Extendable modular foundation and building method

Abstract

Extensible modular foundation with one or several layers of foundation (or modules), each with an extension higher than the previous one, superimposed on an existing or newly built base footing, joined only in its central part by means of anchor bolts and extensions, working structurally as a laminar foundation, constituted by the outermost foundation layer, combined with a lower counterweight constituted by the previous layers and the base footing, with great effectiveness to support the necessary stresses in high-rise elements, being able to build successive layers of foundation on top of the already existing ones. It is a modular structure that can be extended from its conception, evolving over time, adding more layers according to future needs without penalising the initial investment, avoiding the modification of the base shoe, reducing construction time and economic cost, while generating much less waste in line with the sustainability objective of "Zero Waste".

Description

[0001] As its title indicates, the present specification refers to an expandable modular foundation, usable in wind turbine farms, both for metal, hybrid or concrete towers, as well as in communications, lighting, bridge and viaduct piles, etc., which comprises one or more layers of foundation, each with an extension greater than the previous one, superimposed on the base shoe of the initial phase, joined only in its central part to the anchoring bolts of the base shoe by means of extensions, which behaves as a laminar foundation, constituted by the outermost foundation layer, combined with a lower counterweight constituted by the previous layers and the base shoe, allowing a great effectiveness to withstand the necessary stresses in a tower or stack of great height, being able to build successive layers of foundation, in modular form, on the previously existing phases. This expansion capacity also makes it suitable for use in wind farm repowering processes.Field of the invention

[0002] The invention relates to the field of footings or foundations for towers, piles or vertical elements, especially for wind turbine towers.State of the art

[0003] In the process of designing the foundations, there are circumstances in which it is known that in the near future it will be necessary to expand the capacity of the foundation. In the case of bridges due to increased traffic capacity or increased traffic loads; in the case of wind turbines due to increased wind turbine capacity due to increased power and / or increased tower height. This fact leads to the need to increase the size of the foundation assuming, for an element already built, an extension or allowing to establish an expandable modular construction strategy in order not to penalize the initial investment with oversizing. For example, in the case of piles of bridges or viaducts in which there is a failure in the field, to compensate for design errors, to increase the size of poles or communication towers, or, in the case of wind turbine parks, to carry out a process of expansion or repowering, also known as "repowering", which involves replacing the wind turbines with others of greater productive power, greater height, and therefore with greater extension and greater foundation needs. In the case of wind turbine farms, it is a fairly frequent situation due to the need to repower existing farms, replacing existing wind turbines with more modern models, with new technologies, more powerful and with greater energy production and larger size, which require a larger foundation to withstand greater stresses.

[0004] In all these cases we find the problem of an existing foundation, and the need to make a new one of greater capacity. Several ways of dealing with it are known in the state of the art, always starting from an existing foundation but never raised as an expandable modular element, the most common being to proceed with an excavation of the previous foundation, demolish it, extract the remains and build the new foundation of greater dimensions in its place. This is a long, expensive process that generates a high number of construction waste that must be eliminated.

[0005] In many cases this procedure is so tremendously expensive and time-consuming that it used to be chosen to install the wind turbines at another site, wasting the previous site, and causing great environmental impact. Obviously, this would not be applicable to piles of bridges or viaducts.

[0006] To solve this and take advantage of the previous foundation, methods are known, such as those described in patents ES-2493722 "Method of execution of a wind turbine to repower an existing wind farm and obtained wind turbine" ("Procedimiento de ejecución de un aerogenerador para repotenciar un parque eólico existente y aerogenerador obtenido"), KR20190101219 "Wind turbine Re-powering Foundation structures" and KR20200057954 "Wind turbine structure for retrofitting spread footing in partial repowering and construction method for the same", which perform a large excavation around the pre-existing foundation, and perform a new foundation around and above it, using conventional techniques, achieving a new foundation of greater size. This presents many drawbacks, mainly due to the large excavations and necessary earthworks, as well as the need to use a large amount of both concrete and metal reinforcement or rebar, in addition to a high section. The connection of this rebar with the existing foundation is very handmade, slow and expensive to execute and with a questionable quality guarantee. All this implies a great economic cost and a high construction time. To these problems we must add that, for a correct setting, the concreting must be done continuously, without interruptions, requiring a stable supply of a high volume of concrete, which in many regions or countries is difficult or impossible to achieve. Extreme temperature conditions, both cold and warm weather, for example, in desert areas, complicate the setting of concrete because it is a chemical reaction, and many optimal wind sites are in forests or semi-deserts due to strong thermal winds.

[0007] Another additional problem is that for the necessary excavation, ramps are required for the descent of heavy machinery as they have to excavate at such depth, increasing work time. Likewise, the bottom of the excavation needs to be leveled and smoothed.

[0008] All this means that the usual time of excavation, preparation, concreting and setting is several weeks, which multiplied by the high number of wind turbines of each park requires very large economic costs.

[0009] Some types of foundations are known that solve some of the problems mentioned above of large excavations, high volume of concrete and rebar, such as that described in ES2764468 "Foundation for wind towers" ("Cimentación para torres eólicas"), which propose the use of prefabricated concrete beams combined with small footings, these beams being structurally related in the central part of the foundation by means of joining and support elements of the tower, but presents the problem that the construction on an existing foundation is not planned or possible, nor its reuse, and also has the drawback of needing in some cases of the embodiment a structure with ballast or weight functions, made in situ with concrete in the joining area of the beams.

[0010] There are also foundations that overcome these problems by taking advantage of the existing foundation, as for example we find described in ES2894337 "Procedure for the extension of foundations in wind farms" ("Procedimiento de extensión de cimientos en parques eólicos") that uses a structure of beams superimposed on the existing foundation and attached to it, supported with new peripheral foundations of smaller size, forming a new foundation suitable for a larger structure, but also presents a remarkable constructive complexity and needs the transport of large prefabricated beams.

[0011] There is also a solution, such as the one described in ES2493722 "Execution procedure of an existing wind turbine and wind turbine obtained to repower a wind farm" ("Procedimiento de ejecución de un aerogenerador obtenido para repotenciar un parque eólico") that takes advantage of the existing foundation to merge it with the new foundation, making a new foundation completely joined to the previous foundation, forming a unit circumscribed to the previous foundation and integral with it, at the same level. As both foundations, the new and the existing one, need to be completely joined, it is necessary to carry out enough drilling or partial demolition of the previous foundation to be able to implement the means of union with the new one, which also generates waste, and, being at the same level, the large amount of earth removed in the necessary excavation must be taken to another site, generating environmental impact problems.

[0012] Foundation re-growth techniques are also known, such as the one described in patent CN114753403A "Foundation structure for replacing small wind turbine generator with large wind turbine generator and construction method" for the re-growth of wind turbine parks by means of the re-growth of the footing, as in the previous case, building a new footing structurally joined at the reinforcement level with the previous footing, but this requires chiseling the concrete from the surface of the previous footing, removing its outer layer and extracting the remains until the ends of the internal reinforcement are discovered, which must then be joined to the new reinforcement for the extension. It is an expensive process, in which a single monolithic footing is obtained as a result of the union of the existing previous foundation with the new foundation built by joining the two reinforcements. In this foundation, the previous footing is a structural part of the new one.Description of the invention

[0013] In order to solve the existing problem in the expansion of foundations, the expandable modular foundation object of the present invention has been devised, which comprises a base shoe, built in a first phase or existing, containing at least one conventional foundation made by any conventional method, provided with anchor bolts for a tower, the reference to tower in this specification being extrapolable to any type of vertical construction that can be erected on a shoe-type foundation, one or more foundation layers, preferably with a frustoconical structure, each of greater extension than the previous one, superimposed, one on another, on the base shoe, at an upper level, each provided with bolts for anchoring a tower on the last foundation layer built and reusable for connection with the subsequent foundation layers, a plurality of extensions of the anchor bolts of the previous layer built up to the upper elevation of the new phase under construction, the anchor bolts being distributed diametrically around a larger diameter in each layer, to allow the anchoring of larger diameter towers or larger capacity structural elements, each successive foundation layer being mechanically linked, by conventional bolt extensions, exclusively with the shoe module of the immediately preceding foundation layer, the outermost foundation layer being the support of the tower, or of a structural element of greater capacity, by means of its own anchoring bolts to the effect and the one mainly in charge of its stability as a laminar foundation, and the interior modules of previous phases being in charge of acting mainly as a counterweight.

[0014] Considering each of the foundation layers as a module, the foundation behaves like a laminar foundation, constituted by the outermost foundation module, combined with a lower counterweight constituted by the base shoe and by the interior modules previously made. This modular structure, based on superimposed layers, allows its expansion in later phases without more than adding a new module, or foundation layer, on top of the previous ones.

[0015] The modular foundation can be executed on previous foundation layers previously built as an extension, on an existing conventional built footing or conceived as modular expandable from its origin.

[0016] Each layer of the foundation can be made with the separation in time that mark the evolutionary needs of the element they support, wind turbine farm, viaduct, etc., such as increase in size, height, efforts, etc.

[0017] The different layers of the foundation can be concreted in-situ, or alternatively be made up of prefabricated reinforced concrete and / or prestressed elements joined together, and both technologies can be combined in different layers.

[0018] Preferably, most of the outermost foundation layer will be covered with earth, emerging only the central part coinciding with the base of the tower, thus minimising the visual impact.

[0019] This expandable modular foundation involves a characteristic construction method that comprises: an optional preliminary phase of initial construction of the structure, a phase of removal from the existing tower, a phase of removal of fillings until the existing footing is discovered and excavation of the housing for the new modular foundation layer around said existing footing, considering as an existing footing the one that supported the tower previously, and the base footing may be the base footing, or the base footing plus one or more layers of modular foundation resulting from previous processes, a phase of cleaning the upper surface of the existing shoe, a phase of installation of the extensions on the existing outermost anchor bolts, where the existing tower was previously anchored, a phase of realization of the new foundation layer, a filling phase of the remaining housing by means of the soil extracted in the excavation of the housing in the second phase, and its compaction leaving the central part of the new foundation layer and the upper ends of the new anchor bolts accessible, a phase of tightening the connecting bolts between the new module and the immediately preceding one, and a phase of placing the new tower, securing it on the new anchor bolts by conventional mechanical means.

[0020] The optional preliminary phase of initial construction of the structure comprises: a stage of construction of the base shoe, provided with anchor bolts for a tower, a stage of placing the tower, and a stage of operation of the infrastructure.

[0021] The phase of making the new foundation layer comprises, in a preferred embodiment with in-situ concreting: a stage of placement of the reinforcement hardware for the new module, a stage of placement of the new bolt cage of the new module a stage of concreting, and a stage of setting the concrete.

[0022] The phase of making the new foundation layer comprises, in an alternative embodiment with prefabricated concrete elements: a stage of placing the prefabricated parts that make up the new foundation layer, with the new bolt cage incorporated, a stage of execution of the union between the prefabricated elements, by mechanical means or by concreting of concrete joints with passive reinforcement.

[0023] These phases will be performed sequentially. The set of phases, except for the optional preliminary phase of initial construction of the structure, can be repeated as many times as necessary to create new modules or foundation layers over the existing ones, whenever it is necessary to expand the tower by one of greater dimensions and greater foundation requirements, creating each time a new outer foundation layer of greater extension, evolving in parallel with the support needs of the towers.

[0024] Likewise, foundation modules built with in-situ concreting can be combined with foundation modules built with prefabricated concrete elements in any order, according to need or availability.

[0025] The preferred use of this expandable modular foundation is as a support for towers, more preferably as a support or an integral part of a wind turbine, and even more preferably when the wind turbine towers are part of a process of expansion or repowering, also known as "repowering", of the wind turbine park, which involves replacing the wind turbines with others of greater productive power, greater height, and therefore with greater extension and greater foundation needs. Obviously, it can be used for any type of towers, both metal, concrete or mixed, and both wind turbines and communications, lighting, poles, piles of bridges or viaducts, etc.Advantages of the invention

[0026] This expandable modular foundation that is presented provides multiple advantages over the foundations currently available, the most important being that it works structurally as a laminar foundation, constituted by the outermost foundation layer, combined with a lower counterweight constituted by the previous layers, allowing a great effectiveness to withstand the necessary stresses in a tower or high pile.

[0027] It is worth highlighting the advantage that in the design phase it can contemplate and foresee the future use of extensions, minimizing future expansion costs and reducing the initial investment, avoiding oversizing. It is a process that can be expanded and modular from the conception of the structure, allowing the foundation to be conceived as an expandable structure from the beginning, making it possible to make adaptations or extensions later, including repowering. This evolution is possible due to its modular structure that allows its expansion in later phases by superimposing layers on the previous ones.

[0028] Another important advantage is that the foundation layer or layers are superimposed on the existing foundation, at a higher level, avoiding the need to demolish and remove the old foundations, with the consequent economic and working time savings. It is important to note that the new foundation layer and the existing foundation are only joined in the central area and by means of mechanical joints, the existing ballast foundation acting.

[0029] It is also important to note that, unlike foundations known in the state of the art, this expandable modular foundation does not require any action on the existing foundation, since it is not chiseled, drilled or modified in any way, it is only joined by means of the already existing bolts and threaded extensions. As a consequence, no waste is generated from the previous foundation that has to be transported and thrown into a landfill, resulting in a faster and more environmentally friendly process, aligned with the sustainability objective of "Zero Waste".

[0030] It should also be noted that the internal reinforcement of the new foundation is not joined with the internal reinforcement of the existing footing, being independent, since the existing footing is not an integral part of the new foundation, it does not perform support tasks, but is only used as a counterweight, being joined exclusively in its central part by conventional extensions of the bolts Another advantage to highlight is that this foundation that is presented needs a minimum excavation, much smaller than in the case of known foundation techniques, which implies less earth movement and, in addition, the earth that is removed is reused to cover the new foundation layer, with which the environmental impact is almost zero.

[0031] We must not forget that this expandable modular foundation is especially useful in processes of expansion or repowering of the wind turbine park, which implies replacing the wind turbines with others of greater productive power, greater height, and therefore with greater extension and greater foundation needs.

[0032] Another of the most important advantages to note is that it is an evolutionary modular foundation since the set of phases can be repeated as many times as necessary to create new layers of foundation when there are greater foundation requirements due to the expansion of the tower, creating each time an outer foundation layer of greater extension, evolving in parallel with the support needs of the towers, and therefore being applicable and easily adaptable to future support needs. As successive layers of foundation can be built on top of those already existing, the capacity of the foundation can be increased successively.

[0033] It is also important to note that, being able to be used for any type of towers, both metallic, concrete or mixed, and both wind turbines and communications, lighting, poles, stacks of bridges or viaducts, etc. opens up a wide spectrum of application both in construction and in repair and maintenance of existing facilities.Description of the figures

[0034] In order to better understand the object of the present invention, a preferential practical embodiment of an extendable modular foundation has been represented in the attached drawings.

[0035] In said drawings, Figure -1- shows a perspective sectional view of a foundation with two layers and the expandable modular foundation base shoe. Figure -2- shows a sectional side view of a foundation from an optional preliminary phase of initial construction of the structure. Figure -3- shows a sectional side view of an expandable modular foundation constituted by a layer on the base shoe, with an enlarged detail showing the anchor bolts and the extensions of the anchor bolts of the lower foundation. Figure -4- shows a sectional side view of an expandable modular foundation constituted by two layers on the base shoe. Figure -5- shows a sectional side view of a base shoe with the existing tower mounted, coming from the optional preliminary phase of the initial construction of the structure. Figure -6- shows a sectional side view of the base shoe with the existing tower already disassembled, after the removal stage of the existing tower. Figure -7- shows a sectional side view of the foundation after the fill removal phase until the existing footing is discovered and the housing is excavated. Figure -8- shows a sectional side view of the foundation after the first step of the fourth phase of placing the new anchor bolt cage, the extensions of the existing anchor bolts, and the rebar reinforcement, in the preferred embodiment with in-situ concreting. Figure -9- shows a sectional side view of the foundation after the installation phase of the extensions on the anchor bolts and the construction phase of the new foundation layer, in the preferred embodiment with in-situ concreting. Figure -10- shows a sectional side view of the foundation after the placement phase of the new tower. Preferred embodiment of the invention

[0036] The constitution and characteristics of the invention may be better understood with the following description made with reference to the attached figures.

[0037] As can be seen in Figures 1, 2, 3, and 4, it is illustrated how the expandable modular foundation comprises: a base shoe (2), containing at least one conventional foundation made by any conventional method, built in a preliminary or existing phase, provided with anchoring bolts (3) for a tower (6), the reference to tower in this specification being extrapolable to any type of vertical construction that can be erected on a shoe-type foundation, one or more foundation layers (1a, 1b), preferably with a frustoconical structure, each of greater extension than the previous one, superimposed, one on another, on the base shoe (2), at an upper level, each provided with anchor bolts (5) for a tower (6) on the last foundation layer (1a, 1b) built and reusable for connection with the subsequent foundation layers (1a, 1b), a plurality of extensions (4) of the anchoring bolts (3,5) of the previous layer built up to the upper level of the new phase under construction, located below the outermost foundation layer (1a, 1b) to match its height with that of the anchoring bolts (5) of said outermost foundation layer (1a, 1b), the anchor bolts (3,5) being distributed diametrically around a larger diameter in each layer, to allow the anchoring of larger diameter towers or larger structural elements, each successive foundation layer (1a, 1b) being mechanically joined, by means of extensions (4) of the anchoring bolts (3,5), exclusively with the immediately lower foundation layer (1a, 1b), or with the base shoe (2) in case of being the first foundation layer (1a), the outermost foundation layer (1b) being the support of the tower or a larger structural element, through its own anchoring bolts (5) for this purpose and mainly responsible for its stability as a laminar foundation, and the interior modules (1a, 2) of previous phases being responsible for mainly acting as a counterweight.

[0038] The base shoe 2 may be a conventional foundation made by any conventional method, or be the initial stage of an expandable modular foundation conceived as such.

[0039] Considering each of the foundation layers as a module, the foundation behaves like a laminar foundation, constituted by the outermost foundation module (1b), combined with a lower counterweight constituted by the base shoe (2) and by the interior modules (1a) previously made. This modular structure, based on superimposed foundation layers (1a, 1b), allows its expansion in subsequent phases without more than adding a new module, or foundation layer, superimposed on the previous ones.

[0040] The modular foundation can be executed on previously built foundation layers (1a, 1b), by way of extension, or on an existing conventional built base shoe (2), or be the initial phase of an expandable modular foundation conceived as such. Each layer of the foundation (1a, 1b) can be made with the separation in time that mark the evolutionary needs of the element they support, wind turbine farm, viaduct, etc., such as increase in size, height, stresses, etc.

[0041] The different foundation layers (1a, 1b) can be concreted in-situ, or alternatively be made up of prefabricated reinforced concrete and / or prestressed elements joined together, and both technologies can be combined in different layers.

[0042] Preferably, most of the outermost foundation layer will be covered with a filling (7) of earth, or other elements, emerging only the central part coinciding with the base of the tower, thus minimising the visual impact.

[0043] This foundation involves a characteristic construction procedure, as illustrated in Figures 5, 6, 7, 8, 9 and 10, which comprises: an optional preliminary phase of initial construction of the structure, a phase of removal of the existing tower (6). a phase of removal of the backfill (7) until the existing footing is discovered and excavation of the housing (9) for the new modular foundation module (1a, 1b) around said existing footing, considering as the existing footing the one that supported the tower (6) previously, being the base footing (2), or the base footing (2) plus one or more layers of modular foundation (1a, 1b...) resulting from previous processes, a phase of cleaning the upper surface (10) of the existing shoe, a phase of installation of the extensions (4) on the existing outermost anchoring bolts (3,5), where the existing tower (6) was previously anchored, a phase of realization of the new foundation layer (1a, 1b), a phase filling (7) of the remaining housing by means of the soil extracted previously in the excavation of the housing (9), and its compaction leaving the central part of the new foundation layer (1a) and the upper ends of the new anchor bolts (5) accessible, a phase of tightening the extensions (4) that make up the connecting bolts between the new foundation layer (1b), and the immediately preceding layer (1a), or between the new foundation layer (1a) and the base shoe (2) in the case of the first module, by conventional mechanical means (8), and a phase of placing the new tower (6), securing it on the new anchor bolts (5) by conventional mechanical means (8).

[0044] The optional preliminary phase of initial construction of the structure comprises: a stage of construction of the base shoe (2), provided with anchor bolts (3) for a tower, a stage of placing the tower (6), and a stage of operation of the infrastructure.

[0045] This optional preliminary phase of initial construction of the structure may have been carried out at a much earlier time and any known and possible technology for the different stages that compose it.

[0046] The phase of making the new foundation layer (1a, 1b), comprises, in a preferred embodiment with in-situ concreting: a stage of placement of the hardware of the reinforcement (11), a stage of placement of the new anchor bolt cage (5), a stage of concreting the new foundation layer (1a, 1b), and a stage of setting the concrete.

[0047] The phase of making the new foundation layer (1a, 1b) comprises, in an alternative embodiment with prefabricated concrete elements, a step of placing the prefabricated parts that make up the new foundation layer (1a, 1b), with the new anchor bolt cage (5) incorporated, a stage of execution of the union between the prefabricated elements, by mechanical means or by concreting of concrete joints with passive reinforcement.

[0048] These phases will be performed sequentially. The set of phases, except for the optional preliminary phase of initial construction of the structure, can be repeated as many times as necessary to create new foundation modules on top of the existing ones, whenever it is necessary to expand the tower by one of greater dimensions and greater foundation requirements, creating an external foundation module of greater extension each time, evolving in parallel with the support needs of the towers.

[0049] This modular structure defined by a superposition of foundation layers (1a, 1b) can also be made by combining foundation layers (1a, 1b) constructed with in-situ concreting, with foundation layers (1a, 1b) constructed with precast concrete elements in any order, according to need or availability.

[0050] The preferred use of this expandable modular foundation is as a support for towers, more preferably as a support or an integral part of a wind turbine, and even more preferably when the wind turbine towers are part of a process of expansion or repowering, also known as "repowering", of the wind turbine park, which involves replacing the wind turbines with others of greater productive power, greater height, and therefore with greater extension and greater foundation needs. Obviously, it can be used for any type of towers, both metal, concrete or mixed, and both wind turbines and communications, lighting, poles, piles of bridges or viaducts, etc.

[0051] Any person skilled in the art will easily understand that the characteristics of different embodiments can be combined with characteristics of other possible embodiments whenever such a combination is technically possible.

[0052] All the information referring to examples or modes of embodiment are part of the description of the invention.

Claims

1. - Expandable modular foundation, characterised in that it comprises: - a base shoe (2), containing at least one conventional foundation made by any conventional method, built in a preliminary or existing phase, equipped with anchoring bolts (3) for a tower (6), - one or more foundation layers (1a, 1b), each of greater extension than the previous one, superimposed, one on another, on the base shoe (2), at an upper level, each provided with anchor bolts (5) for a tower (6) on the last foundation layer (1a, 1b) built and reusable for connection with the subsequent foundation layers (1a, 1b), - a plurality of extensions (4) of the anchoring bolts (3,5) of the previous foundation layer built up to the upper level of the new phase under construction, located below the outermost foundation layer (1a, 1b) to match its height with that of the anchoring bolts (5) of said outermost foundation layer (1a, 1b), the anchor bolts (3,5) being distributed with an upper extension in each layer according to the height, each successive foundation layer (1a, 1b) being mechanically joined, by means of extensions (4) of the anchoring bolts (3,5), exclusively with the immediately lower foundation layer (1a, 1b), or with the base shoe (2) in case of being the first foundation layer (1a), the outermost foundation layer (1b) being the support of the tower or a larger structural element, by means of its own anchoring bolts (5) for this purpose.

2. - Expandable modular foundation, according to the preceding claim, characterized in that each modular foundation layer (1a, 1b) is made up of prefabricated reinforced or prestressed concrete elements, joined together.

3. - Expandable modular foundation, according to claim 1, characterized in that each modular foundation layer (1a, 1b) is concreted in-situ.

4. - Expandable modular foundation, according to any of the preceding claims, characterized in that the base shoe (2) is a conventional foundation with one or more layers of modular foundation (1a, 1b) on it.

5. - Expandable modular foundation, according to any of the preceding claims, characterized in that the majority of the outermost modular foundation layer (1a, 1b) is covered with an earth fill (7), emerging only the central part coinciding with the base of the tower.

6. - Expandable modular foundation, according to any of the preceding claims, characterized in that the modular foundation layers (1a, 1b) adopt a frustoconical structure.

7. - Assembly method of a hybrid tower with prefabricated self-supporting elements, according to any of the preceding claims, characterized in that it comprises: - an optional preliminary phase of initial construction of the structure, - a phase of removal of the existing tower (6). - a phase of removal of the backfill (7) until the existing footing is discovered and excavation of the housing (9) for the new modular foundation module (1a, 1b) around said existing footing, considering as the existing footing the one that supported the tower (6) previously, being the base footing (2), or the base footing (2) plus one or more layers of modular foundation (1a, 1b...) resulting from previous processes, - a phase of cleaning the upper surface (10) of the existing shoe, - a phase of installation of the extensions (4) on the existing outermost anchor bolts (3), where the existing tower (6) was previously anchored, - a phase of realization of the new foundation layer (1a, 1b), - a phase of filling (7) of the remaining housing by means of the soil extracted previously in the excavation of the housing (9), and its compaction leaving the central part of the new foundation layer (1a) and the upper ends of the new anchor bolts (5) accessible, - a phase of tightening the extensions (4) that make up the connecting bolts between the new foundation layer (1b), and the immediately preceding layer (1a), or between the new foundation layer (1a) and the base shoe (2) in the case of the first module, by conventional mechanical means (8), and - a phase of placing the new tower (6), securing it on the new anchor bolts (5) by conventional mechanical means (8).

8. - Method of construction of an expandable modular foundation, according to claim 7, characterized in that the optional preliminary phase of initial construction of the structure comprises: - a stage of construction of the base shoe (2), provided with anchor bolts (3) for a tower, - a stage of placing the tower (6), and - a stage of operation of the infrastructure.

9. - Method of construction of an expandable modular foundation, according to claim 7, characterized in that the phase of realization of the new foundation layer (1a, 1b) comprises: - a stage of placement of the hardware of the reinforcement (11), - a stage of placement of the new anchor bolt cage (5), - a stage of concreting the new foundation layer (1a, 1b), and - a stage of setting the concrete.

10. - Method of construction of an expandable modular foundation, according to claim 7, characterized in that the phase of realization of the new foundation layer (1a, 1b) comprises: - a stage of placing the prefabricated parts that make up the new foundation layer (1a, 1b), with the new anchor bolt cage (5) incorporated, and - a stage of execution of the union between the prefabricated elements, by mechanical means or by concreting of concrete joints with passive reinforcement.

11. - Method of construction of an expandable modular foundation, according to claim 7, characterized in that the set of phases, except the optional preliminary phase of initial construction of the structure, can be repeated as many times as necessary to create new layers of foundation each time it is necessary to expand the tower by one of greater dimensions and greater foundation requirements.

12. - Use of an expandable modular foundation, according to any of the preceding claims, characterized in that the foundation serves as a support for towers.

13. - Use of an expandable modular foundation, according to claim 12, characterized in that the towers are support or integral part of a wind turbine.

14. - Use of an expandable modular foundation, according to claim 12, characterized in that the wind turbine towers are part of a process of repowering the wind turbine farm.

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