An assembled box foundation for onshore wind turbines and its construction method

Abstract

The present invention discloses an assembled box foundation for onshore wind turbines, belonging to the technical field of wind power generation. The present invention has the advantages of low cost, large overall stiffness, short construction period, and less on-site labor input. At the same time, there is no problem of high hydration heat of cast-in-place mass concrete, and no concrete cushion is required, having broad engineering application prospects. The present invention not only effectively reduces the consumption of reinforced concrete materials, but also realizes the prefabrication of most components in the factory, and is assembled on-site using a standardized assembly process, with high construction efficiency. Combining a small amount of concrete pouring can improve the overall mechanical properties of the foundation structure, and it is a foundation type very suitable for large-capacity high-tower wind turbines. The present invention adopts an assembled structure to solve problems such as difficulties in material transportation and on-site construction, and uncontrollable concrete pouring quality.

Description

Technical Field

[0001] The invention belongs to the technical field of wind power generation, and particularly relates to an assembled box foundation for onshore wind turbines and a construction method thereof. Background Art

[0002] With the increase in the single-unit capacity of wind turbines and the increase in hub height, the load transmitted to the foundation has increased significantly. The use of traditional solid gravity spread foundations and beam-slab foundations will lead to a significant increase in the foundation size and a huge amount of reinforced concrete used, resulting in a series of problems such as structural safety, manufacturing and transportation, installation technology, and cost control. The use of a box-type structure for the wind turbine foundation can reduce the amount of materials used and lower the cost. In addition, wind power generation units are often installed in remote areas with sparse population. Especially for mountainous and desert areas where transportation and on-site construction are difficult, the use of an assembled structure can solve problems such as material transportation, on-site construction difficulties, and uncontrollable concrete pouring quality. Summary of the Invention[[ID= 11]]

[0003] The purpose of the invention is to overcome the shortcomings of the above-mentioned prior art and provide an assembled box foundation for onshore wind turbines and a construction method thereof.

[0004] To achieve the above purpose, the invention adopts the following technical solutions:

[0005] An assembled box foundation for onshore wind turbines includes a foundation bottom plate, a pedestal column, side walls, partition plates, and a top plate;

[0006] The foundation bottom plate is arranged inside the foundation pit. A pedestal column is provided at the center of the foundation bottom plate. Side walls are provided on the periphery of the foundation bottom plate. Partition plates are connected between the pedestal column and the side walls. The partition plates divide the cavity formed by the foundation bottom plate, the pedestal column, and the side walls into several independent cavities; the inside of the pedestal column is a cavity, and prestressed anchor bolts are provided inside the pedestal column; the cavity of the pedestal column and the cavities separated by the partition plates are all filled with backfill soil;

[0007] The top plate is provided at the top of the pedestal column, the side walls, and the partition plates;

[0008] The foundation bottom plate, the pedestal column, the side walls, the partition plates, and the top plate are all spliced by corresponding precast sub-components.

[0009] Furthermore, the precast sub-components of the bottom plate, the side walls, and the partition plates are connected by grouting with steel sleeve;

[0010] The precast sub-components of the pedestal column are connected by mechanical connection of steel bars and by setting a cast-in-place concrete section; at the corners where the precast sub-components of the bottom plate, the side walls, the partition plates, and the top plate meet, they are connected by steel bars and a cast-in-place concrete section 6;

[0011] The prestressed anchor bolts are used to connect the wind turbine tower barrel.

[0012] Further, the base floor slab is in the shape of a regular dodecahedron prism;

[0013] The center of the base floor slab in the shape of a regular dodecahedron prism is composed of two precast components of 1 / 2 cylinders and two precast components of 1 / 2 hollow cylinders. The hollow cylinders are sleeved outside the cylinders to form the central cylinder of the base floor slab;

[0014] The remaining part of the base floor slab is divided into 12 equal parts, and each of the 12 equal parts is further divided into two, which are the 24 precast components outside the base floor slab.

[0015] Further, the structure of the precast components of the top plate is the same as that of the base floor slab.

[0016] Further, each precast component of the top plate reserves the steel bars for the connection parts of the cast-in-place segments at the intersections with the three components of the pedestal column, side wall and partition board.

[0017] Further, the pedestal column is spliced by 4 identical precast components of the pedestal column, and the adjacent precast components of the pedestal column are connected by a cast-in-place concrete segment.

[0018] Further, each partition board is composed of two precast components, and a total of 24 precast components form 12 partition boards;

[0019] The precast components of the partition board reserve the steel bars for the connection parts of the cast-in-place segments at the intersections with the base floor slab, pedestal column, side wall and top plate components.

[0020] Further, the precast components of the side wall are the same as those of the partition board, and a total of 24 precast components form 12 side walls;

[0021] The precast components of the side wall reserve the steel bars for the connection parts of the cast-in-place segments with the base floor slab, partition board and top plate.

[0022] A construction method for an assembled box foundation of an onshore wind turbine includes the following steps:

[0023] (1), Splice the four precast components of the pedestal column. For the main bars between the components at the splicing joints, mechanical connection is adopted, and the stirrups are tied on site and then the concrete of the splicing segment is cast in place; Connection steel bars are reserved on the precast pedestal column components; Prestressed anchor bolt holes are reserved during the precasting of the pedestal column components;

[0024] (2), Splice the base floor slab. The base floor slab of each cavity is composed of the splicing of two precast components of the base floor slab, a total of 24 pieces, and they are connected by grouting with steel bar sleeves; The circular base floor slab in the middle of the pedestal column is composed of the splicing of two precast components, and the precast components are connected by grouting with steel bar sleeves. The precast components outside the base floor slab and the pedestal column, and the circular base floor slab and the pedestal column are both connected by a cast-in-place concrete segment 6;

[0025] (3) The spliced partition boards. Each precast sub-component is connected by grouting with a steel bar sleeve. The precast partition boards are reserved with steel bars for connecting with the cast-in-place sections of the bottom plate, side walls, top plate, and pedestal columns. The bottom of the partition board is connected to the bottom plate and the top of the partition board is connected to the top plate by cast-in-place concrete sections after mechanical connection of steel bars. The two sides of the partition board are connected to the side walls and the partition board by cast-in-place concrete sections after mechanical connection of steel bars.

[0026] (4) The spliced side walls. The side wall of each unit cavity is composed of two spliced precast sub-components, a total of 24 pieces. Each precast sub-component is connected by grouting with a steel bar sleeve. The intersections of the side walls with the bottom plate, partition boards, and top plate are connected by cast-in-place concrete sections after mechanical connection of steel bars.

[0027] (5) Backfill soil is filled and compacted in the cavities formed by the partition boards, pedestal columns, side walls, and bottom plate.

[0028] (6) The spliced top plate. The top plate of each cavity is composed of two spliced precast sub-component plates, a total of 24 pieces. Each precast sub-component is connected by grouting with a steel bar sleeve. The intersections of the top plate with the pedestal columns, side walls, and partition boards are all connected by cast-in-place concrete sections after mechanical connection of steel bars. The circular top plate in the middle of the pedestal column is composed of two spliced precast sub-components, and the precast sub-components are connected by grouting with a steel bar sleeve. The circular top plate is connected to the pedestal column by the cast-in-place concrete section 6.

[0029] (7) Prestressed anchor bolts are installed in the cavity of the pedestal column.

[0030] Further, the prestressed anchor bolts in the step are replaced with a foundation ring.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The prefabricated box foundation of the onshore wind turbine of the present invention solves the problems of material transportation and on-site construction difficulties, uncontrollable concrete pouring quality, etc. by adopting a prefabricated structure. The prefabricated box foundation of the onshore wind turbine of the present invention has the advantages of low cost, large overall stiffness, short construction period, and few on-site labor inputs. At the same time, there is no problem of high hydration heat of cast-in-place large-volume concrete, and no concrete cushion is required, having a broad engineering application prospect. The present invention not only effectively reduces the consumption of reinforced concrete materials, but also can realize the prefabrication of most components in the factory, and is assembled on-site using a standardized assembly process, with high construction efficiency, and combines a small amount of concrete pouring to improve the overall mechanical performance of the foundation structure. It is a very suitable foundation type for large-capacity high-tower wind turbines.

[0033] The construction method of the prefabricated box foundation of the onshore wind turbine of the present invention has low cost, fast construction, and little environmental pollution, and can be widely promoted and applied. Description of the Drawings

[0034] Figure 1Front view of the assembled box foundation structure of the onshore wind turbine of the present invention;

[0035] Figure 2 Schematic structural diagram of the present invention sectioned along line A-A;

[0036] Figure 3 Schematic diagram of the precast blocks of the pedestal column of the present invention;

[0037] Figure 4 Schematic diagram of the precast blocks of the bottom plate and the top plate of the present invention;

[0038] Figure 5 Schematic diagram of the precast blocks of the partition board and the side wall of the present invention;

[0039] Figure 6 Schematic diagram of the cast-in-place section of the present invention.

[0040] Wherein, 1-bottom plate; 2-pedestal column; 3-side wall; 4-partition board; 5-top plate; 6-concrete cast-in-place section; 7-backfill soil; 8-prestressed anchor bolt. Detailed implementation manners

[0041] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0042] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0043] Due to the large - volume cavity inside, the box - type fan foundation fills the backfill soil inside the cavity as a counterweight, which can effectively reduce the consumption of reinforced concrete and improve the seismic performance of the foundation itself. Compared with the traditional on - land fan circular plate and beam - plate foundation types with large engineering quantities, it has more advantages. For remote areas with difficult cast - in - place concrete construction and projects with tight construction periods, the present invention proposes an assembled box - type foundation for on - land wind turbines and its construction method.

[0044] A prefabricated and assembled box - type structure wind turbine generator foundation can not only effectively reduce the consumption of reinforced concrete materials, but also realize the prefabrication of most components in the factory. It is assembled on - site using a standardized assembly process, with high construction efficiency. By combining a small amount of concrete pouring, it improves the overall mechanical performance of the foundation structure. It is a very suitable foundation type for large - capacity high - tower wind turbine generators.

[0045] The following further describes the present invention in detail with reference to the drawings:

[0046] See Figure 1 and Figure 2 , Figure 1 is the front view of the assembled box - type foundation structure of the on - land wind turbine generator of the present invention, Figure 2 is the schematic structural view of the present invention sectioned along the A - A line. An assembled box - type foundation for on - land wind turbine generators includes a foundation bottom plate 1, a pedestal column 2, side walls 3, partition plates 4, and a top plate 5. The foundation bottom plate 1, pedestal column 2, side walls 3, partition plates 4, and top plate 5 are all spliced by corresponding prefabricated parts; the foundation bottom plate 1 is arranged inside the foundation pit. A pedestal column 2 is provided at the center of the foundation bottom plate 1. Side walls 3 are provided around the foundation bottom plate 1. Partition plates 4 are connected between the pedestal column 2 and the side walls 3, and 12 partition plates 4 are distributed radially; the inside of the pedestal column 2 is a cavity, and backfill soil 7 is filled in the cavity. Prestressed anchor bolts 8 are provided inside the pedestal column 2; at the top of the pedestal column 2, side walls 3, and partition plates 4, there is a top plate 5, forming a closed cavity.

[0047] The prefabricated parts of the bottom plate 1, side walls 3, and partition plates 4 are connected by grouting with steel - bar sleeves; the prefabricated parts of the pedestal column 2 are connected by mechanical connection of steel bars and by setting cast - in - place concrete sections; at the corner parts where the prefabricated parts of the bottom plate 1, side walls 3, partition plates 4, and top plate 5 meet, they are connected by mechanical connection of steel bars and by setting cast - in - place concrete sections 6; the upper - part wind turbine tower barrel is connected to the foundation by the prestressed anchor bolts 8 inside the pedestal column 2.

[0048] For convenient construction, the foundation bottom plate 1 is in the shape of a regular dodecahedron. The cavity is formed by the common enclosure of the bottom plate 1, side walls 3, top plate 5, and pedestal column 2, and the cavity is evenly divided into 12 parts by 12 partition plates 4. Backfill soil 7 is filled as a counterweight in each of the 12 uniform cavities and the cavity in the middle of the pedestal column 2. Each component is spliced by prefabricated parts.

[0049] See Figure 3, Figure 3 This is a schematic diagram of the sectionalization of the pedestal column of the present invention. The pedestal column 2 is composed of 4 identical precast components of the pedestal column. The adjacent precast components of the pedestal column are connected by cast-in-place concrete sections. The main reinforcement bars of the pedestal column adopt mechanical connection, and stirrups are provided for shear resistance.

[0050] See Figure 4 , Figure 4 This is a schematic diagram of the sectionalization of the bottom plate and the top plate of the present invention. The center of the regular dodecahedron-shaped bottom plate 1 is composed of precast components of 1 / 2 of two cylinders and 1 / 2 of two hollow cylinders. The two are spliced together to form the central cylinder of the bottom plate 1. The remaining part of the bottom plate 1 is evenly divided into 12 parts, and each of the 12 divided parts is further divided into two, resulting in 24 precast components;

[0051] The various precast components of the bottom plate 1 are connected by grouting with steel bar sleeves. Each precast component of the bottom plate 1 has reserved steel bars for the connection of the cast-in-place section at the intersection of the three components of the pedestal column 2, the side wall 3, and the partition board 4.

[0052] The precast components of the top plate 5 are the same as those of the bottom plate 1. The precast components of the top plate 5 are connected by grouting with steel bar sleeves. Each precast component of the top plate 5 has reserved steel bars for the connection of the cast-in-place section at the intersection of the three components of the pedestal column 2, the side wall 3, and the partition board 4.

[0053] For the specific implementation of the grouting connection with steel bar sleeves, refer to the relevant requirements of the "Technical Standard for Prefabricated Concrete Buildings" GB / T 51231-2016.

[0054] See Figure 5 , each partition board 4 is composed of two precast components, and a total of 24 precast components form 12 partition boards 4. The precast components of the partition board 4 are connected by grouting with steel bar sleeves; the precast components of the partition board 4 have reserved steel bars for the connection of the cast-in-place section at the intersection of the components of the bottom plate 1, the pedestal column 2, the side wall 3, and the top plate 5.

[0055] The precast components of the side wall 3 are the same as those of the partition board 4. A total of 24 precast components form 12 side walls 3. The precast components of the side wall 3 are connected by grouting with steel bar sleeves; each precast component has reserved steel bars for the connection of the cast-in-place sections with the bottom plate 1, the partition board 4, and the top plate 5.

[0056] See Figure 6 , for the reserved steel bars of the cast-in-place concrete section 6, the main reinforcement bars of the reserved steel bars adopt mechanical connection, and the stirrups are tied on-site, and finally the concrete is poured.

[0057] The present invention also provides a construction method for an onshore wind turbine assembled box foundation, including the following steps:

[0058] 1. Excavate the foundation pit;

[0059] 2. Splice the four precast components of the pedestal column 2. For the main reinforcement bars between components at the splicing joints, mechanical connection is adopted, and the stirrups are tied on-site. Finally, cast-in-place concrete is used for the splicing section; reserved connecting steel bars are provided on the precast components of the pedestal column 2; prestressed anchor bolt holes are reserved during the precasting of the pedestal column 2 components.

[0060] 3. Splice the foundation base plate 1. The base plate 1 of each cavity is composed of two precast components spliced together, with a total of 24 pieces, and they are connected by grouting with steel bar sleeves; the circular base plate 1 in the middle of the pedestal column 2 is composed of two precast components spliced together, and the precast components are connected by grouting with steel bar sleeves. The outer precast components of the base plate and the pedestal column 2, as well as the central precast component of the base plate and the pedestal column 2, are connected by cast-in-place concrete section 6.

[0061] 4. Splice the partition board 4. The partition board 4 of each unit cavity is composed of two precast components spliced together, with a total of 24 pieces, and each precast component is connected by grouting with steel bar sleeves. The precast partition board reserves steel bars for connection with the base plate 1, side wall 3, top plate 5, and cast-in-place section of the pedestal column 2; the bottom of the partition board 4 and the base plate 1, as well as the top of the partition board 4 and the top plate 5, are connected by cast-in-place concrete section after mechanical connection of steel bars; the two sides of the partition board 4 and the side wall 3, as well as the partition board 4, are connected by cast-in-place concrete section after mechanical connection of steel bars.

[0062] 5. Splice the side wall 3. The side wall 3 of each unit cavity is composed of two precast components spliced together, with a total of 24 pieces, and each precast component is connected by grouting with steel bar sleeves; at the intersections of the side wall 3 with the base plate 1, partition board 4, and top plate 5, cast-in-place concrete section is used after mechanical connection of steel bars.

[0063] 6. Fill the cavity formed by the partition board 4, pedestal column 2, side wall 3, and base plate 1 with backfill soil and compact it.

[0064] 7. Splice the top plate 5. The top plate 5 of each cavity is composed of two precast component plates spliced together, with a total of 24 pieces, and each precast component is connected by grouting with steel bar sleeves; at the intersections of the top plate 5 with the pedestal column 2, side wall 3, and partition board 4, cast-in-place concrete section is used after mechanical connection of steel bars; the circular top plate 5 in the middle of the pedestal column 2 is composed of two precast components spliced together, and the precast components are connected by grouting with steel bar sleeves; the circular top plate 5 and the pedestal column 2 are connected by cast-in-place concrete section 6.

[0065] 8. Install prestressed anchor bolts 8 in the cavity of the pedestal column 2.

[0066] The number of partition boards 4 of the concrete precast box foundation and the number of cavities evenly divided by the partition boards 4 can be adjusted according to different tower barrel section dimensions and foundation dimensions.

[0067] The connection between the upper wind turbine tower barrel and the pedestal column 2 can adopt a foundation ring or other forms.

[0068] The assembled box foundation of the onshore wind turbine of the present invention has reliable connections, low cost, fast construction, and little environmental pollution, and can be widely promoted and applied.

[0069] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modifications made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A construction method for an assembled box foundation of an onshore wind turbine generator system, characterized in that: The onshore wind turbine assembly box-type foundation comprises a foundation base plate (1), a platform column (2), a side wall (3), a partition plate (4) and a top plate (5); A foundation base plate (1) is provided inside a foundation pit, a platform column (2) is provided at the center of the foundation base plate (1), a side wall (3) is provided on the periphery of the foundation base plate (1), a partition plate (4) is connected between the platform column (2) and the side wall (3), and the partition plate (4) divides the cavity surrounded by the foundation base plate (1), the platform column (2) and the side wall (3) into a plurality of independent cavities; the interior of the platform column (2) is a cavity, and a prestressed anchor bolt (8) is provided in the platform column (2); the cavity of the platform column (2) and the cavity separated by the partition plate (4) are both filled with backfill soil (7); A top plate (5) is provided on the top of the platform column (2), the side wall (3) and the partition (4); The base plate (1), the platform column (2), the side wall (3), the partition plate (4) and the top plate (5) are all assembled by corresponding prefabricated parts; The prefabricated components of the bottom plate (1), the side wall (3) and the partition (4) are connected by grouting with steel sleeves; The prefabricated components of the platform column (2) are connected by means of mechanical connection with steel bars and provision of cast-in-place concrete sections (6); the bottom plate (1), side walls (3), partitions (4) and top plate (5) are connected at the corners where the prefabricated components meet by means of steel bars and cast-in-place concrete sections (6); Prestressed anchor bolts (8) are used to connect the wind turbine tower; The base plate (1) is in the shape of a regular dodecahedron, comprising 4 inner prefabricated components and 24 outer prefabricated components; The center of the regular dodecagonal prism-shaped base plate (1) is composed of two 1 / 2 cylindrical and two 1 / 2 hollow cylindrical prefabricated parts, and the hollow cylindrical prefabricated parts are sleeved outside the cylindrical prefabricated parts to form the central cylinder of the base plate (1); The remaining portion of the base plate (1) is divided into 12 equal parts, and the portion after the 12 equal parts is further divided into two, namely the 24 prefabricated parts outside the basic base plate (1); The column (2) is formed by splicing four identical column prefabricated parts, and adjacent column prefabricated parts are connected by cast-in-place concrete sections (6); Each partition (4) is composed of two prefabricated parts, and a total of 24 prefabricated parts form 12 partitions (4); The prefabricated parts of the partition (4) are provided with steel bars for connecting the cast-in-situ sections at the intersections of the bottom plate (1), the platform column (2), the side wall (3) and the top plate (5); The prefabricated parts of the side wall (3) are the same as those of the partition (4), with a total of 24 prefabricated parts forming 12 side walls (3); The prefabricated parts of the side wall (3) are provided with steel bars for connection with the bottom plate (1), the partition plate (4) and the cast-in-place section of the top plate (5); The construction method comprises the following steps: (1) The four prefabricated components of the column (2) are spliced together, and the main reinforcements between the components at the splicing locations are mechanically connected. After the stirrups are tied on site, concrete is poured into the splicing sections. Connecting reinforcements are reserved on the prefabricated components of the column (2). Prestressed anchor bolt holes are reserved when the components of the column (2) are prefabricated. (2) Splicing the foundation base plate (1), the base plate (1) of each cavity is composed of two prefabricated base plate parts, a total of 24 parts, which are connected by steel sleeve grouting; the circular base plate (1) in the middle of the platform column (2) is composed of two prefabricated parts, and the prefabricated parts are connected by steel sleeve grouting. The outer prefabricated parts of the base plate (1-1) and the platform column (2), and the circular base plate (1-2) and the platform column (2) are all connected by concrete cast-in-place sections 6; (3) Splicing the partition (4), each prefabricated component is connected by grouting with a steel sleeve, and the prefabricated partition is reserved with steel bars for connection with the bottom plate (1), the side wall (3), the top plate (5), and the cast-in-place section of the platform column (2); the bottom of the partition (4) and the bottom plate (1) and the top of the partition (4) and the top plate (5) are connected by a cast-in-place concrete section after being mechanically connected with steel bars; the two sides of the partition (4) and the side wall (3) and the partition (4) are connected by a cast-in-place concrete section after being mechanically connected with steel bars; (4) Splicing side walls (3). The side walls (3) of each unit cavity are composed of two prefabricated parts, a total of 24 parts, and each prefabricated part is connected by grouting with steel sleeves; the intersections of the side walls (3) and the bottom plate (1), the partition (4), and the top plate (5) are connected by mechanical connection of steel bars and then cast-in-situ concrete sections; (5) Filling the cavity formed by the partition (4), the platform column (2), the side wall (3) and the bottom plate (1) with backfill soil and compacting it; (6) Splicing the top plate (5), the top plate (5) of each cavity is composed of two prefabricated sub-plates, a total of 24 pieces, and each prefabricated sub-plate is connected by steel sleeve grouting; the intersection of the top plate (5) and the platform column (2), the side wall (3), and the partition (4) is connected by a cast-in-place concrete section after the steel bar mechanical connection; the circular top plate (5) in the middle of the platform column (2) is composed of two prefabricated sub-plates, and the prefabricated sub-plates are connected by steel sleeve grouting; the circular top plate (5) and the platform column (2) are connected by a cast-in-place concrete section 6; (7) Install prestressed anchor bolts (8) in the cavity of the column (2).

2. The construction method of the assembled box foundation of an onshore wind turbine generator system according to claim 1, characterized in that: The structure of the prefabricated components of the top plate (5) is the same as that of the bottom plate (1).

3. The construction method of the assembled box foundation of an onshore wind turbine generator system according to claim 2, characterized in that: Each prefabricated component of the top plate (5) is provided with steel bars for connecting with the cast-in-situ section at the intersection of the three components: the platform column (2), the side wall (3) and the partition plate (4).

4. The construction method of the assembled box foundation of an onshore wind turbine according to claim 1, characterized in that: The prestressed anchor bolt (8) in step (7) is replaced by a base ring.

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