AU668264B2 - Lock chamber installation for a device for treating soils with a rotary jet - Google Patents

Abstract

The invention relates to an installation to be used with a device for treating the ground using rotating jet(s) comprising a string of tubes (2) at the base of which is mounted at least one ejection nozzle, this nozzle being supplied with substance to be ejected by means of the string of tubes (2) or of flexible pipes (hoses) (3a, 3b), characterised in that it comprises an enclosure (chamber) (4), provided with at least one orifice (6, 7, 8) fitted with a seal (9, 10, 11) for the passage of the string of tubes and/or of the flexible pipes; a shut-off valve (12) making it possible to close off the borehole, and a pipe (13) for evacuating the substances leaving the borehole, this pipe being coupled up to the said enclosure and provided with an adjustable valve (14) making it possible to alter the flowrate of the said substances. <IMAGE>

Description

rrrrarrrra~ I, 1 LOCK CHAMBER INSTALLATION FOR A DEVICE FOR TREATING SOILS WITH A ROTARY lET.

The invention relates to a lock chamber installation for a device for treating soils with a rotary jet or rotary jets.

The method of treating soils with a rotary jet or rotary jets is well known and is used for producing cut off screens in the mass of permeable ground.

According to this method, an exogenous material or slurry is introduced into the ground in questicn from a borehole, in the form of at le'st one high- S. Ispeed jet which is suitably directed and which, on its trajectory, destructures the ground in place and, depending on the nature of the said ground, either mixes :with the constituent elements of the latter and leads, after setting, to the formation 10 of a soil mortar or concrete (case, for example, of gravelly or sandy ground) or purely and simply replaces the ground and leads, after setting, to the formation of a set slurry or grout (case, for example, of clayey ground). The jet(s), depending on the flow rate, on the driving pressure and on the characteristics of the ground, have a certain radius of action. If the tool forming the jet is set in slow rotation- 15 translation inside the borehole, an approximately cylindrical volume of ground oo treated is obtained, having as radius the radius of action of the jet or jets under the conditions in question, and a height corresponding to the amplitude of the translational movement.

It will be understood that it is thus possible to produce, by this jet technique, cut off screens by juxtaposition of a plurality of cylindrical elements (or columns) of ground thus treated over a certain height, produced using a network of paralle) boreholes with a density such that their elements or columns intersect so as to constitute a continuous mass. It is also possible to use cylindrical columns or elements of this type as bearing elements.

The jets used may be of various types, that is to say that they may consist of a single jet of slurry, or a jet of slurry surrounded by an annular jet of air in order to increase the radius of action thereof, or a combination of a jet of 2 water surrounded by an annular jet of air ensuring destructuring of the ground and a separate jet of slurry, normally provided at a level lower than that of the jet of water.

For implementing this method, a device is normally used which comprises a central unit for producing cement slurry feeding one or more pumps with slurry, which pumps are connected, via a rotating seal, to a string of tubes introduced into the borehole where the jet treatment is to be carried out. The string of tube may be driven in translation and rotation using a hydraulic rotary head clamping the upper end of the string of tubes, which is itself mounted on a drilling jar. The pump or pumps deliver the destructuring fluid (slurry or water) at pressures of the order of 200 to 700 bar or greater.

The string of tubes is formed by connectable tubular unit segments fitted with suitable sealing gaskets, and each segment may be formed by a single tube (single jet) or several coaxial tubes (double or triple jet). The liquids (slurry, water) are ejected through one or more nozzles with a diameter of approximately 2 to 4 mrn. The tube string segments may have a diameter of approximately 50 to 200 ""mm.

Quite recently, an improvement has been proposed by the Applicant, in French Patent Application No. 92 13154, filed on 3 November 1992, this S 20 improvement consisting in using flexible pipes external to the string of tubes for supplying the nozzles, the string of tubes then being used only for mechanical driving and being driven in a rotational movement which is no longer continuous but reciprocating.

A drilling tool may furthermore be provided below the nozzles, at the lower end of the string of tubes, in order to produce the borehole in which the treatment will be carried out. This tool may be solid or be the seat of circulation of a drilling fluid supplied by the string of tubes. In this latter case, this tool may be equipped with a non-return device for preventing sediments blocking the inside of the string of tubes during the operation of adding or withdrawing a tubular segment. As a variant, the drilling may be carried out beforehand with a separate device.

-3- In practice, the jet treatment is started by positioning the jet device at the bottom of the borehole, whilst driving the string of tubes in a movement of rotation and translation towards the head of the borehole, until a column of treated ground with the desired height is obtained.

Under certain working conditions, for example in the case of rising boreholes in which the materials ejected by the jet device tend to escape under gravity from the borehole, or in the case of boreholes whose head is situated at a level lower than that of a groundwater pool, difficulties have arisen in the implementation of the jet devices, linked with the fact that it is not known how to control the flow rate of material which leaves the borehole.

There is therefore a requirement for equipment which makes it possible to fill this gap.

Accordingly, it would be desirable to provide an installation making it possible to •.maintain a pressure in the annular space of the borehole existing between the wall of the S borehole and the string of tubes, and to control the flow rate of material which must inevitably be removed from the borehole.

The present invention provides an installation for use in conjunction with a device having at least one rotary jet for treating soil, the device including a string of tubes having at least one ejection nozzle mounted at one end thereof, said nozzle being supplied with material for ejection into a borehole by means of said string of tubes or by means of flexible pipes optionally provided and separate to said string of tubes, said installation including: a chamber arranged for communication with the open end of the borehole and for sealed connection therewith, said chamber being provided with an orifice fitted with a sealing gasket for the passage therethrough of said striny of tubes and further orifices as necessary, each fitted with a sealing gasket, for the passage of said flexible pipes, a shut-off valve capable of closing the borehole completely and a conduit allowing exit of materials from the borehole, said conduit being connected to said chamber and being provided with an adjustable valve for adjusting the exit flow rate of the said materials in order to avoid excessive pressure in the borehole.

ABM:P55189.doc Optionally, the control of the adjustable valve of the removal conduit may be slaved to the pressure prevailing in the borehole and carried out automatically by a suitable device.

Also, if desired, it is possible to provide on the chamber a tap making it possible to connect the chamber to a pressurized fluid source, with the aim of maintaining a pressure in the borehole in the event when the latter has fallen below a predetermined threshold.

Preferably, the chamber can be dismantled into at least two parts, namely a lower part equipped with the shut-off valve and an upper part provided with an orifice or orifices.

The following description, made with reference to the attached drawings, will more clearly explain the strucure and the operation of es:. an installation constructed in accordance with a preferred embodiment of S* the invention. In the drawings: 5.

Figure 1 is a diagrammatic view of an installation according to the invention; and Figures 2 and 3 are diagrammatic views illustrating the mounting of the rotary jet treatment device in the installtion of Figure 1.

The installation of Figure 1, which is mounted in continuation of a borehole 1 receiving a device for treating soils with a rotary jet or rotary jets, of the type described in the aforementioned French Patent Application, of which only the string of tubes 2 and the flexible pipes, such as 3a and 3b, for supplying the nozzles have been represented, comprises a chamber 4 forming a lock 940 chamber, mounted in extension of the borehole 1, a seal 5 providing leaktightness between the base of the chamber and the wall of the borehole. The chamber 4, made, for example, of steel, consists of a lower part 4a and an Lpper part 4b which are solidly attached, for example, by bolting. The upper part 4b is provided with orifices 6, 7 and 8, for passage of the string of tubes 2 and the pipes 3a and 3b, respectively, annular seals 9, 10 and 11 being provided to ei .wre leaktightness whilst allowing movement or sliding of the members 2, 3a and 3b.

SThe lower part 4a is equipped, in the vicinity of its junction with the part 4b with a shut-off valve 12 of the full-opening type and a conduit 13 for removing the i y n c sl materials leaving the borehole, on which a valve 14 is installed, which is adjusted automatically as a function of the pressure prevailing in the borehole by means of zLA& cs mc re: ,Ako C"5 aeviie a device (15)connected to a pressure probe 16 mounted in the chamber. The role of the valve 14 is to maintain the pressure prevailing in the borehole within a range of predetermined values and to prevent a potentially dangerous excessive pressure from developing in the borehole.

Finally, the installation comprises a pipeline 17 connected to the chamber and provided with a valve 18, which can be connected, if necessary, to a pressurized fluid source in the event that the pressure in the borehole has dropped, for any reason, below a desired value.

Figures 2 and 3 illustrate the mounting of the device for treating soils with a rotary jet or rotary jets in the installation in Figure 1. After the lower part 9 4a is fitted into the borehole 1 and the latter is sealed by the seal 5, as illustrated in Figure 2, the shut-off valve 12 is closed. The nozzle head 2( of the rotary jet treatment device is then positioned on the valve 12, then the string of tubes 2 and the flexible pipes 3a, 3b are connected to this head after they have been passed through the orifices 6, 7 and 8 of the upper part 4b of the chamber, as illustrated by Figure 3. After this, it is necessary only to bolt together the parts 4a and 4b to complete the installation. Before lowering the head 20 into the borehole, the 20 valve 12 is obviously opened. When it is desired to remove the head 20 from the borehole, the reverse operation from that which has just been described is carried out.

It is, of course, self-evident that if the rotary jet device used comprises a string of tubes which simultaneously supplies the nozzles, that is to say is a conventional rotary jet device, not comprising flexible supply pipes, it is suitable to adapt the chamber by providing only the single orifice 6 and omitting the orifices 7 and 8.

The installation thus makes it possible to implement a device for treating soils with a rotary jet or rotary jets under work site conditions which require working with a borehole maintained under pressure, whilst allowing control of the flow rate of the materials leaving the borehole.

Claims (4)

1. An installation for use in conjunction with a device having at least one rotary jet for treating soils, the device including a string of tubes having at least one ejection nozzle mounted at one end thereof, said nozzle being supplied with material for ejection into a borehole by means of said string of tubes or by means of flexible pipes optionally provided and separate to said string of tubes, said installation including: a chamber arranged for communication with the open end of the borehole and for sealed connection therewith, said chamber being provided with an orifice fitted with a sealing gasket for the passage therethrough of said string of tubes and further orifices as necessary, each fitted with a sealing gasket, for the passage of said flexible pipes, a shut-off valve capable of closing the borehole completely and a conduit allowing exit of materials from the borehole, said conduit being connected to said chamber and S being provided with an adjustable valve for adjusting the exit flow rate of the said materials in order to avoid excessive pressure in the borehole.

2. An installation as claimed in claim 1, wherein control of said adjustable valve is 0. I.i: dependent on the pressure in the borehole.

3. An installation as claimed in claim 1 or claim 2, which further includes a tap for connecting said chamber to a pressurized fluid source. .i 4. /n installation as claimed in any one of claims 1 to 3, wherein said chamber can Sbe dismantled into at least two parts, namely a lower part equipped with said shut-off a valve and an upper part provided with said orifices.

5. 5. An installation substantially as herein described with reference to the accompanying drawings. DATED: 21 February 1996 PHILLIPS ORMONDE FITZPATRICK Attorneys For: SONDAGES INJECTIONS FORAGES "SIF" ENTREPRISE BACHY ABM:P55189.doc L Lock chamber installation for a device for treating soils with a rotary et. Invention: Jean-Claude GESSAY Pierre CLEMENT Socidt6 anonyme called SONDAGES INJECTIONS FORAGES ENTREPRISE BACHY ABSTRACT The invention relates to an installation to be used with a device for treating soils with at least one rotary jet, comprising a string of tubes, at the base of which at least one ejection nozzle is mounted, this nozzle being supplied with material to be ejected by means of the string c, tubes or flexible pipes, which comprises a chamber provided with at least one orifice fitted with a sealing gasket for the passage of the string of tubes and/or the flexible pipes; a shut-off valve making it possible to close the borehole, and a conduit for removing the materials leaving the borehole connected to the said chamber and provided with an adjustable valve for adjusting the flow rate of the said materials. FIGURE 1 1 *oooo«