EP2900875B1 - Method of making a foundation - Google Patents

Description

Background of the invention

The present invention relates to the field of drilling techniques in the ground which are carried out with the aim of making foundations and retaining structures in the ground.

The invention relates more specifically to a method for producing an anchor in the ground.

By anchoring, we mean in particular bored piles of small diameters, also called micropiles, or anchoring tie rods.

Traditionally, to make such an anchor, first of all a borehole is made by rotating a cutting tool which will excavate the ground.

During drilling, a liquid, called drilling fluid, is generally injected in order to cool the cutting tool and to evacuate the cuttings.

A reinforcement is then placed in the borehole before injecting a sealing grout.

These different steps are generally carried out successively using different materials depending on the terrain present, as a result of which this traditional process has the disadvantage of being quite slow to implement.

The document DE 3612437 A1 describes a method of making an excavation using a drilling tool having a vibratory drive means. After the drill tool has been driven to a set depth, concrete is injected under a drill bit of the drill tool at a pressure to generate a lifting force to extract the drill tool out of the drill bit. of the excavation.

Object and summary of the invention

An object of the invention is to provide a method for producing an anchor in the ground with better efficiency than the traditional method.

The invention achieves its object by the method according to claim 1.

• on réalise un forage dans le sol à l'aide de l'outil de forage en faisant vibrer le tube de forage, le tube de forage étant amené à une profondeur prédéterminée;
• lorsque le tube de forage a atteint la profondeur prédéterminée, on introduit une armature dans le tube de forage, et on injecte un coulis de scellement dans le forage via le tube de forage avant ou après avoir introduit l'armature dans le tube de forage.

According to the invention there is provided a drilling tool comprising a drill pipe which has an open distal end and means for vibrating the drill pipe;

• drilling is carried out in the ground using the drilling tool by vibrating the drill pipe, the drill pipe being brought to a predetermined depth;
• when the drill pipe has reached the predetermined depth, a reinforcement is introduced into the drill pipe, and a sealing grout is injected into the borehole via the drill pipe before or after having introduced the reinforcement into the drill pipe.

By sealing slurry, we mean any sealing product based on cement, slag, or any other binder.

Thus, at the end of the implementation of the method according to the invention, an anchoring is obtained in the ground in which the reinforcement is embedded in the sealing grout.

Thus, thanks to the invention, the drill pipe can be withdrawn while leaving the armature in the borehole thanks to the fact that the distal end of the drill pipe is open. The drill pipe therefore serves both as a means of excavating the ground, but also as a means of injecting the drilling fluid and the sealing grout into the borehole, in addition to guaranteeing the maintenance of the borehole during the insertion of the frame.

Advantageously, the frequency of vibration is chosen so as to cause the drill pipe to vibrate at its resonant frequency or at the very least at a frequency close to said resonant frequency.

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

It follows that the rapid implementation of the method according to the invention results in particular from the fact that the drilling is carried out by vibrating the drill pipe. The vibration, which causes the drill pipe and in particular its distal end to enter at the resonant frequency or at the very least at a frequency close to the resonant frequency, facilitates the penetration of the drill pipe into the ground.

Preferably, but not necessarily, during drilling, the drill pipe is also rotated to change the position of cutting teeth disposed at the distal end of the drill pipe.

Also, according to the invention, the drill pipe serves both as a drill member and as a protection pipe for placing the reinforcement.

More preferably, a drilling fluid is injected into the drill pipe while the drilling is being carried out.

According to a first variant, the reinforcement is introduced into the drill pipe before the injection of sealing grout.

Advantageously, after having introduced the reinforcement into the drill pipe, said reinforcement is maintained by appropriate means during the injection of grout. An interest is to obtain an anchor provided with a reinforcement correctly centered in the anchor. According to another variant, the reinforcement is introduced into the drill pipe after the injection of sealing grout.

Preferably, the armature is held so that its lower end is slightly distant from the bottom of the borehole, which makes it possible to ensure that the distal part of the armature is completely embedded in the sealing grout.

According to a first mode of implementation, the drill pipe is removed after having injected the sealing grout into the borehole. In this case, the reinforcement is preferably introduced before the withdrawal of the drill pipe.

According to a second mode of implementation, the drill pipe is removed while injecting the sealing grout into the borehole.

Advantageously, the sealing grout is injected while vibrating said drill pipe. This setting in vibration can be carried out within the framework of the first or the second mode of implementation of the invention.

One advantage is to improve the flow and the distribution of the sealing grout in the borehole.

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

According to an implementation variant, the drill pipe is withdrawn while vibrating it and while injecting the sealing grout. In this case, one advantage of vibrating the drill pipe is to allow the drill pipe to be withdrawn without rotation, which has the effect of substantially reducing the risk of sealing grout circulating 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 sealing grout between the drill pipe and the ground.

According to a third mode of implementation, the sealing grout is put under pressure, the drill pipe is withdrawn while injecting the pressurized grout through the drill pipe, and while vibrating the drill pipe.

To carry out this pressurization, a pump is preferably used which makes it possible to inject the sealing grout at a pressure of between 0.5 and 5 MPa.

Injection under pressure makes it possible to create a bulb of sealing grout whose diameter is substantially greater than the diameter of the borehole, which has the effect of further improving the support.

As mentioned above, the setting in vibration advantageously makes it possible to tighten the ground around the drill pipe. This tightening has the effect of consolidating the ground and thus makes it possible to carry out injection under pressure of the sealing grout in numerous types of ground without requiring the traditional use of additional accessories of the sleeve tube type.

Most often, the drilling direction is vertical. In this case, the distal end is constituted by the lower end of the drill pipe.

According to a variant, the direction of the drilling is inclined with respect to a vertical direction.

An advantage is to be able to make inclined anchorages. An advantageous application lies in the manufacture of inclined anchor rods.

Preferably, the direction of the drilling is inclined with respect to the vertical direction by an angle strictly greater than 90°. One advantage is, for example, to be able to carry out ascending anchorages in a tunnel.

Alternatively, the sealing grout is used as the drilling fluid.

According to the invention, a target vibration frequency is calculated, and the drill pipe is vibrated at said target vibration frequency when drilling.

This target vibration frequency, which is applied to the drill pipe, is chosen optimally in order to facilitate the drilling operation, in particular in particularly hard soils. In general, the calculation is carried out from a modeling of the perforation phenomena.

Advantageously, the calculation uses the length of the drill pipe. Preferably, the target vibration frequency is a function of the length of the drill pipe, while being limited by a predetermined maximum frequency value, denoted Fmax. This predetermined maximum frequency value, which preferably corresponds to the maximum frequency that the means for vibrating the drill pipe can develop, is preferably between 100 and 160 Hz.

Again 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.

• 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 propagation velocity of the compression 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 observed that this formula makes it possible to obtain an optimum vibration target frequency which substantially increases the efficiency of the drilling operation.

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

According to the invention, to make deep boreholes, the length of the drill pipe is increased during the making of the borehole. To do this, sections of pipe are used which are fixed end to end during the drilling in order to increase the length of the drilling. Consequently, within the meaning of the invention, drill pipe is understood to mean both a single drill pipe, that a plurality of tubular elements fixed end to end, for example by screwing.

According to the invention, the target vibration frequency is recalculated each time the length of the drill pipe increases.

One advantage is to ensure drilling with optimum efficiency over the entire depth of the drilling.

According to a first advantageous embodiment, the method is a method for producing an anchor tie rod in which the reinforcement is a tie rod reinforcement.

According to a second advantageous embodiment, the method is a method for producing a micropile, in which the reinforcement is a micropile reinforcement.

Brief description of the drawings

• la figure 1A illustre l'étape de forage du procédé selon l'invention ;
• la figure 1B illustre l'étape d'introduction d'une armature à l'intérieur du tube de forage ;
• la figure 1C illustre l'étape d'injection du coulis de scellement dans le tube de forage afin de noyer l'armature ;
• la figure 1D illustre l'étape de retrait du tube de forage ;
• la figure 1E illustre de manière schématique un micropieu obtenu à l'issue des étapes 1A à 1D ;
• la figure 2A illustre une variante dans laquelle on injecte du coulis de scellement dans le forage tout en retirant le tube de forage ;
• la figure 2B illustre l'étape d'introduction de l'armature dans le forage rempli de coulis de scellement ;
• la figure 3A illustre une autre variante de l'invention dans laquelle on injecte du coulis de scellement sous pression tout en remontant et en faisant vibrer le tube de forage afin de former un bulbe de coulis de scellement ;
• la figure 3B illustre l'introduction de l'armature dans le bulbe de coulis de scellement ;
• la figure 3C illustre l'ancrage obtenu à l'issue de l'étape de la figure 3B ;
• la figure 4 illustre des variantes de l'ancrage obtenu par la mise en œuvre du procédé selon l'invention ; et
• la figure 5 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 of the invention given by way of non-limiting examples, with reference to the appended drawings, in which:

• the Figure 1A illustrates the drilling step of the method according to the invention;
• the figure 1B illustrates the step of introducing an armature inside the drill pipe;
• the figure 1C illustrates the step of injecting the sealing grout into the drill pipe in order to embed the reinforcement;
• the figure 1D illustrates the drill pipe removal step;
• the Figure 1E schematically illustrates a micropile obtained at the end of steps 1A to 1D ;
• the figure 2A illustrates a variant in which sealing grout is injected into the borehole while withdrawing the drill pipe;
• the figure 2B illustrates the step of introducing the reinforcement into the borehole filled with sealing grout;
• the Figure 3A illustrates another variant of the invention in which sealing grout is injected under pressure while raising and vibrating the drill pipe in order to form a bulb of sealing grout;
• the Figure 3B illustrates the introduction of the reinforcement into the sealing grout bulb;
• the Fig . 3C illustrates the anchor obtained at the end of the step of Figure 3B ;
• the figure 4 illustrates variants of the anchoring obtained by implementing the method according to the invention; and
• the figure 5 schematizes the process for optimizing the vibration frequency applied to the drill pipe.

Detailed description of the invention

Using the figures 1A to 1E , a first embodiment of the method for producing an anchor in a ground according to the present invention will be described. In this first embodiment, a micropile M is produced provided with a reinforcement 30 which is particularly visible on the Figure 1E .

In accordance with the method according to the invention, a drilling tool 10 is provided which comprises a drilling tube 12 consisting of a plurality of tubular elements 12a, 12b, 12c ,.... These tubular elements are fixed to each other end to end so as to form the drill pipe 12.

It is therefore understood that the length L of the drill pipe 12 varies during the drilling. More precisely, during the drilling, a new tubular element is added as the drilling tool penetrates into the ground, to those already introduced into the ground, in order to increase the length L of the tube. drilling 12.

Drill pipe 12 includes a distal end 14 that is open. In the example of the Figure 1A , the direction of drilling is vertical downwards, so that the distal end here corresponds to the lower end of the drill pipe.

The drill pipe 12 further comprises a proximal end 16 which is connected in this example to means 18 for driving the drill pipe 12 in rotation and to means 20 for causing the drill pipe 12 to vibrate. means 18 for driving drill pipe 12 in rotation comprise a hydraulic motor.

The means 20 for vibrating the drill pipe, in this case a vibration generator 20, make it possible to generate compression waves which are transmitted along the drill pipe 12 from the proximal end 16 towards the distal end 14 .

By open distal end, it is meant that the distal end 14 of the drill pipe 12 has a through opening which is formed in the center of the distal end 14. As will be explained below, this through opening has a section of dimension sufficient to be crossed by the reinforcement 30.

In this embodiment, the distal end 14 is completely open, which means in particular that the distal end is in particular devoid of a diametral cutting member.

The open distal end 14 has an annular peripheral edge which is provided with cutting teeth 22. By cutting teeth is meant drill tools in general, such as pins, buttons, tungsten carbide pellets, etc. These cutting teeth 22 are sized to excavate the ground S when drilling.

On the Figure 1A , the length of the drill pipe 12 has been referenced by L. This length corresponds in fact to the distance between the means 20 for vibrating the drill pipe 12 and the distal end 14 of the drill pipe 12, which essentially corresponds to the distance between the distal and proximal ends of the drill pipe.

In accordance with the invention, a drilling F is carried out in the ground S using the drilling tool 10 by rotating the drilling tube around the vertical axis A thanks to the rotation drive means 18 and by making it vibrate thanks to the means 20 for vibrating the drill pipe 12.

During the drilling, a drilling fluid is injected into the drill pipe so as to evacuate the debris excavated by the cutting teeth 22. As can be seen in the Figure 1A , the distal end 14 includes perforations 26 through which the drilling fluid flows out of the drill pipe 12 before rising to the surface while flowing between the drill pipe and the wall of the borehole F.

The drilling is carried out in such a way as to bring the distal end of the drill pipe to a predetermined depth H.

In this non-limiting example, after the drill pipe has reached the predetermined depth H, the armature 30 is introduced into the drill pipe. One could also introduce the reinforcement in the drill pipe before the substitution of the drilling fluid by the grout of sealing. In this example, the reinforcement 30 is a metal bar whose length is slightly greater than the height H of the borehole F.

The armature 30 is lowered to the bottom of the borehole while being held substantially centered in the drill pipe by holding means 32. As can be seen in the figure 1C , the armature 30 is held so that its distal end 30a is slightly raised relative to the bottom Fa of the borehole F.

While maintaining the reinforcement 30, a sealing grout C, for example a cement grout, is injected into the drill pipe via its upper end 15 in order to embed the reinforcement 30 in the sealing grout. In another variant, the reinforcement is tubular so that it can advantageously be used as a pipe and inject the sealing grout from its upper end. The grout then gradually replaces the drilling fluid from the lower end by driving it towards the upper end of the borehole.

In this example, the sealing grout is injected into the drill pipe 12 while vibrating the drill pipe thanks to the vibration generator 20.

After having injected the sealing grout into the borehole 12, the drill pipe 12 is removed as shown in the figure 1D . Alternatively, we can begin to extract the drill pipe before having completely filled the borehole with the sealing grout.

We then obtain the micropile M represented on the Figure 1E .

Of course, connection means (not shown here) could, if necessary, be fixed to the proximal end 30b of the armature 30 which emerges from the ground.

On the figures 2A and 2B , a second mode of implementation has been shown in which the drill pipe 12 is removed while injecting the sealing grout C. According to a variant, the withdrawal of the drill pipe is accompanied by a vibration of the drilling in order to prevent the grout from circulating between the drill pipe 12 and the ground S. In this example, the reinforcement 30 is introduced after removal of the drill pipe. However, without departing from the scope of the invention, the armature could be introduced before the drill pipe is removed.

The figures 3A to 3C disclose a third embodiment of the invention.

This third mode of implementation differs from that of the figures 1A to 1E in that the sealing grout C is pressurized by a pump P in order to be injected under pressure into the drill pipe 12. In this example, the pressure of the grouting grout injected is of the order of 5 MPa .

During the injection of the sealing grout under pressure, the drill pipe is raised while being vibrated. The vibration has the effect of tightening the ground around the drill pipe 12 and makes it possible to carry out injection under pressure, which has the effect of creating a bulb B of sealing grout whose diameter is much greater than that of the drilling.

In this example, the bulb B is made over the entire height of the borehole. However, without departing from the scope of the invention, the bulb could be shorter, for example by being located at the bottom of the borehole.

In this example, armature 30 is inserted into bulb B after drill pipe 12 is removed. Again, armature 30 could be inserted before drill pipe 12 is removed.

On the figure 4 , there is shown another embodiment of anchors obtained by the implementation of the method according to the invention.

In this example, the anchors made are anchor tie rods referenced T1 and T2, which are obtained by implementing the method described above, except that the directions of the boreholes F1 for the tie rod T1 and F2 for the tie rod T2 , are inclined with respect to a vertical direction.

It is noted in particular that the direction of the drilling F1 is inclined with respect to the vertical direction by an angle strictly greater than 90°, while the direction of the drilling F2 is inclined with respect to the vertical direction by an angle less than 90° but strictly greater than 0°.

According to a particularly advantageous aspect of the invention, when drilling the boreholes F, F1, and F2 described above, it is sought to optimize the vibration frequency in order to maximize the drilling energy transmitted by the drill pipe 12. For To do this, a target frequency of vibrations is calculated which is applied thanks to the vibration generator to the drill pipe 12.

The drill pipe 12 is therefore vibrated at the target vibration frequency when performing the various boreholes F, F1 and F2. We therefore understands that this vibration target frequency is a vibration frequency which is applied to the drill pipe. In this case, these vibrations are compression waves which are transmitted along the drill pipe defining antinodes and nodes. These vibration waves bring the drill pipe 12 into resonance, or at least at a frequency close to its resonant frequency, which produces maximum energy at the distal end 14 carrying the cutting teeth 22, with effect of substantially increasing the efficiency of the drilling, and therefore the overall efficiency of the method according to the invention.

As shown in the figure 5 , the calculation of the target vibration frequency first of all comprises a step S100 during which the length L of the drill pipe 12 is manually entered or determined automatically. It is therefore assumed here that the drill pipe is placed vibrating along its entire length.

Then, from this length, the target vibration frequency is calculated during a step S102 from the length L of the drill pipe, the speed of propagation of the compression wave in the drill pipe 12 In this example , the drill pipe is made of steel.

Again 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 12 increases during the drilling due to the successive addition of the tubular elements 12a, 12b, ..., the target frequency of vibrations is recalculated at each increase in the length of the drill pipe. This helps to maintain an optimal vibration frequency throughout the duration of the drilling.

The calculated vibration target frequency is then displayed as a suggestion to the operator. It can also in another embodiment be sent as an instruction to the vibration generator 20 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)/(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 propagation velocity of the compression 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,

In the following example, V is equal to 5000 m/s, Fmax is equal to 130 Hz. L, the length of the borehole, is equal to the sum of the lengths of the tubular elements 12a, 12b, 12c ,.... In this example, the tubular elements have the same unit length, namely a length of 3 meters.

We get the following table of results: 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 (12)

1. A method for making an anchorage in the ground, said method comprising the following steps:

   a drilling tool (10) is provided comprising a drilling tube (12) that has an open distal end (14), and means (20) for vibrating the drilling tube, characterized in that a target vibration frequency is calculated;

   a borehole (F, F1, F2) is carried out in the ground (S) using the drilling tool (10) by vibrating the drilling tube (12) at said target vibration frequency, the drilling tube being brought to a predetermined depth;

   the length of the drilling tube (12) is increased during drilling, and the target vibration frequency is recalculated each time the length of the drilling tube is increased;

   when the drilling tube (12) has reached the predetermined depth (H), a reinforcement is introduced into the drilling tube (12) and a sealing grout is injected into the borehole (F) via the drilling tube before or after having introduced the reinforcement into the drilling tube.
2. The method according to claim 1, wherein the drilling tube is withdrawn after having injected the sealing grout into the borehole (12).
3. The method according to claim 1, wherein the drilling tube (12) is withdrawn while injecting the sealing grout into the borehole.
4. The method according to any one of claims 2 or 3, wherein the sealing grout is injected while vibrating said drilling tube (12).
5. The method according to claims 3 and 4, wherein the sealing grout is pressurized, the drilling tube is withdrawn while injecting the pressurized sealing grout into the borehole, and while vibrating the drilling tube (12).
6. The method according to any one of claims 1 to 5, wherein the direction of the borehole (F1, F2) is inclined with respect to a vertical direction.
7. The method according to claim 6, wherein the direction of the borehole (F1) is inclined with respect to the vertical direction by an angle strictly greater than 90°.
8. The injection method according to any one of claims 1 to 7, wherein the sealing grout is injected into the drilling tube during the drilling so that the sealing grout is also used as drilling fluid.
9. The method according to any one of claims 1 to 8, wherein, to calculate the target frequency, at least the length (L) of the drilling tube (12), the propagation speed (V) of the compression waves in the drilling tube (12) and a predetermined maximum frequency value (Fmax) are used.
10. The method according to any one of claims 1 to 9, wherein the target vibration frequency is equal to:

    • a predetermined maximum frequency value, denoted Fmax, if Fmax<(V)/(2^∗L), where V is the propagation speed of the compression waves in the drilling tube, and where L is the length of the drilling tube, 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.
11. A method for making an anchoring tie rod (T1, T2) implementing the method according to any one of claims 1 to 10, wherein the reinforcement is a tie rod reinforcement.
12. A method for making a micropile (M) implementing the method according to any one of claims 1 to 10, wherein the reinforcement is a micropile reinforcement.

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