NL2006974C2

NL2006974C2 - Underwater floor connector.

Info

Publication number: NL2006974C2
Application number: NL2006974A
Authority: NL
Inventors: Sander Pasterkamp
Original assignee: Univ Delft Tech
Priority date: 2011-06-21
Filing date: 2011-06-21
Publication date: 2012-12-28

Description

Underwater floor connector

Field of the invention

The invention relates to a process for the production of a concrete structure, to 5 such concrete structure per se as well as to the use of such structure, for instance in the construction of tunnels, parking garages, rail and road structures, buildings, especially below the surface level in areas with a high ground water level. The invention further relates to a connecting anchor.

10 Background of the invention

In the art, several methods are known to provide concrete structures in the ground. For instance, W02005028759 describes a method of constructing a pile foundation, wherein a foundation structure is built on the ground, which has at least one through hole, and a connecting member fixed to the foundation structure, adjacent to 15 the hole, and having at least one portion projecting upwards. A pile is inserted through the hole and a number of thrusts are applied statistically on the pile, to drive the pile into the ground by means of a thrust device, which is located over the pile, cooperating with a top end of the pile, and being connected to the projecting portion of the connecting member which, when driving the pile, acts as a reaction member for the 20 thrust device.

W02005038146 describes a hollow column structurally connected and sealed to a hollow pedestal embedded in a sea-bed by pumping water from within the pedestal. Continued pumping through a water-filter and an outlet provides stability for installing a pile within piling leaders and incorporating it into the foundation with concrete. A 25 temporary working platform with piling equipment on it can be secured to the platform from which the piling work can be carried out. For some types of sea-bed an impermeable blanket covers the surrounding surface and is sealed to the pedestal by means of a sliding collar. This can assist installation of the foundation and with continuation of pumping can offer some protection against liquefaction of the sea-bed 30 adjacent to the completed structure under cyclical loading and vibration.

US2005232697 describes a dowel including a corrosion-resistant sleeve, and a rod positioned within the sleeve. A sealant connects the corrosion-resistant sleeve and the rod. Further, this documents describes a method for constructing a dowel including 2 positioning a rod within a corrosion-resistant sleeve, and sealing the rod with respect to the corrosion-resistant sleeve.

W02004001139 describes a foundation pile having an innermost element and a structural tubular element surrounding the innermost element and composed of a non-5 metallic material. There is a tubular layer of composite material surrounding the structural tubular element and connected with the latter. There is a friction coating applied on an outer surface of the layer of composite material.

Summary of the invention 10 In the art, several methods are known to create underwater floors, for instance floors of tunnels, parking garages, rail and road structures, buildings, especially (partly) below the surface level in areas with a high ground water level. Such configurations may comprise a first concrete floor, also called “underwater concrete floor”, and a second concrete floor, also called “structural slab”, the latter being arranged above the 15 upper.

To build a parking garage or tunnel entrance below the water level, an underwater concrete floor may be created. After hardening, the water may be pumped out of the pit. To prevent the concrete floor from being pushed upwards by the pressure of the ground water, this floor may be connected to anchors or concrete piles, the latter 20 often being the cheaper solution. This underwater concrete floor may only have a temporary function. After pumping out the water, the final structural reinforced concrete floor (structural slab) may be cast on (top of) the underwater concrete floor. This structural floor should then take the water pressure without leaking.

However, the anchors, piles and underwater concrete floor may restrict the 25 deformations that would occur in the structural concrete floor due to shrinkage and temperature variations, resulting in aquiferous crack formation.

One may try to avoid or reduce those problems. For instance, a system of cooling pipes can be embedded in the concrete. The cooling of hardening concrete reduces heating from the exothermal concrete mixture reaction, thus reducing early-age thermal 30 stresses and cracking. However, this may not reduce cracking in a later stage due to external temperature variations and shrinkage. It may also be expensive.

3

Further, the structural slab can be reinforced with extra reinforcement to reduce crack width in order to enable 'self healing'. This method may be uncertain and may also be expensive.

An intermediate layer of sand between the underwater concrete floor and the 5 structural slab may be applied to reduce the friction between the two floors, thus allowing movement of the structural slab and reducing tension. In this case the concrete tension piles may be used to connect them. However, concrete piles are quite stiff so the method may not perform well. Also, the shear forces that occur in the piles may be too high for the piles.

10 When leaking cracks occur, these may be repaired. For instance, leaking cracks may be injected with filling means to close them. This may especially be expensive when asphalt concrete layers have to be removed first. Also, cracks may re-open later.

Hence, a disadvantage of such solutions may the inflexibility in which the structural slab is fixed. During setting, the structural slab may need some freedom of 15 movement in horizontal direction. Nevertheless, the structural design should be chosen in such a way, that groundwater may not penetrate through the (structural slab) layer due to the formation of cracks.

Hence, it is an aspect of the invention to provide an alternative structural design as well as an alternative process for the production of such structure, which preferably 20 further or at least partly obviate one or more of the above-described drawbacks.

In a first aspect, the invention provides process for the production of a concrete structure comprising: a. arranging tension anchors in a cavity the ground; b. forming a first concrete layer in the cavity, with the tension anchors 25 penetrating at least part of the first concrete layer; c. providing a flexible layer (“intermediate layer”) on (top of) the first concrete layer; d. providing a second concrete layer on (top of) the flexible layer, with the tension anchors not penetrating the second concrete layer; and 30 e. connecting the first concrete layer and the second concrete layer to each other with connecting anchors (“connectors”), with a first connecting anchor part in the combination of first concrete layer and tension anchors, with an intermediate 4 connecting anchor part in the flexible layer, and with a second connecting anchor part in the second concrete layer.

In a further aspect the invention provides concrete construction comprising: a. tension anchors, wherein the tension anchors have top ends; 5 b. a first concrete layer with the tension anchors penetrating at least part of the first concrete layer; c. a flexible layer (“intermediate layer”) on (top of) the first concrete layer; d. a second concrete layer on (top of) the flexible layer, with the tension anchors not penetrating the second concrete layer; and 10 e. connecting anchors (“connectors”), with a first connecting anchor part in the combination of first concrete layer and tension anchors, with an intermediate connecting anchor part in the flexible layer, and with a second connecting anchor part in the second concrete layer.

The invention allows the structural concrete floor (i.e. the structural slab) to move 15 more freely. This reduces the tension forces in the floor and thus the chances for leaking cracks. Hence, the invention may reduce water leakage through the second concrete layer in comparison with prior art solutions.

An intermediate layer of for instance sand may be placed between the first concrete layer, such as an underwater concrete floor, and the second concrete layer, 20 such as the structural slab. The two floors are not connected by concrete piles but by (thinner) connecting anchors, such as steel bars. This allows the floors to move more freely relative to one another. The connecting anchors may need proper corrosion protection where they go through the flexible layer, e.g. by an epoxy coating or by choosing specific connecting anchor materials.

25 In an embodiment, after placing the tension anchors, such as tension piles, a connecting anchor, such as in the form of a prefabricated steel structure, is placed on (top of) the tension anchor head, such as a pile head. The height of the pile head is preferably such that it does not protrude from the (underwater) concrete of the first concrete layer; only the steel structure does. Then, if present, water over the first 30 concrete of the first layer may be removed. A layer of sand, or another material, may be arranged on the first concrete layer. Subsequently, the second concrete layer, the structural concrete floor or structural slab, is made. The steel structure connects the structural floor to the underwater concrete with a few steel bars, covered in corrosion 5 protection. This allows tension forces to be transferred but allows a certain amount of horizontal movement.

Above, the term “concrete structure” is applied. This term especially refers to a structure comprising two or more layers of concrete. Such structure can be part of a 5 larger structure, such as a floor of a tunnel, a parking garage, a rail structure, a road structure, a sluice, a building, such as a house, an office building, a department store, etc.

The invention may be of especial relevance for water-retaining structures, i.e. structures wherein it is relevant that groundwater should be kept out of the structure. 10 Hence, the structure of the invention and the process of the invention can especially be used in or for (building) water-retaining structures. For instance, the structure and the process of the invention may be used at a river delta location (where in general the groundwater level is close to the earth’s surface). Hence, the structure can be used at a location where the (ground)water level is higher than a predetermined location of the 15 first concrete layer. The specific type of structure of the invention may especially be applied (under such conditions as the (ground)water level being higher than a predetermined location of the first concrete layer) for the reduction of cracks in the second concrete layer.

In general, the process for the production of such structure starts with arranging 20 tension anchors (or ground anchor) in the ground. This may be performed under water in a building pit. An example of tension anchors are tension piles. Such anchors are in general vertically arranged in the ground and have the function of keeping the (later) first concrete layer in place. The tension anchors may for instance be concrete piles.

In an embodiment, at the top of the tension anchors, connecting anchors may be 25 arranged. Those connection anchors may be part of the tension anchors before arranging the tension anchors in the ground, but may also be applied to the tension anchors after arranging the tension anchors in the ground.

After the tension piles are arranged in the ground, the first concrete layer may be arranged. As is known in the art, cement may harden under water and form an 30 underwater concrete layer. Hence, also this part of the process may be applied under water. The application of the first concrete layer will result in the formation of a substantial horizontal first concrete layer (underwater). The (top of the) previously arranged tension anchors will extend into the first concrete layer. They may partly 6 penetrate, or optionally also fully penetrate the first concrete layer (i.e. protrude from the first concrete layer). In a preferred embodiment, the tops of the tension anchors are within the first concrete layer, and do not penetrate entirely through the first concrete layer but penetrates partly the first concrete layer. Hence, in a preferred embodiment, 5 the tops of the tension anchors, such as the pile heads, are embedded in the first concrete layer. The first concrete layer has a top (on which a subsequent layer may be applied, see below).

As indicated above, the connection anchors might already have been applied to the tension anchors. In such case, the tension anchors will (of course) penetrate through 10 the first concrete layer. In another embodiment, which may be applied additionally or alternative, the tension anchors are arranged in the first concrete layer. Therefore, the phrase “with a first connecting anchor part in the combination of first concrete layer and tension anchors” is applied, as the tension anchors (i.e. the first connecting anchor part) may be integrated in the top of the tension piles, with either the top of the tension 15 piles penetrating the first concrete layer or being embedded in the first concrete layer, and/or the connecting anchors may be integrated in the first concrete layer.

After application of the first concrete layer (and in general some hardening of the first concrete layer, as needed for transferring the water pressure to the tension piles) the flexible layer may be applied.

20 When the (ground)water level is higher than the first concrete layer, the application of the flexible layer to the first concrete layer may be preceded by removal of the water over the first concrete layer. In such instance, the concrete structure might have been embedded between closures or water-retaining wall, such as for instance of a cofferdam. A cofferdam is an enclosure within a water environment or environment 25 with relative high (ground)water level, constructed to allow water to be pumped out to create a dry work environment. The cofferdam is usually a welded steel structure that is temporary and is typically dismantled after work is completed.

The flexible layer may be any kind of layer with flexible properties. The flexible layer may also comprise a plurality of layers. Examples of flexible layers are a soil-30 based layer, like a sand layer, a soil layer or a gravel layer, or a flexible polymer based layer, such as an expanded polystyrene (EPS) layer, or a rubber layer. The flexible polymer based layer may be a single layer and/or may comprise particles or units of such material. Also combinations of layers of different types of materials may be 7 applied. Especially, the layer is a solid layer; i.e. the intermediate layer is not liquid based. In an embodiment, the flexible layer comprises one or more of sand and soil. The mean thickness or height of the layer may for instance be in the range of 0.5 - 100 cm, especially 1-50 cm. Hence, in an embodiment the flexible layer between the first 5 concrete layer and the second concrete layer has a mean layer height in the range of 2-50 cm, like a mean height of at least 10 cm, such as 20-30 cm.

Especially, sand may be applied as intermediate layer. The layer height of the intermediate layer and length of the connecting anchor are selected such as to allow a part (the second connecting anchor part) of the connecting anchor being available for 10 penetration in the second concrete layer (to be applied). The intermediate layer has a top (on which a subsequent layer may be applied, see below).

After application of the intermediate layer, the second concrete layer may be applied. This may be done by introducing cementious material, and often also reinforcement bars, nets or fibers. Hence, the second concrete layer may comprise a 15 reinforced concrete layer.

The connecting anchors penetrate (with the second connecting anchor part) in at least part of the second concrete layer. Due to the presence of the connecting anchors, the combination of first concrete layer and tension piles and the second concrete layer are connected, and indirectly, the second concrete layer is connected to the tension 20 anchor. Due to the presence of the flexible layer, the second concrete layer may laterally move with respect to the first concrete layer. Therefore, the connecting anchors of the invention allow horizontal movement or deformation and provide tension effects. In this way, the second concrete layer, the structural slab, may be formed and hardened without substantial crack formation. In this way, water leakage 25 through the second concrete layer may be prevented.

As indicated above, the tension anchors may penetrate the first concrete layer and thus at least partly also penetrate into the flexible layer. However, the layer height of the flexible layer and the penetration height above the first concrete layer of the tension anchors are chosen such that the tension anchors do preferably not extend into the 30 second concrete layer. In a specific embodiment, between the anchor head and the second concrete layer, a foil may be provided, such as a sliding foil. Hence, in a further embodiment, the method of the invention includes providing a foil, such as a sliding foil, between the tension anchor head and the second concrete layer. Likewise, the 8 invention also includes a concrete structure as defined herein, with a foil, such as a sliding foil, between the tension anchor head and the second layer. Especially when the concrete structure is in use, due to pressure, the distance between the tension pile (head) and the second concrete layer may then be practically zero. Hence, the layer 5 height of the flexible layer and the penetration height above the first concrete layer of the tension anchors are chosen in such way that they do not limit the lateral movement of the second concrete layer.

Since the connecting anchor may especially be applied in conditions where the (ground)water level is high, higher than the predetermined location of the first concrete 10 layer, the connecting anchor may also be indicated as “underwater anchor” or “underwater connector” or “underwater floor connector”.

As indicated above, the invention may especially be applied in environments wherein the (ground)water level is high, such as in delta’s or even in lakes, rivers, canals, or in the sea. Hence, in a further aspect, the invention provides a process as 15 defined above, wherein preceding to arranging the tension anchors, the process includes arranging cofferdam elements in the ground and removing ground between cofferdam elements to provide the cavity, and wherein the process further comprises: a. arranging tension anchors in the cavity the ground; b. forming underwater a first concrete layer in the cavity with the tension 20 anchors penetrating at least part of the first concrete layer, and removing water over the thus formed concrete layer; c. providing a flexible layer on (top of) the first concrete layer; d. providing a second concrete layer on (top of) the flexible layer, with the tension anchors not penetrating the second concrete layer; and 25 e. connecting the first concrete layer and the second concrete layer with connecting anchors, with a first connecting anchor part in the combination of first concrete layer and tension anchors, with an intermediate connecting anchor part in the flexible layer and with a second connecting anchor part in the second concrete layer.

It may be possible that with time water penetrates into the flexible layer. Besides, 30 some water may already be present when forming this layer. Due to the presence of water in the flexible layer, the connecting anchor may corrode, when not protected against corrosion.

9

Hence, preferably the intermediate connecting anchor part has a surface of non-corrosive material. In this way, the intermediate part is protected from corrosion. In an embodiment, the intermediate part comprises stainless steel. Of course, this embodiment may also include that the entire connecting anchor comprises stainless 5 steel. In yet another embodiment, the intermediate part comprises an anti-oxidation coating. Of course, this embodiment may also include that the entire intermediate part comprises anti-oxidation coating. Both embodiments may also be combined. The term coating may also include a plurality of coatings. The anti-oxidation coating may be any kind of coating suitable of protecting the connection anchor against corrosion, such as 10 for instance a Teflon coating or an epoxy coating. Also other types of coatings may be applied, such as inorganic coatings. An example thereof is described in US2008233295.

Further, the connection anchors are preferably of a material that is more flexible than of the tension anchors. Tension anchors are often from concrete, which is rather 15 inflexible. In this invention, the connecting anchors are of another material than concrete, and may for instance substantially be of steel or iron.

In a further aspect, the invention also provides a building structure comprising a concrete structure as described herein, wherein the building structure may selected be selected from the group consisting of a tunnel, a parking garage, a rail structure, a road 20 structure, a sluice, and a building, such as a such as a house, an office building, a department store, etc.

In yet a further aspect, the invention also provides the connecting anchor per se, especially a connecting anchor, suitable for connecting a first and a second concrete layer, which are separated by a flexible layer, with a first connecting anchor part for 25 (use) in the first concrete layer, with an intermediate connecting anchor part for (use) in the flexible layer, and with a second connecting anchor part for (use) in the second concrete layer, wherein the intermediate connecting anchor part has a surface of non-corrosive material.

The term “substantially” herein will be understood by the person skilled in the 30 art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or 10 higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many 5 alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such 10 elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device or apparatus claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination 15 of these measures cannot be used to advantage.

The invention further pertains to a method or process comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide 20 additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

Further embodiments

The invention especially relates to the following embodiments, which are for the 25 sake of reference numbered 1. A process embodiment for the production of a concrete structure comprising: a. arranging tension anchors in a cavity the ground; b. forming a first concrete layer in the cavity, with the tension anchors 30 penetrating at least part of the first concrete layer; c. providing a flexible layer on (top of) the first concrete layer; d. providing a second concrete layer on (top of) the flexible layer, with the tension anchors not penetrating the second concrete layer; and 11 e. connecting the first concrete layer and the second concrete layer to each other with connecting anchors, with a first connecting anchor part in the combination of first concrete layer and tension anchors, with an intermediate connecting anchor part in the flexible layer, and with a second connecting anchor part in the second concrete 5 layer.

2. The process embodiment according to process embodiment 1, wherein the intermediate connecting anchor part has a surface of non-corrosive material.

3. The process embodiment according to any one of the preceding process embodiments, wherein the intermediate part comprises stainless steel.

10 4. The process embodiment according to any one of the preceding process embodiments, wherein the intermediate part comprises an anti-oxidation coating.

5. The process embodiment according to any one of the preceding process embodiments, wherein the flexible layer comprises one or more of sand and soil.

6. The process embodiment according to any one of the preceding process 15 embodiments, wherein the flexible layer between the first concrete layer and the second concrete layer has a mean layer height in the range of 1-50 cm.

7. The process embodiment according to any one of the preceding process embodiments, wherein preceding to arranging the tension anchors, the process embodiment includes arranging cofferdam elements in the ground and removing 20 ground between cofferdam elements to provide the cavity, and wherein the process embodiment further comprises: a. arranging tension anchors in the cavity the ground; b. forming underwater a first concrete layer in the cavity with the tension anchors penetrating at least part of the first concrete layer, and removing water over the 25 thus formed concrete layer; c. providing a flexible layer on (top of) the first concrete layer; d. providing a second concrete layer on (top of) the flexible layer, with the tension anchors not penetrating the second concrete layer; and e. connecting the first concrete layer and the second concrete layer with 30 connecting anchors, with a first connecting anchor part in the combination of first concrete layer and tension anchors, with an intermediate connecting anchor part in the flexible layer and with a second connecting anchor part in the second concrete layer.

12 8. The process embodiment according to any one of the preceding process embodiments, wherein the second concrete layer comprises a reinforced concrete layer.

9. The process embodiment according to any one of the process embodiments, at a location where the (ground)water level is higher than a predetermined location of 5 the first concrete layer.

10. A concrete structure embodiment comprising: a. tension anchors, wherein the tension anchors have top ends; b. a first concrete layer with the tension anchors penetrating at least part of the first concrete layer; 10 c. a flexible layer on (top of) the first concrete layer; d. a second concrete layer on (top of) the flexible layer, with the tension anchors not penetrating the second concrete layer; and e. connecting anchors, with a first connecting anchor part in the combination of first concrete layer and tension anchors, with an intermediate connecting anchor part 15 in the flexible layer, and with a second connecting anchor part in the second concrete layer.

11. A building structure embodiment comprising the concrete structure embodiment according to concrete structure embodiment, wherein the building structure embodiment is selected from the group consisting of a tunnel, a parking 20 garage, a rail structure, a road structure, a sluice, and a building.

12. Use embodiment of a structure according structure embodiment 10, for the reduction of cracks (i.e. for the reduction of crack formation) in the second concrete layer.

13. Use embodiment of a structure according structure embodiment 10, at a 25 location where the (ground)water level is higher than a predetermined location of the first concrete layer.

14. Use embodiment according to use embodiment 13, at a river delta location.

15. Use embodiment according to any one of use embodiments 12-14, in water-retaining structures.

30 16. A connecting anchor embodiment, suitable for connecting a first and a second concrete layer, which are separated by a flexible layer, with a first connecting anchor part for (use) in the first concrete layer, with an intermediate connecting anchor part for (use) in the flexible layer, and with a second connecting anchor part for (use) in 13 the second concrete layer, wherein the intermediate connecting anchor part has a surface of non-corrosive material.

Brief description of the drawings 5 Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figures 1 a-lh schematically depict an embodiment of the application of the concrete structure of the invention, wherein the building method of a structural slab on 10 an underwater concrete layer is shown. Further, some other details of embodiments are shown (figs lg-lh).

The drawings are not necessarily on scale.

Description of preferred embodiments 15 Figures la-If schematically depicts an application of the concrete structure of the invention (in cross-sectional view). Fig. la shows the arrangement of a closure element 2a in ground 1, such as a cofferdam element. The closure may especially be intended to block (ground)water out of a (later) building pit.

Fig. lb shows how the (future) building pit is surrounded by closure elements 2a 20 and 2b and ground 1 between the closure elements 2a,2b being removed until a level, which is indicated as well bottom 5.

The pit 4 has filled with (ground)water. Note that the same configuration and principles may apply to the placements of such closures 2a,2b, like cofferdam elements in water, such as in a canal, a river, a lake or the sea. Reference 3 indicates 25 (ground)water.

Now tension anchors 110 may be arranged in the ground 1, between the closure elements (fig. lc). Note that the tension anchors 110 extend above well bottom 5. After arrangement of the well bottom 5, first concrete floor 120 can be applied (fig. Id). In this schematically depicted embodiment, this is an underwater concrete layer. The first 30 concrete layer 120 is kept in its position due to the incorporation of part of the tension piles 110. Hence, these figures show how the connecting anchor 150 may especially be applied in conditions where the (ground)water level is high, higher than the predetermined location of the first concrete layer 120.

14

Subsequently, the (ground)water 3, if any, may be removed over the first concrete floor (fig. le). Thereafter, the intermediate or flexible layer 130 may be applied, and subsequently the structural slab or second concrete layer 140 (fig. If).

Note that in fig. If also connecting anchors 150 are depicted. The connecting 5 anchors 150 connect the combination of the first concrete layer 120 and the tension piles 110 on the one hand and the second concrete layer 140 on the other hand. The connecting anchors 150 are integrated in the tension pile top and/or are integrated in the first concrete layer 120. Hence, the connecting anchors 150 may be placed on placing the tension anchors 110, after placing the tension anchors 110 or after producing the 10 first concrete layer 120. Combinations of differently arranged connecting anchors 150 may also be applied.

Hence, the tension anchors 110 fixate the first concrete layer 120 to the ground 1 and the connecting anchors 150 fixate the second concrete layer to the tension anchors 110 and/or the first concrete layer.

15 After application of the flexible layer 150 and the second concrete layer 140, with the first connecting anchor part in the first concrete layer, the intermediate connecting anchor part in the flexible layer 150 and the second connecting anchor part in the second concrete layer, further elements may be arranged. This may be any type of elements, like one or more of wall elements, pillars, road or railway elements, etc.

20 Figure lg schematically depicts an embodiment of the connecting anchor 150 in more detail, in an enlargement of fig. If. In this schematic embodiment, the connecting anchor 150 apparently is a straight bar, but as will be clear to the person skilled in the art, the connecting anchor may also include branches, for further reinforcement. Fig. lg indicates the height h of the flexible layer 130. This is the mean height between the top 25 121 of the first concrete layer 120 and the top 131 of the flexible layer. Note that h will in general be an average value, since the height may locally vary. In general, the variation will not be more than 10 cm (i.e. h +/- 10 cm), in general not more than 5 cm, or even not more than 2 cm. Reference 111 indicates the top of the tension anchor 110, which is in this embodiment substantially equal to the top 121 of the first concrete layer 30 120. Reference 141 indicates the top of the second concrete layer 140. The mean thickness of the first concrete layer may for instance be in the range of 0.8 - 2.0 m, and the thickness of the second concrete layer may for instance be in the range of 0.25 - 0.40 m. Here, in this example, the top (or head) 111 of the tension anchor 110, is at the 15 same level as the top 121 of the first concrete layer 120. Hence, in this schematically depicted embodiment, the penetration height of the tension anchor 110 above the first layer 120 is substantially zero. As indicated above, the penetration height above the first layer may in some embodiments even be substantially equal to height h of the 5 flexible layer 130. Optionally, when the top (or head) 111 is penetrating the first concrete layer 120, a sliding foil may be arranged between the top (or head) 111 and the second concrete layer 140. This may support lateral movement of the second concrete layer 140.

In fig. lg, the connecting anchor 150 may for instance be of steel. In this way, the 10 connecting anchor 150 has a surface 153 of non corrosive material. Fig. lh schematically depicts another embodiment of the connecting anchor 150, wherein the material of the connecting anchor may be corrosive, but where the intermediate connecting part, indicated with reference 150b is provided with a anti-oxidation coating 151. The length/height h2 of the coating 151 is such, that the entire intermediate anchor 15 part 150b is protected by the coating. The height h2 will be at least 100% of the height h of the intermediate layer 130 in which it will be applied. In general, the height h2 will be 2 x 4 cm larger, to a maximum of about 100 % of the height hi of the connecting anchor 130. The height hi of the connecting anchor 150 will in general be in the range of about 80-220 cm, such as 120-180 cm. References 150a and 150c indicate the first 20 connecting part which is (will be) at least partly embedded in the first concrete layer 120, and the second connecting part which is (will be) at least partly embedded in the second concrete layer 140, respectively.

Note that part of the intermediate connecting part 150b may preferably extend partly into the first concrete layer 120 and/or partly into the second concrete layer 140, 25 for optimal protection.

Claims

A method for producing a concrete structure, comprising: a. Introducing tension anchors into a well in the ground; 5 b. forming a first concrete layer in the well, wherein the tension anchors are integrated in at least a part of the first concrete layer; c. applying a flexible layer to the first concrete layer; d. applying a second concrete layer to the flexible layer, wherein the tension anchors are not integrated in the second concrete layer, and e. connecting the first concrete layer and the second concrete layer with connecting anchors, with a first connecting anchor part in the combination of the first concrete layer and tension anchors, with an intermediate connecting anchor part in the flexible layer, with a second connecting anchor part in the second concrete layer, and wherein the intermediate connection anchor part has a surface made of corrosion-resistant material.

The method according to any of the preceding claims, wherein the intermediate connecting anchor part comprises stainless steel. 20

The method according to any of the preceding claims, wherein the intermediate connecting anchor part is provided with a corrosion-resistant coating.

The method according to any of the preceding claims, wherein the flexible layer consists of one or more of sand and soil. 25

The method according to any of the preceding claims, wherein the flexible layer between the first concrete layer and the second concrete layer has an average layer height in the range of 1-50 cm.

6. The method according to any of the preceding claims, wherein prior to the introduction of the tension anchors, the process comprises placing coffer dam elements in the ground and removing soil between the coffer dam elements, thereby providing the well, and wherein the process further comprises: a. the introduction of tension anchors into the well in the ground; b. underwater forming the first concrete layer in the well with the tension anchors being integrated in at least a part of the first concrete layer, and removing water above the concrete layer thus formed; 5 c. applying a flexible layer to the first concrete layer; d. applying a second concrete layer to the flexible layer, wherein the tension anchors are not integrated in the second concrete layer, and e. connecting the first concrete layer and the second concrete layer to each other with connecting anchors, with the first connecting anchor part in the combination of the first concrete layer and tension anchors, with the intermediate connecting anchor part in the flexible layer, with the second connecting anchor part in the second concrete layer, and wherein the intermediate connecting anchor part has a surface of non-corrosive material.

The method according to any of the preceding claims, wherein the second concrete layer comprises a reinforced concrete layer.

The method according to any of the preceding claims, at a location where the (ground) water level is higher than a predetermined location of the first concrete layer.

9. A concrete structure consisting of: a. Tension anchors, the tension anchors having upper ends; b. a first concrete layer, wherein the tension anchors are integrated in at least a part of the first concrete layer; c. a flexible layer on the first concrete layer; 25 d. a second concrete layer on the flexible layer, wherein the tension anchors are not integrated in the second concrete layer, and e. connecting anchors, with a first connecting anchor part in the combination of the first concrete layer and tension anchors, with an intermediate connecting anchor part in the flexible layer, with a second connecting anchor part in the second concrete layer, and wherein the intermediate connecting anchor part has a surface of corrosion-resistant material.

A building structure consisting of a concrete structure according to claim 9, wherein the building structure is selected from the group consisting of a tunnel, a parking garage, a rail construction, a road construction, a lock, and a building.

Use of a structure according to claim 9, for the reduction of cracking in the second concrete layer.

Use of a structure according to claim 9, at a location where the (ground) water level is higher than a predetermined location of the first concrete layer.

Use according to any of claims 11-12, in a river delta.

Use according to any of claims 11-13, in water-retaining structures.

15. A connecting anchor suitable for connecting a first and a second concrete layer, separated by a flexible layer, with a first connecting anchor part suitable for use in the first concrete layer, with an intermediate connecting anchor part suitable for use in the flexible layer, and with a second connecting anchor part suitable for use in the second concrete layer, wherein the intermediate connecting anchor part has a surface of corrosion-resistant material. 20