5 m, for example, about 3 m.Compared to a sheet pile wall running around the inside of the floating structure, the horizontal distance between the borehole exit opening and the sheet pile wall increases by this amount. This greater distance significantly increases the safety against hydraulic heave.

[0011] Another advantage of the large lateral distance between the sheet pile wall and the opening is that it also results in a greater vertical distance to the borehole below the sheet pile wall. With a typical horizontal drilling angle of approximately 20°, the vertical distance between the borehole and the bottom edge of the sheet pile wall increases by more than 1 m due to the greater lateral distance of the sheet pile wall from the opening. This also improves the resistance to hydraulic heave.

[0012] A further advantage over the excavation enclosure known from the aforementioned publication EP 3 653 795 A1 is the better accessibility of the opening from the top of the floating body arrangement, because the sheet pile wall arranged externally in the invention, which projects upwards significantly above the top of the floating body arrangement serving as a working platform, does not have to be overcome.

[0013] In one embodiment, sealing elements are provided that are designed to seal a gap between the base of the floating assembly and the riverbed when the assembly is lowered to the riverbed. These sealing elements can be positioned, in particular, at the lower edge of the opening or along the lower edge of the opening on the base of the floating assembly. The sealing of the area of ​​the riverbed surrounding the opening by these elements prevents drilling fluid, bentonite, and / or other substances escaping from the borehole from wetting the riverbed outside the opening. This significantly simplifies the complete cleaning of the work area and effectively prevents any adverse effects on the surrounding tidal flats / water body.Therefore, increasing the area enclosed by the sheet pile wall does not lead to a correspondingly larger wetting of the riverbed with potentially harmful substances.

[0014] In one embodiment, the sealing elements are sandbags. After lowering the floating assembly and pumping out the water from the opening, the sandbags can simply be placed directly on the bottom of the body of water along the lower edge of the opening. In this way, an effective seal is created using simple and flexible means.

[0015] In one embodiment, vertically displaceable guide beams are arranged on the outside of the floating structure, to which the sheet pile wall is attached. The guide beams can be arranged vertically. The guide beams can, in particular, be made of steel. Due to their vertically displaceable mounting, the guide beams can be raised and fixed to the floating structure for transporting the excavation shoring, so that they do not protrude downwards, or only minimally, above the bottom of the floating structure. This achieves a minimal draft. After the floating structure is positioned and lowered, the guide beams can be lowered until they are embedded in the riverbed to the desired depth. This depth can, in particular, correspond to the desired position of the bottom edge of the sheet pile wall.

[0016] In one embodiment, the floating assembly comprises several rectangular pontoons, each with multiple couplings for connecting them to one another. These couplings can be, for example, fastening openings for bolted connections or other fastening devices for inserting steel profiles or other complementary connecting elements. Such pontoons are also called coupling pontoons and are available in various standardized dimensions. They can be joined together to form a rectangular ring, thereby creating the opening. The working platform formed by the coupling pontoons can have a uniform width around the opening, for example, in the range of 2 m to 5 m. The couplings allow the coupling pontoons to be easily separated from one another, simplifying storage of the floating assembly and, if necessary, transport by land.Before the excavation pit enclosure is transported to the site, the pontoons can be coupled together in the port so that the entire floating assembly can be towed to the site.

[0017] In one embodiment, the guide beams are slidably mounted on mounting plates attached to the pontoon couplings. The mounting plates can be, in particular, rectangular steel plates that are bolted to the pontoon couplings. This, as well as the attachment of the guide beams to the mounting plates, can be done in the port before the floating assembly is transported to its deployment location.

[0018] In one embodiment, a sealing profile is inserted into a joint between two coupled pontoons. The sealing profile can, in particular, seal an inner wall of the opening. The joint can run vertically on the inside of the joined pontoons. The sealing profile can, in particular, be a rubber profile, especially of the fir-tree type. The sealing profile prevents potentially harmful substances from escaping from the opening into the space between the pontoons and thus into the water surrounding the opening.

[0019] In one embodiment, the sheet pile wall has a waler arranged on its outer side. The waler can, in particular, be a steel profile. The waler runs essentially horizontally along the outer side of the sheet pile wall and prevents the sheet pile wall from deforming under load. In conventional excavation pits, the waler is usually arranged on the inner side of a wall supporting the excavation pit, as also shown in the aforementioned publication. In the invention, however, the floating body is located on the inner side of the sheet pile wall, so that arranging the waler on the outer side is easier to manufacture, especially in conjunction with the desired vertical adjustability of the sheet pile wall.

[0020] In one configuration, the walers are attached to the guide beams. This attachment can also be carried out in the port. The walers and guide beams form a single unit that is vertically displaceable and mounted to the floating structure. During the final on-site construction of the excavation shoring, the walers can be lowered together with the guide beams, thus already forming a stable unit. This simplifies the subsequent installation of the sheet pile wall.

[0021] In one embodiment, the guide beams have outward-facing brackets on which the webbing rests. These brackets can, for example, be steel profiles welded to the guide beams, with a horizontal bearing surface on their upper side. One advantage of this arrangement is that vertical loads are optimally transferred to the guide beams. A further advantage arises during assembly. The webbing can be placed on the brackets before being attached to the guide beams (for example, by means of bolts).

[0022] In one configuration, the sheet pile wall consists of numerous sheet piles arranged in a row and connected along their longitudinal edges. In another configuration, the sheet piles are made of plastic. Such a modular design of the sheet pile wall significantly simplifies its construction. The individual sheet piles can be installed one after the other and driven into the riverbed to the desired depth.

[0023] In one embodiment, the sheet piles have a receiving groove on one longitudinal edge and a counterpart on the other longitudinal edge, so that a counterpart of one sheet pile can be positively inserted into a receiving groove of an adjacent sheet pile, with a sealing profile arranged in the receiving groove or on the counterpart. In this way, a reliable seal of the sheet pile wall is achieved without the need for any separate measures after the sheet piles have been installed.

[0024] In one embodiment, the sheet pile wall, in addition to the sheet piles, has at least one intermediate sheet pile element that is either narrower or wider than one of the sheet piles. This intermediate sheet pile element can also be equipped with longitudinal edges corresponding to those of the sheet piles, thus enabling easy connection to the sheet piles. By choosing a width of the intermediate sheet pile element that deviates from the standardized width of the sheet piles, a grid dimension between adjacent guide beams, as defined by the pontoon couplings, can be maintained. Nevertheless, standardized sheet piles can be used for the majority of the sheet pile wall.

[0025] In one embodiment, at least one stoplog is provided, which can be attached to the inside of the floating structure across the opening and is designed to separate a section of the riverbed containing a borehole exit point from the rest of the riverbed within the opening. The precise point at which the borehole exits the riverbed can usually only be reliably determined shortly before it emerges. For this reason, the opening must be of a considerable size so that all exit points expected within the tolerance range are located within it. The stoplog allows a portion of the riverbed within the opening to be separated without altering the position of the excavation shoring. This significantly reduces the area that comes into contact with potentially harmful substances.Preferably, two stop logs are provided, which can be arranged on both sides of a borehole exit point. In the case of a rectangular opening, at least one stop log can be arranged parallel to a short side of the rectangle. When using two stop logs with this orientation, a very small surface area around the borehole exit point can be precisely demarcated from the surrounding area.

[0026] In one embodiment, at least one mounting plate is provided, which includes a fastening device for attachment to the float and a guide rail for the at least one stoplog. This allows for easy installation of the stoplog within the opening.

[0027] In one embodiment, the mounting device is adapted to the couplings of a pontoon, allowing the mounting plate to be attached to a coupling facing the opening of the pontoon. In this way, the mounting plate enables the stoplog to be positioned freely within the grid spacing defined by the couplings. Typically, the grid spacing of the couplings is approximately 1 m to 2 m, allowing for a correspondingly precise positioning of the stoplog.

[0028] The invention will now be explained in more detail with reference to an embodiment illustrated in the figures. The figures show: Fig. 1. A perspective view of an excavation enclosure, Fig. 2 the excavation enclosure Fig. 1 in a side view of a front face, Fig. 3 the floating body arrangement of the excavation pit closure Fig. 1, Fig. 4 guide beams and bracing of the excavation enclosure made of Fig. 1 in a perspective view, Fig. 5 the sheet pile wall of the excavation enclosure Fig. 1 in a perspective view, Fig. 6 two longitudinal edges of adjacent sheet piles in cross-section, and Fig. 7 a sealing profile in cross-section.

[0029] Fig. Figure 1 shows the excavation shoring in its fully assembled state during operation, shortly before a borehole emerges. The excavation shoring consists of a floating arrangement of pontoons 1 to 8, which enclose a centrally located, rectangular opening 25, the so-called moonpool. The pontoons 1 to 8 have different dimensions and are connected to each other via couplings (not shown in detail). Two pontoons 1 and 7, each 3 m wide and 6 m long, are arranged at the short sides of the rectangle. Three pontoons 2, 3, 4 and 5, 6, 8 are located at each of the long sides of the rectangle. These pontoons 2, 3, 4, 5, 6, 8, also each have a width of 3 m, but a greater length.

[0030] Inside opening 25 is the seabed (tidal flat), which is located in the Fig. 1 is not shown in detail. The floating structure with pontoons 1 to 8 is anchored in the riverbed by means of two piles 9, 10.

[0031] Vertical joints 27 between each pair of adjacent pontoons on the inside forming the opening 25 are each fitted with a sealing profile 23 (see Fig. 7) sealed. A gap between the bottom of pontoons 1 to 8 and the riverbed is sealed with sandbags 16.

[0032] A sheet pile wall runs around the outer side of the floating body arrangement formed by pontoons 1 to 8 in a ring shape, comprising a large number of sheet piles 11 arranged in a row and connected to each other. There are also sheet pile intermediate elements 13, which have a different width than the sheet piles 11.

[0033] A waler 14 runs along the outside of the sheet pile wall at approximately the level of the top of pontoons 1 to 8. This waler 14 is supported on brackets 20, which are arranged on guide beams 15 pointing outwards (see also Fig. 4) The belt 14 is screwed to the guide carriers 15.

[0034] Inside the opening 25 are two stop logs 18, which separate a relatively small area of ​​the riverbed located between the stop logs 18 from the surrounding areas. This is best seen in the enlarged section in Fig. As can be seen in Figure 1 below right, the stop logs 18 are held in guide rails 28, which are arranged on mounting plates 17. The mounting plates 17 have fastening devices 26 that are connected to inwardly facing couplings of the middle pontoons 2 and 5, respectively. A stairway 19 leads into the working area located between the two stop logs 18.

[0035] The in Fig. The arrangement of the stop logs 18 shown in Figure 1 results from the expected exit point of the borehole being located approximately in the center of the opening 25. The stop logs 14 were positioned so that they surround this exit point as closely as possible.

[0036] In the side view of the Fig. Figure 2 clearly shows the two downward-pointing piles 9 and 10. The circumferential waler 14, which rests on a bracket 20 of a guide beam 15, is also clearly visible. The side view also clearly shows the uniform width of the sheet piles 11 and the narrower width of a sheet pile intermediate element 13 visible on the left.

[0037] In the perspective view of the Fig. Figure 3 shows only the ring-shaped floating assembly formed from pontoons 1 to 8 with piles 9 and 10. Piles 9 and 10 are attached to the inner sides of the floating assembly so that they can slide vertically.

[0038] Fig. Figure 4 shows only the guide supports 15 and the mounting plates 12, on each of which a guide support 15 is mounted for vertical displacement, as well as the circumferential strapping 14. In the enlarged detail shown at the bottom right, it is particularly clear that the guide supports 15 each have an outwardly projecting bracket 20 on which the strapping 14 is supported. The mounting plate 12 has fastening devices 26 at its four corners, which are aligned with the couplings on the pontoons 1 to 8.

[0039] Fig. Figure 5 shows only the sheet pile wall, which is composed of the sheet piles 11 and a smaller number of sheet pile intermediate elements 13. It forms a rectangular, closed ring.

[0040] In Fig. Figure 6 shows the longitudinal edges of two adjacent sheet piles 11 in cross-section in the upper part. The longitudinal edge of the sheet pile 11 shown on the right has a receiving groove 21 formed by a C-shaped profile. A sealing profile 24 is arranged on the inside of the receiving groove 21. The in Fig. The sheet pile 11 shown in the upper left has a counterpart 22 on its longitudinal edge, which can be inserted into the receiving groove 21 in a form-fitting manner.

[0041] In the lower part of the Fig. Figure 6 shows the elements from the upper part after proper assembly. The counterpart 22 is positively locked in the receiving groove 21. The sealing profile 24 is compressed and forms a seal between the two sheet piles 11.

[0042] In Fig.Figure 7 shows a cross-section of a sealing profile 23. It has a fir-tree profile. This sealing profile 23 is intended for insertion into the vertical joints 27 between two pontoons 1 to 8. List of reference symbols 1 to 8 pontoons 9, 10 stake 11 sheet pile 12 Mounting plate (for guide carrier) 13 sheet pile intermediate element 14 Strapping 15 leaders 16 sandbags 17 Mounting plate (for dam beams) 18 stoplogs 19 Staircase 20 console 21 recordings 22 counterpart 23 Sealing profile (for joint between pontoons) 24 Sealing profile (for sheet piles) 25 Opening 26 Fastening device 27 joint 28 Guide rail QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 653 795 A1 [0003, 0012]

Claims

[1] Excavation enclosure with • a floating body arrangement having a bottom and a central opening (25) and designed to be lowered with its bottom to the bottom of a body of water so that the bottom of the body of water is accessible through the opening, and • a ring-shaped sheet pile wall attached to the floating body arrangement, characterized by , that • the sheet pile wall is arranged on an outside of the floating body arrangement and has a lateral distance from the opening (25). [2] Excavation enclosure according to claim 1, characterized by that sealing elements are present which are designed to seal a gap between the base of the floating assembly and the bottom of the body of water when the floating assembly is lowered to the bottom of the body of water. [3] Excavation enclosure according to claim 2, characterized by , that the sealing elements are sandbags (16). [4] Excavation enclosure according to one of claims 1 to 3, characterized by that vertically displaceable guide beams (15) are arranged on the outside of the floating body arrangement, to which the sheet pile wall is attached. [5] Excavation enclosure according to one of claims 1 to 4, characterized by , that the floating arrangement comprises several rectangular pontoons (1 to 8), each having several couplings with which they can be coupled to one another. [6] Excavation enclosure according to claim 5, characterized by , that the guide carriers (15) are slidably mounted on retaining plates (12) which are attached to the couplings of the pontoons (1 to 8). [7] Excavation enclosure according to claim 5 or 6, characterized by , that a sealing profile (23) is inserted into a joint (27) between two coupled pontoons (1 to 8). [8] Excavation pit enclosure according to one of claims 1 to 7, characterized by, that the sheet pile wall has a waler (14) arranged on an outside of the sheet pile wall. [9] Excavation enclosure according to claim 8, characterized by , that the strapping (14) is attached to the guide carriers (15). [10] Excavation enclosure according to one of claims 4 to 9, characterized by , that the guide carriers (15) have outwardly facing brackets (20) on which the belting (14) is supported. [11] Excavation enclosure according to any one of claims 1 to 10, characterized by , that the sheet pile wall has a large number of sheet piles arranged in a row and connected to each other at their longitudinal edges (11). [12] Excavation enclosure according to claim 11, characterized by , that the sheet piles (11) are made of plastic. [13] Excavation enclosure according to claim 11 or 12, characterized by, that the sheet piles (11) have a receiving groove (21) on one longitudinal edge and a counterpart (22) on the other longitudinal edge, so that a counterpart (22) of a sheet pile (11) can be positively inserted into a receiving groove (21) of an adjacent sheet pile (11), wherein a sealing profile is arranged in the receiving groove (21) or on the counterpart (22). [14] Excavation pit enclosure according to one of claims 11 to 13, characterized by , that the sheet pile wall has at least one sheet pile intermediate element (13) in addition to the sheet piles (11), which has a smaller or larger width than one of the sheet piles (11). [15] Excavation enclosure according to any one of claims 1 to 14, characterized by, that at least one stoplog (18) is present which can be attached to the inside of the floating body arrangement with a diameter through the opening (25) and is designed to separate an area of ​​the riverbed which has a borehole exit point from the rest of the riverbed within the opening (25). [16] Excavation enclosure according to claim 15, characterized by , that at least one retaining plate (17) is provided which has a fastening device (26) for attachment to the float and a guide rail (28) for the at least one stoplog (18). [17] Excavation enclosure according to claim 16, characterized by , that the fastening device (26) is adapted to the couplings of a pontoon (1 to 8) so that the retaining plate (17) can be attached to a coupling of a pontoon (1 to 8) facing the opening (25).

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