Reinforced concrete drill pipe

Abstract

The invention relates to a reinforced drill pipe (1, 1') for supporting drill holes for the production of concrete piles, comprising a top end (4) and an upper connecting piece (5) arranged at the top end (4) and comprising a base end (6) and a lower connecting piece (5) arranged at the base end (6), wherein the drill pipe (1, 1') has at least one outer pipe (2) made of concrete and at least one inner pipe (3) arranged therein and made of a metal material or of an abrasion-resistant plastic, and wherein the drill pipe (1, 1') has a central section (8) between the upper connecting piece (5) and the lower connecting piece (7). The inner pipe (3), made of steel in the central section (8), has a plurality of recesses (10) with the same cross-sectional area in the casing wall, wherein the plurality comprises at least ten recesses (10), and wherein the central section (8) with the recesses (10) extends over at least one quarter of the total length of the drill pipe (1, 1') and over a maximum of seven eighths of the total length of the drill pipe (1, 1').

Description

[0001] Reinforced concrete drill pipe

[0002] Technical area

[0003] The invention relates to a concrete drill pipe for drilling systems in special foundation engineering.

[0004] State of the art

[0005] Drill pipes for drilling systems in special foundation engineering are usually made of steel or another metal and are pulled back up during or after the borehole has been filled with concrete and reused. Such drill pipes are described, for example, in DE20008887U1. However, it is also possible to use drill pipes that remain in the ground after the borehole has been filled. Such drill pipes are also referred to as lost drill pipes and are described, for example, in US10648146B1. KR101847906B1 discloses a composite pipe body that is primarily inserted into the ground to cast a pile and consists of a precast concrete retaining pipe and a steel retrieval pipe. When the composite pipe body has reached a certain depth, the retrieval pipe is pulled out and retrieved, and concrete is poured into the retaining pipe to complete the pile.CN216809867U describes a double-walled pipe body with an inner side made of steel and an outer side made of concrete, which is used as a drill pipe.

[0006] Conventional drill pipes have several disadvantages. With the steel drill pipes commonly used, reinforcing iron is inserted into the borehole to reinforce the concrete pile before the borehole is filled with concrete, ensuring sufficiently stable concrete piles. Furthermore, the steel pipes must be pulled back up from the borehole after the borehole has been filled with concrete. During the pulling up process, there is a risk of constriction of the freshly drilled concrete pile, causing a soil layer in the borehole to collapse and mix with the filled concrete, preventing the concrete pile from forming a continuous pile. The use of reinforcing iron and the pulling up and cleaning of the drill pipes used requires additional time and material.

[0007] The common lost drill pipes are often not stable enough. For stabilization, the drill rods and bits are sometimes left in the ground, serving as a substitute for reinforcement. Lost drill pipes, in which a continuous layer of steel is used, pose a risk of corrosion of the steel pipes. Furthermore, the concrete of the concrete pile inside the steel pipe does not bond with the soil outside the steel pipe. This creates little skin friction, and the concrete piles are therefore less stable. Likewise, with a continuous steel pipe, a lot of material remains in the ground and does not decompose.

[0008] The existing solutions therefore either require additional reinforcement to create sufficiently stable concrete piles, or they require a lot of material that is "lost" in the ground. Furthermore, such drill pipes are very heavy. Therefore, the existing solutions are neither economically nor ecologically efficient, are time-consuming to produce the concrete piles, and have high material consumption.

[0009] Object of the invention

[0010] The present invention is based on the object of creating a stable drill pipe which can be left in the ground, which consumes little material, and with which stable concrete piles can be produced without additional reinforcement and with little expenditure of time, thus saving time and material.

[0011] Description of the invention

[0012] This object is achieved by a reinforced drill pipe for supporting boreholes for the production of concrete piles or anchors, wherein the drill pipe has a head end and an upper connection piece arranged at the head end and a foot end and a lower connection piece arranged at the foot end, wherein the drill pipe has at least one outer pipe made of concrete and at least one inner pipe made of a metallic material or of an abrasion-resistant plastic arranged therein, and wherein the drill pipe has a central section between the upper connection piece and the lower connection piece. The inner pipe made of a metallic material or of an abrasion-resistant plastic has a plurality of recesses with the same cross-sectional area in the central section, wherein the central section with the recesses extends over at least a quarter of the total length of the drill pipe and over a maximum of seven-eighths of the total length of the drill pipe.

[0013] The advantage of such a reinforced drill pipe with an outer pipe made of concrete and an inner pipe made of a metallic material or an abrasion-resistant plastic is that the drill pipe serves simultaneously as the drill pipe, as the reinforcement, and as the concrete casing. This eliminates the need for additional reinforcement to produce the concrete pile. Such a reinforced drill pipe according to the invention is also referred to as a reinforced concrete drill pipe. The drill pipe is left in the ground and does not need to be pulled out of the ground after the borehole has been filled with concrete. The recesses in the middle section of the drill pipe can, on the one hand, save material. On the other hand, the recesses in the middle section are filled with concrete during production of the drill pipe when the inner pipe is encased with the outer pipe made of concrete. Despite the recesses in the inner pipe, the drill pipe is therefore very stable.If the borehole drilled with the drill pipe is filled with concrete after the soil material has been removed, the liquid concrete filled into the borehole comes into contact with the concrete casing of the outer pipe. This creates a force-locking connection between the tank anchor and the outer pipe, resulting in a very stable concrete pile. The middle section with the recesses is located between the upper and lower connecting pieces of the head and foot ends of the drill pipe. The upper connecting piece is located at the head end of the drill pipe and the lower connecting piece at the foot end of the drill pipe; both are part of the drill pipe. The head end with the upper connecting piece is understood to be the end of the drill pipe that is at the top of the drill pipe above the foot end and the middle section when the drill pipe is inserted into a borehole.The base end with the lower connecting piece is understood to be the end of the drill pipe which, when the drill pipe is inserted into a borehole, is at the lower end of the drill pipe below the head end and the middle section. The casing wall of the inner pipe of the upper and lower connecting pieces is preferably made entirely of a metallic material or an abrasion-resistant plastic and has a closed casing wall and no recesses. However, it is possible for the upper connecting piece at the head end of the drill pipe to have two to four openings at the same height to accommodate fastening devices, for example bolts, for fastening the drill pipe arranged above, which is screwed or plugged into the drill pipe below.

[0014] The middle section extends over at least one-quarter and a maximum of seven-eighths of the total length of the drill pipe, preferably over a maximum of three-quarters, even more preferably over a maximum of two-thirds of the total length of the drill pipe. Particularly preferably, the middle section with the recesses extends over at least one-third and a maximum of two-thirds of the total length of the drill pipe, particularly preferably over half of the total length of the drill pipe. Such drill pipes are particularly stable while simultaneously having a high number of recesses to save material. The total length of the drill pipe is understood to be the entire length between the head end and the foot end of the drill pipe in the longitudinal direction of the pipe.In a preferred embodiment, the central section with the recesses extends completely over the area between the upper and lower connecting pieces and has a plurality of equally spaced recesses in the jacket wall of the inner tube. In a further embodiment, the central section has a plurality of sections with a plurality of recesses and, in between, sections in the longitudinal direction without recesses.

[0015] The drill pipes preferably have a length of 1 to 10 meters, more preferably 1 to 6 meters, and an inner diameter of preferably 10 to 300 cm, even more preferably 100 to 250 cm. The wall thickness of the steel inner pipe is preferably 2 mm to 15 cm, even more preferably 3 cm to 10 cm, and the wall thickness of the outer pipe is preferably 7 mm to 20 cm, even more preferably 7 cm to 12 cm.

[0016] A plurality of cutouts, also called multiple cutouts, with the same cross-sectional area in the central section is understood to mean that the jacket wall of the inner tube has a plurality of openings or holes in the central section, whereby each cutout, or each opening or hole in the jacket wall, has the same cross-sectional area. The term plurality is understood to mean at least ten, preferably at least 100 cutouts. The plurality of cutouts in the central section are preferably arranged so as to be evenly distributed over the jacket surface of the central section of the inner tube. By arranged so as to be evenly distributed is understood that the distance between the individual cutouts is the same everywhere, and they are thus distributed evenly and at the same distance over an area.

[0017] The recesses preferably have a diameter of 4 mm to 10 cm, more preferably 0.5 cm to 5 cm, depending on the size of the concrete aggregate. The recesses preferably have a diameter that is larger than the diameter of the concrete aggregate so that the concrete can flow into the recesses and fill the recesses with concrete. The middle section preferably has one to thirty, preferably three to thirty, recesses on an area of ​​10x10 cm. The wall thickness of the edges between the recesses or the distance of the closed area between the recesses is preferably the same. The middle section with the recesses preferably has a mesh structure or a grid or lattice structure, in which the recesses are present as open cells between the solid edges formed from the casing wall of the inner pipe.The central section consists predominantly of open recesses, and the diameter of the recesses or openings or cells is at least twice, preferably at least three times, and even more preferably at least four times the diameter of the edges or the distance between the recesses. The wall thickness of the edges between the recesses is at most half, preferably at most one-quarter, of the diameter of the cross-sectional area of ​​the recesses. A mesh structure is particularly preferred.

[0018] The cross-sectional area of ​​the recesses or the cross-section of the holes or openings in the central section is preferably round, oval or square, preferably triangular to octagonal. In a particularly preferred embodiment, the cross-sectional area of ​​the recess is hexagonal and the central section has a hexagonal mesh structure. The advantage of a hexagonal mesh structure is that the greatest possible stability is achieved with the least possible material. This means that the central section with a hexagonal mesh structure has a predominantly open structure, the wall thickness of the edges around the recesses and the material consumption are kept low, and yet a high level of stability is achieved in the central section. Compared to conventional drill pipes, the hexagonal mesh structure results in particularly stable drill pipes with particularly low material consumption.

[0019] The reinforced drill pipe comprises at least one outer pipe made of concrete and at least one inner pipe made of a metallic material or an abrasion-resistant plastic, and is preferably a double-walled drill pipe. In addition to the outer pipe and the inner pipe, the drill pipe may comprise additional pipe layers and thus additional casing walls, for example, to reinforce or protect the outer pipe or the inner pipe, and is then referred to as a multi-walled drill pipe. For example, within the inner pipe made of a metallic material or an abrasion-resistant plastic, an additional inner pipe made of concrete may be arranged, such that the inner pipe made of a metallic material or an abrasion-resistant plastic is arranged between two concrete pipes in a sandwich-like structure.

[0020] The outer concrete pipe is preferably made of standard concrete or ultra-high-strength concrete, preferably as a precast component. The outer concrete pipe can be manufactured, for example, using formwork or the centrifugal casting process. Formwork is the mold into which fresh concrete is poured to produce concrete components. It is usually removed after the concrete has hardened. The formwork is the corresponding hollow mold for the concrete component. In the centrifugal casting process, concrete pipes are manufactured by rapidly rotating a concrete-filled pipe mold around its longitudinal axis. During rotation, the concrete is thrown against the mold wall due to centrifugal force, thereby compacting it. In the process, some of the mixing water is separated inward, creating a favorable water-cement ratio.In the centrifugal casting process, for example, the inner pipe according to the invention made of a metallic material or of an abrasion-resistant plastic can be inserted into a pipe mold, the pipe mold is then filled with concrete, and by rotating the pipe mold around the longitudinal axis, the concrete is thrown onto the wall inside and outside the inner pipe, thereby creating a reinforced concrete drilling pipe with an outer pipe made of concrete, an inner pipe made of a metallic material or abrasion-resistant plastic and an innermost layer, inside the inner pipe, made of concrete.

[0021] A particularly preferred outer pipe made of concrete additionally comprises fibers for reinforcing the concrete, preferably basalt fibers, steel fibers, or glass-ceramic fibers. Concrete reinforced with basalt fibers, so-called basalt fiber-reinforced concrete, is particularly preferred. A particularly stable drill pipe can be achieved by manufacturing the inner pipe from a metallic material or an abrasion-resistant plastic. An inner pipe made of a metallic material is preferred. For example, a hard metal, steel, chromium steel, iron, or aluminum can be used as the metallic material. A steel inner pipe is particularly preferred. Suitable abrasion-resistant plastics include, for example, a hard plastic, a glass-fiber-reinforced plastic, or a carbon-fiber-reinforced plastic, also known as carbon.The inner tube with the upper connecting piece, the middle section and the lower connecting piece is preferably manufactured in one piece.

[0022] Both the outer pipe and the inner pipe preferably have a circular cross-section throughout. Preferably, the outer concrete pipe completely encloses the inner pipe with the recesses in the central section, and the inner pipe is arranged concentrically within the outer pipe. In the central section, the recesses of the inner pipe can be filled with concrete from the outer pipe, so that in the central section, in addition to enclosing the inner pipe, the outer pipe can also be arranged between the edges surrounding the recesses, and the inner pipe thus also has a closed surface. Preferably, the outer concrete pipe encloses the inner pipe over the entire length of the drill pipe, with the exception of the connecting piece, which is inserted into an adjacent connecting piece.This end section of the drill pipe, with a connecting piece that can be inserted into an adjacent connecting piece, does not have an outer pipe and is thus formed solely from the material of the inner pipe. Preferably, the inner pipe is arranged in a form-fitting manner within the outer pipe, and the concrete outer pipe is cast directly around the inner pipe. The inner pipe can also be firmly bonded to the outer pipe, for example, by bonding the inner and outer pipes together, preferably using a polymer adhesive, such as a two-component adhesive. This improves the mechanical properties of the drill pipe, such as its torsional rigidity.

[0023] To produce the reinforced drill pipe, the outer pipe is either cast from concrete as a preform, or manufactured using formwork or centrifugal casting, and the inner pipe, made of a metallic material or an abrasion-resistant plastic, is inserted into the preformed concrete part. In this case, the recesses of the inner pipe remain open and are filled with concrete when the borehole is filled. In a preferred manufacturing process, the outer pipe is cast from concrete around the inner pipe, and the recesses in the middle section of the inner pipe are filled with concrete during the production of the drill pipe, producing a particularly stable drill pipe. In this case, the reinforced concrete drill pipe also has a closed surface on the inside of the inner pipe.

[0024] In a preferred embodiment, to produce the reinforced drill pipe, half-shells of the reinforced drill pipe are first produced. This has the great advantage that the half-shells can be stacked on top of each other and transported easily and in a space-saving manner. On site, two half-shells are joined together to form one pipe and used as the reinforced drill pipe. To produce the half-shells for the reinforced drill pipe, the outer concrete pipe is cast as a half-shell using formwork or centrifugal casting. The inner pipe, made of a metallic material or an abrasion-resistant plastic, is also manufactured as a half-shell and placed inside the half-shell of the outer concrete pipe or, preferably, the half-shell of the outer concrete pipe is cast directly around the half-shell of the inner pipe.The half-shells each have two longitudinal folds, also called longitudinal joints, on their long edges, which are offset from one another so that they lie positively on top of one another when joined. The longitudinal folds are preferably fastened to one another using rivets or screws through holes drilled in the longitudinal fold. In a further embodiment, the outer pipe has filter openings at least in the middle section, wherein the filter openings are radially spaced such that the filter openings serve as a filter for a filter well drill pipe. Depending on the length required for filtration, the outer pipe has filter openings over only part of the middle section up to the entire length of the drill pipe. The filter openings are preferably arranged continuously through the entire reinforced drill pipe, so that the inner pipe and possibly other inner layers also have filter openings.The filter openings are preferably in the form of slots or holes. Slots are particularly preferred as filter openings. The slots preferably have a length of 1 to 5 cm and a width of 2 to 5 mm. The filter openings are preferably evenly distributed and arranged in rows offset from one another. The filter openings can be created, for example, using high-pressure water jets or milling machines in the outer concrete pipe or in the entire drill pipe. In a preferred embodiment, the filter openings are arranged substantially at the same height as the recesses in the central section of the inner pipe. The filter openings can also be arranged only partially in the central section and do not have to be distributed over the entire central section.The only important thing is that if the filter openings in the outer pipe are not at the same height as the recesses in the inner pipe directly below them, the filter openings must extend continuously through the entire drill pipe. This ensures that when the reinforced drill pipe is used as a filter well pipe, the water to be filtered passes through the filter openings in the outer pipe and through the recesses or filter openings in the inner pipe into the interior of the drill pipe. In a filter well pipe, the inner pipe is preferably made of chrome steel. This is particularly preferred when filtering drinking water.

[0025] The upper connecting piece and the lower connecting piece serve to connect several drill pipes to each other, or to connect the drill pipe to a drive device or to a drilling or cutting head. The connecting pieces preferably have a coupling structure such that the upper connecting piece at the head end of a first drill pipe can be connected in a form-fitting manner in the longitudinal direction of the drill pipe to a lower connecting piece at the foot end of a second drill pipe connected above it. The coupling structure is arranged in the end region of each connecting piece and has, for example, a threaded connection, a flange, or a toothing.With a threaded connection using a rotary coupling, the head end and foot end of the drill pipes have a rotary coupling half, and two drill pipes are screwed together in a form-fitting manner in the longitudinal direction of the drill pipes by adjoining one another at the ends and then rotating the two rotary coupling halves relative to one another by a rotation angle. With a flange or a toothing, two drill pipes are inserted into one another by inserting the lower connecting piece at the foot end of a first drill pipe into an upper connecting piece at the head end of a second drill pipe connected below it in the longitudinal direction of the drill pipe. The upper and lower connecting pieces are designed to complement one another in such a way that a form-fitting connection is achieved.The connecting piece, which is inserted into an adjacent connecting piece, has no outer tube at the end of the drill pipe and is therefore formed solely from the material of the inner pipe. Several interconnected drill pipes are also referred to as an extended drill pipe or drill string. The drill string, consisting of several drill pipes, has the length of the desired borehole or concrete pile.

[0026] In one embodiment, the lower connecting piece at the base end of the drill pipe has a drill bit for drilling the drill pipe into a subsurface. Preferably, the lowest drill pipe of the drill string, also called the base pipe, has a drill bit at the base end. The base pipe with a drill bit at the base end preferably has no coupling structure on the lower connecting piece. The drill bit can, for example, have a toothed arrangement, a cutting structure, or be reinforced with abrasive particles, for example diamond particles. The drill pipe is suitable for drilling into various types of subsurface. Examples of the subsurface include cohesive soils such as loam, clay, marl, or silt, or non-cohesive soils such as sand, gravel, scree, or rock.

[0027] The invention also relates to the use of the reinforced drill pipe as a side wall of a concrete pile or anchor, wherein the inner pipe made of a metallic material or of an abrasion-resistant plastic, preferably of steel, serves as reinforcement.

[0028] Furthermore, the invention relates to a method for producing a concrete pile or an anchor, comprising the following steps:

[0029] (A) screwing a first reinforced drill pipe according to the invention, preferably with a drill bit at the base end, into a subsoil and removing the subsoil from the drill pipe to form a borehole;

[0030] (B) Form-fitting connection of the lower connecting piece of a further drill pipe according to the invention with the upper connecting piece of the first drill pipe below;

[0031] (C) Repeat steps (A) and (B) until the desired drilling depth is reached;

[0032] (D) leaving this extended drill pipe in the borehole; and then

[0033] (E) Filling the borehole with concrete and allowing the concrete to harden in the drill casings.

[0034] The reinforced drill pipes according to the invention can be used for the production of bored piles, concrete piles, and anchors of all kinds in both large and small boreholes. These drill pipes and the method according to the invention are particularly preferred for the production of cast-in-place concrete piles. Micropiles and anchors can also be produced with them.

[0035] Known methods for constructing bored piles or concrete piles include the Kelly drilling method, in which, however, separate reinforcing bars are inserted into the boreholes after drilling to reinforce the concrete piles, and the drill pipes are pulled up into the boreholes before the concrete hardens. The method according to the invention can be carried out in a similar way to the Kelly drilling method, with the difference that no reinforcing bars are required, and the drill pipes are left in the borehole before and after filling the borehole and are not pulled up. In this way, on the one hand, the reinforcement material can be saved and, at the same time, a considerable amount of time can be saved because there is no need to unload the reinforcement and install it separately, no need to pull the drill pipes back, no need to clean, load, transport, and repair the drill pipes, and thus less fuel consumption.Furthermore, concreting the bored pile is simplified because only the core of the concrete pile needs to be concreted, and no additional material is required due to the gap that would be created by pulling up the drill pipe. Furthermore, with conventional methods, there is a risk of soil extraction or constriction in soft soil when pulling up the drill pipe. This risk is eliminated with the inventive method because the drill pipe remains in the borehole, eliminating the need for ultrasonic tubes for testing, thus saving additional time. All of these advantages can halve or even reduce construction time. This leads to lower fuel consumption, less wear, and is overall more environmentally friendly. Thus, the reinforced drill pipe according to the invention creates a stable drill pipe that saves time and money and is therefore economically and ecologically sensible.

[0036] Combinations of two or more of the above-listed designs and variants are conceivable and claimed.

[0037] Further advantages of the invention will become apparent from the following description, in which the invention is explained in more detail with reference to embodiments shown in the drawings.

[0038] Short description of the figures Showing:

[0039] Fig. 1A is a schematic perspective view of a reinforced drill pipe with a drill bit, with the outer pipe partially removed,

[0040] Fig. 1 B a cross-section through the upper connecting piece of a drill pipe with coupling structure,

[0041] Fig. 2A is a longitudinal section through the drill pipe of Figure 1A with the outer pipe partially removed,

[0042] Fig. 2B is a schematic view of a drill pipe of Figure 1A on the outside of the drill pipe with the outer pipe partially removed,

[0043] Fig. 3 is a perspective view of a reinforced drill pipe of Figure 1A with a continuous outer pipe,

[0044] Fig. 4A is a schematic perspective view of a reinforced drill pipe with coupling structure on the upper and lower connectors,

[0045] Fig. 4B is a schematic perspective view of a reinforced drill pipe with coupling structure at the upper and lower connection piece consisting of two half shells,

[0046] Fig. 5A a cross-section through the upper connecting piece of a drill pipe made of two half shells,

[0047] Fig. 5B a section of Fig. 5A with the cross-section through the corresponding joints of the two half-shells,

[0048] Fig. 6A is a schematic perspective view of a half-shell of the drill pipe shown in Fig. 4B, Fig. 6B is a cross-section through the upper connecting piece of the drill pipe in Fig. 6A, and

[0049] Fig. 7 is a schematic perspective view of a filter well drill pipe.

[0050] In the figures, the same reference symbols are used for the same elements and explanations of a specific reference symbol apply to all figures unless expressly stated otherwise.

[0051] Embodiments of the invention

[0052] Figure 1A shows a schematic perspective view of a reinforced, here double-walled, drill pipe 1 with an inner pipe 3 made of steel and an outer pipe 4 made of concrete and a drill bit 11 at the base end 6 of the drill pipe 1. Such a drill pipe 1 is also called a base pipe and is used as the first and lowest drill pipe when drilling a borehole into a subsurface. The drill bit 11 has teeth 15 for drilling into the subsurface, is made entirely of steel and can additionally be reinforced with abrasive particles, for example diamond particles. The drill pipe 1 or base pipe shown here has a head end 4 and an upper connecting piece 5 arranged at the head end with a coupling structure 12 in the form of a toothing, wherein the coupling structure 12 with the toothing is arranged in the upper region, preferably in the upper half of the upper connecting piece 5.The toothing is arranged on the inside of the inner tube and serves to receive a complementary toothing of a drill pipe arranged above it (shown in Fig. 4), which has a coupling structure in the form of a toothing on the outside of the inner tube of the lower connecting piece at the base end of the drill pipe. The upper connecting piece 5 has four openings 13 in the area of ​​the coupling structure 12 for receiving bolts (not shown), which serve to fasten the nested drill pipes (not shown). The upper connecting piece 5 extends up to the middle section 8 with the recesses 10, wherein the upper connecting piece 5, with the exception of the openings 13, has a closed inner tube 3 and a closed outer tube 2. In the view shown in Figure 1A, the outer tube.

[0053] 2 in the area of ​​the middle section 8 removed for a better view of the inner pipe 3 in the middle section 8. In reality, the outer pipe 2 made of concrete completely encloses the inner pipe 3 from the head end 4 to the foot end 6. The outer pipe 3 preferably has a wall thickness of 7 to 12 cm.

[0054] The inner pipe 3 is preferably made of steel and has a plurality of recesses 10 with the same cross-sectional area in the casing wall in the middle section between the upper connecting piece 5 and the lower connecting piece 7. The inner pipe 3 preferably has a wall thickness of approximately 3 to 6 cm. The middle section 8 with the recesses 10 extends over at least a quarter of the total length of the drill pipe 1, preferably over at least half the total length of the drill pipe 1. In the embodiment shown in Figure 1A, the middle section 8 extends over half the total length of the drill pipe, and the upper section 5 and the lower section each extend over a quarter of the total length of the drill pipe 1.The lower connecting piece 7 has no coupling structure, but is formed by a continuous inner pipe 3 made of steel and a continuous outer pipe 2 made of concrete, with a drill bit 11 made of steel at the end of the lower connecting piece 7 of the drill pipe 1 .

[0055] The middle section 8 has several, preferably at least 100, recesses 10 in the jacket wall of the inner tube at the same distance

[0056] 3. The recesses 10 in the central section 8 are evenly distributed and equidistant from one another over the outer surface of the central section 8 of the inner tube 3, and the cross-sectional area of ​​the recesses 10 preferably has a diameter of 1 cm to 10 cm. The recesses 10 are enclosed by edges 14. The wall thickness of the edges 14 between the recesses 10 is the same everywhere and amounts to at most half, preferably at most one-fifth, of the diameter of the cross-sectional area of ​​the recesses 10. The evenly distributed recesses 10 have a grid structure in which the recesses are present as open cells between the solid edges 14, which are formed from the outer wall of the inner tube 3. The cross-sectional area of ​​the recesses 10 is hexagonal, and the grid structure is a hexagonal grid structure 9.The advantage of a hexagonal mesh structure 9 is that the greatest possible stability is achieved with the least possible material.

[0057] Figure 1B shows a cross-section through the upper connecting piece 5 of the drill pipe 1 with coupling structure 12. This shows the outer pipe 2, which encloses the inner pipe 3 with coupling structure 12.

[0058] Figure 2A shows a longitudinal section through the drill pipe 1, or base pipe, as described in Figure 1A, with the outer pipe partially removed. The middle section 8 of the inner pipe 3 with the hexagonal mesh structure 9, the recesses 10, and the edges 14 between the recesses 10 extends over half of the drill pipe 1. Above and below the middle section 8 are the upper connecting piece 5 with the coupling structure 12 on the inside of the upper connecting piece 5, and the lower connecting piece 7 with a drill bit 11 at the lower end of the lower connecting piece 7. The upper connecting piece 5 and the lower connecting piece 7 each extend over approximately one-quarter of the total length of the drill pipe 1. The coupling structure 12 with the toothing extends over the upper half of the upper connecting piece 5.

[0059] Figure 2B shows a side view of a drill pipe 1 as described in Figure 1A, with the outer pipe 2 partially removed.

[0060] Figure 3 shows a perspective view of a reinforced drill pipe 1, as described in Figure 1A, but with the outer pipe 2 shown continuously. The outer pipe 2 completely encloses the inner pipe 3. During the manufacture of the drill pipe 1, the preform for the outer pipe 2 made of concrete is cast around the inner pipe 3 made of steel, and the concrete flows into the open recesses 10 (not shown). As a result, the recesses fill with concrete, creating a stable drill pipe 1 with integrated reinforcement, a so-called reinforced concrete drill pipe.

[0061] Figure 4A is a schematic perspective view of a reinforced drill pipe 1', as described in Figure 1A, with the difference that the drill pipe 1' does not have a drill bit and that, in addition to the coupling structure 12 on the upper connecting piece 5, it has a coupling structure 12' on the lower connecting piece 7 instead of the drill bit. The coupling structure 12' on the lower connecting piece 7 is arranged on the outside of the steel inner pipe 3 and extends over the lower half of the lower connecting piece 7. The coupling structure 12' has a complementary shape to the coupling structure at the upper end of the upper connecting piece 5, such that the upper connecting piece 5 at the head end 4 of a first drill pipe 1 (shown in Figure 1A) can be positively connected in the longitudinal direction of the drill pipe to a lower connecting piece 7 at the foot end 6 of a second drill pipe 1' connected above it.The coupling structure 12' of the lower connecting piece 12' of the upper drill pipe 1' is pushed into the coupling structure 12 of the upper connecting piece 5 of the underlying drill pipe 1.

[0062] The outer tube 2 encloses the inner tube 3 in a drill pipe 1' with an upper inner coupling structure 12 and a lower outer coupling structure 12' only up to the upper end of the lower coupling structure 12', such that the lower coupling structure 12' can be pushed completely into a drill pipe 1 (shown in Figure 1A) connected thereunder.

[0063] The drill pipe 1' has the same recesses 10 in the central section 8 as described in Figure 1A. The recesses 10 are not visible in the illustration shown in Figure 4 because the outer pipe 2 is shown as a continuous section. The curly brackets represent the areas of the upper connecting piece 5, the central section 8, and the lower connecting piece 7, which are described in Figure 1A, with the difference that the lower connecting piece 7 does not have a drill bit, as shown in Figure 1A, but rather a lower coupling structure 12'.

[0064] Figure 4B shows a schematic perspective view of a reinforced drill pipe 1' as described in Fig. 4A, wherein the drill pipe 1' is made of two half-shells 16 (shown in Fig. 6A). The two half-shells 16 are each connected to each other via two offset longitudinal folds (17). The two longitudinal folds (17) are placed on top of each other in a form-fitting manner and fastened to each other via rivets or screws. The rivets or screws are guided through pre-drilled holes (18) in the longitudinal fold (17).

[0065] Figure 5A shows a cross-section through the upper connecting piece 5 of a drill pipe 1' as described in Figure 4B. The drill pipe 1' consists of two half-shells 16, which are connected to each other via a longitudinal fold 17.

[0066] Figure 5B shows a section of Figure 5A with the cross section through the corresponding longitudinal folds 17 of the two half-shells 16.

[0067] Figure 6A shows a schematic perspective view of a half-shell 16 of the drill pipe 16 described in Figure 4B. The half-shell 16 has a longitudinal fold 17 on each of the respective longitudinal edges, wherein the shape of the longitudinal folds 17 is offset from one another or opposite to one another, such that the longitudinal fold 17 of one half-shell 16 can be placed on top of a longitudinal fold 17 of the second half-shell 16 in a form-fitting manner and can be connected to one another via rivets or screws through drill holes 18,

[0068] Figure 6B shows a cross-section through the half-shell 16 of the drill pipe 1' as described in Figure 6A with the two longitudinal folds 17 opposite in shape to each other.

[0069] Figure 7 shows a filter well drill pipe 20. The filter well drill pipe 20 is a drill pipe 1' as described in Figure 4A, wherein the filter well drill pipe 20 additionally has filter openings 19 in the form of slots 21 in the central section 8. The slots 21 are arranged radially spaced apart. The distances between the individual slots 21 are evenly distributed and arranged offset from one another in rows. The filter openings 19 are arranged in the central section 8 essentially at the same height as the recesses 10 of the inner pipe 3 (shown in Figures 1 and 2). They can also be arranged only partially in the central section 8 or across the entire drill pipe 1'. The only essential thing is that when the reinforced drill pipe is used as a filter well drill pipe, the water to be filtered reaches the interior of the drill pipe through the filter openings in the outer pipe and through the recesses or filter openings in the inner pipe.

[0070] List of reference symbols

[0071] 1 , 1' Reinforced drill pipe

[0072] 2 outer pipe

[0073] 3 inner tube

[0074] 4 headboard

[0075] 5 upper connecting piece

[0076] 6 foot end

[0077] 7 lower connecting piece

[0078] 8 middle section

[0079] 9 Network structure

[0080] 10 recess

[0081] 11 core bit

[0082] 12, 12' coupling structure

[0083] 13 Opening

[0084] 14 edge

[0085] 15 teeth

[0086] 16 half shells

[0087] 17 Longitudinal fold

[0088] 18 Drill hole in longitudinal fold

[0089] 19 Filter opening

[0090] 20 filter well drill pipes

[0091] 21 slot

Claims

Patent claims 1. Reinforced drill pipe (1, 1') for supporting boreholes for the production of concrete piles or anchors, with a head end (4) and an upper connecting piece (5) arranged at the head end (4), and with a foot end (6) and a lower connecting piece (5) arranged at the foot end (6), wherein the drill pipe (1, 1') has at least one outer pipe (2) made of concrete and at least one inner pipe (3) made of a metallic material or of an abrasion-resistant plastic arranged therein, wherein the drill pipe (1, 1') has a central section (8) between the upper connecting piece (5) and the lower connecting piece (7), characterized in that the inner pipe (3) made of steel has a plurality of recesses (10) with the same cross-sectional area in the central section (8) in the casing wall, the plurality comprising at least ten recesses (10).and wherein the middle section (8) with the recesses (10) extends over at least a quarter of the total length of the drill pipe (1, 1') and over a maximum of seven-eighths of the total length of the drill pipe (1, 1').

2. Reinforced drill pipe (1, 1') according to claim 1, characterized in that the cross-sectional area of the recesses (10) is round, oval or square.

3. Reinforced drill pipe (1, 1') according to claim 1 or 2, characterized in that the cross-sectional area of the recesses (10) is hexagonal and the central section (8) has a hexagonal network structure (9).

4. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the recesses (10) in the central section (8) are arranged evenly distributed over the outer surface of the inner pipe (3).

5. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the middle section (8) with the recesses (10) extends over a maximum of two thirds of the total length of the drill pipe (1, 1').

6. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the recesses (10) in the central section (8) have a diameter of 4 mm to 10 cm.

7. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the middle section (8) has three to thirty recesses (10) on an area of 10x10 cm.

8. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the middle section (8) has several sections with a plurality of recesses (10) and sections without recesses in between.

9. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the drill pipe (1, 1') or the inner pipe (3) and the outer pipe (2) have a continuous round cross-section and the inner pipe (3) is arranged concentrically within the outer pipe (2).

10. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the inner pipe (3) is made of steel.

11. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the outer pipe (2) has filter openings (19) at least in the middle section (8), wherein the filter openings (19) are radially spaced such that the filter openings (19) serve as a filter for a filter well drill pipe (20).

12. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the upper connecting piece (5) and / or the lower connecting piece (7) has a coupling structure (12, 12') such that the upper connecting piece (5) at the head end (4) of a first drill pipe (1) is positively engaged in Longitudinal direction of the drill pipe (1) with a lower connecting piece (7) at the foot end (6) of a second drill pipe (1') connected above it.

13. Reinforced drill pipe (1, 1') according to one of the preceding claims, characterized in that the lower connecting piece (7) at the foot end (6) of the drill pipe (1) has a drill bit (11) for drilling the drill pipe (1) into a subsoil.

14. Use of a reinforced drill pipe (1, 1') according to one of the preceding claims as a side wall of a concrete pile or anchor, wherein the inner pipe (3) made of a metallic material or of an abrasion-resistant plastic serves as reinforcement.

15. A method for producing a concrete pile or anchor, comprising the following steps: (A) screwing a first reinforced drill pipe (1) according to one of claims 1 to 13 into a subsoil and conveying the subsoil out of the drill pipe (1) to form a borehole; (B) positive connection of the lower connecting piece (7) of a further drill pipe (1 ') according to one of claims 1 to 11 with the upper connecting piece (5) of the first drill pipe (1 ); (C) Repeat steps (A) and (B) until the desired drilling depth is reached; (D) Remaining this extended drill pipe (1 , 1 ') in the borehole; and then (E) Filling the borehole with concrete and allowing the concrete to harden in the drill pipes (1 , 1 ').

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