Field of the invention

[0001] The present invention relates to drainage blocks of the sort used for buffering or attenuating of water. In particular, the invention relates to drainage blocks formed of drainage block elements retained together for improved stability. The invention further relates to a method of manufacturing such a drainage block and to a method of providing a pavement or substructure on a dike or urban space with drainage.

Background art

[0002] A drainage block for dikes or urban settings is known from EP3577278A1 , which discloses a drainage block having four lateral faces, a base, and at least one stem connecting the slab and the base, which stem has a cross-sectional area that is smaller than the smallest or minimum cross- sectional areas of the slab and the base, thereby forming a water buffering space between the slab and the base; and wherein spacing projections are provided on sides of the slab and base to create drainage openings. The hollow space between the slab and the base is intended for receiving surface water and buffering water by slowly releasing it into the ground or for redirecting the received surface water. By surface water it is meant herein any fluid resulting or coming from rainfall or waves from bodies of water (whether natural or manmade).

[0003] In order to, for example, allow inspection and maintenance, such as manual cleaning, by persons, relatively large drainage blocks may be required, which have hollow spaces in which a person can fit. These blocks also provide capacity for ever increasing volumes of water to be attenuated. A downside of these relatively large drainage blocks has been found to be caused by production limitations of current manufacturing facilities, resulting in a maximum depth of each block to be around 300 mm. In order to fit a person, the hollow space generally has a height significantly larger than 300 mm, resulting in a centre of mass of these drainage blocks being relatively high above their base, compared to a depth of said base. As a result, these drainage blocks are unstable when standing upright and free, such as may occur during installation, and can easily fall over. This falling over is highly undesirable, since it may both cause damage to the drainage block and surroundings as well as results in dangerous situations with personnel becoming injured by the falling drainage block.

[0004] The present invention seeks to provide a drainage block for creating attenuating structures, that may be produced at the current manufacturing facilities and which has improved stability when produced at larger sizes.

Summary of the invention

[0005] According to the present invention, a drainage block is provided for use as pavement or as substructure for urban spaces, the drainage block defining a height in a vertical direction, a width in a transverse direction and a length in a longitudinal direction of the drainage block and comprising a plurality of concrete drainage block elements, each comprising a slab, comprising an upper face and two longitudinal faces, extending in a horizontal direction of the drainage block element, a base, comprising a lower face and two longitudinal faces, extending in a horizontal direction of the drainage block element, and at least one stem, structurally connecting said slab and base, wherein the at least one stem has a cross-sectional area that is smaller than a cross-sectional area of the slab and of the base, with each cross-sectional area taken along a horizontal plane, such that an open space exists between the slab and the base for holding a volume of water, wherein a length of each drainage block element is smaller than a height thereof, and the drainage block consists of a plurality of drainage block elements held together by at least one attachment element, wherein said plurality of drainage block elements are positioned with the respective slabs and bases aligned with one another and retained to one another via the at least one attachment element.

[0006] Since each drainage block element has a length which is smaller than its height, the individual drainage block elements are unstable when standing upright. By joining a plurality of the drainage block elements together by use of the attachment elements, the drainage block can be made to have a total length which is larger. The composite drainage block has increased stability compared to the individual drainage block elements, thereby overcoming the stability issues resulting from the manufacturing limitations. The number of drainage block elements forming the drainage block will be chosen in dependence of the height and width of the drainage block, as well as the achievable length (or thickness) at which each individual drainage block element can be manufactured.

[0007] It will be understood that the dimensions and orientations are given for the usual position in use. It is of course not excluded that drainage block elements and drainage blocks may be manufactured, stored and transported in other orientations. It is also not excluded that they could be installed in different orientations although the intended objective is for the upper faces of the slabs of the drainage block elements to collectively form a supporting surface that is capable of withstanding loads such as may be encountered due to vehicle traffic. The stems must also be able to withstand the intended loading and the junctions between stems and slab and base respectively, should be engineered accordingly.

[0008] In the present context, reference to concrete is intended to denote such aggregates of cement with sand, gravel, stone or the like as will be understood by the skilled person as suitable for manufacturing such drainage blocks. It is not excluded that composites and reinforcing substances may be included in the aggregate. The drainage block elements are preferably monolithic. That is, the entire block element is manufactured as a single monolithic element in a single casting. This may be achieved by using a mould.

[0009] The drainage block and the drainage block elements may have a height of at least 300 mm, although generally they will be greater than 600 mm and preferably at least 900 mm. The individual elements may have a length of between 100 mm and 400 mm. The drainage block elements may be cast or moulded on a suitable table. Tables currently used allow such drainage block elements to be produced with a maximum height and width of around 1200 mm. The maximum thickness at which such blocks can be practically cast or moulded in a single form is presently around 400 mm. In order to manufacture larger blocks, significant investment and development would be required to build new manufacturing facilities. Furthermore, casting or moulding thicker drainage blocks may result in a longer and less controllable manufacturing process, resulting in drainage blocks having lower manufacturing tolerances compared to what is relatively easily achievable for the currently proposed drainage blocks.

[0010] The attachment element or elements preferably provide a force or loading on the drainage block elements in an axial or lengthwise direction. The force or loading may be provided on the respective outermost drainage block elements of the drainage block. The drainage block can be retained using just one attachment element e.g. at a central location.

[0011] In an embodiment at least two attachment elements are provided, located at two or more different height positions along the height of the plurality of drainage block elements. A first attachment element may be located at around the height of the slab and a second attachment element may be located at around the height of the base. Having attachment elements spaced apart along the height of the drainage block can ensure a balanced load. The drainage block elements are thus not only held together, but are also restricted in their rotational movement with respect to one another. Thus the spacing apart of the attachment elements results in increased stability.

[0012] In an embodiment, each of the attachment elements attaches all of the drainage block elements together within a drainage block. This allows a relatively low number of components to be used to make the drainage block, such that assembly of the block is fast and relatively cheap. Furthermore, joining all drainage block elements together allows significant stability being achieved more easily than when using, for example, multiple attachments elements in series to attach all of the drainage block elements to one another.

[0013] In one embodiment, the attachment element may comprise a strap. This can be applied as a closed loop, extending around the plurality of drainage block elements in a horizontal or vertical plane. Straps are relatively cheap, reliable and easy to attach. The strap can be made of any material sufficiently strong to withstand tension caused by the weight of the drainage block elements during normal use, including transport and installation. In particular, the strap may be made from or comprise one of a metal, a plastic, a textile web or a fibre reinforced composite material. It will be understood that the purpose of the attachment element is to ensure stability during installation and it is not primarily intended to be of a strength sufficient to lift the complete drainage block by the attachment means alone.

[0014] The plurality of drainage block elements may also comprises a slot or recess through which such a strap can extend. Such recesses or slots prevent the strap from moving along the outer surface of the drainage block elements, which could otherwise result in drainage block elements slipping out from the drainage block assembly and thereby releasing tension from the strap such that the strap becomes ineffective at holding the other drainage block elements together. This slipping out may otherwise particularly be a risk during lifting of the drainage blocks Preferably a height of the recess or slot is slightly larger than a width of the strap, allowing relatively small movement along the height direction of each of the drainage block elements with respect to the other drainage block elements to compensate for ground onto which the drainage block is to be placed being somewhat uneven. [0015] In an alternative, the at least one attachment element may comprise a tension rod. Each of the plurality of drainage block elements may be provided with a through-opening through which said tension rod extends. Preferably the through-openings are included in the drainage block elements during the manufacturing of said drainage block elements, and are for example incorporated into the mould with which the drainage block elements are cast or moulded. This results in the least amount of additional manufacturing steps being required to make the drainage blocks. However, it will occur to the skilled person that through holes can also be included in each of the drainage block elements in a subsequent step, for example through drilling.

[0016] Preferably, the through-holes have a shape without angular corners, to prevent stressconcentrations from occurring, which may otherwise cause cracks to form at these corners. Thus the through-holes are preferably round, oval or oblong with semi-circular ends.

[0017] The tension rod or rods, may be made of any suitable material, including metal, plastic, textile web or a fibre reinforced composite material. A preferred material is metal e.g. steel. The tension rod may also be provided with one or more spacer rings, each of which being positioned on the rod in between a respective pair of adjacent drainage block elements. The spacer rings can prevent the drainage block elements from directly abutting one another and thus generate gaps of a predetermined size in between the drainage block elements through which liquid may drain away. [0018] Although a mix of different attachment elements may be used within a single drainage block, preferably all attachment elements used within a single drainage block are of the same type. This results in lower manufacturing costs, due to the amount of different materials being required for making the drainage block is limited, and the manufacturing being more straightforward due to the same installation procedure being used for each of the attachment elements.

[0019] The same applies to the drainage block elements, which in a preferred embodiment are all identical. The skilled person will understand that theoretically the end drainage block elements within a drainage block could be different from intermediate elements. Nevertheless, producing different elements e.g. end or middle elements or male and female elements adds complexity to the production and assembly operations.

[0020] According to an important aspect of the present invention, at least one of the plurality of drainage block elements further comprises a plurality of spacing projections, for maintaining a spacing between said drainage block element and a further drainage block element. The presence of the spacing projections on the drainage block elements may be in addition to or instead of the aforementioned spacer rings. The result is that a slab drainage opening is formed between the two slabs of the two drainage block elements, on either side of the contacting spacing projections. Such draining gaps on either side of the spacing projections have an elongate cross- section and may have a width of between 10 mm and 100 mm, preferably between 20 mm and 60 mm.

[0021] The hollow space between the slab and the base is intended for receiving surface water and buffering water by slowly releasing it into the ground or for redirecting the received surface water. By surface water it is meant herein any fluid resulting or coming from rainfall or waves from bodies of water (whether natural or manmade). It will thus be understood that a drainage block, assembled as a plurality of drainage block elements is distinct from e.g. a series of pipe sections forming a pipeline. In the former case, water is intended to flow in and out through the gaps, whereas in a pipeline, this is generally not intended and the joints between segments may even be hermetic. [0022] A particular advantage of the spacing projections is that these are incorporated in the drainage block element design, such that they can be made together with the drainage block elements in a single manufacturing step. Furthermore, spacing projections present on a surface of a drainage block element which also forms an outer surface of the drainage block allow for spacing between adjacent drainage blocks being achieved. As noted above, preferably, all elements are identical and thus all elements will be provided with the same spacing projections.

[0023] The spacing projections may be configured in any number of ways. For example, a single spacing projection may comprise multiple sub-projections. Preferably each spacing projection has a surface that lies on a plane that is parallel to and offset from, a plane through the longitudinal faces of the slab and base. When two drainage block elements are arranged adjacent to each other, the spacing projection of a first element is in contact with a surface of the second element, resulting in a gap corresponding to the offset or height of the spacing projection.

[0024] In an alternative, adjacent drainage block elements may have spacing projections on both sides that engage against one another and the gap may be twice the height of the respective spacing projections. The spacing projections of adjacent elements may also seat, engage or nest together to prevent or restrict transverse movement, thus providing additional stability to the drainage block, once the attachment element is applied. It is nevertheless preferred that each drainage block element has spacing projections only on one side and that the other side is generally flat. The skilled person will recognise the advantages of moulding a concrete form having a flat upper side.

[0025] The spacing projections may be provided on the longitudinal faces of the slab and base but may additionally or alternatively be provided on the stem or stems, of the second block. In an embodiment, the spacing projections are distributed in a balanced manner over the element. There may be e.g. three, four, six or eight spacing projections. The projections may have a height or offset, measured in the length direction of the drainage block, of between 10 mm and 100 mm, preferably between 20 mm and 60 mm. It will be understood that if engaging projections are provided on both sides of a drainage block element, then they may be only half of this height.

[0026] In one embodiment, each drainage block element has at least two stems, whereby an opening is formed bounded by the two stems, the base and the slab and the openings in each drainage block element align. In a particular embodiment, there are two stems and the element is in the form of a frame having a generally rectangular central opening.

[0027] When the drainage block is assembled, the openings in the drainage block elements preferably align to form an access opening. The access opening preferably has dimensions through which a person may pass. These may allow for a minimum dimension of no less than 40 cm, preferably 50 cm and more preferably 60 cm.

[0028] The invention also relates to individual drainage block elements as described above and hereinafter, to be used and assembled to form a drainage block. [0029] The invention further relates to a method of manufacturing a drainage block for use as pavement or as substructure for urban spaces, comprising casting a plurality of concrete drainage block elements, each having a height of at least 300 mm, preferably at least 900 mm, a width of at least 300 mm and a length between 100 mm and 400 mm, and comprising a slab and a base, each having two longitudinal faces extending along said width, and at least one stem structurally connecting said slab and base, wherein the at least one stem has a cross-sectional area that is smaller than a cross-sectional area of the slab and of the base; and joining the plurality of drainage block elements together, such that said plurality of drainage block elements are positioned with the respective slabs and bases aligned with one another to form a drainage block.

[0030] The step of joining the plurality of drainage block elements can be performed on site, during or prior to installation of the blocks to form an attenuating element. In an embodiment, this is performed at the same manufacturing facility where the step of casting the plurality of drainage block elements is performed. The block can then be stored transported and installed as a single item.

[0031] In an embodiment, each of the plurality of drainage block elements is provided with a recess or through-opening in a location which is the same for each of the plurality of drainage block elements. The step of joining the plurality of drainage block elements may comprise the extending of an attachment element through or around said recess or through-opening of each of the plurality of drainage block elements. The attachment element may be one of a strap or tensioning rod.

[0032] The invention also relates to a method of providing an attenuating pavement or substructure for an urban space, comprising providing at least one drainage block as described above, preparing a ground surface for receiving the at least one drainage block; and lowering the at least one drainage block onto said ground surface. A plurality of such blocks may be provided and installed in abutting relation, with the respective upper surfaces of the slabs aligned to form a load bearing surface. In general, this surface will then be covered with suitable layers of ground, including geotextile and any such further membranes as may be required for the intended function.

[0033] Thus the at least one drainage block may arrive pre-assembled at the location where the pavement or substructure is to be made and be simply lifted into place. The attachment elements thus hold together the plurality of drainage block elements present in the drainage block throughout transport, lifting and lowering into position and may remain part of the drainage block also after installation. Thus the attachment elements may be considered as being a permanent part of the drainage block. It is however not excluded that these attachment elements may be removed or arranged to decay or degrade during use, should that be so required.

[0034] The invention also provides for an attenuating pavement or substructure, comprising a plurality of drainage blocks assembled in this manner or as described above. The blocks may be arranged with openings between the base and the slab of the respective drainage block elements that align to form access openings having dimensions sufficient for a person to pass. Brief description of the drawings

[0035] The present invention will be discussed in more detail below, with reference to the attached drawings, in which:

[0036] Fig. 1 shows a perspective view of a drainage block according to an embodiment of the invention;

[0037] Fig. 2 shows a front view of the drainage block of Fig. 1 ;

[0038] Fig. 3A to 3E each respectively show a front view of alternative embodiments of a drainage block element; and

[0039] Fig. 4 shows a perspective view of another embodiment of a drainage block according to the invention.

Description of embodiments

[0040] Figs. 1 and 2 respectively show a perspective view and a front view of a drainage block 100 according to an embodiment of the invention, comprising a plurality of drainage block elements 1 which are held together by two straps 10. In this case, five drainage block elements 1 are shown although it will be understood that any number of elements may be joined together to form a block. Each of the drainage block elements 1 comprises a slab 2, two stems 4, and a base 3. In the depicted embodiment, the two stems 4 interconnect the slab 2 and the base 3 at respective ends thereof, such that the drainage block elements 1 each have a substantially rectangular cross- sectional shape when seen from the front. Each of the drainage block elements 1 is provided with eight spacing projections 8 on a front surface thereof, evenly divided over the slab 2, the base 3 and the two stems 4.

[0041] Each of the drainage block elements 1 has a height H, which also is the height of the drainage block 100, a width B, which is also the width of the drainage block 100, and a length D. The total length D of the drainage block 100 is the sum of the lengths of the individual drainage block elements 1 , including the length of the projections 8.

[0042] Each drainage block element 1 is provided with a recess 12 at each transverse end of the slab 2 and the base 3, a transverse direction of the slab 2 and base 3 being defined along the width B of the drainage block element 1 . The plurality of drainage block elements 1 are held together by two straps 10, with each of the drainage block elements 1 being parallel to one another with their respective slabs and their respective bases aligned such that their upper and lower surfaces are coplanar. A first one of said straps 10 encircles the slabs 2 and a second one of said straps 10 encircles the bases 3, each of the straps 10 extending through the respective recesses 12 of the slabs and bases.

[0043] A width of each of the stems 4 in the transverse direction is smaller than the width B of the drainage block element 1 , such that an opening 5 is defined in between the slab 2, the base 3 and the two stems 4, having an opening width OB and an opening height OH. This opening 5 may be made sufficiently large for access by a person. The overall shape of the drainage block element 1 may be described as a rectangular frame shape, with suitable rounded or curved comers, which are designed and engineered to ensure that the element may be correctly cast and extracted from a mould and will be load bearing without stress concentrations. [0044] Positioning of both recesses 12 and spacing projections 8 is such that the strap 10 is not looped around the spacing projections 8. In the depicted drainage block elements, the spacing projections 8 have a height X, and are placed such that the spacing projections 8 on the slab 2 and base 3 respectively adjoin a top and bottom face thereof, while the recesses 12 are provided in an outer side surface of said slab 2 and base 3 at a distance which is at least equal to X from the top surface of the slab 2 and bottom surface of the base 3. It may be desired, for example depending on the height X of the spacing projections 8 and the height of the slab 2 and/or base 3, to provide the recesses for holding the straps into the stems 4 instead.

[0045] It will occur to the skilled person that the particular geometry of the listed elements, such as for example the cross-sectional shape of the stems or the shape and/or positioning of the spacing projections may be adjusted depending on specific project and/or manufacturing demands, without departing from the spirit of the invention. In the illustrated embodiment, eight spacing projections 8 are provided, two on each face of the slab 2, base 3 and stems 4.

[0046] Fig. 3A to 3E each respectively show a front view of alternative embodiments of a drainage block element 1 , as an example of possible design variations. Like reference numerals are provided for like elements in each of the embodiments.

[0047] The drainage block element 1 depicted in Fig. 3A is provided with three stems 4, , interconnecting the slab 2 and the base 3 of the drainage block element 1 . Similar to the drainage block element 1 of Figs. 1 and 2, the drainage block element 1 of Fig. 3A has two stems 4 connected to respective ends of the slab 2 and the base 3, such that a cross-sectional shape of the drainage block element 1 when seen from the front is substantially rectangular. The third stem 4 is a centrally positioned stem. As a result, the drainage block element 1 has two openings 5 defined between the slab 2 and the base 3.

[0048] The drainage block element 1 depicted in Fig. 3B is provided with a single stem 4 which is centrally positioned, spaced apart in the width direction from the respective ends of the slab 2 and the base 3, such that a cross-sectional shape of the element seen from the front is l-shaped. As a result, the drainage block element 1 has two open-sided openings defined between the slab and the base. It will be understood that once a drainage block is formed by assembly of a plurality of such drainage block elements together, these open-sided openings may be closed to form an actual opening by positioning another drainage block alongside.

[0049] The drainage block element 1 depicted in Fig. 3C is provided with two stems 4, which are both positioned spaced apart in the width direction from the respective ends of the slab 2 and the base 3, as well as from each other. As a result, the drainage block element 1 has one closed opening 5 and two open-sided openings defined between the slab 2 and the base 3. These may also be assembled as discussed above in relation to Figure 3B to form openings between adjacent blocks.

[0050] Figure 3D shows another alternative drainage block element 1 , having slanted or diagonal stems 4. It will be understood that the function of the stems 4 is primarily spacing and load bearing and any suitable configuration that can ensure the load bearing function in an adequate manner may be contemplated. [0051] Figure 3E shows a further alternative design of drainage block element 1 which is similar to the embodiment of Figure 3A but includes an additional horizontal or transverse stem 4. The overall configuration is thus a cross structure with four openings 5 of smaller size than those of Figure 1 . The embodiment of Figure 3E however has the advantage that it can be placed upright or on its side, with the slab 2 and base 3 effectively providing the load bearing function. If the height H is different to the width B, then two alternative heights may be achieved for the drainage block or attenuating structure by choosing the orientation of the drainage block elements 1 accordingly.

[0052] Fig. 4 shows a perspective view of another embodiment of a drainage block 200 according to the invention. The drainage block 200 differs from the drainage block 100 depicted in Figs. 1 and 2 in that the recesses and straps have been replaced by tensioning rods 20 and through-holes 22.

Each of the drainage block elements 21 is provided with a through-opening 22 in the same position as the others, extending in the length-direction of the element. The positions are defined by locations where a stem adjoins one of the slab and base.

[0053] The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.