Drilling device

Description

[0001] The present invention relates to a drilling device for in situ mixing of soil with a binder to form in each case a pile in the ground, comprising a drivable shaft with a bottom end, means mounted at the bottom end of the shaft for loosening the soil and injection means for injecting the binder into the loosened soil, according to the preamble of claim 1.

[0002] Such drilling devices are generally known and are typically used in ground improvement and the construction of earth-retaining walls, such as a sheet piling for a pit excavation. An example of such a drilling device is described in, among others, US 5,368,415. The known devices generally have the drawback that they display problems when adjacent, possibly already partly hardened piles must be partly overcut in order to form a closed wall. In addition, many helical mixing blades are usually required to achieve a good mixing of the soil with the binder, particularly when working in clay soils.

[0003] JP 59088532 discloses a drilling device according to the preamble of claim 1 to construct an underground structure of a high bearing strength by a method in which as soon as the ground is excavated, a fluid solidifying agent is injected to form a pillar-shaped fluid body, the peripheral part of the pillar-shaped fluid body is preferentially solidified, and a steel material is penetrated into the central part of the fluid body.

[0004] US 4,902,172 discloses a multi-shaft drilling installation comprising two drilling devices mounted such that partly overlapping piles can be formed.

[0005] The invention has for its object to provide a drilling device of the type stated in the preamble, with a simple structure, with which piles can be formed by in situ mixing, and adjacent piles can be overcut without problem.

[0006] For this purpose the drilling device according to the invention is distinguished by the features of the characterizing portion of claim 1. A bore-crown is mounted on the shaft, which is provided on at least a part of its periphery with cutting means for overcutting a pile adjacent to the pile for forming and that the means for loosening the soil comprise an array of first teeth arranged on at least one arm extending between the shaft and the bore-crown and oriented obliquely downward from the bore-crown in the direction of the bottom end. By providing a bore-crown adjacent piles can be overcut, while a pile is simultaneously formed by in situ mixing.

[0007] According to a preferred embodiment, the cutting means comprise a number of cutting teeth distributed regularly along the periphery of the bore-crown such that sufficiently neat outer contours are obtained for the pile.

[0008] The bore-crown is preferably mounted on the shaft by means of a bracket. This bracket provides for a strengthening of the drilling device and ensures a further mixing of the material situated above the bore-crown as seen in axial direction.

[0009] The means for loosening the soil comprise an array of first teeth which are arranged at a distance from the shaft and which are located substantially under the bore-crown. These teeth have substantially the function of a rake with which the soil is loosened. These teeth must be oriented such that optimum loosening of the soil is obtained, and will for instance be oriented substantially perpendicularly of the at least one arm.

[0010] The first teeth are arranged on at least one arm which extends substantially between the shaft and the bore-crown. In this manner the teeth can readily be placed at different distances from the shaft.

[0011] The means for loosening the soil can also comprise a number of second teeth, which are arranged around the shaft close to the bottom end thereof. These second teeth serve for the first central cutting into the soil for loosening.

[0012] According to a further developed embodiment, there are provided spray nozzles for enhancing loosening and mixing of the soil. In order to also achieve a good mixing of the material above the bore-crown, and to avoid the drilling device getting stuck when used in clay soils, it is recommended to provide first spray nozzles which are oriented substantially upward from the plane of the bore-crown. These spray nozzles can for instance be arranged along the periphery of the bore-crown.

[0013] Second spray nozzles can further be provided in the vicinity of the means for loosening the soil. A first number thereof can thus be arranged for instance close to the first teeth and a second number thereof close to the second teeth. These second spray nozzles likewise contribute toward a good mixing of the soil with the binder.

[0014] According to yet another variant, mixing means for mixing the loosened soil can be provided above the bore-crown as seen in axial direction. These mixing means can for instance comprise mixing arms or helical mixing blades.

[0015] Drive means are preferably provided for driving the shaft at a speed of 50 to 180 revolutions per minute. This is a speed which is higher than the usual speed for normal drilling installations and which ensures that a good mixing is achieved.

[0016] The invention further relates to a multi-shaft drilling installation comprising at least two drilling devices according to the invention, wherein the two drilling devices are mounted such that partially overlapping piles can be formed.

[0017] According to a preferred embodiment, the shafts of the at least two drilling devices are accommodated in a fixed support structure. This support structure provides for additional stabilization of the drilling devices, particularly when drilling takes place in difficult soils.

[0018] According to a possible embodiment, the bore-crown of a first drilling device, as seen in the plane of the shafts, is mounted higher than the bore-crown of a second adjacent drilling device, wherein the bore-crowns partly overlap each other as seen in a perpendicular projection onto a plane lying perpendicularly of the shafts.

[0019] In a first drilling device with a bracket this bracket preferably has axial dimensions which are considerably greater than those of the bracket of an adjacent second drilling device. In this manner overlapping piles can be formed without the brackets of two adjacent drilling devices impeding each other.

[0020] According to a further developed embodiment of this variant, the second drilling device with the bracket with smaller axial dimensions is provided above the bracket with mixing arms mounted on its shaft. These mixing arms compensate the loss of mixing capacity resulting from the smaller bracket.

[0021] The first drilling device is further preferably axially displaceable relative to the second drilling device, wherein this axial displacement can be controlled as a function of the diameter of the piles for forming.

[0022] Finally, it is advantageous in some cases when the bottom end of the shaft of the first drilling device with larger bracket is located lower than the bottom end of the adjacent second drilling device, although this will of course depend on the dimensions of the two drilling devices. With this measure a better guiding of the drilling installation is after all achieved since the first drilling device engages in the as yet unloosened soil.

[0023] The invention will now be further elucidated on the basis of the following figure description of a number of exemplary embodiments, which have in no way a limiting character, and which are illustrated in the accompanying figures, in which:

figure 1 is a perspective view of a first embodiment of a drilling device according to the invention;

figure 2 is a perspective view of a second embodiment of a drilling device according to the invention;

figure 3 is a schematic front view of a third embodiment of a drilling device according to the invention;

figure 4 is a schematic bottom view of the third embodiment of figure 3;

figure 5 is a perspective view of a first embodiment of a two-shaft drilling installation according to the invention;

figure 6 is a schematic front view of a second embodiment of a two-shaft drilling installation according to the invention;

figure 7 is a schematic front view of an embodiment of a three-shaft drilling installation according to the invention.

[0024] Figure 1 shows a drilling device for in situ mixing of soil with a binder for the purpose of forming a pile in the ground. In the figure can be seen a rotatingly drivable shaft 1 with a bottom end 2. Mounted on the side of bottom end 2 of shaft 1 are means for loosening the soil, which here consist of:

• an array of first teeth 3 which are arranged at a distance from the shaft and which are arranged on two arms 5;
• a number of mixing blades 9 which are arranged around shaft 1, close to the bottom end thereof.

[0025] Further mounted on the shaft is a bore-crown 4 which is provided on its periphery with cutting teeth 6 for overcutting a pile adjacent to the pile for forming. The cutting teeth can for instance take the form of a number of cutting blocks oriented substantially axially downward. This overcutting will be better understood with reference to figures 8a and 8b, which show how a series of mutually adjacent piles can be obtained using a drilling device according to the invention. The bore-crown is mounted on shaft 1 by means of a bracket 7. This bracket brings about strengthening of the whole and during drilling also contributes toward a further mixing of the binder with the soil above bore-crown 4.

[0026] In the embodiments shown in figures 1, 2 and 3 the bracket has a longer form in axial direction than is usual in order to enhance this mixing. This bracket can however also be given a shorter form, in which case it is recommended to provide additional mixing means. As shown in the schematic view of a two-shaft drilling installation of figure 6, in the case of second drilling device B mixing arms 10a-c are provided as seen in axial direction above bracket 7', which arms partly fulfill the function of the larger bracket 7 of first drilling device A.

[0027] The binder is injected through hollow shaft 1 into the loosened soil (at 16 in figure 3) at the bottom of this hollow shaft. This is a known principle for drilling devices for in situ mixing, and will therefore not be described here in detail.

[0028] In order to further enhance loosening of the soil and/or mixing of the soil with the binder, binder can be injected at different positions in the vicinity of the drilling device. In the variants shown in figures 1-4 this takes place using a number of spray nozzles:

• first spray nozzles 12 (shown in broken lines in figure 3), each with an outlet and oriented substantially upward relative to the bore-crown. In the shown embodiments these are arranged on the inside of bore-crown 4, but these spray nozzles can also be arranged in other manner, wherein all that is important is that they spray in the direction of the matter located above bore-crown 4;
• second spray nozzles 13, 14 in the vicinity of means 5, 8, 9 for loosening the soil, of which a number of second spray nozzles 13 are arranged between and/or behind the first teeth, and another number of second spray nozzles 14 are provided close to mixing blades 9 (figure 1) or close to the second teeth 8 (figures 2-4).

[0029] Figures 5 and 6 illustrate embodiments of a two-shaft drilling device according to the invention. This comprises a first drilling device A, which has already been explained with reference to figures 2-4, and a second drilling device B. The second drilling device B differs from the first drilling device A in that its bracket 7', as seen in axial direction, is shorter than bracket 7 of the first drilling device. In this manner brackets 7 and 7' do not touch each other during the rotation of shafts 1, 1'. These two drilling devices are mounted such that two partially overlapping piles can be formed.

[0030] The method for forming two such piles is illustrated in figures 8a and 8b, which show how a series of adjacent piles can be arranged to form for instance a sheet piling for a pit excavation. The figure shows the step in which two piles 20a and 20b are formed simultaneously by the two-shaft drilling installation. A pile 20c, which has been formed together with pile 20d during a previous step, is herein partly overcut in grey coloured area 21 of pile 20c. This overcutting takes place without problem owing to the presence of bore-crown 4' of the second drilling device B.

[0031] The drivable shafts 1, 1' of drilling devices A, B of figures 5 and 6 are accommodated in a fixed support structure 15 which imparts extra stability to the whole. As seen in axial direction, bore-crown 4 of the first drilling device A is in a higher position than bore-crown 4' of the second adjacent drilling device B and, as seen in a perpendicular projection onto a plane perpendicularly of the shafts, bore-crowns 4, 4' overlap each other partly to form two partially overlapping piles 20a, 20b. Additional mixing blades 10a-c are further provided in the second drilling device B, above bracket 7', so as to further enhance the mixing.

[0032] Figure 7 finally shows a three-shaft drilling installation comprising three drilling devices A, B, C. The skilled person will understand that, depending on the desired applications and the available drive means, one-, two-, three- or multi-shaft installations can be provided, and that the invention is not limited to the above exemplary embodiments, but is defined by the claims.

Claims

1. Drilling device for in situ mixing of soil with a binder to form a pile in the ground, comprising

- a drivable shaft (1) with a bottom end (2),

- means mounted at the bottom end of the shaft for loosening the soil;

- injection means for injecting the binder into the loosened soil;

a bore-crown (4) mounted on the shaft, which bore-crown is provided on at least a part of its periphery with cutting means (6); wherein the means for loosening the soil comprise an array of first teeth (3) arranged at a distance from the shaft;
characterized in that the array of first teeth is located under the bore-crown, wherein the first teeth (3) are arranged on at least one arm (5) which extends between the shaft and the bore-crown and which is oriented obliquely downward from the bore-crown in the direction of the bottom end.

2. Drilling device as claimed in claim 1, characterized in that the cutting means (6) comprise cutting teeth distributed regularly along the periphery of the bore-crown.

3. Drilling device as claimed in claim 1 or 2, characterized in that the bore-crown (4) is mounted on the shaft by means of a bracket (7).

4. Drilling device as claimed in claim 1, characterized in that the first teeth (3) are oriented perpendicularly of the at least one arm (5).

5. Drilling device as claimed in claim 4, characterized in that the means for loosening the soil comprise a number of second teeth (8), which are arranged around the shaft close to the bottom end thereof.

6. Drilling device as claimed in any of the foregoing claims, characterized in that spray nozzles (12, 13, 14) are provided for the purpose of enhancing loosening and mixing of the soil.

7. Drilling device as claimed in claim 6, characterized in that first spray nozzles (12) are provided which are oriented upward from the plane of the bore-crown.

8. Drilling device as claimed in claim 7, characterized in that the first spray nozzles are arranged along the periphery of the bore-crown.

9. Drilling device as claimed in any of the claims 6-8, characterized in that second spray nozzles (13, 14) are provided in the vicinity of the means for loosening the soil.

10. Drilling device as claimed in claim 9 and claim 5, characterized in that a number of second spray nozzles are provided on the at least one arm (5) on which the first teeth (3) are arranged.

11. Drilling device as claimed in claims 5 and 9 or 10, characterized in that a number of second spray nozzles are provided close to the second teeth (8).

12. Drilling device as claimed in any of the foregoing claims, characterized in that mixing means (9) for mixing the loosened soil are provided above the bore-crown.

13. Drilling device as claimed in claim 12, characterized in that the mixing means comprise mixing arms mounted on the shaft.

14. Drilling device as claimed in any of the foregoing claims, characterized in that drive means are provided for driving the shaft at a speed of 50 to 180 revolutions per minute.

15. Multi-shaft drilling installation, comprising at least two drilling devices (A, B) as claimed in any of the foregoing claims, wherein the two drilling devices are mounted such that partially overlapping piles can be formed.

16. Multi-shaft drilling installation as claimed in claim 15, characterized in that the shafts of the at least two drilling devices are accommodated in a fixed support structure.

17. Multi-shaft drilling installation as claimed in claim 15 or 16, characterized in that the bore-crown (4) of a first drilling device (A), as seen in the plane of the shafts, is mounted higher than the bore-crown (4') of a second adjacent drilling device (B) of the at least two drilling devices, wherein the bore-crowns (4,4') partly overlap each other as seen in a perpendicular projection onto a plane lying perpendicularly of the shafts.

18. Multi-shaft drilling installation as claimed in any of the claims 15-17, characterized in that the bracket (7) of a first drilling device of the at least two drilling devices has axial dimensions which are greater than those of an adjacent second drilling device.

19. Multi-shaft drilling installation as claimed in claim 18, characterized in that the second drilling device with the bracket (7') of smaller axial dimensions is provided above the bracket (7') with mixing blades (10a, 10b, 10c) mounted on its shaft.

20. Multi-shaft drilling installation as claimed in any of the claims 15-19, characterized in that the bottom end of the shaft of a first drilling device of the at least two drilling devices is located further downward relative to the bottom end of an adjacent second drilling device.

21. Multi-shaft drilling installation as claimed in any of the claims 15-20, characterized in that a first drilling device of the at least two drilling devices is axially displaceable relative to an adjacent second drilling device.

Ansprüche

1. Bohrvorrichtung zum In-Situ-Mischen von Erde mit einem Bindemittel, um einen Pfahl im Boden zu bilden, aufweisend

- eine antreibbare Welle (1) mit einem unteren Ende (2),

- Mittel zum Lockern der Erde, die an dem unteren Ende (2) der Welle montiert sind,

- Einbringmittel zum Einbringen des Bindemittels in die gelockerte Erde hinein,

eine Bohrkrone (4), die an der Welle montiert ist, wobei die Bohrkrone zumindest an einem Teil ihres Umfangs mit Schneidemitteln (6) versehen ist, wobei die Mittel zum Lockern der Erde einen Bereich von ersten Zähnen (3) aufweisen, der in einem Abstand von der Welle angeordnet ist, dadurch gekennzeichnet, dass sich der Bereich von ersten Zähnen unter der Bohrkrone befindet, wobei die ersten Zähne (3) an zumindest einem Arm (5) angeordnet sind, welcher sich zwischen der Welle und der Bohrkrone erstreckt und welcher von der Bohrkrone in der Richtung des unteren Endes schräg nach unten orientiert ist.

2. Bohrvorrichtung gemäß Anspruch 1, dadurch gekennzeichnet, dass die Schneidemittel (6) Schneidezähne aufweisen, die regelmäßig entlang des Umfangs der Bohrkrone angeordnet sind.

3. Bohrvorrichtung gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Bohrkrone (4) an der Welle montiert ist mittels einer Backe (7).

4. Bohrvorrichtung gemäß Anspruch 1, dadurch gekennzeichnet, dass die ersten Zähne (3) rechtwinklig von dem zumindest einem Arm (5) angeordnet sind.

5. Bohrvorrichtung gemäß Anspruch 4, dadurch gekennzeichnet, dass die Mittel zum Lockern der Erde eine Anzahl von zweiten Zähnen (8), welche um die Welle nahe bei dem unteren Ende davon angeordnet sind, aufweisen.

6. Bohrvorrichtung gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass Sprühdüsen (12, 13, 14) bereitgestellt sind zum Zweck des Verbesserns des Lösens und Mischens der Erde.

7. Bohrvorrichtung gemäß Anspruch 6, dadurch gekennzeichnet, dass erste Sprühdüsen (12) bereitgestellt sind, die von der Ebene der Bohrkrone nach oben orientiert sind.

8. Bohrvorrichtung gemäß Anspruch 7, dadurch gekennzeichnet, dass die ersten Sprühdüsen entlang des Umfangs der Bohrkrone angeordnet sind.

9. Bohrvorrichtung gemäß einem der Ansprüche 6 bis 8, dadurch gekennzeichnet, dass die zweiten Sprühdüsen (13, 14) in der Nähe der Mittel zum Lockern der Erde bereitgestellt sind.

10. Bohrvorrichtung gemäß Anspruch 9 und Anspruch 5, dadurch gekennzeichnet, dass eine Anzahl von zweiten Sprühdüsen an dem zumindest einem Arm (5), an welchem die ersten Zähne (3) angeordnet sind, bereitgestellt sind.

11. Bohrvorrichtung gemäß Ansprüchen 5 und 9 oder Anspruch 10, dadurch gekennzeichnet, dass eine Anzahl von zweiten Sprühdüsen nahe bei den zweiten Zähnen (8) bereitgestellt sind.

12. Bohrvorrichtung gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass Misch-Mittel zum Mischen der gelockerten Erde über der Bohrkrone bereitgestellt sind.

13. Bohrvorrichtung gemäß Anspruch 12, dadurch gekennzeichnet, dass die Misch-Mittel Mischarme, die an der Welle montiert sind, aufweisen.

14. Bohrvorrichtung gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass Antriebsmittel zum Antreiben der Welle mit einer Drehzahl von 50 bis 180 Umdrehungen pro Minute bereitgestellt sind.

15. Multi-Wellen-Bohrinstallation, aufweisend zumindest zwei Bohrvorrichtungen (A,B) gemäß irgendeinem der vorstehenden Ansprüche, wobei die beiden Bohrvorrichtungen so montiert sind, dass teilweise überlappende Pfähle gebildet werden können.

16. Multi-Wellen-Bohrinstallation gemäß Anspruch 15, dadurch gekennzeichnet, dass die Wellen der zumindest zwei Bohrvorrichtungen in einer festen Stützstruktur aufgenommen sind.

17. Multi-Wellen-Bohrinstallation gemäß Anspruch 15 oder 16, dadurch gekennzeichnet, dass die Bohrkrone (4) einer ersten Bohrvorrichtung (A), in der Ebene der Wellen betrachtet, höher montiert ist als eine Bohrkrone (4') einer zweiten benachbarten Bohrvorrichtung (B) der zumindest zwei Bohrvorrichtungen, wobei die Bohrkronen (4, 4') einander, in einer rechtwinkligen Projektion auf eine Ebene, die rechtwinklig zu den Wellen liegt, betrachtet, teilweise überlappen.

18. Multi-Wellen-Bohrinstallation gemäß einem der Ansprüche 15 bis 17, dadurch gekennzeichnet, dass die Backe (7) einer ersten Bohrvorrichtung der zumindest zwei Bohrvorrichtungen Axialabmessungen hat, die größer sind als diejenigen einer benachbarten zweiten Bohrvorrichtung.

19. Multi-Wellen-Bohrinstallation gemäß Anspruch 18, dadurch gekennzeichnet dass die zweite Bohrvorrichtung mit der Backe (7') mit kleineren Axialabmessungen über der Backe (7') mit Mischklingen (10a, 10b, 10c) bereitgestellt ist, die an der Welle davon montiert sind.

20. Multi-Wellen-Borinstallation gemäß einem der Ansprüche 15 bis 19, dadurch gekennzeichnet, dass das untere Ende der Welle einer ersten Bohrvorrichtung der zumindest zwei Bohrvorrichtungen relativ zu dem unteren Ende einer benachbarten zweiten Bohrvorrichtung weiter unten angeordnet ist.

21. Multi-Wellen-Bohrinstallation gemäß einem der Ansprüche 15 bis 20, dadurch gekennzeichnet, dass eine erste Bohrvorrichtung der zumindest zwei Bohrvorrichtungen axial versetzbar ist relativ zu einer benachbarten zweiten Bohrvorrichtung.

Revendications

1. Dispositif de forage destiné à mélanger in situ de la terre et un liant de façon à former une pile dans le sol, comprenant :

- un arbre qui peut être entraîné (1) avec une extrémité inférieure (2) ;

- des moyens montés au niveau de l'extrémité inférieure de l'arbre, destinés à ameublir la terre ;

- des moyens d'injection destinés à injecter le liant dans la terre ameublie ;

- une couronne de forage (4) montée sur l'arbre, laquelle couronne de forage est dotée, sur une partie au moins de sa périphérie, de moyens tranchants (6) ;

dans lequel les moyens destinés à ameublir la terre, comprennent un ensemble de premières dents (3) qui est agencé à une distance à partir de l'arbre ;
caractérisé en ce que l'ensemble de premières dents se situe sous la couronne de forage, dans lequel les premières dents (3) sont agencées sur un bras (5) au moins qui s'étend entre l'arbre et la couronne de forage, et qui est orienté de manière oblique vers le bas à partir de la couronne de forage dans la direction de l'extrémité inférieure.

2. Dispositif de forage selon la revendication 1, caractérisé en ce que les moyens tranchants (6) comprennent des dents tranchantes réparties de manière régulière le long de la périphérie de la couronne de forage.

3. Dispositif de forage selon la revendication 1 ou 2, caractérisé en ce que la couronne de forage (4) est montée sur l'arbre à l'aide d'un support (7).

4. Dispositif de forage selon la revendication 1, caractérisé en ce que les premières dents (3) sont orientées de manière perpendiculaire par rapport au, ou aux, bras (5).

5. Dispositif de forage selon la revendication 4, caractérisé en ce que les moyens destinés à ameublir la terre comprennent un certain nombre de secondes dents (8), qui sont agencées autour de l'arbre à proximité de son extrémité inférieure.

6. Dispositif de forage selon l'une quelconque des revendications précédentes, caractérisé en ce que des buses de pulvérisation (12, 13, 14) sont prévues de façon à améliorer l'ameublissement et le mélange de la terre.

7. Dispositif de forage selon la revendication 6, caractérisé en ce que lesdites premières buses de pulvérisation (12) sont prévues avec une orientation vers le haut à partir du plan de la couronne de forage.

8. Dispositif de forage selon la revendication 7, caractérisé en ce que les premières buses de pulvérisation sont agencées le long de la périphérie de la couronne de forage.

9. Dispositif de forage selon l'une quelconque des revendications 6 à 8, caractérisé en ce que des secondes buses de pulvérisation (13, 14) sont prévues à proximité des moyens destinés à ameublir la terre.

10. Dispositif de forage selon la revendication 9 et la revendication 5, caractérisé en ce qu'un certain nombre de secondes buses de pulvérisation sont prévues sur le ou les bras (5) sur lequel ou lesquels sont agencées les premières dents (3).

11. Dispositif de forage selon les revendications 5 et 9 ou 10, caractérisé en ce qu'un certain nombre de secondes buses de pulvérisation sont prévues à proximité des secondes dents (8).

12. Dispositif de forage selon l'une quelconque des revendications précédentes, caractérisé en ce que des moyens de mélange (9) destinés à mélanger la terre ameublie, sont prévus au-dessus de la couronne de forage.

13. Dispositif de forage selon la revendication 12, caractérisé en ce que les moyens de mélange comprennent des bras de mélange montés sur l'arbre.

14. Dispositif de forage selon l'une quelconque des revendications précédentes, caractérisé en ce que des moyens d'entraînement sont prévus de façon à entraîner l'arbre à une vitesse comprise entre 50 et 180 tours par minute.

15. Installation de forage à plusieurs arbres, comprenant au moins deux dispositifs de forage (A, B) selon l'une quelconque des revendications précédentes, dans laquelle les deux dispositifs de forage sont montés de façon à pouvoir former des piles qui se chevauchent en partie.

16. Installation de forage à plusieurs arbres selon la revendication 15, caractérisée en ce que les arbres des deux dispositifs de forage au moins sont reçus dans une structure de support fixe.

17. Installation de forage à plusieurs arbres selon la revendication 15 ou la revendication 16, caractérisée en ce que la couronne de forage (4) d'un premier dispositif de forage (A), quand on regarde dans le plan des arbres, est montée plus haut que la couronne de forage (4') d'un second dispositif de forage adjacent (B) des au moins deux dispositifs de forage, dans laquelle les couronnes de forage (4, 4') se chevauchent en partie l'une l'autre quand on regarde dans une projection perpendiculaire sur un plan qui se situe de manière perpendiculaire par rapport aux arbres.

18. Installation de forage à plusieurs arbres selon l'une quelconque des revendications 15 à 17, caractérisée en ce que le support (7) d'un premier dispositif de forage des deux dispositifs de forage au moins, présente des dimensions axiales qui sont supérieures à celles d'un second dispositif de forage adjacent.

19. Installation de forage à plusieurs arbres selon la revendication 18, caractérisée en ce que le second dispositif de forage avec le support (7') qui présente de plus petites dimensions axiales, est disposé au-dessus du support (7') avec des lames de mélange (10a, 10b, 10c) montées sur son arbre.

20. Installation de forage à plusieurs arbres selon l'une quelconque des revendications 15 à 19, caractérisée en ce que l'extrémité inférieure de l'arbre d'un premier dispositif de forage des deux dispositifs de forage au moins, se situe davantage vers le bas par rapport à l'extrémité inférieure d'un second dispositif de forage adjacent.

21. Installation de forage à plusieurs arbres selon l'une quelconque des revendications 15 à 20, caractérisée en ce qu'un premier dispositif de forage des deux dispositifs de forage au moins, peut être déplacé de manière axiale par rapport à un second dispositif de forage adjacent.

Drawing