EP0096622B1 - Method and apparatus for earth drilling - Google Patents

Description

The invention relates to a method and a device for drilling the soil of the type known from US-A-3726506, more particularly but not exclusively with a view to laying pipes.

To date, it is generally necessary to open a trench to ensure the laying of rigid or flexible pipes, that of gas transport pipes, protective sheaths of electric and telephone cables or supply and evacuation pipes water from buildings or from an underground watering or irrigation network on cultivated land.

This opening of trenches in the surface of a road or the lawn of a park obviously destroys the structure of the land to its surface, a structure which will then have to be restored at great cost.

It also prevents the normal use of the surface as it forces to remove a very large volume of soil that then, to backfill the trench, it will be necessary to bring back.

In order to remedy these drawbacks, several devices known to date are intended to drill a simple hole in the ground in order then to be able to slide the pipe longitudinally therein.

For example, for a pipe to pass under a roadway, the hole is drilled from a starting pit in which the device is lowered to a depth which is linked to that of drilling, for which the device comprises a tool which, from the starting pit, will work progressing to an ending pit.

Instead of a whole trench, it suffices to dig the end pits which can even be made by pre-existing pits such as cellars.

One of the tools known to date includes (FR-A-2 372 309) a nozzle which is supplied with pressurized fluid which is sprayed in the form of a jet responsible for disintegrating the ground.

This device is however of limited application because it cannot be suitable for hard ground and for example for a drilling of road where the tool is called to meet as well earth as stones and other obstacles.

Another tool known to date has a generally conical shape and comprises (FR-A-2 280 748 and 2416307) a motor driving in eccentrics which gradually create the hole by compacting the soil until the hole is obtained , diameter equal to that of the base of the tool cone.

As in the known devices, the orientation of the tool is not ensured by the device but by the hole on the wall of which the tool is applied; in particular in the case of non-homogeneous grounds, creating variable lateral stresses, this work by eccentrics often causes deviations of the tool.

However, these deviations make the end point of the tool more than uncertain and can, despite the passage of the tool, prevent the passage of the pipe which is much longer.

Another tool known to date (FR-A-2,399,305, 2,336,519, 2,240,321, 2,198,507 and 2,161,732) consists of a tip or a striking nose associated with a tubular body provided with a means of percussion controlled by a pneumatic circuit.

Although the strokes are parallel to the axis of the tool, the jerk and the slight rebound which are obtained also have the disadvantage, when the tip of the tool arrives on an area of great resistance, to favor the deviation of said tool.

With the devices known to date, in addition to the guiding problem, it is generally regrettable that the device for threading the pipes into the hole drilled by the tool still requires the creation of a very large pit which, for short drilling , practically eliminates the interest of said device compared to the trenches.

A result which the invention aims to obtain is a method and a device for drilling the soil which guarantee high precision and thereby allow drilling between two very distant points.

Another result which the invention aims to obtain is a device which suffices from small pits.

• a) des moyens formant glissière, solidaires de l'ossature et orientés parallèlement au sens de forage,
• b) un coulisseau porté par les moyens formant glissière et guidé à la translation le long de ceux-ci parallèlement au sens de forage, par rapport à l'ossature, ce coulisseau délimitant intérieurement un logement au moins partiellement fermé latéralement et ouvert vers l'avant, en référence au sens de forage,
• c) des moyens de poussée agissant entre l'ossature et le coulisseau, dans le sens d'une translation de ce dernier le long des moyens formant glissière par rapport à l'ossature au moins dans le sens de forage,
• d) un organe allongé présentant un axe rectiligne, l'organe allongé étant emboîté dans le logement et en butée à l'intérieur de celui-ci, par rapport au coulisseau, vers l'arrière et latéralement en référence au sens de forage, dans une position dans laquelle l'axe de l'organe allongé est parallèle à ce sens, et la dimension de l'organe allongé parallèlement à son axe étant supérieure à la dimension du logement parallèlement au sens de forage si bien que l'organe allongé présente une zone d'extrémité en saillie vers l'avant, en référence au sens de forage, hors du logement du coulisseau, une zone d'extrémité portant de façon solidaire le trépan ayant les caractéristiques définies dans la partie caractérisante de la revendication 1.

To this end, it relates to a soil drilling device of the type known from US-A-3 726 506, comprising a bearing frame, a drill bit, means for moving the bit in translation relative to the frame in a determined direction of drilling, and means for supporting the frame on the ground at least rearward with reference to this direction in which the means for moving the drill bit in translation relative to the frame in the direction of drilling include:

• a) means forming a slide, integral with the framework and oriented parallel to the direction of drilling,
• b) a slide carried by the means forming a slide and guided in translation along these parallel to the direction of drilling, relative to the frame, this slide internally delimiting a housing at least partially closed laterally and open towards the before, with reference to the direction of drilling,
• c) thrust means acting between the frame and the slide, in the direction of translation of the latter along the means forming a slide relative to the frame at least in the direction of drilling,
• d) an elongated member having a rectilinear axis, the elongated member being fitted into the housing and abutting therein, with respect to the slide, rearward and laterally with reference to the direction of drilling, in a position in which the axis of the elongated member is parallel to this direction, and the dimension of the elongated member parallel to its axis being larger than the dimension of the housing parallel to the direction of drilling so that the elongated member has an end zone projecting forward, with reference to the direction of drilling, outside the slide housing, an end zone bearing integrally the drill bit having the characteristics defined in the characterizing part of claim 1.

• a) on cale par rapport au sol l'ossature du dispositif de manière que l'axe des moyens formant tube corresponde exactement avec un axe de trou à forer, le coulisseau occupant une position extrême arrière compte tenu du sens de forage, et, dans la zone d'extrémité avant du tube, on monte le trépan,
• b) à l'aide des moyens de poussée poussant régulièrement le coulisseau et du tube retransmettant cette poussée régulière dans le sens de forage, on engage à force le trépan dans le sol pour y forer un trou,
• c) à l'aide des moyens de poussée, on ramène en sens inverse du sens de forage le coulisseau qui coulisse sur le tube,
• d) on place dans le logement du coulisseau un tronçon de tube dont on assemble l'avant sur l'arrière dudit tube pour prolonger les moyens formant tube et on pousse le coulisseau et les moyens formant tube, portant le trépan, dans le sens de forage à l'aide des moyens de poussée pour prolonger le trou,
• e) on répète les étapes c et d jusqu'à l'arrivée du trépan dans ladite fosse où le trépan est démonté des moyens formant tube de la manière définie dans la partie caractérisante de la revendication 11.

It also relates to a method of drilling to a pit using this device according to which:

• a) the framework of the device is wedged with respect to the ground so that the axis of the tube-forming means corresponds exactly with an axis of the hole to be drilled, the slide occupying an extreme rear position taking account of the direction of drilling, and, in the front end zone of the tube, we mount the drill bit,
• b) using the pushing means regularly pushing the slide and the tube retransmitting this regular pushing in the direction of drilling, the drill bit is forced into the ground to drill a hole therein,
• c) using the thrust means, the slide which slides on the tube is brought back in the opposite direction to the direction of drilling,
• d) a section of tube is placed in the slide housing, the front of which is assembled on the rear of said tube to extend the tube forming means and the slide and the tube forming means, carrying the drill bit, are pushed in the direction of drilling using the pushing means to extend the hole,
• e) repeating steps c and d until the drill bit arrives in said pit where the drill bit is removed from the tube-forming means in the manner defined in the characterizing part of claim 11.

In the case where the drilled hole must be lined with a metal sheath, the tube-forming means are left in place to directly produce this sheath.

• a) on verrouille mutuellement les moyens formant tube et le coulisseau occupant une position extrême avant compte tenu du sens de forage, puis
• b) on actionne les moyens de poussée pour tirer le coulisseau et les moyens formant tube en sens inverse du sens de forage et, lorsque le coulisseau parvient dans une position extrême arrière, en référence au sens de forage, et qu'un tronçon de tube est dégagé du trou foré,
• c) on sépare ce tronçon des moyens formant tube, on le dégage du coulisseau et l'on recommence les étapes a, b, c jusqu'à sortie totale des moyens formant tube hors du trou foré.

In the case where the drilled hole does not have to be lined with a metal sheath, after having fixed on the tube, in place of the drill bit, a pipe or a cable that we want to place in the hole, the framework being set in relation to the ground forward with reference to the direction of drilling,

• a) mutually locking the tube means and the slide occupying an extreme position before taking into account the direction of drilling, then
• b) the thrust means are actuated to pull the slider and the tube means in the opposite direction to the direction of drilling and, when the slider reaches an extreme rear position, with reference to the direction of drilling, and only a section of tube is released from the drilled hole,
• c) this section is separated from the tube-forming means, it is released from the slide and steps a, b, c are repeated until the tube-forming means have completely left the drilled hole.

• figure 1 le dispositif selon l'invention dans une phase intermédiaire d'une opération de forage, de fosse à fosse, dans un sens horizontal, en une vue en coupe verticale passant par l'axe des moyens formant tube,
• figure 2 le dispositif vu de dessus, tel que prêt au forage,
• figure 3 une coupe selon III-III de la fig. 2,
• figure 4 une coupe selon IV-IV de la fig. 2,
• figure 5 une vue analogue à celle de la fig. 1, illustrant la phase finale du forage,
• figure 6 une vue analogue à celle de la fig. 1, illustrant une possibilité de réalisation directe d'un fourreau dans le trou foré,
• figure 7 une vue analogue à celle de la fig. 1, illustrant la mise en place d'une canalisation souple dans le trou foré.

The invention will be clearly understood with the aid of the description below, given by way of nonlimiting example, with reference to the attached drawing, which schematically represents:

• FIG. 1 the device according to the invention in an intermediate phase of a drilling operation, from pit to pit, in a horizontal direction, in a view in vertical section passing through the axis of the tube-forming means,
• FIG. 2 the device seen from above, as ready for drilling,
• Figure 3 a section on III-III of fig. 2,
• Figure 4 a section on IV-IV of FIG. 2,
• Figure 5 a view similar to that of FIG. 1, illustrating the final phase of drilling,
• Figure 6 a view similar to that of FIG. 1, illustrating a possibility of direct production of a sheath in the drilled hole,
• Figure 7 a view similar to that of FIG. 1, illustrating the installation of a flexible pipe in the drilled hole.

Referring to fig. 1, it can be seen that in this embodiment of the invention, in the ground 1 two pits 2, 3 are provided, one (2) at the start of the hole 4 to be drilled, the other (3) to the arrival of this hole.

In the starting pit 2, the device-5 is lowered, which is provided with a drilling tool (6) intended to attack the ground at the desired depth, starting from one face 7 of the pit start 2, called the front face, which is of course the one located on the side of the arrival pit, in a direction of drilling 43 here horizontal, which will serve as a reference to the terms “front and” rear used subsequently; the device 5 ready for drilling is visible in FIGS. 2 to 4.

Before this attack, the orientation and the inclination of the trajectory of the tool are controlled by a sighting system 8 which, by vertical risers 9 positioned on a framework 29 of the device 5, is carried above the level of the ground, at a height that is preferably adjustable, which aiming system cooperates with a vertical stake 10 positioned in the arrival pit 3.

In order to ensure the device 5 for a good seat, the starting pit 2 has its bottom 11, which can be more or less closed, which is provided with a floor or at least cross members 12 duly wedged.

The framework 29 of the device 5 rests on this support, preferably, by means of jacks 13 making it possible to correct the inclination of the device, that is to say the direction of drilling 43.

Similarly, so that the rear face 53 of the pit 2 can serve as a support for the frame 29 of the device towards the rear, it is provided with a cross member 14 on which this device is supported by means of jacks 15 making it possible to correct its orientation, that is to say that of the direction of drilling 43.

Tool 6 consists of a drill bit having externally, successively from front to rear, a flat face 52 transverse to an axis 44 fixed relative to the frame 29 and defining the direction of drilling 43, a face 16 frustoconical of revolution around the axis 44 and converging towards the front, a cylindrical face 17 of revolution around the axis 44 with a diameter D corresponding to that of the hole 4 to be drilled and identical to that of the large base of the cone trunk defining the face 16, and this drill bit integrally bears, immediately behind the cylindrical face 14, a centering shank 18, cylindrical of revolution around the axis 44 and engaging in a front end region 19 of a rectilinear tube 20 delimited externally by a cylindrical face of revolution around the axis 44 with a diameter d less than D and a length L, measured parallel to the axis 44, with respect to which the corresponding dimension λ of the face 17 is negligible: the tail 18 of the drill bit 6 is fixed in a solid but removable manner inside the front end zone 19 of the tube 20, by any suitable removable means 21, such as a bolt or a pin.

The tube 20, which at the start of a borehole can be in a single section 20a, is then obligatorily, taking into account the limited length of the pit, made up of several sections (three in number referenced 20a, _20b , 20 _e , at the end of drilling in the nonlimiting example illustrated, this number being able to be different) which, in order to form a rigid and rectilinear assembly of axis 44, are assembled together for example by points or a cord (such as illustrated in 22) of welding (for example between the sections 20b and 20c) or by a removable means (as illustrated in 23) such as a sleeve (such as 49) welded in one of the sections (such as 20a) and held removably in the other section (such as 20b) by a pin (such as 24) generally the same assembly method can be used for all of the sections, different modes having been shown for illustrative purposes only.

By a rear end zone 25, the tube 20 is engaged over a part 1 of its length L in a housing 46 of a slide 26 guided in translation parallel to the axis 44 by slides 27, 28 integral with the framework 29 and parallel to this axis.

The housing 46 is closed rearward and laterally with respect to the axis 44 but open towards the front, so as to receive the tube 20 when sliding relative to the slide 26 along the axis 44, constituting a stop for the tube towards the rear and laterally without opposing the sliding of the tube towards the front with respect to the slide 26.

In a rear end zone, the slide 26 carries for this purpose, integrally, a stop plate 30 for the rear end 25 of the tube 20, this plate closing the housing 46 rearwards, transversely to the axis 44.

On this stop plate is mounted forwardly, in an integral manner, a ring 31 of axis 44, which, directly or via a reduction fitting, centers the rear end 25 of the tube 20 relative to at axis 44.

In addition, in a front end zone, the slide 26 carries a collar 32 closed around an intermediate zone 47 of the tube 20 and which, directly or by means of a pad, centers this tube 20 relative to axis 44.

The collar 32 comprises a sector 33 which is integral with the slide 26 and a sector 34 which can be dismantled in order to open the collar 32 to free access between the interior and the exterior thereof, for the tube 20 , laterally relative to the direction of drilling 43, that is to say allow the release or engagement of the tube 20 in the housing 46 from above the device if we refer to the position illustrated in FIG. 1. This removable sector 34 is for example, at one of its ends, articulated around an axis 35 carried by the fixed sector 33 and parallel to the axis 44, while at its other end, this removable sector 34 is removably fixed to the fixed sector 33 by a screw 36.

Centered with respect to the axis 44, at the front by the collar 32 and at the rear by the ring 31, the tube 20 is perfectly guided in the slide 26 itself perfectly guided by the slides 27, 28 relative to the frame 29; also, the adjustment of the frame 29 in inclination and orientation by action on the support cylinders 13 and 15 does it ensure that the tube 20 has the same adjustments.

The fixed sector 33 of the collar 32 is also integrally associated with a yoke 37 for pushing the slide 26 and therefore for the tube 20, a yoke on which act pushing means such as two jacks 38 each placed on one side of the slide 26 and tube 20, parallel to the axis 44, the cylinder 39 of which is integral with the framework 29 of the device behind the yoke 37 while the piston (not shown) has its rod 40 terminated by means 41, such as a yoke, gripping the yoke 37 of the collar which, for this purpose, carries for example two pins 42.

The jacks 38 are preferably hydraulic and double-acting and the fluid under pressure is supplied to them via a distributor and pipes 54 connected to a group not shown, preferably separated from the device to be left on the surface and for authorize the use of a group having other uses, such as that of the shovel having dug the pit.

In the case where the rear face 53 of the pit might not resist the thrust of the jacks 38, it is obvious that a rear stop plate (not shown) carried by the arrow of said shovel can serve as a support to the device.

• en calant l'ossature 20 par dessous et par derrière par rapport au sol 1 grâce aux vérins 15 et 13, on place le dispositif de manière telle que l'axe 44 du tronçon 20a du tube 20 qu'il porte initialement corresponde exactement avec l'axe du trou à forer 4 ; les vérins 38 sont initialement rétractés, le coulisseau 26 et le tube 20 occupant par rapport à l'ossature 29 une position extrême arrière illustrée à la figure 2 ;
• dans la zone d'extrémité avant 19 du tube 20, on monte le trépan 6,
• on actionne les vérins 38 dans le sens 43 et à l'aide de ces vérins 38 poussant ainsi régulièrement vers l'avant le coulisseau 26 et à l'aide du tube 20 retransmettant au trépan 6 cette poussée régulière, on engage à force le trépan 6 dans le sol 1 dans l'axe du trou à forer 4, c'est-à-dire dans le sens de forage 43 défini par l'axe 44, jusqu'à ce que le coulisseau 26 atteigne une position extrême avant (visible à la figure 5) par rapport à l'ossature 9, le long des glissières 27, 28 ;
• à l'aide des vérins 38 que l'on actionne en sens inverse, on ramène alors le coulisseau 29 en sens inverse du sens 43 mais le coulisseau 29 n'étant pas fixé au tube 20 qu'il centre uniquement, il revient seul à la position extrême arrière, laissant le tronçon 20a de tube et le trépan 6 dans le trou foré 4 ;
• en ouvrant le collier 37, on place alors dans la bague de guidage arrière 31, un tronçon 20b de tube 20 dont l'avant est alors assemblé sur l'arrière du tronçon 20a de tube précédent, puis on referme le collier 37 sur ce tronçon 20b, et l'on pousse dans le sens 43, au moyen des vérins 38, l'ensemble formé par le coulisseau 26, les tronçons 20a et 20b et le trépan 6 ;
• on répète ces deux dernières étapes jusqu'à l'arrivée du trépan 6 dans la fosse 3 où le trépan est démonté du tronçon de tube 20a ; cette arrivée, illustrée à la figure 5, nécessite dans l'exemple illustré l'assemblage d'un tronçon de tube 20c supplémentaire en arrière du tronçon 20b, un nombre différent de tronçons ne sortant naturellement pas du cadre de la présente invention ; la figure 1 illustre une phase intermédiaire du forage, le tronçon 20c ayant été assemblé au tronçon 20b mais le coulisseau 26 occupant encore sa position extrême arrière.

With the device which is the subject of the invention, the drilling process is as follows:

• by wedging the frame 20 from below and from behind with respect to the ground 1 by means of the jacks 15 and 13, the device is placed in such a way that the axis 44 of the section 20a of the tube 20 which it carries initially corresponds exactly with the 'axis of the hole to be drilled 4; the jacks 38 are initially retracted, the slide 26 and the tube 20 occupying with respect to the frame 29 an extreme rear position illustrated in FIG. 2;
• in the front end zone 19 of the tube 20, the drill bit 6 is mounted,
• the jacks 38 are actuated in the direction 43 and using these jacks 38 thus regularly pushing the slide 26 forward and using the tube 20 retransmitting to the drill bit 6 this regular thrust, the drill bit 6 is forcibly engaged in the ground 1 in the axis of the hole to be drilled 4, that is to say in the direction of drilling 43 defined by the axis 44 , until the slide 26 reaches an extreme front position (visible in Figure 5) relative to the frame 9, along the slides 27, 28;
• using the jacks 38 which are actuated in the opposite direction, the slide 29 is then brought back in the opposite direction to the direction 43 but the slide 29 not being fixed to the tube 20 which it centers only, it comes back only to the rear extreme position, leaving the section 20a of tube and the drill bit 6 in the drilled hole 4;
• by opening the collar 37, a section 20b of tube 20 is then placed in the rear guide ring 31, the front of which is then assembled on the rear of the section 20a of the preceding tube, then the collar 37 is closed on this section 20b, and pushing in the direction 43, by means of the jacks 38, the assembly formed by the slide 26, the sections 20a and 20b and the drill bit 6;
• these last two steps are repeated until the bit 6 arrives in the pit 3 where the bit is removed from the tube section 20a; this arrival, illustrated in FIG. 5, requires in the example illustrated the assembly of an additional section of tube 20c behind the section 20b, a different number of sections naturally not departing from the scope of the present invention; Figure 1 illustrates an intermediate phase of drilling, the section 20c having been assembled to the section 20b but the slide 26 still occupying its rear extreme position.

At this stage, in the case where the drilled hole 4 must be lined with a metal sheath, the tube 20 can be left in place to make this sheath directly, as shown in Figure 6: the drill bit 6 is removed from the tube 20 and the slide 26 is brought backwards, then the collar 37 is opened if necessary to release the rear section 20c therefrom.

In this case, the assembly between the sections of the tube 20 is preferably carried out by butt welding.

In the case where the drilled hole does not have to be lined with such a metal sheath as shown in FIG. 7, after having fixed on the front end zone 19 of the tube 20, instead of the drill bit 16, one end d 'a flexible sheath or pipe 50 or a cable that is to be placed in the drilled hole 4, and having wedged against the face 7 of the pit 2 the front of the frame 29 of the device by means for example of two hydraulic struts known to those skilled in the art and shown diagrammatically at 48, the slide 26 being in the extreme front position, the section 20c of the tube 20 is mutually locked, that is to say the rear end zone of the latter and the slide 26, for example by means of a pin 51 passing through the collar 37 and the tube 20 which for this purpose can be pierced from place to place (see FIG. 2).

Then, the jacks 38 are actuated in the opposite direction to the direction 43, towards their retracted state, in order to pull the slide 26 and the tube 20 backwards using the jacks 38; as soon as the slide 26 reaches the rear extreme position, this section 20c is completely disengaged from the drilled hole 4, this rear section 20c is separated from the other sections, then the slide 26 is brought back to the front extreme position using the jacks 38, the section 20b is secured to the collar 37 in the same way as above and the slide 26 is returned to its rear extreme position, in which the section 20b is detached from the section 20a; then these operations are repeated for the section 20a which, when the slider 26 reaches the rear extreme position, is completely released from the drilled hole 4 and releases from it the end of the flexible sheath 50 or of the cable that can be then detach from this section 20a.

In this case, obviously, the assembly between the sections is of a removable type.

In all cases, the tube and the drill bit forming a rigid unit perfectly guided in the device itself rigged and rigorously positioned, it is understood that the drilling is done with great precision, all the more that, from its initiation, everything the tube engaged in drilling then also contributes to guiding.

The possibility of course deviation over a distance of about ten meters remains less than a few centimeters.

The average time for drilling such a hole of ten meters is of the order of two hours.

Naturally, these figures are given by way of nonlimiting example.

In the drill bit 6 can obviously be included a striker, of which, due to the guiding, the jerks would not risk disturbing the trajectory, but preferably, the drill bit will not have such a striker and will therefore advance under the single thrust cylinders 38, regularly.

Obviously, within the limit of the setting possibilities, this device can be used for drilling not only horizontal but also inclined and even vertical, as well as for blind holes.

Claims (13)

1. A device for earth drilling, comprising a chassis (29), a drill bit (6), means for displacement of the drill bit (6) in translation with respect to the chassis (29) in a determined drilling direction (43), and means (13, 15) for supporting the chassis (29) against the earth (1) at least rearwards with reference to the said direction (43), the means for displacing the drilling bit (6) in translation with respect to the chassis (29) in the drilling direction (43) comprising :

a) means forming a slideway (27, 28) rigid with respect to the chassis (29) and oriented parallel to the direction of drilling (43),

b) a slide (26) carried by the slideway forming means (27, 28) and guided in translation along the length of them, parallel to the drilling direction (43), with respect to the chassis (29), this slide (26) delimiting internally a housing (46) at least partially laterally closed and forwardly open, with reference to the drilling direction (43),

c) thrust means (37, 38) acting between the chassis (29) and the slide (26) in the direction of translation of this latter along the slideway form-. ing means (27, 28), with respect to the chassis (29), at least in the direction of drilling (43),

d) an elongate member (20) having a rectilinear axis (44), the elongate member (20) being housed in the housing (46) and in abutment inside it, with respect to the slide (26), rearwards and sideways with respect to the drilling direction (43), in a position in which the axis (44) of the elongate member (20) is parallel to this direction (43), and the dimension (L) of the elongate member (20) parallel to its axis (44) being greater than the dimension (1) of the housing (46) parallel to the direction of drilling (43) so that the elongate member (20). has, projecting in front, with reference to the drilling direction (43), from the housing (46) of the slide (26), an end zone (19) carrying the drill (6) in a rigid manner, characterised in that the housing (46) of the slide (26) is rearwardly closed, with reference to the drilling direction (43), so that the elongate member (20) is in abutment inside the housing (46) rearwardly, with reference to the drilling direction (43), with respect to the slide (26) but is free in translation in this housing (46), with respect to the slide (26), in the reverse direction, in that the elongate member (20) forms a tube (20), and in that the drill bit (6) has externally, successively from front to rear with reference to the drilling direction (43), a plane face (52) transverse to the axis (44) of the tube (20), a face (16) - trunco-conical circularly about the axis (44) - converging forwardly with respect to the drilling direction (43), a face (17)-circularly cylindrical about the axis (44) of the tube (20) - connected to the said trunco-conical face, the said cylindrical face (17) having a diameter (D) greater than the dimensions (d) that the tube (20) has externally transverse with respect to its axis (44) and a dimension (X), measured parallel to this axis (44), negligible with respect to the corresponding dimension (L) of the tube (20), and carries in a solid manner a tail (18), immediately behind the said cylindrical face (17) with reference to the direction of drilling (43), the said tail (18) being engaged in the said end zone (19) of the tube forming member (20), removable fixing means (21) ensuring fixing of the said tail (18) with respect to the tube (20).

2. A drilling device according to claim 1, characterised in that the slide (26) has a rear end zone, with reference to the drilling direction (43), in which it carries in a fixed manner a plate (30) rearwardly closing the housing (46), with reference to the drilling direction (43), for constituting an abutment for an end (25) of the tube (20) opposite the said end zone (19) of this, and carrying in a fixed manner, inside the housing (46) and forwardly with reference to the drilling direction (43), a collar (31) fitting the said opposite end (25) of the tube (20) and immobilising it transversely with respect to the drilling direction (43).

3. A drilling device according to claim 1, characterised in that the slide (26) has a front end zone, with respect to the drilling direction (43), in which it carries in a fixed manner a clamp (32) closing the housing (46) laterally, with reference to the drilling direction (43), fitting the tube (20) and immobilising it transversely with respect to the drilling direction (43) in an intermediary zone (47) of the tube (20).

4. A drilling device according to claim 1, characterised in that the slide (26) has a rear end zone, with reference to the drilling direction (43), in which it carries in a fixed manner a plate (30) closing the housing (46) rearwardly, with reference to the drilling direction (43), for constituting an abutment for an end (25) of the tube (20) opposite the said end zone (19) of this, and carrying in a fixed manner, inside the housing (46) and forwardly with reference to the drilling direction (43), a collar (31) fitting the said opposite end (25) of the tube (20) and immobilising it transversely with respect to the drilling direction (43), and in that the slide (26) has a forward end zone, with respect to the drilling direction (43), in which it carries in a fixed manner a clamp (32) closing the housing (46) laterally, with reference to the drilling direction (43), fitting the tube (20) and immobilising it transversely with respect to the drilling direction (43) in an intermediary zone (47) of the tube (20).

5. A drilling device according to either of claims 3 and 4, characterised in that the clamp (32) comprises two sectors (33, 34) in the ratio of a sector (33) permanently fixed to the slide (26) and of a sector (34) removably fixed to the slide (26), and means for mutual removable fixing of these two sectors for closing the clamp (32) about a tube (20) or opening the clamp (32) and disengaging the access for a tube (20), between the inside of the clamp and the outside of it, transversely with respect to the drilling direction (43).

6. A drilling device according to any one of claims 3 to 5, characterised in that the thrust means (37, 38) comprise two jacks placed behind the clamp (32), respectively on either side of the slide (26), parallel to the direction of drilling (43), and acting on the slide (26) in the immediate proximity of the clamp.

7. A drilling device according to any one of claims 1 to 6, characterised in that the support means (13, 15) for the chassis (29) against the earth (45) comprises jacks (13, 15) for adjusting the drilling direction (43).

8. A drilling device according to any one of claims 1 to 7, characterised in that the tube (20) comprises a plurality of sections (20a, 20b, 20c) assembled in a rigid rectilinear assembly.

9. A drilling device according to any one of claims 1 to 8, characterised in that it comprises in addition support means (48) against the earth (45) forwardly, with reference to the direction of drilling (43).

10. A drilling device according to any one of claims 1 to 9, characterised in that the thrust means (37, 38) comprise double acting jacks (38).

11. A method of earth drilling to a trench (3) with the aid of a device according to any one of claims 1 to 10, according to which :

a) the chassis (29) of the device is supported against the earth (1) in such manner that the axis (44) of the tube forming means (20) corresponds exactly with an axis of a hole to be bored, the slide (26) occupying an extreme rear position with respect to the direction of drilling (43), and, in the front end zone (19) of the tube (20), a drill bit (6) is mounted,

b) with the aid of the thrust means (37, 38) thrusting regularly the slide (26) and from the tube (20c) retransmitting this regular thrust in the direction of drilling (43), the drill bit (6) is forcibly engaged in the earth (1) for drilling in it a hole (4),

c) with the thrust means (37, 38) the slide (26), which slides on the tube (20) is returned in the direction opposite from the direction of drilling (43),

d) a section (20b) of tube is placed in the housing (46) of the slide (26) and assembled in front on the rear of the said tube (20c) for extending the tube forming means (20), and the slide (26) and the tube forming means (20), carrying the drill bit (6), are thrust in the direction of drilling (43) with the thrust means (37, 38) for extending the hole (4),

e) if necessary the steps c) and d) are repeated until the arrival of the drill bit (6) in the said trench (3) where the drill bit (6) is dismounted from the tube forming means (20), characterised in that, during stage b), a thrust from the slide (26) is transmitted to the tube (20c) by application of this latter, towards the rear with respect to the drilling direction (43), inside the housing (46) leaving the tube (20c) free in translation in the reverse direction in this housing (46).

12. A method of drilling according to claim 11, characterised in that, in the case where the bored hole (4) needs to be provided with a metallic sheath, the tube forming means (20) are disengaged from the housing (46) of the slide (26) and the tube forming means (20) are left in place to in fact become this sheath.

13. A method of drilling according to claim 11, characterised in that, in the case where the bored hole (4) does not need to be provided with a metallic sheath, after having fixed on the tube forming means (20) in place of the drill bit (6) a piping (50) or a cable which is to be placed in the hole, the chassis (29) being supported against the earth (1) forwardly with reference to the drilling direction (43),

a) the tube forming means (20) and the slide (26) are mutually locked in an extreme forward position with respect to the drilling direction, then

b) the thrust means (37, 38) are activated for drawing the slide (26) and the tube forming means (40) in the opposite direction from the drilling direction (43) and, when the slide (26) arrives in an extreme rear position, with reference to the drilling direction (43), and when a section of tube is freed from the bored hole (4),

c) this section of the tube forming means (20) is separated and disengaged from the slide (26), and the stages a), b) and c) are repeated until total removal of the tube forming means (20) from the bored hole (4).

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