EP2925935B1 - Method of placing a tubular offshore foundation - Google Patents

Description

Background of the invention

The present invention relates to the field of ground drilling techniques which are carried out for the purpose of improving the characteristics of the soil and of making foundations and retaining structures in the ground, as known from EP 1 939 394 A .

The invention more specifically relates to a method of placing and sealing a tubular element in a soil located behind a screen. By screen, also called retaining screen, is meant in particular, but not exclusively, the concrete walls and in particular the diaphragm walls.

Such a tubular element can be used to inject fluid into the soil to improve its physical characteristics.

The tubular element may also constitute a structural element for making a anchor.

The invention will find particular application in the case where the soil behind the screen is disposed below a water load, such as a water table. In this case, the soil is saturated with water having a very high pressure, which can in some cases go up to 10 MPa. It is known that the drilling and the establishment of a tubular element, for example a tie rod, under a sheet are operations that are difficult to execute, particularly because of the large value of the ground water pressure.

Object and summary of the invention

An object of the present invention is first of all to provide a method of setting up and sealing a tubular element in a soil under water load located behind a retaining wall.

• on fournit un dispositif d'étanchéité, et un dispositif de forage comprenant un tube de forage qui présente une extrémité distale portant un outil de coupe détachable du tube de forage ;
• on solidarise ledit dispositif d'étanchéité à l'écran de soutènement;
• on introduit le dispositif de forage dans le dispositif d'étanchéité solidarisé à l'écran de soutènement ;
• on réalise un forage dans le sol à l'aide du dispositif de forage en faisant vibrer le tube de forage, le tube de forage étant amené à une profondeur déterminée ;
• on introduit un élément tubulaire dans le tube de forage après que le tube de forage a atteint la profondeur déterminée ;
• on détache l'outil de coupe du tube de forage et on remonte le tube de forage tout en maintenant l'élément tubulaire dans le forage ; et
• on injecte un coulis de scellement dans le forage afin de sceller l'élément tubulaire dans le sol.

The invention achieves its object by the fact that the method according to the invention comprises the following steps:

• providing a sealing device, and a drilling device comprising a drill pipe having a distal end carrying a detachable cutting tool of the drill pipe;
• said sealing device is secured to the retaining screen;
• introducing the drilling device into the sealing device secured to the retaining screen;
• drilling is carried out in the ground by means of the drilling device by vibrating the drill pipe, the drill pipe being brought to a determined depth;
• introducing a tubular element into the drill pipe after the drill pipe has reached the determined depth;
• detaching the cutting tool from the drill pipe and raising the drill pipe while maintaining the tubular element in the borehole; and
• a grout is injected into the borehole to seal the tubular element in the soil.

Sealing grout is any sealant based on cement, slag or any other binder.

"Distal" end means the end of the drill pipe that is intended to be at the bottom of the borehole, while "proximal" end means the end of the drill pipe which is opposite the end. distal, and which is on the surface out of the borehole.

The sealing device used in the implementation of the process is well known elsewhere. It may in particular be the device marketed by the French company TEC SYSTEM under the name "SAS BOP".

The sealing device makes it possible to seal against the water contained in the soil behind the screen, the pressure of which can be up to 10 MPa. Preferably, the sealing device makes it possible to seal either by functioning as a valve when no member passes through the sealing device, or by making a sealed contact with the drill pipe or the tubular element passing through the sealing device. sealing device. It is therefore understood that the sealing device prevents the ground water from gushing into the working area in which the operators are.

Preferably, the sealing device is secured to the screen after pre-drilling the screen all or part of its thickness. Optionally, the pre-perforation of the screen will be finalized after the positioning of the sealing device.

Preferably, but not necessarily, the securing of the sealing device consists of fixing by appropriate means, by example of the screws, the sealing device on the screen. According to another variant, the fastening could be achieved by firmly holding the sealing device against the screen.

Still preferably, the screen extends vertically and the drilling direction is inclined relative to the vertical.

Thus, at the end of the implementation of the method according to the invention, a tubular element is obtained embedded in the grout. It is also understood that the cutting tool, which is not raised to the surface, is found embedded in the grout, preferably while remaining attached to the tubular element.

Advantageously, the grout is injected into the drill pipe.

Thus, thanks to the invention, the drill pipe is removed while leaving the tubular element and the cutting tool in the borehole, thanks to the fact that the drill pipe is detached from the cutting tool. The drilling device thus serves both as means for excavating the ground, but also means for injecting the grout into the borehole, in addition to keeping the bore open during the insertion of the tubular element.

Advantageously, the vibration frequency is chosen so as to vibrate the cutting tool at its resonant frequency or at least at a frequency close to said resonant frequency. An interest is to improve the efficiency of drilling.

Advantageously, during drilling, the vibration frequency applied to the drill pipe is between 50 Hz and 200 Hz.

It follows that the speed of the implementation of the method according to the invention results in particular from the fact that the drilling is performed by vibrating the drill pipe. The vibration, which brings the cutting tool into resonance, or at least at a frequency close to the resonant frequency, has the effect of facilitating the penetration of the drill pipe into the ground.

Preferably, but not necessarily, during drilling, the drill pipe is also rotated to modify the position of the teeth of the cutting tool.

Advantageously, during the execution of the drilling, a drilling fluid is injected into the drill pipe, the drilling fluid flowing via the cutting tool, and cuttings of the borehole being evacuated via the sealing device.

The sealing device comprises for this purpose a discharge pipe for the discharge of cuttings drilling.

The cutting tool is preferably provided with orifices permitting the flow of the drilling fluid.

According to an advantageous aspect of the invention, the cutting tool is detached from the drill pipe by pushing the cutting tool with the tubular element while maintaining the drill pipe.

To do this, the drilling device comprises connecting means for detachably securing the cutting tool and the drill pipe.

Alternatively, and without departing from the scope of the present invention, one could detach the cutting tool by pulling on the drill pipe, and maintaining or pushing the cutting tool with the tubular member.

According to a preferred embodiment, the tubular element is secured to the detachable cutting tool before pushing the cutting tool with the tubular element.

This fixing is preferably carried out by screwing the tubular element to the cutting tool. It could however be a fitting by interlocking. An advantage of the fastening by screwing is that the operator can feel if the fixation has correctly occurred.

According to a first embodiment, the grout is injected into the borehole while raising the drill pipe. During this injection phase, it is understood that the tubular element and the cutting tool remain in the borehole. The sealing slurry, which flows into the bore, coats the tubular element over at least a portion of its height, whereby the tubular element is sealed in the soil.

Advantageously, the drill pipe is vibrated during the injection of the grout.

An interest is to improve the flow and distribution of the grout in the borehole.

Thus, thanks to the vibration of the drill pipe during drilling, and during the injection of the grout, the speed of execution of the process is improved.

According to an alternative embodiment, the drill pipe is raised while vibrating said drill pipe. This lift may or may not be accompanied by the injection of grout.

An interest in vibrating the drill pipe is to allow the withdrawal of the drill pipe without rotation, which has the effect of substantially reducing the risk of circulation of grout between the drill pipe and the ground. Another advantage of vibrating the drill pipe is to tighten the ground around the drill pipe, which further reduces the risk of circulation of the grout between the drill pipe and the ground.

Advantageously, the sealing grout is injected into the tubular element via its proximal end, and flows at the bottom of the borehole via the cutting tool. It is therefore understood that the tubular element serves to bring the grout to the bottom of the borehole, the sealing grout flowing through the orifices in the cutting tool. In this case, it is understood that the sealing slurry flows from the distal end of the borehole and rises towards the proximal end of said borehole.

Alternatively, the grout is injected between the tubular member and the drill pipe.

In this variant, the sealing slurry flows into the borehole through the distal end of the drill pipe. Since the drill pipe is progressively extracted, the injection between the drill pipe and the tubular element makes it possible to perform an injection according to the height of the borehole during the raising of the drill pipe, and not only since the distal end of the borehole.

In a preferred embodiment, the sealing grout is pressurized, the drill pipe is raised while injecting the pressurized grout into the bore, and while vibrating the drill pipe.

To carry out this pressurization, a pump is preferably used which makes it possible to inject the grout at a pressure of between 0.1 and 5 MPa.

The pressure injection makes it possible to create a grouting bulb with a diameter substantially greater than the diameter of the borehole, which has the effect of further improving the support. The bulb may extend over all or part of the height of the borehole. Of preferably, the bulb extends from the bottom of the borehole to the middle of the borehole.

As already mentioned above, the vibration setting advantageously makes it possible to tighten the ground around the drill pipe. This tightening has the effect of consolidating the soil and thus makes it possible to perform a pressure injection of the grout in many types of soil. In addition, thanks to the presence of the sealing device at the drilling head, it is possible to perform the injection under high pressure, for example at a pressure of between 0.5 and 5 MPa.

Preferably, predefined amounts of grout are injected into predefined soil slices, depending on the initial characteristics of the soil and the improvement objective.

Alternatively, the direction of drilling is inclined relative to a vertical direction. An interest is to be able to achieve inclined anchors. An advantageous application lies in the manufacture of inclined tie rods, for example to ensure the stability of a diaphragm wall during a terracing operation.

According to an advantageous embodiment, a vibration target frequency is calculated, and the drill pipe is vibrated at said vibration target frequency during drilling.

This vibration target frequency, which is applied to the drill pipe, is optimally selected to facilitate the drilling operation, particularly in particularly hard soils. In a general way, the computation is carried out starting from a modelization of the phenomena of perforation.

Advantageously, the calculation uses the length of the drill pipe. Preferably, the vibration target frequency is a function of the length of the drill pipe, while being bounded by a predetermined maximum frequency value, denoted Fmax.

This predetermined maximum frequency value, which preferably corresponds to the maximum frequency that can develop the means for vibrating the drill pipe is preferably between 100 and 160 Hz.

Still preferably, the calculation uses a constant value corresponding to the speed of propagation of the compression waves in the drilling tube, this speed depending on the constituent material of the drill pipe.

• Fmax (la valeur de fréquence maximale prédéterminée) si Fmax<(V)/(2*L), où V est la vitesse de propagation des ondes de compression dans le tube de forage, et L la longueur du tube de forage, OU :
• (n*V)/(2*L) si Fmax>(V)/(2*L), où n est un nombre entier supérieur ou égal à 1 choisi de sorte que (n*V)/(2*L)<=Fmax et ((n+1)*V)/(2*L)>Fmax.

Preferably, but not necessarily, the reference target frequency is equal to:

• Fmax (the predetermined maximum frequency value) if Fmax <(V) / (2 * L), where V is the speed of propagation of compressional waves in the drill pipe, and L the length of the drill pipe, OR:
• (n * V) / (2 * L) if Fmax> (V) / (2 * L), where n is an integer greater than or equal to 1 chosen so that (n * V) / (2 * L) <= Fmax and ((n + 1) * V) / (2 * L)> Fmax.

The inventors have found that this formula makes it possible to obtain an optimal target frequency of vibration which substantially increases the efficiency of the drilling operation.

This calculation is performed by a computer having appropriate calculation means.

For deep drilling, the length of the drill pipe is increased during drilling. To do this, tube sections are used that are attached end to end during drilling to increase the length of the borehole.

Consequently, within the meaning of the invention, the term "drill pipe" is understood to mean a single drill pipe, a plurality of tubular elements attached end to end, for example by screwing.

Advantageously, the target frequency of vibration is recalculated with each increase in the length of the drill pipe.

An interest is to ensure drilling with optimum efficiency over the entire depth of drilling.

The invention furthermore relates to a method for producing a tie rod in which the steps of the method according to the invention are implemented and then cables are sealed in the tubular element placed in the borehole.

• un élément tubulaire ;
• un dispositif de forage qui comprend un tube de forage ayant une extrémité distale portant un outil de coupe détachable du tube de forage,
• un dispositif d'étanchéité configuré pour être solidarisé à l'écran de soutènement et être traversé de manière étanche par l'élément tubulaire ou le tube de forage;
• des moyens pour faire vibrer le tube de forage ;
• des moyens pour réaliser un forage dans le sol à l'aide du dispositif de forage, le dispositif de forage traversant le dispositif d'étanchéité, et pour amener le tube de forage à une profondeur prédéterminée ;
• des moyens pour introduire l'élément tubulaire dans le tube de forage après que le tube de forage a atteint la profondeur prédéterminée ;
• des moyens pour détacher l'outil de coupe du tube de forage ;
• des moyens pour remonter le tube de forage tout en maintenant l'élément tubulaire dans le forage ; et
• des moyens pour injecter un coulis de scellement dans le forage afin de sceller l'élément tubulaire dans le forage.

The invention further relates to an installation for carrying out the method of placing and sealing a tubular element in a floor located behind a screen according to the invention, comprising:

• a tubular element;
• a drilling device which comprises a drill pipe having a distal end carrying a detachable cutting tool of the drill pipe,
• a sealing device configured to be secured to the retaining screen and to be leaktight through the tubular element or the drill pipe;
• means for vibrating the drill pipe;
• means for drilling into the ground using the drilling device, the drilling device passing through the sealing device, and for bringing the drill pipe to a predetermined depth;
• means for introducing the tubular member into the drill pipe after the drill pipe has reached the predetermined depth;
• means for detaching the cutting tool from the drill pipe;
• means for raising the drill pipe while maintaining the tubular element in the borehole; and
• means for injecting a grout into the borehole to seal the tubular member in the borehole.

The means for detaching the cutting tool from the drill pipe comprise in particular the tubular element.

Preferably, the cutting tool comprises a fixing sleeve having a diameter smaller than the diameter of the drill pipe, said sleeve being configured to be attached to a distal end of the tubular member. Preferably, the sleeve has a thread or a thread configured to cooperate with a thread or a complementary thread located at the distal end of the tubular element.

Advantageously, the cutting tool comprises a channel connecting the sleeve to one end of the cutting tool provided with a cutting edge and injection orifices, said channel making it possible to feed the injection orifices with fluid, and the cutting tool further comprises a non-return valve arranged to close the channel when no fluid flows from the sleeve to the injection ports.

Thus, during the injection of the grout (or drilling fluid) into the tubular element, the non-return valve opens to let the grout (or drilling fluid) pass, the latter flowing in the bore through the injection ports.

The non-return valve makes it possible to avoid the rise of fluid towards the proximal end of the borehole.

Advantageously, the installation according to the invention comprises releasable holding means for holding together the cutting tool and the drill pipe during drilling.

Preferably, these releasable holding means comprise a pin attached to the cutting tool and engaging in a groove or recess formed at the distal end of the drill pipe or a tool holder attached to the distal end of the drill pipe. The pin is configured to disengage groove when an axial force of predetermined intensity is applied to the cutting tool.

According to an advantageous aspect of the invention, the installation comprises an annular sealing member for sealing between the drill pipe and the cutting tool. Preferably, but not exclusively, the sealing member is integral with the drill pipe and bears against the sleeve or the body connected to the sleeve.

Preferably, the sealing member is configured to pass a fluid only in the case where said fluid flows axially towards the distal end of the drill pipe. This fluid can be water, grout, or any other type of fluid. It is thus understood that the sealing member is configured to prevent the fluid from returning to the proximal end of the drill pipe by circulating between the sleeve and the drill pipe.

Advantageously, the sealing member is also configured to seal between the drill pipe and the tubular element after attachment of the tubular member to the sleeve and detachment of the cutting tool.

It is understood that during the raising of the drill pipe, while the tubular element remains at the bottom of the borehole, the sealing member bears against the outer surface of the body or sleeve and that of the tubular element, thanks to the sealing is made between the drill pipe and the tubular element throughout the rise of the drill pipe. An interest is to prevent a backward circulation of the grout between the drill pipe and the tubular element during the injection of the grout that takes place during the withdrawal of the drill pipe.

According to another advantageous aspect of the invention, the drilling installation further comprises a damper disposed between the sealing device and the drill pipe in order to prevent the transmission of the vibrations of the drill pipe towards the sealing device. An interest is to avoid vibrating the sealing device and the screen.

Brief description of the drawings

• la figure 1 illustre la mise en place d'un dispositif d'étanchéité de l'installation selon l'invention dans une réservation réalisée dans un écran de soutènement ;
• la figure 2 illustre le montage de l'outil de coupe détachable à l'extrémité distale du tube de forage ;
• la figure 3 illustre l'étape de forage dans le sol après introduction du dispositif de forage dans le dispositif d'étanchéité ;
• la figure 4 illustre l'introduction de l'élément tubulaire dans le tube de forage et sa fixation à l'outil de coupe par vissage ;
• la figure 5 illustre l'étape au cours de laquelle on détache l'outil de coupe du tube de forage ;
• la figure 6 illustre l'étape d'injection de coulis de scellement tout en remontant le tube de forage ;
• la figure 7 illustre le démontage du tube de forage du dispositif d'étanchéité ;
• la figure 8 est une vue de détail de l'extrémité distale du dispositif de forage ;
• la figure 9 est une vue de face de l'outil de coupe ;
• la figure 10 est une vue en coupe longitudinale de l'extrémité distale du dispositif de forage montrant l'outil de coupe connecté au tube de forage ;
• la figure 11 est une vue en coupe longitudinale de l'extrémité distale du dispositif de forage montrant l'outil de coupe détaché du tube de forage ; et
• la figure 12 schématise le procédé d'optimisation de la fréquence de vibration appliquée au tube de forage.

The invention will be better understood on reading the following description of embodiments and embodiments of the invention given as non-limiting examples, with reference to the accompanying drawings, in which:

• the figure 1 illustrates the installation of a sealing device of the installation according to the invention in a reservation made in a retaining screen;
• the figure 2 illustrates the mounting of the detachable cutting tool at the distal end of the drill pipe;
• the figure 3 illustrates the drilling step in the soil after introduction of the drilling device into the sealing device;
• the figure 4 illustrates the introduction of the tubular element into the drill pipe and its attachment to the screw cutter;
• the figure 5 illustrates the step during which the cutting tool is detached from the drill pipe;
• the figure 6 illustrates the step of grouting injection while raising the drill pipe;
• the figure 7 illustrates the disassembly of the drill pipe of the sealing device;
• the figure 8 is a detail view of the distal end of the drilling device;
• the figure 9 is a front view of the cutting tool;
• the figure 10 is a longitudinal sectional view of the distal end of the drilling device showing the cutting tool connected to the drill pipe;
• the figure 11 is a longitudinal sectional view of the distal end of the drilling device showing the cutting tool detached from the drill pipe; and
• the figure 12 schematizes the method of optimizing the vibration frequency applied to the drill pipe.

Detailed description of the invention

With the help of Figures 1 to 7 First of all we shall describe an embodiment of the implementation and method of sealing a tubular in a soil S in a water load which is located behind a retaining screen E. In this example , the screen E is a retaining screen consisting of a vertical molded wall. One of the faces E1 of the screen E is disengaged while the opposite face E2 is located on the side of the soil layer S.

The soil layer S which is supported by the screen E is, in this example, disposed below a water load, such as a water table. Since the method of manufacturing the screen E is well known, it will not be described in detail here.

It is just mentioned that it may be a molded wall made using a bucket or a hydrofraise.

The purpose of the method according to the invention is to set up and seal a tubular element 90 in the soil S located behind the screen E. This tubular element may be for example a reinforcement or a perforated tube intended for making injections in the ground S. in other words, preferably, the method according to the invention may be implemented to manufacture a tie rod or to perform injections in the ground S.

According to the invention, there is first provided a sealing device 10 which is secured to the screen.

For this purpose, in this nonlimiting example, the screen E is drilled along part of its thickness in order to make a reservation R in the screen E. In this example, the drilling axis A is inclined at an angle α with respect to the horizontal. The drill axis A is also inclined with respect to the vertical.

The sealing device 10 comprises a front tubular end 12 which is introduced into the reservation R. It is found that the diameter of the tubular end 12 is substantially equal to the diameter of the reservation R. The reservation is then drilled according to any the thickness of the screen.

According to another variant, more traditional, it sets up the reservation R at the time of the execution of the screen E. In this case the reservation R is in the form of a tube and a plate to allow the sealing device 10 to be secured . The reservation R is integral with an armature cage (not shown here) constituting the skeleton of the retaining shield E.

In a manner known moreover, the sealing device 10 further comprises a chimney chamber 14 which is connected to the tubular end 12; this chimney chamber has a discharge chimney 16 for evacuating the excavation cuttings. In this example, the sealing device 10 further comprises a valve 18 connected to the chimney chamber 14 and a first half-chamber 20 connected to the valve 18. In this example, the valve 18 is a pinch valve with elastic deformation, well known elsewhere. Its function is to seal by virtue of the fact that the sleeve engages a tubular member passing through the valve 18. It also makes it possible to close the sealing device when no member passes through the sealing device.

The sealing device 10 is part of an installation 100 according to the invention which further comprises a drilling device 30. This drilling device 30 comprises a drilling tube 32 having a distal end 34 which carries a cutting tool 36 . According to the invention, this cutting tool 36 is detachable from the drill pipe 32.

Traditionally, the drill pipe 32 consists of a string of rods that are attached end to end to increase the length of the drill pipe during drilling. According to the invention, the drilling device 30 is introduced into the sealing device 10. For this purpose, the distal end of the device of the drill pipe is equipped in this example with a stuffing box 38, a second half-chamber 40 which surrounds the drill pipe 32. As can be understood by means of the figures 2 and 3 , The second half-chamber 40 is assembled with the first half-chamber 20 of the sealing device 10.

According to an advantageous aspect of the invention, the first half-chamber 20 and the second half-chamber 40 are fixed to each other while enclosing a thick rubber ring 42, so that the assembly consisting of the first half-chamber 20, the second half-chamber 40 and the rubber ring 42 constitutes a vibration damper 44.

This damper 44, which is disposed between the sealing device 10 and the drill pipe 32, has the role of preventing the transmission of vibrations from the drill pipe to the sealing device.

It is furthermore understood that the sealing device, and in particular the valve 18, makes it possible to prevent the ground water from spouting on the working area of the operators, this zone being separated from the ground S by the screen E .

The installation 100 furthermore comprises means 50 for vibrating the drill pipe 32. The means 50 for vibrating the drill pipe 32, in this case a vibration generator 50, make it possible to generate compressional waves which transmit along the drill pipe 32 to its distal end 34 and to the cutting tool 36. Here L is the length of the drill pipe 32 between its distal end and the vibration generator 50. The length L of the tube drilling 32 therefore increases during the drilling.

According to the invention, a drilling F is carried out in the ground S by means of the installation 100 by means of the drilling device 30 of the installation 100 by vibrating the drill pipe 32 by means of the vibration generator 50.

In this example, but not necessarily, during the drilling step, the drill pipe 32 is also rotated about the drill axis A by means of rotational drive means 52.

During the drilling, a drilling fluid G is injected into the drill pipe from the proximal end 37 of the drill pipe 32. This drilling fluid G flows into the drill pipe 32 to the tool Headers 36. the cutting tool 36 is provided with ports 35 for injecting the G drilling fluid into the drilling F. G drilling fluid then rises along the borehole in carrying along cuttings, and then passes through the E screen flowing between the drill pipe 32 and the tubular end 12 of the sealing device, before joining the chimney chamber 14 and the exhaust chimney 16, the latter thus making it possible to evacuate the fluid from drilling G.

The drilling is carried out until the drill pipe, and more precisely the cutting tool is brought to a given depth H represented on the figure 4 . In this example, determined depth H is the distance between the face E2 of the screen E facing the ground S and the bottom F1 of the bore F.

Before describing the other steps of the method according to the invention, we will now take a closer look at the cutting tool 36 of the installation 100.

With the help of Figures 8 to 11 it is found that the detachable cutting tool 36 is initially mounted on a tool holder 37 which is attached to the distal end 34 of the drill pipe 32.

The cutting tool 36 further comprises a fixing sleeve 60 which has a diameter smaller than the inside diameter of the drill pipe 32. The sleeve 60 is integral with a body 64 in which is formed a channel 62 which extends along the axial direction X of the drill pipe. This channel 62 connects the sleeve 60 to the cutting edge 66 of the cutting tool 36. Consequently, the channel 62 makes it possible to feed the injection orifices 35 with fluid, in particular, but not exclusively, with drilling fluid during the step drilling.

According to an advantageous aspect of the invention, the cutting tool 36 further comprises a check valve 68 which is arranged at the downstream end 62a of the channel 62 so as to close said channel 62 when no fluid s flows from the sleeve 60 to the injection ports 35. In this example, the non-return valve 68 consists of a part 70 mounted on a spring 72 so that the non-return valve allows a flow to pass through. which flows towards the orifices 35 of the cutter 66, but prevents a flow from flowing through the channel 62 towards the sleeve 60. It is thus clear that the body 64 in which the channel 62 is formed is disposed between the anti-tamper valve. back 68 and the fixing sleeve 60.

The cutting tool 36 is detachable from the tool holder 37 and thus from the drill pipe 32. To maintain the cutting tool 36 of the drill pipe 32 during the drilling operation, the cutting tool 36 comprises a pin 74 which extends transversely with respect to the axis of rotation X of the cutting tool so as to be housed in two notches 76 formed in the tool holder 37.

The pin 74 is dimensioned so that it is mounted tightly in the notches 76 in order to avoid inadvertent detachment of the cutting tool 36 with respect to the tool holder 37. The notches 76 open axially towards the end distal 37a of the tool holder 37 which is directed towards the cutter 66. It is therefore understood that an axial thrust on the sleeve 60 directed towards the cutter 66 having an intensity greater than a predetermined threshold makes it possible to disengage the pin 74 from the indentations 76 and thus to detach the cutting tool 36 from the drill pipe 32.

It is therefore understood that the pin 74 and the notches 76 are releasable holding means for holding together the cutting tool and the drill pipe during drilling.

Referring again to Figures 10 and 11 , it is found that the installation 100 comprises a sealing member 80 to ensure axial sealing between the drill pipe 32 and the body 64 sleeve 60. In this example, the sealing member 80 is an annular seal which is integral with the drill pipe 32. On the example of the figure 10 , the sealing member 80 is also integral with the tool holder 37. The sealing member 80 thus bears against the outer surface of the body 64 in order to seal between the drill pipe 32 and the cutting tool 36.

More specifically, in this example, the sealing member 80 is configured to pass a fluid only in the case where said fluid flows axially towards the distal end 34 of the drill pipe 32. In other words, the sealing member 80 passes only the flows directed to the cutter 66. It thus makes it possible to prevent a upward circulation of fluid between the sleeve 60 and the drill pipe 32.

In this example, when the cutting tool 36 is attached to the tool holder 37, the sealing member 80 bears against the body 64. Insofar as the sleeve 60 has an outside diameter which is substantially equal to the outside diameter of the body 64, it is understood by means of the figure 11 when the cutting tool 36 is detached from the tool holder 37, the sealing member 80 moves axially and bears against the sleeve to maintain the axial seal between the drill pipe 32 and the sleeve 60.

Referring again to the figure 10 , it is found that the end of the sleeve 60a which is opposite the body 64 has a thread 82.

The following steps of the process according to the invention will now be described with reference again to figure 4 .

After the drill pipe 32 has reached its predetermined depth H, a tubular element 90 is introduced into the tube of drilling 32. This tubular element 90 is also comprised of a plurality of portions of tubes which are secured end to end. The tubular element 90 is introduced into the drill pipe 32 until the distal end 90a of the tubular element 90 comes into contact with the end 60a of the sleeve 60. The tubular element 90 is then subjected to rotation to screw the distal end 90a of the tubular member 90 to the thread 82 of the sleeve 60. Once the tubular member is attached to the sleeve 60 of the detachable cutting tool 36, a thrust is exerted on the tubular member 90 to push the cutting tool 36, which causes the detachment of the cutting tool 36 from the drill pipe 32.

Preferably, the drill pipe 32 is held while pushing the tubular member 90 attached to the cutting tool. The separation of the cutting tool 36 from the drill pipe 32 is illustrated in FIG. figure 5 . In this example, after the detachment of the cutting tool 36, as shown in FIG. figure 6 , a cementitious grout C, for example a grout of cement, is injected into the borehole in order to seal the tubular element 90 in the soil S. To do this, the grout C is injected into the tubular element 90 by its proximal end and flows at the bottom of the bore through the orifices 35 of the cutting tool 36.

According to the invention, in the example of figure 6 , the injection of the grout C is carried out by raising the drill pipe 32 while vibrating the drill pipe 32. As mentioned above, the vibrations make it possible to tighten the soil S around the drill pipe, which makes it possible to avoid a rising circulation of the grout between the drill pipe 32 and the ground S.

In this example, the vibration frequency of the drill pipe applied during the rise of the drill pipe 32 is of the order of 50 Hz to 130 Hz depending on the length of the drill pipe.

Alternatively, the grout C is pressurized by a pump, not shown here, before its injection into the tubular element. An interest is to be able to form a bulb of grout having a larger diameter. The pressurized sealing slurry may reach a pressure of the order of 0.5 to 5 MPa.

According to another variant, not shown here, the injection of grout could be achieved by an injection between the element tubular and the drill pipe as soon as the sealing member 80 allows the flow of the grout to the cutting edge 66.

With the damper 44, the vibrations emitted by the vibration generator 50 are transmitted to the drill pipe 32 but not to the sealing device 10 or the screen E.

As shown on the figure 7 , the drill pipe 32 is raised until the distal end of the drill pipe 32 reaches the sealing device 10. The drill pipe 32 is then removed from the sealing device 10.

As we see on this figure 7 , The tubular member 90 is then sealed in a bulb B bedding grout.

This tubular element 90 can then be used to manufacture a anchor by sealing cables (not shown here) in the tubular element set up and sealed in the borehole.

According to a particularly advantageous aspect of the invention, during the realization of drilling F described above, it is sought to optimize the vibration frequency to maximize the drilling energy transmitted by the drill pipe 32. To do this, it calculates a target vibration frequency that is applied by the vibration generator to the drill pipe 32.

The drill pipe 32 is thus vibrated at the vibration target frequency during the drilling. It is therefore clear that this vibration target frequency is a vibration frequency that is applied to the drill pipe. In this case, these vibrations are compressional waves that are transmitted along the drill pipe defining bellies and nodes. These vibration waves bring the drill pipe 32 into resonance, or at least at a frequency close to its resonant frequency, which produces a maximum energy at the cutting tool 36, with the effect of substantially increase the drilling efficiency, and thus the overall efficiency of the process according to the invention.

As shown on the figure 12 The calculation of the target vibration frequency comprises firstly a step S100 at which manually enters or automatically determining the length L of the drill pipe 32. It is therefore assumed here that the drilling tube is in vibration over its entire length.

Then, from this length, the target frequency of vibration during a step S102 is calculated from the length L of the drill pipe, the speed of propagation of the compression wave in the drill pipe 32 . in this example, the drill pipe 32 is made of steel.

Still preferably, the calculation uses a constant value corresponding to the speed of propagation of the compression waves in the drill pipe, this speed depending on the constituent material of the drill pipe.

According to the invention, insofar as the length of the drill pipe 32 increases during drilling because of the successive addition of the tubular elements, the target vibration frequency is recalculated at each increase in the length of the tube. drilling. This keeps an optimal vibration frequency throughout the duration of the drilling.

The vibration target frequency thus calculated is then displayed as a suggestion to the operator. It may also in another embodiment be sent as a setpoint to the vibration generator 50 during a step S104.

• Fmax (la valeur de fréquence maximale prédéterminée) si Fmax<(V)/(2*L), où V est la vitesse de propagation des ondes de compression dans le tube de forage, et L la longueur du tube de forage, OU :
• (n*V)/(2*L) si Fmax>(V)/(2*L), où n est un nombre entier supérieur ou égal à 1 choisi de sorte que (n*V)/(2*L)<=Fmax et ((n+1)*V)/(1*L)>Fmax,

Preferably, but not necessarily, the reference target frequency is equal to:

• Fmax (the predetermined maximum frequency value) if Fmax <(V) / (2 * L), where V is the speed of propagation of compressional waves in the drill pipe, and L the length of the drill pipe, OR:
• (n * V) / (2 * L) if Fmax> (V) / (2 * L), where n is an integer greater than or equal to 1 chosen so that (n * V) / (2 * L) <= Fmax and ((n + 1) * V) / (1 * L)> Fmax,

In the following example, V is equal to 5000 m / s, Fmax is equal to 130 Hz. L, corresponds to the sum of the lengths of the tubular elements placed end to end.

In this example, the tubular elements have the same unit length, namely a length of 3 meters.

The following result table is obtained: Number of tubes L (m) 2L V / (2 * L) not F target (Hz) 5 15 30 167 130 (Fmax) 6 18 36 139 130 (Fmax) 7 21 42 119 1 119 8 24 48 104 1 104 9 27 54 93 1 93 10 30 60 83 1 83 11 33 66 76 1 76 12 36 72 69 1 69 13 39 78 64 2 128 14 42 84 60 2 120 15 45 90 56 2 112 16 48 96 52 2 104 17 51 102 49 2 98 18 54 108 46 2 93 19 57 114 44 2 88 20 60 120 42 3 126 21 63 126 40 3 120 22 66 132 38 3 114 23 69 138 36 3 108 24 72 144 35 3 105 25 75 150 33 3 99 26 78 156 32 4 128 27 81 162 31 4 124

Claims (15)

1. A method for placing and sealing a tubular element in a ground (S) under a water head situated behind a retaining screen (E), comprising:

   providing a sealing device (10), and a drilling device (30) comprising a drill pipe (32) that has a distal end (34) bearing a cutting tool (36) detachable from the drill pipe;

   securing said sealing device (10) to the retaining screen;

   inserting the drilling device (30) into the sealing device (10) secured to the retaining screen;

   drilling a borehole in the ground using the drilling device (30) by vibrating the drill pipe, the drill pipe being brought to a determined depth (H);

   inserting a tubular element (90) in the drill pipe (32) after the drill pipe has reached the determined depth;

   detaching the cutting tool (36) from the drill pipe (32) and raising the drill pipe while keeping the tubular element (90) in the borehole; and

   injecting a sealing grout (C) into the borehole in order to seal the tubular element (90) in the ground (S).
2. The method according to claim 1, comprising, during the performance of the drilling, injecting a drilling fluid (G) into the drill pipe, the drilling fluid flowing via the cutting tool, and the debris from the drilling being discharged via the sealing device (10).
3. The method according to claim 1 or 2, comprising detaching the cutting tool (36) from the drill pipe (32) by pushing the cutting tool using the tubular element while maintaining the drill pipe (32).
4. The method according to any one of claims 1 to 3, comprising injecting the sealing grout (C) into the borehole while raising the drill pipe (32).
5. The method according to any one of claims 1 to 4, comprising vibrating the drill pipe (32) during the injection of the sealing grout.
6. The method according to any one of claims 1 to 5, comprising pressurizing the sealing grout (C), raising the drill pipe while injecting the sealing grout under pressure into the borehole, and all while vibrating the drill pipe.
7. A method for producing a ground anchor in which the method according to any one of claims 1 to 6 is implemented, then cables are sealed in the tubular element placed in the borehole.
8. An installation (100) for carrying out the method for placing and sealing a tubular element in a ground (S) under a water head situated behind a retaining screen (E) according to any one of claims 1 to 7, the installation including:

   a tubular element;

   a drilling device (30) that comprises a drill pipe (32) having a distal end (34) bearing a cutting tool (36) detachable from the drill pipe;

   a sealing device (10) configured to be secured to the retaining screen (E) and to be traversed tightly by the tubular element or the drill pipe;

   means (50) for vibrating the drill pipe (32);

   means for producing a borehole (P) in the ground using the drilling device, the drilling device traversing the sealing device, and for bringing the drill pipe to a predetermined depth;

   means for inserting the tubular element into the drill pipe after the drill pipe has reached a predetermined depth;

   means for detaching the cutting tool from the drill pipe;

   means for raising the drill pipe while keeping the tubular element in the borehole; and

   means for injecting a sealing grout into the borehole in order to seal the tubular element in the borehole.
9. Installation according to claim 8, characterized in that the cutting tool (36) includes a fastening sleeve (60) having a diameter smaller than the diameter of the drill pipe, said sleeve being configured to be fastened to a distal end (90a) of the tubular element (90).
10. The installation according to claim 9, characterized in that the cutting tool (36) includes a channel (62) connecting the sleeve (60) to an end of the cutting tool provided with a bit (66) and injection orifices (35), said channel making it possible to supply the injection orifices with fluid, and in that the cutting tool (36) further includes a non-return valve (68) arranged to close off the channel (62) when no fluid is flowing from the sleeve (60) toward the injection orifices (35).
11. The installation according to any one of claims 8 to 10, characterized in that it comprises releasable maintaining means (74, 76) to keep the cutting tool (36) and the drill pipe (32) together during drilling.
12. The installation according to any one of claims 8 to 11, characterized in that it includes a sealing member (80) to provide sealing between the drill pipe (32) and the cutting tool (36).
13. The installation according to claim 12, characterized in that the sealing member (80) is configured to allow a fluid to pass only if said fluid flows axially toward the distal end (34) of the drill pipe (32).
14. The installation according to claim 9 or 10 combined with claim 12 or 13, characterized in that the sealing member is also configured to provide sealing between the drill pipe and the tubular element after the tubular element is fastened to the sleeve and the cutting tool is detached.
15. The drilling installation according to any one of claims 8 to 14, characterized in that it further includes a shock absorber (44) arranged between the sealing device (10) and the drill pipe (32) in order to prevent vibrations of the drill pipe (32) from being transmitted toward the sealing device (10).

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