Wind turbine foundation and construction method

Abstract

The invention relates to a wind turbine foundation and a construction method, the foundation comprising a bottom slab with a plurality of rectangular arms, optionally ending in footings; a core with means for securing a wind turbine tower on the central part of the bottom slab; and a plurality of arms comprising two flat parallel vertical side walls, the space between the two walls being filled up to the upper edge with one or more filler materials. The foundation may optionally include an upper closure slab on each pair of side walls and / or an external wall with anchors. The invention allows simple and efficient assembly with conventional auxiliary assembly means, using a smaller volume of concrete and steel to be able to withstand the same stresses as equivalent conventional foundations, by designing the arms with a structurally highly efficient hollow cross-section and optionally filling same with earth or other filler materials as counterweight.

Description

[0001] DESCRIPTION

[0002] Foundation for wind turbines and construction procedure

[0003] This descriptive report refers, as its title indicates, to a foundation for wind turbines, and its specific construction procedure, comprising a lower slab with a plurality of rectangular arms, preferably terminated in footings, a core with anchoring means for a wind turbine tower on the central part of the lower slab, and a plurality of arms comprising two parallel flat vertical side walls with the space between the two side walls filled to the upper edge with one or more filling materials, optionally including a top closing slab on each pair of side walls, and / or an external wall with anchors.

[0004] Field of invention

[0005] The invention relates to the field of concrete foundations for wind turbine towers.

[0006] Current state of the art

[0007] Currently, wind turbine towers or wind turbines are widely used, primarily for generating electricity. Their considerable height necessitates a firm anchor to the ground, which, in most installations, is achieved through a foundation, typically truncated cone-shaped, made of reinforced concrete, as described in patents ES2659523 “Method for erecting a wind turbine,” ES2685834 “A wind turbine tower and method for altering the natural frequency of a wind turbine tower,” and ES2347742 “Wind turbine foundation.” Patent ES2571731 “Foundation for a wind power plant, as well as a wind power plant” specifically describes the reinforcement used for conventional foundations.This type of foundation presents several drawbacks, including the need for a deep preliminary excavation, typically over 18 meters in diameter and at least 4 meters deep. It also requires a large quantity of concrete, around 400 m³ or more, and reinforcing steel, weighing 38,000 kg or more, with a substantial cross-section. These dimensions depend on the loads transmitted by the tower. All of this results in significant costs, a lengthy construction time, and the need for specialized personnel.

[0008] In order to use less concrete and reinforcing steel, in some cases a mostly cylindrical structure is used, with peripheral structural reinforcements in the form of spokes or braces, both cast in situ. Examples of these structures can be seen in patents WO2016116645 “Concrete Tower”, WO2015185770 “Foundation System for Towers and Installation Procedure for the Foundation System for Towers”, and ES2524840 “Foundation System for Towers and Installation Procedure for the Foundation System for Towers”. In other cases, these lateral reinforcements take the form of prefabricated concrete braces or metal bars or elements, as can be seen in patents ES2544806 “Improved Foundation for a Wind Turbine Tower” or ES2601232 “Foundation for Wind Power Plants”.

[0009] However, these solutions fail to resolve the main problems stemming from the large volume of foundation to be cast in situ, as well as the complexity and volume of the reinforcement, as previously mentioned. To these problems we must add that, for proper curing, the concreting must be done continuously, without interruption, requiring a stable supply of a high volume of concrete, which is difficult or impossible to obtain in many regions or countries. Furthermore, in many countries with limited economies, it is not easy to obtain the large volume of reinforcing steel needed, nor the specialized personnel for this type of construction.

[0010] Another problem is that the necessary excavation requires the construction of ramps for the descent of heavy machinery, given the depth at which it must be excavated, thus increasing working time. All of this means that the typical time for excavation, preparation, concreting, and curing is around three or four weeks, which, multiplied by the large number of wind turbines in each wind farm, results in very high costs.

[0011] There are also some types of shell-type foundations, designed to simplify their construction. For example, one described in WO2023187235, "Foundation for wind turbine towers and construction procedure for said foundation," combines a hollow truncated cone shape with a flat base of a larger diameter than the base of the hollow truncated cone. These types of closed structures also require complex formwork and concreting, demanding specialized personnel and equipment, and do little to reduce the preliminary excavation work.

[0012] There is also some foundation, such as the one described in US10982406 “Tower foundation with concrete box girder beams” which forms a semi-hollow support structure based on the union of prefabricated concrete pieces, managing to lighten the structure a little, but with the problem of needing many different prefabricated pieces with their specific joining and assembly systems greatly complicates its manufacture.

[0013] This state of the art shows us that there is a technical and commercial need for foundations that require less concrete and reinforcing steel, and that can be built using simple concreting techniques familiar to any builder, thus eliminating the need for specialized personnel, who are difficult or nearly impossible to find in many countries, and if found, come at a very high cost. Therefore, it is desirable that they be faster, simpler, and cheaper to construct.

[0014] Description of the invention

[0015] To solve the current problems in the construction of foundations for wind turbines, by simplifying and improving the current state of the art, the wind turbine foundation that is the subject of the present invention has been devised, which comprises

[0016] - a lower slab formed with a plurality of radially distributed rectangular arms joined on their inner side, forming a star shape, preferably with a hollow relief in the central part of the lower slab, and

[0017] - a concrete core located rigidly on the central part of the lower slab, the core rigidly containing anchoring means for a wind turbine tower that partially emerge from its upper part,

[0018] - a plurality of arms radially arranged around the core, in a number coinciding with the rectangular arms of the lower slab and located one on each rectangular arm, each arm comprising two parallel flat side walls, made of concrete, located vertically on the sides of the rectangular arm, this location being understood as either on the sides of the rectangular arm or slightly towards the interior of the slab, and each side wall being attached in a fixed manner by one of its sides to the core, and the space between the two side walls of each arm, on the lower slab, being filled up to the upper edge of the side walls with one or more filling materials, the core having a height equal to or greater than the maximum height of the side walls.

[0019] Although the foundation can be made with any number of rectangular arms of the lower slab, and therefore the number of arms, the preferred number is five.

[0020] In a preferred embodiment, the space between the two side walls of each arm, as well as the filling material or materials placed between them, are covered by an upper concrete slab as a closure, supported on the upper sides of the side walls of each arm.

[0021] In a preferred embodiment, the rectangular arms that make up the lower slab have footings at their outer ends, which are larger and thicker than the rectangular arms themselves. These footings can be supplemented with other foundation elements, such as piles, to achieve different support options depending on the characteristics and conditions of the underlying ground or soil: with or without a water table; with high bearing capacity; good or poor soil, etc.

[0022] In an alternative embodiment of the invention, each arm further comprises an external wall, made of concrete, perpendicular and rigidly attached to both side walls at their outermost end, and vertically and rigidly positioned on the outer end of its corresponding rectangular arm of the lower slab. Optionally, each external wall also has a plurality of vertically arranged anchors, passing through the external wall, emerging from the underside of the external side wall, and rigidly embedded in the rocky ground on which the foundation is constructed, resulting in a specific anchored foundation ideal for rocky terrain. In this embodiment, the rectangular arms of the lower slab can be shorter, resulting in a more compact foundation.

[0023] The core preferably has a hollow central section, which may or may not be filled with filler material. Both the core and the hollow central section may have a circular or polygonal cross-section. The space between the arms is also preferably filled with filler material up to the upper edge of the side walls. Preferably, the entire foundation, except for the top of the core and the top of the anchoring means for a wind turbine tower, is also covered with filler material.

[0024] The fill material or materials are chosen from the group consisting of soil from the excavation itself, soil from other sites, gravel, recycled material, lean concrete, other waste materials, or a mixture of them.

[0025] This foundation allows for both surface construction, without external filling, and buried construction, through the appropriate excavation of the hole for its accommodation.

[0026] This foundation is defined as a hollow concrete structure, preferably filled with earth or other filler materials, although it allows for an alternative solution without internal filling.

[0027] The lower slab, the footings if applicable, the side walls, the external walls if applicable, the core, and the upper slabs if applicable, can be in-situ concrete elements, or prefabricated concrete elements, or a combination of them.

[0028] This foundation for wind turbines involves a characteristic construction procedure that includes:

[0029] - an optional first phase of excavation of the hole necessary to build the foundation below ground level, with the excavated earth subsequently being used as fill material,

[0030] - a second phase of construction of the lower slab and the footings, if applicable,

[0031] - a third phase of construction of the side walls, the external walls with their anchors where applicable, and the core with the anchoring means for a wind turbine tower,

[0032] - an optional fourth phase of filling with fill material or materials up to the level of the side walls,

[0033] - an optional fifth phase of construction of the upper slabs and

[0034] - a sixth phase of final backfilling to the defined level. The construction phase of the foundation slab, side walls, and core, and the construction of external walls and upper slabs, if applicable, is carried out using a technique chosen from the group consisting of cast-in-place concrete, formwork with preliminary placement of reinforcing steel, precast concrete elements joined in-situ, or a combination of both. Preferably, the construction of the side walls and the core will be carried out simultaneously.

[0035] Subsequently, the wind turbine tower will be assembled by fixing its base to the anchoring means provided in the core.

[0036] Advantages of the invention

[0037] This wind turbine foundation offers multiple advantages over currently available systems, the most important being that it achieves a much simpler and more efficient assembly than any of the foundations known in the state of the art, allowing the use of standard auxiliary assembly means: in the case of in-situ concrete construction, only simple formwork on the ground, or conventional formwork for side walls, based on construction technologies with simple auxiliary assembly means without the need for complex or specific systems, which avoids the need for highly specialized personnel in its construction process, making its installation universal for all types of countries.

[0038] Another significant advantage is the use of a much smaller volume of concrete than conventional foundations to withstand the same stresses, resulting in lower costs and optimized use of materials. Part of this concrete saving is achieved through the closed, hollow structure of the arms, which gives the system optimal structural performance for the demands of a wind turbine tower foundation. The optional use of earth or other filler materials inside the arms as a counterweight further contributes to this reduction.

[0039] Also noteworthy is the advantage of the reduced slope of the arms, similar to and lower than the internal friction coefficient of the fill material, to facilitate the internal distribution of the fill material, coupled with the fact that the width between side walls allows the passage of conventional machinery to easily place, compact and distribute the fill material.

[0040] It should also be noted that the upper slabs are built on a flat surface, formed by the upper edge of the side walls and the fill between them, which facilitates simple construction, without the need for complex overhead formwork, since a simple lateral formwork is sufficient and the reinforcing steel is placed on the ground as in the case of the construction of the slab.

[0041] Also noteworthy is the advantage of being able to use the excavated soil, in the case of excavation, along with recycled or non-recycled materials, as part of the fill material, which significantly reduces the amount of concrete used, thus generating a smaller carbon footprint.

[0042] We cannot fail to mention the advantage of the enormous versatility of this foundation in adapting to the needs of different terrains and their different support capacities, since it can be used as a base from a simple flat slab, to a slab with footings, or even, if necessary, complement the footings with piles or other additional elements.

[0043] Another advantage of this foundation is the possibility of constructing a more compact, anchored pier with an external wall and fixed in place on rocky ground on which the foundation is built, resulting in a foundation specifically designed for rocky or high-strength terrain, where the overall stabilizing behavior is achieved primarily through the tension of the anchors rather than solely through gravitational weight.

[0044] Description of the figures

[0045] To better understand the object of the present invention, a preferred practical embodiment of a foundation for wind turbines has been represented in the attached drawing.

[0046] In this plan, figure -1- shows a perspective rendered view of a three-arm foundation, with upper slabs and footings in the lower slab, in which the fill material that must cover the arms and the gaps between them is not shown, for a better appreciation of the structure.

[0047] Figure -2- shows a plan view and cross-section of a five-arm foundation, with upper slabs and footings on the lower slab.

[0048] Figure -3- shows a plan view and two cross-sections of one of the arms of a five-arm foundation, with upper slabs and footings on the lower slab.

[0049] Figure -4- shows a perspective view of the lower slab of a five-arm foundation without footings, illustrating the second phase of the construction process in one of the varantas.

[0050] Figure -5- shows a perspective view of the lower slab of a five-arm foundation with footings, illustrating the second phase of the construction process in another of the vahantes.

[0051] Figure -6- shows a perspective view of the core with the anchoring means for a wind turbine tower, in this example a bolt cage, and of the side walls of the arms already built, illustrating the third phase of the construction process in another of the wings, in this case with a polygonal section core and lower slab with footings.

[0052] Figure -7- shows a perspective view of the gaps between the side walls filled with filler materials up to the level of the side walls, illustrating the fourth phase of the construction process in another of the variants, in this case with a polygonal section core.

[0053] Figure -8- shows a perspective view with the upper slabs built on the side walls, illustrating the fifth optional phase of the construction process in another of the variants, in this case with a polygonal section core.

[0054] Figure -9- shows a perspective view of the top of the core, with the anchoring means for a wind turbine tower, in this example a cage of bolts, emerging from the fill for fixing the wind turbine tower, illustrating the sixth phase of the construction process in another of the spans, in this case with a polygonal section core.

[0055] Figure -10- shows a perspective view of the core with the anchoring means for a wind turbine tower, in this example a bolt cage, and of the side walls of the arms already built, illustrating the third phase of the construction process in another of the wings, in this case with a circular section core and lower slab with footings.

[0056] Figure -11- shows a perspective view of the gaps between the side walls filled with filler materials up to the level of the side walls, illustrating the fourth phase of the construction process in another of the variants, in this case with a circular cross-section core.

[0057] Figure -12- shows a perspective view with the upper slabs built on the side walls, illustrating the fifth optional phase of the construction process in another of the vahant, in this case with a circular cross-section core.

[0058] Figure -13- shows a perspective view of the top of the core, with the anchoring means for a wind turbine tower, in this example a cage of bolts, emerging from the fill for fixing the wind turbine tower, illustrating the sixth phase of the construction process in another of the vahant, in this case with a core of circular section.

[0059] Figure -14- shows a perspective view of the lower slab of a five-arm foundation without footings, with the arms of shorter length, illustrating the second phase of the construction process in the vahante with external wall and anchors for rocky or very competent ground.

[0060] Figure -15- shows a perspective view of the core with the anchoring means for a wind turbine tower, in this example a bolt cage, and of the side walls of the arms already built, illustrating the third phase of the construction process in the vahante with external wall and anchors for rocky or very competent ground.

[0061] Figure -16- shows a perspective view of the gaps between the side walls filled with filler materials up to the level of the side walls, illustrating the fourth phase of the construction process in the variant with external wall and anchors for rocky or very competent ground.

[0062] Figure -17- shows a perspective view with the upper slabs built on the side walls, illustrating the optional fifth phase of the construction process in the vahante with external wall and anchors for rocky or very competent ground.

[0063] Preferred embodiment of the invention

[0064] The constitution and characteristics of the invention may be better understood with the following description made with reference to the attached figures.

[0065] As can be seen in the figures, it is illustrated how the foundation for wind turbines comprises

[0066] - a lower concrete slab (1) formed with a plurality of radially distributed rectangular arms (1a) joined on their inner side, forming a star shape,

[0067] - a concrete core (2) rigidly located on the central part of the lower slab (1), the core (2) rigidly containing anchoring means (4) for a wind turbine tower that partially emerge from its upper part,

[0068] - a plurality of arms radially arranged around the core (2), in a number coinciding with the rectangular arms (1a) of the lower slab (1) and located one on each rectangular arm (1a), each arm comprising two parallel flat side walls (3), made of concrete, located vertically on the sides of the rectangular arm (1a), this location being understood as either on the sides of the rectangular arm (1a) or slightly inwards, and each side wall being attached in a fixed manner on one of its sides to the core (2).each arm comprising two parallel flat side walls (3), made of concrete, located vertically on the rectangular arm (1a), in a position close to the end of the lateral edges of each rectangular arm (1a), either on the sides of the rectangular arm (1a) or slightly inwards, and each side wall being attached in a fixed manner on one of its sides to the core (2), and the space between the two side walls (3) of each arm, on the lower slab (1), optionally filled up to the upper edge of the side walls (3) with one or more filling materials (6) of different characteristics than the material used for the side walls (2), the core (2) having a height equal to or greater than the maximum height of the side walls (3).

[0069] Preferably the number of rectangular arms (1a) of the lower slab, and therefore the number of arms, is five.

[0070] In a preferred embodiment, the space between the two side walls (3) of each arm, as well as the filling material (6) arranged between them, are covered by a top concrete slab (7) supported on the upper sides of the side walls (3) of each arm.

[0071] In a preferred embodiment, the rectangular arms (1a) that make up the lower slab (1) have footings (1b) at their outer ends, which are larger and thicker than the rectangular arms. These footings (1b) can be supplemented with other foundation elements, such as piles, to achieve different support options depending on the characteristics and conditions of the underlying ground or soil: for different cases: with or without a water table; with high bearing capacity, good or poor soil, etc.

[0072] In an alternative embodiment of the invention, each arm further comprises an external wall (8), made of concrete, perpendicular and rigidly connected to both side walls (3) at its outermost end, and vertically and rigidly positioned on the outer end of its corresponding rectangular arm (1a) of the lower slab (1). Optionally, each external wall (8) also has a plurality of vertically arranged anchors (9) passing through the external wall (8), emerging from the top of the external side wall (8), and rigidly embedded in rocky or high-bearing-capacity soil on which the foundation is constructed, resulting in a foundation anchored to the ground, specifically designed for rocky or high-bearing-capacity soils, in which the support and overall stabilizing behavior are obtained primarily through the tension of the anchors rather than by gravity.In this embodiment the rectangular arms (1a) of the lower slab (1) can be shorter, resulting in a more compact foundation.

[0073] The shape of the side walls (3) is chosen from the group consisting of triangular, trapezoidal, rectangular where the longer base is the side adjacent to the core (2), and the shorter base is the outermost side, rectangular, or a combination thereof. These side walls (3) are placed at the end, or slightly inwards, of the lateral edges of each rectangular arm (1a) of the slab (1).

[0074] The core (2) preferably has a hollow central section (5) filled with filler material (6). The core (2) may have a circular or polygonal cross-section, preferably with a number of sides corresponding to the number of rectangular arms (1a) of the lower slab, and to the number of arms. The hollow central section (5) may also have a circular or polygonal cross-section. Polygonal sections are preferred due to their ease of formwork.

[0075] The space between two arms is preferably also filled with filler material or materials (6) up to the upper edge of the side walls (3). Also preferably, the entire foundation, except for the upper part of the core (2) and the upper part of the anchoring means (4) for a wind turbine tower, is covered with filler material or materials (6).

[0076] The fill material or materials (6) is chosen from the group consisting of soil from the excavation itself, soil from other sites, gravel, recycled material, lean concrete, treated soils, other waste materials, or a mixture of these.

[0077] This foundation allows for both surface construction, without external filling, and buried construction, through the appropriate excavation of the hole for its accommodation.

[0078] The lower slab (1), the footings (1b) where applicable, the side walls (3), the external walls (8) where applicable, the core (2), and the upper slabs (7) where applicable, may be cast-in-place concrete elements, or prefabricated concrete elements, or a combination thereof.

[0079] This foundation is suitable for any type of wind turbine tower: metal, cast-in-place concrete, precast concrete, or hybrid. The anchoring means (4) for the wind turbine tower will be those specifically required for each type of tower, which may include, for example, bolt cages for metal towers, tendons or tendon anchors and cables for post-tensioning for concrete or hybrid towers, or any other means known in the prior art that may be applicable.

[0080] This foundation for wind turbines involves a characteristic construction procedure that comprises

[0081] - an optional first phase of excavation of the hole necessary to build the foundation below ground level,

[0082] - a second phase of construction of the lower slab (1) and the footings (1b) where applicable,

[0083] - a third phase of construction of the side walls (3), the external walls (8) with their anchors (9) where applicable, and the core (2) with the anchoring means (4) for a wind turbine tower,

[0084] - an optional fourth phase of interior filling with filling material or materials (6) up to the level of the side walls (3),

[0085] - an optional fifth phase of construction of the upper slabs (7) and

[0086] - a sixth phase of final filling up to the defined level.

[0087] The construction phase of the lower slab (1) and the footings (1b), if applicable, the construction phase of the side walls (3), the external walls (8), if applicable, and the core (2), and the construction phase of the upper slabs (7), if applicable, shall be carried out using a technique selected from the group consisting of cast-in-place concrete, formwork with preliminary placement of reinforcing steel, precast concrete elements joined in-situ, or a combination of both. Preferably, the construction of the side walls (3), the external walls (8), if applicable, and the core (2) shall be carried out simultaneously.

[0088] The wind turbine tower will then be assembled by fixing its base to the anchoring means (4).

[0089] A person skilled in the technique will easily understand that they can combine features of different embodiments with features of other possible embodiments, provided that such a combination is technically possible.

[0090] All information relating to examples or modes of embodiment forms part of the description of the invention.

Claims

- Foundation for wind turbines characterized in that it comprises - a lower concrete slab (1) formed with a plurality of arms 5 rectangular shapes (1 a), radially distributed and joined on their inner side, forming a star shape, - a concrete core (2) rigidly located on the central part of the lower slab (1), the core (2) rigidly containing anchoring means (4) for a wind turbine tower, which partially emerge from its upper part, 10 - other arms radially arranged around the core (2), in a number coinciding with the rectangular arms (1 a) of the lower slab (1) and located one on each rectangular arm (1 a) of the lower slab (1), each arm radially arranged around the core (2) comprising two parallel flat side walls (3), made of concrete, located vertically on the 15 sides of a rectangular arm (1 a) of the lower slab (1 ), and each side wall (3) being attached in a fixed manner by one of its sides to the core (2). 2 - Foundation for wind turbines, according to the previous claim, characterized in that the space between the two lateral walls (3) of each radially arranged arm 20 around the core (2), on the lower slab (1), is filled up to the top edge of the side walls (3) with one or more filling materials (6). 3 - Foundation for wind turbines, according to any of the above claims, characterized in that the space between the two side walls (3) of each arm 25 radially arranged around the core (2), as well as the filling material or materials (6) arranged between them, are covered by a top slab (7) of concrete supported on the upper sides of the side walls (3) of each arm radially arranged around the core (2). 30 4 - Foundation for wind turbines, according to any of the above claims, characterized in that each arm comprises an external wall (8), made of concrete, perpendicular in a way that is integral with both side walls (3) and located vertically in a way that is integral with the external end of its corresponding rectangular arm (1 a) of the lower slab (1). 35 5 - Foundation for wind turbines, according to claim 4, characterized in that each external wall (8) has a plurality of vertically arranged anchors (9), passing through the external wall (8), emerging from the lower part of the external side wall (8) and inserted in a solid manner in a rocky terrain on which the foundation is built. 5 6 - Foundation for wind turbines, according to any of the above claims, characterized in that the number of rectangular arms (1a) of the lower slab (1), and therefore the number of arms radially arranged around the core (2), is five. 10 7 - Foundation for wind turbines, according to any of the above claims, characterized in that the rectangular arms (1 a) that make up the lower slab (1) have at their outer end footings (1 b), of greater dimensions and thickness than the rectangular arms (1 a) that make up the lower slab (1 ). 15 8 - Foundation for wind turbines, according to any of the above claims, characterized in that the central part of the lower slab (1 ) has a hollow lightening (1c). 9 - Foundation for wind turbines, according to any of the above claims, 20 characterized in that the shape of the side walls (3) is chosen from the group formed by triangular, trapezoidal, rectangular in which the larger base is the side adjacent to the core (2), and the smaller base is the outermost side, rectangular or a combination of them. 10 Foundation for wind turbines, according to any of the above 25 claims, characterized in that the core (2) has a hollow central part (5), filled with filling material or materials (6). 11 Foundation for wind turbines, according to any of the preceding claims, characterized in that the core (2), at its outer edge and at its edge 30 interior, has a section chosen from the group formed by circular and polygonal. 12 Foundation for wind turbines, according to any of the preceding claims, characterized in that the space between two arms radially arranged around the core (2) is filled with material or materials of 35 fill (6) up to the top edge of the side walls (3). 13 - Foundation for wind turbines, according to any of the above claims, characterized in that the foundation assembly, except for the top part of the core (2) and the top part of the anchoring means (4) for a wind turbine tower, is covered by filler material or materials (6). 5 14 Foundation for wind turbines, according to any of the preceding claims, characterized in that the fill material or materials (6) are chosen from the group consisting of soil from the excavation itself, soil from other sites, gravel, recycled material, lean concrete, treated soils, other materials 10 of waste, or a mixture of them. 15 - Procedure for constructing a foundation for wind turbines, according to any of the preceding claims, characterized in that it comprises - an optional first phase of excavating the hole needed to build the 15 foundation below ground level, - a second phase of construction of the lower slab (1) and the footings (1 b) where applicable, - a third phase of construction of the side walls (3), the external walls (8) with their anchors (9) where applicable, and the core (2) with the anchoring means (4) 20 for a wind turbine tower, - an optional fourth phase of filling with fill material or materials (6) up to the level of the side walls (3), - an optional fifth phase of construction of the upper slabs (7) and - a sixth phase of final filling up to the defined level, 25 carrying out the construction phase of the lower slab (1) and the footings (1 b) where applicable, the construction phase of the side walls (3), the external walls (8) where applicable, and the core (2), and the construction of the upper slabs (7) where applicable, using a technique chosen from the group consisting of in-situ concreting, using formwork with preliminary placement of reinforcing steel, prefabricated concrete elements joined in-situ, or 30 a combination of both.

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