Apparatus for improving ground

Description

[0001] The present invention relates to an apparatus for improving ground comprising a rod to be inserted into the ground to a predetermined depth, a bit attached to the forward end of the rod and rotatable when the rod is inserted into the ground to guide the rod into the ground, the bit having a discharge outlet for injecting a ground improving liquid agent into an agitated portion of the ground while the rod is withdrawn from the ground with the bit held in continued rotation, and at least one arm cutter having a discharge outlet and attached to a lower portion of the rod for agitating the ground and simultaneously injecting the ground improving agent into the agitated ground portion when the rod is withdrawn from the ground, a first drive assembly being provided for rotating the arm cutter about its own axis in a manner remotely controllable above ground when the rod is inserted into and withdrawn from the ground.

[0002] Such ground improving apparatus are known which comprise a rod having a bit at its forward end, and an arm cutter attached to the rod, retractable into or extendable from the rod and rotatable about its own axis by being controlled above ground. When the rod is inserted into the ground to be improved to a predetermined depth by being guided by the rotation of the bit, the arm cutter retracted in its stowed position during the insertion is turned through 90° to a position at right angles to the rod while being rotated. Subsequently while slowly lifting the rod with the arm cutter held in rotation to agitate the neighbouring soil, a ground improving liquid agent is injected into the agitated ground portion from openings in the arm cutter and the bit to improve the ground.

[0003] Since the known apparatus is adapted to agitate the ground and, at the same time, fill the agitated portion of the ground with the injected liquid agent to improve the ground, the apparatus has the advantage of being capable of effectively improving the ground with stability without being influenced by the quality of the soil.

[0004] However, such known apparatus is adapted to merely improve the portion of ground through which the arm cutter passes in rotation, so that the width of ground improved at a time approximately corresponds to the diameter of cross section of the arm cutter and is not very large. Accordingly if the apparatus is used for improving the ground over a large width or for improving soft ground which must be treated over a wide area, the apparatus must be operated repeatedly many times to result in a low work efficiency. Thus the apparatus is substantially unusable for such purposes.

[0005] Further because the arm cutter is adapted to be stowed in or extended from the rod, the apparatus of the type described is complex in construction and is also complicated to operate owing to the necessity of turning the arm cutter through 90° in the ground from its stowed position to the extended position at right angles to the rod.

[0006] An object of the present invention is to provide a ground improving apparatus of the type described which achieves such a high work efficiency that the ground can be improved at a time over a circular area having a radius corresponding to the length of an arm cutter.

[0007] Another object of the invention is to provide a ground improving apparatus of the type described which is simple in construction and easy to operate for the improvement of the ground.

[0008] To achieve this, the apparatus of the invention is characterized in that the arm cutter extends permanently from the lower portion of the rod at right angles therewith and a second drive assembly is provided for revolving the arm cutter about the axis of the rod in a manner remotely controllable above ground when the rod is withdrawn from the ground.

[0009] With the ground improving apparatus of the present invention, the bit and the arm cutter are rotated each about its own axis by the first drive assembly when the rod is to be inserted into the ground. The bit and the arm cutter thus rotated excavate the ground, guiding the rod into the ground.

[0010] When the rod is inserted into the ground to a predetermined depth, the arm cutter is revolved about the axis of the guide rod by the second drive assembly while maintaining the bit and the arm cutter in rotation about their axes. The rotation and revolution of the arm cutter agitate a circular portion of the ground having a radius corresponding to the length of the arm cutter.

[0011] While slowly lifting the rod with the bit maintained in rotation and the arm cutter in rotation and revolution, a ground improving liquid agent is injected from the discharge outlets into the portion of the ground agitated by the rotation, whereby the ground can be improved with a greatly increased efficiency over a wide area having a radius corresponding to the length of the arm cutter.

[0012] Further because the arm cutter in rotation progressively excavate the ground with the insertion of the rod into the ground, there is no need to provide a complex structure wherein the arm cutter is adapted to be stowed in the rod and made extendable therefrom. Accordingly the present apparatus is simple in construction and easy to operate, assuring an improved work efficiency.

[0013] Embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

Fig. 1 is a front view showing an apparatus of the single arm cutter type embodying the invention;

Fig. 2 is an enlarged view in vertical section of arm cutters shown in Fig. 1;

Fig. 3 is a front view showing the apparatus of Fig. 1 in operation to improve the ground;

Fig. 4 is a diagram showing the position of a cleaning arm while a rod is being lifted during the operation of the apparatus of Fig. 1;

Fig. 5 is a plan view schematically showing ground portions improved by the apparatus of Fig. 1 and formed continuously;

Fig. 6 is a similar view showing ground portions improved by the apparatus of Fig. 1 and formed continuously in a different arrangement;

Fig. 7 is a front view showing an apparatus of the double arm cutter type embodying the invention;

Fig. 8 is an enlarged view in vertical section showing double arm cutters of the apparatus of Fig. 1;

Fig. 9 is a front view of Fig. 8;

Fig. 10 is a view in section taken along the line X-X in Fig. 9;

Fig. 11 is a view showing the arrangement of spur gears included in the apparatus of Fig. 7; and

Fig. 12 is a front view showing the apparatus of Fig. 7 in operation to improve the ground.

[0014] Figs. 1 to 4 show a ground improving apparatus of the single arm cutter type according to the invention. A rod 1 has at its lower end a bit 2 rotatable about its own axis and controlled above ground and arm cutters 3 extending from a lower portion of the rod 1 at right angles thereto. The arm cutters 3 are revolvable about the axis of the rod and are also each rotatable about its own axis and controlled above ground. While two arm cutters 3 are shown as spaced apart by an angle of 180° about the rod 1, at least one arm cutter 3 may be provided.

[0015] It is required that the cutter portion of the arm cutter 3 be so constructed as to excavate the ground and agitate the soil when rotating. The arm cutter 3 illustrated comprises a group of cutter blades 3a aligned on its arm axially thereof at a spacing in upper and lower two rows. The cutter portion may have some other different construction.

[0016] To control the arm cutters 3 and the bit 2 on the ground for rotation, the rod 1 has a double pipe structure comprising inner and outer pipes 1a and 1b as shown in detail in Fig. 2. The inner pipe 1a and the outer pipe 1 b are respectively supported in their upper portions and rotated by drive means 4 and 5 of a boring machine A installed on the ground as seen in Fig. 1. As shown in Fig. 2, the lower end of the inner pipe 1a of the rod 1 is coupled by a bevel gear transmission mechanism 6 to a horizontal shaft 3b extending through a lower portion of the outer pipe 1b, whereby the arm cutters 3, 3 fixedly mounted on opposite ends of the horizontal shaft 3b are rotated each about its own axis. The shaft 3b is further coupled by a bevel gear transmission mechanism 7 to a stem 2a of the bit 2 which stem is positioned immediately below the shaft 3b to rotate the bit 2. Since the shaft 3b fixedly supporting the cutter arms 3 thereon extends through the outer pipe 1b, the outer pipe, when rotated by the drive means 5, revolves the arm cutters 3 about the axis of the outer pipe 1b. The mechanism for effecting the rotation and revolution may be of some other type.

[0017] To inject cement milk, cement-bentonite mixture or like ground improving liquid agent (grout) into the agitated ground portion through the bit 2 and each of the arm cutters 3, the arm cutter 3 and the bit 2 are respectively formed with liquid channels 9a and 9a' having discharge outlets 8 and 8'. These liquid channels 9a and 9a' are in communication with a liquid channel 9b formed in the lower portion of the outer pipe 1 and communicating with a liquid channel 9c formed in the inner pipe 1a, whereby the channels 9a and 9a' are made to communicate with a liquid agent feeder 10 on the ground (see Figs. 1 and 3). A feeder 10 is connected to the upper portion of the inner pipe 1a by a swivel joint 17. Although the outlets 8 and 8' are shown as provided at the forward end of the arm 3 and at the forward end of the bit 2, such outlets may be formed at some other suitable portions additionally or without providing them at these ends.

[0018] To clean the cutter portion of each arm cutter 3, a cleaning arm 11 having a comb-like portion 11 a is provided on a lower peripheral side portion of the outer pipe 1 of the rod 1, in parallel with the arm cutter 3 so as to freely revolve about the axis of the arm cutter 3. The comb-like portion 11a is in mesh with the cutter blades 3a of the cutter portion which are arranged like comb teeth. The cleaning arm 11 is provided at its base end and forward end with annular portions 11 and 11 α concentric with the arm cutter 3. The base end annular portion 11 b is rotatably supported by a support portion 1b' at the lower peripheral side part of the outer pipe 1b, while the forward end annular portion 11c is similarly supported by a forward end rod portion--af--the arm cutter 3. A plurality of such cleaning arms 11 may be provided for each arm cutter 3. Indicated at 12a in Fig. 2 is a circumferential groove formed in the inner periphery of the base end annular portion 11 b, at 12b an annular projection formed on the outer periphery of the support portion 1 b' and loosely fitting in the circumferential groove 12a, and at 13 a bearing for the forward end annular portion 11c.

[0019] When the ground is to be improved with use of the apparatus of the invention, the inner pipe 1a a and the outer pipe 1 b of the rod 1 are respectively held to the drive means 4 and 5 of the boring machine A as shown in Figs. 1 and 3. The drive means 4 and 5 are mounted on a lift member a3 which is movable upward and downward along a guide rail a2 by lift means a1.

[0020] Fig. 1 shows the apparatus when it is about to start operation. When the inner pipe 1a is rotated by the drive means 4 in this state, the arm cutters 3 and the bit 2 are rotated each about its own axis. In the state of Fig. 1, the drive means 5 is out of operation to hold the outer pipe 1 b at rest, so that the arm cutters 3 are not revolved.

[0021] As the lift member a3 is lowered along the guide rail a2 by the lift means a1 from the position shown in Fig. 1, the bit 2 and the arm cutters 3 vertically bore the ground while guiding the rod 1 into the ground. While the rod 1 is thus being guided into the ground, each cleaning arm 11 is subjected to the resistance of soil and is positioned on the rear side of the arm cutter 3 with respect to the direction of excavation, i.e., vertically above the arm cutter 3 (see Fig. 2), thus smoothly following the arm cutter 3 into the soil excavated and agitated by the cutter. When clayey soil adheres to the cutter portion of the arm cutter 3, the cleaning arm 11 acts to scrape the soil off the cutter portion. Since the cleaning arm 11 is substantially held to the position vertically above the arm cutter 3 by being subjected to the resistance of excavation, the cleaning arm 11 effectively cleans the cutter arm with stability in position without any likelihood that it will rotate with the arm cutter 3.

[0022] When a predetermined depth is reached within the ground as seen in Fig. 3, the drive means 5 is driven to rotate the outer pipe 1b while rotating the bit 2 and the arm cutters 3 through the inner pipe 1a, whereupon the arm cutters 3 start to revolve while rotating to excavate and agitate the soil within the range of its revolution. Accordingly the rod 1 is gradually lifted while injecting a ground improving liquid agent into the agitated soil within the range of the revolution through the outlets 8 and 8' of the cutters 3 and the bit 2, whereby the ground within the above range can be improved at once. If there is an obstacle in the ground to hinder the revolution of the arm cutters 3 during the lift of the rod 1, the arm cutters 3 may be held out of revolution until the obstacle is cleared while being held in rotation only.

[0023] During the operation of the arm cutters 3 involving their rotation and revolution, the cleaning arms 11 are positioned behind the arm cutters 3 with respect to the direction of excavation as seen in Fig. 4 and are substantially held in this position by being subjected to the resistance of soil, thus effectively cleaning the cutters as contemplated while smoothly passing through the excavated and agitated soil in the same manner as when advancing into the ground. With reference to Fig. 4, an arrow 13 shows the direction of revolution of the arm cutters 3, an arrow 14 shows the direction of lift of the rod 1, and an arrow 15 indicates the direction of excavation.

[0024] With use of the present apparatus, the ground can be improved at a time over a wide area covered by the revolution of the arm cutters 3 and having a radius corresponding to the length of each arm cutter 3. When such improved ground portions a are formed continuously in series as seen in Fig. 5, an underground continuous wall can be built with a large thickness, while if such portions are formed in rows in staggered arrangement as seen in Fig. 6, the ground can be improved over an increased area. Thus the present apparatus is very useful for forming an underground continuous wall of large thickness or for improving the ground over a wide area, as in soft ground.

[0025] Throughout the entire process of excavation and agitation carried out by the present apparatus, the cleaning arms 11 clean the cutter portions of the arm cutters 3 to eliminate adhesion of clayey soil that would impair the excavation-agitation efficiency, consequently assuring efficient improvement of the ground.

[0026] Furthermore, the ground can be improved by the apparatus of the invention with its arm cutters held in their extended position without the necessity of stowing and extending the cutters unlike the conventional apparatus. The apparatus is therefore simple in construction and easy to operate for the improvement of the ground.

[0027] Figs. 7 to 12 show an apparatus of the double arm cutter type embodying the present invention. With the apparatus of this type, arm cutters 3 are arranged one above another in a multiplicity of stages and aligned vertically, and groups of cutter blades 3a providing cutter portions at different levels are in mesh with each other to clean each other. With the exception of this feature, this type has substantially the same construction as the single type already described. Throughout the drawings, like parts are referred to by like reference numerals.

[0028] With this type, the arm cutters 3 arranged one above another in multi-stages, for examples, upper and lower arm cutters 3, 3 arranged in two stages are coupled together at horizontal shafts 3b, 3b by spur gears 16a, 16b and 16c. To rotate the upper and lower arm cutters 3 at different speeds, the spur gears 16a and 16c are different in diameter. The intermediate gear 16b functions to rotate the upper and lower arm cutters 3, 3 in the same direction to reduce the likelihood that soil will engage in between the cutter portions of the arm cutters 3.

[0029] The apparatus of the second type, in which the arm cutters 3 are arranged one above another in multi-stages, can improve the ground more efficiently than the apparatus of the single arm cutter type.

Claims

1. An apparatus for improving ground comprising a rod (1) to be inserted into the ground to a predetermined depth, a bit (2) attached to the forward end of the rod (1) and rotatable when the rod (1) is inserted into the ground to guide the rod (1) into the ground, the bit (2) having a discharge outlet (8') for-injecting a ground improving liquid agent into an agitated portion of the ground while the rod (1) is withdrawn from the ground with the bit (2) held in continued rotation, and at least one arm cutter (3) having a discharge outlet (8) and attached to a lower portion of the rod (1) for agitating the ground and simultaneously injecting the ground. improving agent into the agitated ground portion when the rod (1) is withdrawn from the ground, a first drive assembly (6) being provided for rotating the arm cutter (3) about its own axis in a manner remotely controllable above ground when the rod (1) is inserted into and withdrawn from the ground, the apparatus being characterized in that the arm cutter extends permanently from the lower portion of the rod at right angles therewith, and a second drive assembly (5) is provided for revolving the arm cutter (3) about the axis of the rod (1) in a manner remotely controllable above ground when the rod (1) is withdrawn from the ground.

2. An apparatus as defined in claim 1, wherein the rod (1) has a double pipe structure including an inner pipe (1a) and an outer pipe (1 b), the first drive assembly (6) including (a) the inner pipe (1 a), (b) first drive means installed above the ground and holding the upper end ofthe inner pipe (1a) for rotating the inner pipe (1a) and (c) a rotation transmitting mechanism (6,7) for transmitting the rotation of the inner pipe (1a) by the drive means to the bit (2) and the arm cutter (3) as rotation about their own axes, the second drive assembly (5) including (d) the outer pipe (1b), (e) second drive means installed aboved the ground and holding the upper end of the outer pipe (1 b) for rotating the outer pipe (1b) and (f) a mechanism for transmitting the rotation of the outer pipe (1b) by the second drive means (5) to the arm cutter (3) as revolution about the axis of the rod (1).

3. An apparatus as defined in claim 1 or claim 2 wherein the arm cutter (3) is provided with a cleaning arm (11) having cleaning blades (110) in mesh with the cutter portion (3a) of the arm cutter (3), the cleaning arm (11) being parallel with the arm cutter (3) and freely revolvable about the axis of the arm cutter (3)..

4. An apparatus as defined in claim 1 or claim 2 wherein a plurality of arm cutters (3) is provided and the arm cutters (3) are arranged one above another in a multiplicity of stages and aligned vertically, the arm cutter (3) in each stage having a group of cutter blades (3a) spaced apart axially of the arm cutter (3) and arranged in at least one row, the groups of cutter blades (3a) in each two adjacent stages in mesh with each other.

5. An apparatus as defined in claim 4wherein the arm cutters (3) differ from stage to stage in the direction of rotation or in the speed of rotation.

6. A method of improving ground comprising inserting into the ground a rod (1) equipped with a bit (2) at its forward end and an arm cutter (3) transversely extending from the lower portion of the rod (1) by the rotation of the bit (2) and the rotation of the arm cutter (3) about its own axis, and gradually withdrawing the rod (1) from the ground when the rod (1) has reached a predetermined depth while revolving the arm cutter (3) about the axis of the rod (1) in addition to its rotation about its own axis to agitate the portion of the ground covered by the revolution and while injecting a liquid agent into the agitated portion of the ground from discharge outlets (8,8') in the arm cutter (3) and the bit (2).

Ansprüche

1. Gerät zur Bodenverbesserung, bestehend aus einer Stange (1), die in den Erdboden bis zu einer vorgegebenen Tiefe einzuführen ist, einer am Vorderende der Stange (1) befestigten Bohrschneide (2), die bei Einführen der Stange (1) in den Erdboden rotierfähig ist, um die Stange (1) bei ihrem Eindringen in den Erdboden zu führen, wobei die Bohrschneide (2) eine Auslaßöffnung (8) zum Einspritzen eines bodenverbessernden flüssigen Mittels in einen aufgewühlten Teil des Erdbodens aufweist, während die Stange (1) mit der in dauernder Drehung gehaltenen Bohrschneide aus dem Erdboden herausgezogen wird, und ferner bestehend aus mindestens einer Armschneidvorrichtung (3) mit einer Auslaßöffnung (8) und Befestigung an einem unteren Teil der Stange (1) zum Aufwühlen des Erdbodens und gleichzeitigem Einspritzen des Bodenverbesserungsmittels in die aufgewühlte Erdscholle, wenn die Stange (1) aus dem Erdboden herausgezogen wird, wobei ein erstes Antriebsaggregat (6) vorgesehen ist; um die Armschneidvorrichtung (3) um ihre eigene Achse in von oberhalb des Erdbodens fernsteuerbarer Weise zu drehen, wenn die Stange (1) in den Erdboden eingesetzt und wieder herausgezogen wird, dadurch gekennzeichnet, daß die Armschneidvorrichtung dauernd aus dem unteren Teil der Stange im rechten Winkel zu dieser herausragt, und daß ein zweites Antriebsaggregat (5) vorgesehen ist, um die Armschneidvorrichtung (3) um die Achse der Stange (1) in einer von oberhalb des Erdbodens fernsteuerbaren Weise zu drehen, wenn die Stange (1) aus dem Erdboden herausgezogen wird.

2. Gerät nach Anspruch 1, dadurch gekennzeichnet, daß die Stange (1) eine doppelte Röhrenanordnung mit einem inneren Rohr (1a) und einem äußeren Rohr (1 b) aufweist, wobei das äußere Antriebsaggregat (6) (a) innere Rohr (1a) einschließt, (b) erste Antriebsmittel oberhalb des Erdbodens eingebaut sind und das obere Ende des inneren Rohres (1a) zwecks Drehung des inneren Rohres (1 a) festhalten, und (c) eine Drehungsübertragungsvorrichtung (6, 8) zum übertragen der Drehung des inneren Rohre (1a) durch das Antriebsmittel zur Bohrschneide (2) und der Armschneidevorrichtung (3) als Drehung um ihre eigenen Achsen vorhanden ist, wobei das zweite Antriebsaggregat (5) (d) das äußere Rohr (1b) einschließt, und (e) ein zweites Antriebsmittel über dem Erdboden eingebaut ist und das obere Ende des äußeren Rohres (1 b) zum Drehen des äußeren Rohres (1b) festhält, und (f) eine Vorrichtung zum übertragen der.Drehung des äußeren Rohres (1 b) durch das zweite Antriebsmittel (5) zur Armschneidevorrichtung (3) als Umdrehung um die Achse der Stange (1) vorhanden ist.

3. Gerät nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, daß die Armschneidevorrichtung (3) mit einem Reinigungsarm (11) mit Reinigungsmessern (110) im Zusammenwirken mit dem Schneidenteil (3a) der Armschneidevorrichtung (3) versehen ist, wobei der Reinigungsarm (11) parallel zur Armschneidvorrichtung (3) liegt und frei drehbar um die Achse der Armschneidvorrichtung (3) ist.

4. Gerät nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, daß eine Vielzahl von Armschneidvorrichtungen vorgesehen ist und die Armschneidvorrichtungen (3) in einer Vielzahl von Stufen und lotrecht fluchtend übereinander angeordnet sind, wobei die Armschneidvorrichtung (3), auf jeder Stufe eine Gruppe von Schneidmessern (3a) mit gegenseitigem Abstand axial zur Armschneidvorrichtung und in mindestens einer Reihe angeordnet, aufweist und die Gruppen von Schneidmessern (3a) in je zwei benachbarten Stufen ineinandergreifen.

5. Gerät nach Anspruch 4, dadurch gekennzeichnet, daß die Armschneidvorrichtungen von Stufe zu Stufe inbezug auf die Drehrichtung oder Drehgerschwindigkeit verschieden sind.

6. Verfahren zur Bodenverbesserung, gekennzeichnet durch Einsetzen einer Stange (1) mit einer Bohrschneide (2) an ihrem vorderen Ende und einer Armschneidvorrichtung (3), die in Querrichtung vom unteren Teilstück der Stange (1) durch die Drehung der Bohrschneide (2) und die Drehung der Armschneidvorrichtung (3) um ihre eigene Achse herausragt, und ferner gekennzeichnet durch allmähliches Herausziehen der Stange (1) aus dem Erdboden beim Erreichen einer vorgegebenen Tiefe durch die Stange (1) während des Drehens der Armschneidvorrichtung um die Achse der Stange (1) zusätzlich zu ihrer Drehung um ihre eigene Achse zwecks Aufwühlens des von der Umdrehung überstrichenen Teilstückes des Erdbodens während ein flüssiges Mittel in das aufgewühlte Teilstück des Erdbodens aus Auslaßöffnungen (8,8') in der Armschneidvorrichtung (3) und der Bohrschneide (2) eingespritzt wird.

Revendications

1. Appareil pour améliorer le sol, comprenant une barre (1) à ère introduite dans le sol jusqu à une profondeur prédéterminée, (2) une tranche d'alésoir attachée à 1 extrémité avant de la barre (1), étant rotative, lors de l'introduction de la barre (1) dans le sol, pour conduire la barre (1) pénétrante la sol, la tranche d'alésoir (2) comportant une ouverture de décharge (8') pour injecter un agent liquide pour l'améliorisation du sol dans une partie fouillée du sol, tandis que la barre (1) avec la tranche d'alésoir tenue dans une rotation continue, et comprenant au moins un outil tranchant monté sur un bras comportant une ouverture de décharge (8) et attaché à la partie inférieure de la barre (1) pour fouiller le sol et simultanément injecter lâgent améliorant le sol dans la partie fouillée, quand la barre (1) est retirée du sol, un premier mécanisme d'entraînement (6) étant prévu pour tourner l'outil tranchant monté sur un bras (3) autour de son propre axe d'une manière télécommandée au-dessus du sol, quand la barre (1) est introduite et retirée du sol, caractérisé en ceque l'outil tranchant monté sur un bras fait saillie de la partie inférieure de la barre (1) et à angles droits à laquelle, et qu'un deuxième mécanisme d'entraînement (5) est prévu pour tourner l'outil tranchant (3) autour de l'axe de la barre (1) d'une manière télécommandée au-dessus su sol, quand la barre (1) est retirée du sol.

2. Appareil conformément à la revendication 1, caractérisé en ce que la barre (1) comporte un système double à tubes muni d'un tuyau intérieur (1a) et d'un tuyau extérieur (1b), le mécanisme d'entraînement extérieur (6) (a) comprenant le tuyau intérieur (1a), (b) des premiers moyens d'entraînement étant installés au-dessus du sol en maintenant l'extrémité supérieur du tuyau intérieur (la) pour tourner le tuyau intérieur (1 a), et (c) un organe de transmission (6, 8) étant prévu pour transmettre la rotation du tuyau intérieur (1a) par la moyen d'entraînement à la tranche d'alésoir (2) et lôutil tranchant monté sur un bras (3) comme rotation autour de leur propre axe, le deuxième mécanisme d'entraînement (5) in- cluyant (d) le tuyau extérieur (1b), et (e) un deuxième mécanisme d'entraînement étant installé au-dessus du sol en maintenant l'extrémité surpérieure du toyau extérieur (1b) pour tourner le tuyau extérieur (1b), et un organe de transmission pour transmettre la rotation du tuyau extérieur (1 b) par le deuxième moyen d'entraînement (5) à l'outil tranchant monté au bras (3) comme rotation autour de l'axe de la barre (1) étant prévuô.

3. Appareil conformément à la revendication 1, ou la revendication 2, caractérisé en ce que l'outil tranchant (3) monté sur un bras est muni d'un bras de nettoyage (11) comportant des lames de nettoayge (11) en coopération avec la partie tranchante (3a) de l'outil tranchant (3), le bras de nettoyage (11) étant parallèle relativement à l'outil tranchant (3) monté sur le bras, à rotation libre autour de l'axe de l'outil tranchant (3).

4. Appareil conformément à la revendication 1 ou la revendication 2, caractérisé en ce qu'un nombre multiple d'outils tranchants montés sur un bras sont prévus et que les outils tranchants (3) sont disposés dans un nombre multiple d'étages à alignement vertical l'un sur l'autre, l'outil tranchant (3) comportant sur tous les étages une groupe de lames tranchantes (3a) à distance axiale à l'outil transchant et disposées dans au moins une rangée, tandis que les groupes de lames tranchantes (3a) s'enchaînent sur tous deux étages.

5. Appareil conformément à la revendication 4, caractérisé en ce que les outils tranchants montés sur un bras sonst différents d'un étage à l'autre en ce qui concerne la sens ou la vitesse de rotation.

6. Methode pour améliorer le sol, caractérisé par l'enfoncement d'une barre (1) munie d'une tranche d'alésoir (2) à l'extrémité avant et un outil tranchant monté sur un bras (3) faisant saillie en sens transversal de la partie inférieure de la barre (1) par la rotation de la tranche dàlésoir (2) et la rotation du l'outil tranchant (3) autour de leur propre axe, et caractérisé en ce que la barre (1) est retirée successivement du sol aussitôt que la barre (1) ait atteint une profondeur prédéterminée pendant la rotation de l'outil tranchant autour de l'axe au but de fouiller la partie du sol touchée pendant la rotation, tandis qu'un agent liquide est injecté dans la partie du sol par des ouvertures de décharge (8,8') dans l'outil tranchant (3) monté sur un bras et la tranche d'alésoir (2).

Drawing