EP1231326B1 - Pressure injection head - Google Patents

Abstract

The injection head, mounted on the end of a string of rods or pipes delivering a liquid under pressure, comprises a housing (32) with its upper end (40) connected to the rods or pipes, an outer wall (34) and an inner nozzle (50). A curved duct (54) inside the housing is connected at one end to the lower end of the liquid feed pipe (48) and at the other tangentially to the nozzle. The curved portion of the duct is of continuously variable radius and has a regularly reducing cross-section towards the nozzle outlet for at least half its length.

Description

The subject of the present invention is an injection head under pressure of a liquid to drill an excavation in the ground and in particular an injection head for implementing the technique known as Anglo-Saxon term of "jet grouting".

The technique known as jet grouting consists in disaggregating the ground using a very high kinetic energy liquid jet set up works in a borehole, the jet of liquid causing soil erosion in which we want to excavate. To form the jet, we use a nozzle which is attached to the end of the drill rods, these rods allowing both the routing to the nozzle or the nozzles of the liquid under high pressure and progressive translation of the nozzle in the ground. More specifically, the nozzle (s) are mounted on a member called the most often monitor or injection head which is attached to the lower end of the drill string, this monitor can itself be equipped at its end bottom of a mechanical drilling tool. As we know, the liquid used most often is a cement-based grout that will allow, after drilling, to make a cement floor element molded into the ground in square.

The liquid which is carried by the rods is sent from the surface by a pump at pressures from one to several tens of MPa. The internal diameter of the rods carrying the liquid must be enough great for limiting pressure drops in the rods. This diameter can typically be of the order of 20 to 50 mm. On the other hand, the diameter of nozzle outlet should be reduced enough to print liquid a sufficient speed at its exit in order to erode the ground at a distance. Typically, the outlet diameter of the nozzle is included, the more often between 2 and 5 mm and the speed of the liquid leaving the nozzle is one to several hundred meters per second.

To obtain a high quality of the jet, it is desirable that the inner shape of the nozzle is optimized to keep the liquid jet as high a speed as possible as the jet moves away from the nozzle towards the ground so that it can erode the ground the most possible by using a minimum of kinetic energy. Forms of optimized nozzles meeting this requirement are commonly used.

However, even with such nozzles, it can be seen that the loss of effectiveness of the jet to cause soil erosion is rapid, if although it takes considerable kinetic energies for that when we causes the rods to translate and eventually rotate, the soil is eroded at a large distance from the nozzle, for example several decimetres. The radius of action of the jet of liquid under pressure to form a column, a column sector or a planar element generally remains poor a few decimeters at 1 or 2 meters depending on the setting method work, the nature of the terrain and the energy used.

To increase the action of the jet, it has been proposed in particular in U.S. Patent 5,228,809 and Japanese Patent 10,195,862 of embodiments of the injection head or monitor which allows improve the quality of this jet.

The injection head of the Japanese patent is composed of a liquid supply line connected to a nozzle by a tubing substantially constant section and the mean line of curvature has the regular shape of a quarter circle. The axis of the nozzle is perpendicular to the axis of the injection head so that the direction main of the liquid jet undergoes a deviation of 90 degrees between the inlet of the tubing and the outlet of the nozzle. As this deviation occurs over a very short distance, this results in pressure losses in the tubing.

On the other hand, in Figure 1 attached, there is shown the head injection device described in US Patent 5,228,809. The injection head 10 comprises a body 12 having a side wall 14 defining a internal cavity. A pressurized liquid injection nozzle 16 is mounted in the external wall 14 of the monitor. In this figure, we have also shown elements 18 for connection to the drill string and elements 20 and 22 for connection to the liquid line under pressure and to an annular air duct circulating in the rods so simultaneously supply the liquid nozzle and an annular air nozzle 16. According to this patent, the nozzle 16 is supplied from the line 22 conveying the pressurized liquid through a passage 24 provided in the body of the monitor 10 and by a tube 26 connecting the end of this passage at the entrance to the nozzle 16. The tubing 26 which has a constant section has a regular curvature in order to limit disturbances pressurized liquid between the drill pipe and the nozzle 16 itself. However, as explained, the injection nozzle has a very large diameter. reduced compared to the diameter of the pipe used to convey the liquid under pressure through the rods. The solutions described in the US patent and in the Japanese patent mentioned above are only therefore not fully satisfactory.

An object of the present invention is to provide a head especially for the implementation of the jet grouting which allows to improve more significantly the quality of the jet provided by the nozzle (s) the injection head mounted at the lower end of the drill string.

To achieve this object, the invention relates to a head for injecting pressure of a soil erosion liquid, mounted at the end of a train of rods or tubes, said train comprising means for pressurized liquid supply, said head comprising a body having an upper end for connection to the lower end of the drill string or tubes and an external wall, body in which is mounted at least one injection nozzle whose diameter d 'inlet is equal to d , and which has an axis x, x', and means forming a conduit for connecting the liquid supply to the inlet of said nozzle, said means forming a conduit having a mean line the first end of which is connected to the axis of the liquid supply pipe at its lower end and the second end of which is tangentially connected to the axis x, x 'of the nozzle, said mean line being defined by at least a portion of curve e continuous and continuously differentiable, injection head according to which the cross section of said means forming a conduit decreases regularly over at least half of its length from its first end to its second end connected to the nozzle.

We understand that the quality and direction of the jet produced by the nozzle are significantly improved due to the gradual reduction and regular cross-section of the duct forming means, for example tubing, at least half its length from its end for connection to the pressure liquid supply line until it is connected to the inlet port of the injection nozzle. This characteristic combined with the fact that the mean line of means forming a conduit has a radius of curvature, which varies regularly, minimizes disruption of liquid flow in this tubing and therefore to obtain a jet whose energy is maximum and whose erosive power is kept at a maximum distance from the nozzle in the field.

According to a first embodiment, the axis of said supply line substantially coincides with the axis of the body of the injection head.
Preferably, the mean line of the means forming a conduit comprises a first part of the curve extending between the first end and an intermediate point and having a regular curvature, the concavity of which has a first sign and a second portion of the curve between said intermediate point and the second end having a regular curvature whose concavity has an opposite sign.

We understand that, thanks to the particular configuration of the means forming a conduit, for example the tubing, with its two portions curve, it is possible for a given external diameter of the head increase the length of the tubing and increase the length of portion of tubing with large radius of curvature immediately connected to the nozzle.

According to a second embodiment, the liquid line under pressure extends into said injection head and the first end of the conduit means is a side tap on said pipe substantially tangential to said pipe.

la figure 1 déjà décrite est une vue en coupe verticale d'une tête d'injection connue ;

la figure 2 est une vue en coupe verticale d'un premier mode de réalisation d'une tête d'injection ou moniteur selon l'invention ;

la figure 3 est une vue en coupe verticale d'un deuxième mode de réalisation de la tête d'injection ; et

les figures 4 et 5 sont des vues partielles en coupe horizontale montrant deux implantations possibles des buses à injection de liquide.

Other characteristics and advantages of the invention will appear better on reading the following description of several embodiments of the invention given by way of non-limiting examples. The description refers to the appended figures in which:

Figure 1 already described is a vertical sectional view of a known injection head;

Figure 2 is a vertical sectional view of a first embodiment of an injection head or monitor according to the invention;

Figure 3 is a vertical sectional view of a second embodiment of the injection head; and

Figures 4 and 5 are partial views in horizontal section showing two possible locations of the liquid injection nozzles.

The injection head 30 shown in Figure 2 has a body 32 consisting of a cylindrical side wall 34, one end lower 36 comprising means, for example a thread 38, of attachment of a mechanical drilling tool and an upper end 40. This upper end 40 comprises on the one hand a thread 42 of connection to the lower end of a drill pipe 44 and other share an internal sleeve 46 for connection to the pipe 48 formed in the drill pipe 44 for conveying the pressurized liquid which is most often, as we have already indicated, a grout. In the particular embodiment described, the annular space 50 between the rod borehole 44 and the pipe 48 is used to convey pressurized air. he goes of course, in some embodiments, we would not find this annular space.

Above its lower end 36, the side wall 34 of the injection head is provided with an injection nozzle 50 of axis x, x '. In the embodiment described, the axis x, x 'of the nozzle 50 is substantially perpendicular to the vertical axis z, z 'of the injection head but, in other embodiments, the axis could make an angulation with the horizontal, for example, between + 15 degrees and - 15 degrees. In Furthermore, as shown in Figures 4 and 5, the nozzle can be in horizontal projection, perpendicular to the external wall of the monitor (nozzle 50 'in FIG. 4) or substantially tangential to this wall (nozzle 50 "in Figure 5) or its axis xx 'can occupy any orientation intermediate. Inside the cavity 52 of the body of the injection head, is mounted a tube 54 used to connect the supply 46 in pressurized liquid at the inlet 50a of the nozzle 50. S1 is called the cross section of the line 46 for supplying pressurized liquid and s1 the straight section of the inlet of the nozzle 50. The tubing 54 of which call L the middle line has a first end 56 of connection to line 46 and a second end 58 of connection to the nozzle. The first end 56 of the tubing 54 has a straight section S'1 equal to section S1 and its second end has a straight section s'1 equal to the section s1 of the nozzle. In addition, the cross section of the tubing 54, that is to say the section of this tubing by planes orthogonal to the mean line L decreases regularly from the value S'1 to the value s'1. In some cases, the tubing 54 may include portions of cylindrical tubing of very limited length.

The cross section of the tubing can be circular but it can also have an oval shape, an ellipse shape, etc. The end sections 56 and 58 are generally circular, but they can also be elliptical. The middle line L of the tube 54 has a non-constant curvature but which varies regularly. In the embodiment shown in FIG. 2, the middle line L of the tube 54 comprises a first portion L ₁ which goes from the end 56 to an intermediate point A and a second portion L ₂ which goes from the intermediate point A to 'at the second end 58. The portion L ₁ has a radius of curvature which keeps the same sign, the same applies to the portion L ₂ but the sign of this last radius of curvature is the opposite of that of the portion L ₁ . In other words, at point A, the portions L ₁ and L ₂ are tangentially connected but the mean line L has an inflection point at point A.

This embodiment makes it possible in particular thanks to the portion L ₂ of the mean line and therefore the corresponding portion of tubing to increase the length of the part of the tubing having a large radius of curvature in its zone of connection to the nozzle. This arrangement makes it possible to stabilize even better the flow of the liquid under pressure in the tube 54 near the nozzle 50.

It goes without saying that the tubing 54 could have other shapes as soon as when its middle line shows regular variations in curvature and that its cross section decreases substantially regularly from its first end 56 to its second end 58 of connection to the nozzle. Tubing may have only one radius of curvature and also might not have a midline arranged in a plane but be constituted by a form of propeller or spiral, that is, to be a three-dimensional curve.

It also goes without saying that we would not leave the invention if the injection head had several nozzles and that this same head injection therefore had several tubing similar to the tubing 54 and each connected to a liquid supply line under pressure contained in the drill pipes.

It should also be observed that, thanks to the shape of the tube 54 shown in FIG. 2, it is possible to increase the total length of the mean line L of this tube while maintaining the external dimensions of the useful part of the head. injection at reduced values corresponding to the diameter D ₁ and the height H ₁ . The increase in the length of the tube 54 makes it possible to improve the progressiveness of the reduction in cross section for straight sections given at the two ends of the tube. In the embodiment described, the diameter D ₁ is less than 15 cm and the useful height of the injection head H ₁ is less than 50 cm.

Figure 3 shows a second embodiment of a monitor according to the invention. This monitor essentially stands out by the fact that the line 48 for supplying pressurized liquid is extends into the monitor via a tool supply pipe 70 mechanical which can be fixed in the threaded sleeve 78. When it is mounted, the tool is supplied by line 70 via a controllable valve 72. In this case the first end 56 'of the tube 54' is a lateral stitching on the pipe 70. Preferably, this stitching is substantially tangential to the wall of the pipe 70.

It is understood that, in the embodiment described above, the middle line L 'of tubing 54' is a three-point curve dimensions. Tubing 54 '"wraps" around line 70 to go from the nozzle 56 'at the inlet of the nozzle 50.

In the preceding description, the tubing 54 is an element separate line, mounted in the body of the injection head. However, we would not go out of the invention if the body of the head injection was carried out by molding and that the tubing 54 was produced during of this molding using an appropriate technique. In this case, the body of the injection head would be a massive part in which the tube 54 would be formed by a recess.

Claims (10)

1. A head for injecting liquid under pressure from a borehole to break up soil, said head being mounted at the end of a drill string, said string including liquid feed means for feeding liquid under pressure, said head comprising a body (32) having an outside wall (34) and a top end (40) for connection to the bottom end of the drill string, at least one injection nozzle (50) mounted in said body, the inlet diameter of said nozzle being equal to d, said nozzle possessing an axis x,x', and duct-forming means for connecting the feed of liquid to the inlet of said nozzle, said duct-forming means (54, 54') presenting a mean line (L) having a first end (56) connected to the bottom end of the axis of the liquid feed pipe (48) and having a second end (58) connected to the nozzle (50) tangentially to said axis x,x', said mean line (L) being defined by at least one curved portion that is continuous and that varies continuously, injection head whereby the right section of said duct-forming means decreases regularly over at least half of its length from its first end to its second end connected to the nozzle (50).
2. An injection head according to claim 1, characterised in that said liquid feed means include a liquid pipe under pressure (48) extended into said injection head by a pipe (70) for feeding a tool and in that said first end of the duct-forming means (54') is a side branch (56') on said pipe (70) for feeding a tool with said branch being substantially tangential to said pipe.
3. An injection head under pressure according to claim 1, characterised in that the first end (56) of the mean line (L) of said duct-forming means (54) is connected tangentially to the axis of the bottom end of the liquid feed pipe (48).
4. An injection head under pressure according to claim 1, characterised in that the axis of said liquid feed pipe (48) coincides substantially with the axis of the body (32) of the injection head.
5. An injection head under pressure according to claim 4, characterised in that the mean line (L) of the duct-forming means (54) comprises a curved first portion (L₁) extending between the first end (56) and an intermediate point (A) and presenting regular curvature whose concavity presents a first sign, and a second curved portion (L₂) extending between said intermediate point (A) and said second end (58) connected to the nozzle (50), presenting regular curvature whose concavity presents an opposite sign.
6. An injection head according to any one of claims 1 to 5, characterised in that said duct-forming means (54, 54') are of substantially circular right section.
7. An injection head according to any one of claims 1 to 5, characterised in that said duct-forming means (54, 54') have a right section that is oval in shape.
8. An injection head according to any one of claims 1 to 7, characterised in that it has a plurality of injection nozzles and a plurality of duct-forming means, each being connected to a respective injection nozzle.
9. An injection head according to any one of claims 1 to 8, characterised in that said duct-forming means (54, 54') consist in a tube, which is separate from said body (32) of the injection head.
10. An injection head according to any one of claims 1 to 8, characterised in that the injection head body is made by moulding, and the duct-forming means are formed during the moulding.

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