DEVICE FOR PROTECTING A GEOTECHNICAL OR GEOPHYSICAL PROBE

Abstract

A device (1) for protecting a geotechnical or geophysical probe (13) having an elongated shape and capable of undergoing radial deformation, includes: a plurality of flexible members (2) having an elongated shape and capable of undergoing radial deformation in a functional configuration of the device (1); elements for the longitudinal compensation of the radial deformation of the flexible members (2) in a functional configuration of the device (1); two flexible member bearings (301, 302) each receiving an end of the flexible members (2), the bearings (301, 302) being capable of longitudinal movement on the probe (13) so that the flexible members (2) longitudinally protect the outer portion of the probe (13) between the bearings (301, 302) in a functional configuration of the device (1).

Description

The present invention relates to a device for protecting elongate-shaped geotechnical or geophysical probes, in particular probes able to deform radially. It also concerns a probe covered with such a device.

Various types of probe are known for determining the characteristics of a soil. Geotechnical probes are used for determining the technical characteristics of a soil, such as for example the mechanical strength. Geophysical probes are also used for evaluating the physical and chemical characteristics of soils.

One well known type of geotechnical probe is the probe for a pressure meter. A pressure meter is an apparatus that measures in situ the characteristics of resistance and deformability of a soil. It consists of a radially expandable three-cell cylindrical probe, a set of pressurisation and pneumatic regulation components, and a volume controller. This apparatus makes it possible to know the increase in volume of a drilling slice according to the pressures applied.

These pressure meters have been well known to persons skilled in the art since their invention by L Ménard in 1955. They are in particular described in the application FR 1 117 983.

Since then devices for protecting these probes have been developed, in order to protect the probes when they are disposed in cohesion-lacking, gravelly or fractured soils.

Thus a probe protection device is known consisting of a flexible tube provided with slots, as described in the applications FR 1 234 756 and FR 2 702 565. A device consisting of two half-tubes provided with slots is also known.

However, when the probe expands, very high stresses develop at the ends of the slots, which may lead to a plastic deformation causing an irreversible widening of the slots.

Disposing metal blades on a rubber sheath or a frame composed of springs embedded in a layer of plastics material as described in the application EP 0 146 324 is also known.

Such a device is however very rigid, which interferes with the pressure-measurement tests.

The invention proposes a device for protecting a geotechnical or geophysical probe, and in particular a pressure-measuring probe, remedying these drawbacks.

In particular, the invention proposes a device for protecting the probe in hard cutting soils, adapted to high expansion of the probe cells, and which does not impair the measurement of the deformation of the probe. In particular, the protection device according to the invention has no inertia vis-à-vis the probe.

The subject matter of the invention is thus a device for protecting a geotechnical or geophysical probe, the probe being elongate in shape and able to deform radially. The device according to the invention comprises:

• • a plurality of elongate-shaped flexible elements, able to undergo radial deformation, in the operational configuration of the device,
  • means of longitudinal compensation for the radial deformation of the flexible elements, in the operational configuration of the device,
  • two flexible-element supports, each accepting one end of the flexible elements, the supports being able to move longitudinally on the probe,

so that the flexible elements longitudinally protect the external part of the probe lying between said supports, in the operational configuration of the device.

The means for longitudinal compensation of the radial deformation of the flexible elements advantageously consist of an interstice in at least one of the flexible-element supports and a curved end of the flexible elements, each end being disposed in reversible sliding in said interstice.

To facilitate the acceptance of the ends of the flexible elements, the interstice is preferable delimited by two annular zones with different diameters.

The means for longitudinal compensation of the radial deformation of the flexible elements preferably also comprise at least one damper intended to damp the longitudinal movements of at least one of the flexible-element supports, in the operational configuration of the device. The presence of these dampers optimises the longitudinal compensation for the radial deformation of the flexible elements and reduces the inertia of the probe protection device.

In another embodiment, the flexible elements are fixed to the flexible-element supports, and the means of longitudinal compensation for the radial deformation of the flexible elements comprise at least one damper intended to damp longitudinal movements of at least one of the flexible-element supports, in the operational configuration of the device.

The dampers used in the device according to the invention can be of any nature. It is possible in particular to use springs, or elements made from elastic material, such as polyurethane. The dampers can in particular be elastic rings.

In order to adapt well to the currently used geotechnical and geophysical probes, which are generally cylindrical in shape, the flexible element supports are preferably cylindrical in shape. To facilitate their assembly on the probe, the flexible-element supports comprise a plurality of cylinder portions assembled together. It is in particular possible to use two half cylinders or four quarter cylinders.

The flexible elements can be produced from any flexible material, and in particular a material able to completely resume its shape after having lost it by deformation during the radial deformation of the probe.

The flexible elements are preferably steel blades, and in particular made from stainless steel. The flexibility of the blade will be chosen according to the envisaged deformation of the blade during geotechnical or geophysical tests.

Another subject matter of the invention is a geotechnical or geophysical probe covered with a protection device described above.

The device is particularly suitable for the protection of pressure-measurement probes, in particular of the type comprising three inflatable sleeves aligned along the longitudinal axis of the probe.

In this case, the flexible element supports are preferably disposed on each side of the assembly formed by the three inflatable sleeves, for optimum protection of the probe.

When the device comprises a damper intended to damp the longitudinal movements of at least one of the flexible-element supports, each flexible-element support is advantageously able to move longitudinally between two stops of the probe, the movement being damped by the damper.

Other aims, features and advantages of the invention will emerge from a reading of the following description, given solely by way of example, and made with reference to the accompanying drawings, in which:

FIG. 1 is a view in perspective of a part of an end of a protection device according to the invention,

FIG. 2 is a view in partial and divided longitudinal section of part of a pressure-measurement probe according to the invention, before radial deformation of the probe, and

FIG. 3 is a view in partial and divided longitudinal section of part of a pressure measurement probe according to the invention, expanded radially during a pressure-measurement test.

The protection device 1 according to the invention comprises a plurality of flexible elements 2, disposed at each of their ends in a flexible-element support 3.

The flexible elements 2 are stainless steel blades. Each flexible element 2 is curved at its end, for example by a fold.

Each flexible-element support 3, which accepts an end of the flexible elements 2, consist of two semi-cylindrical half-supports 4, only one of which has been shown in FIG. 1. The two half-supports 4 are connected together by means of screws, not shown, disposed in threaded holes 6. Each half-support 4 comprises a half-support body 8 onto which an annular element 5 is screwed by means of screws 7.

The half-support body 8 comprises an annular zone 9 that is extended by a shoulder 10 onto which the annular element 5 is screwed.

The annular element 5 and the annular zone 9 of the half-support body 8, which have different diameters, delimit an interstice 11 in which the ends of the flexible elements 2 are disposed.

The half-support 4 is advantageously provided with a pin 12 at each end of the half-support 4. The pins 12 hold the two flexible elements 2 situated at the ends of the half-support 4, which makes it possible to hold all the flexible elements 2 in the half-support 4. To accept the pin 12, the ends of the flexible elements 2 can be in the form of forks.

The other end of the flexible elements 2 is disposed in an identical manner in the same flexible element support 3.

FIG. 2 illustrates a pressure-measurement probe 13 covered with the protection device 1, before a pressure-measurement test.

The pressure-measurement probe 13 comprises a central probe body 12 intended to supply a zone 15 adjacent to the probe body 12 with liquid and gas, by means of a gas supply duct 14, provided in a solid zone of the probe body 12, and a liquid supply duct 26. The liquid supply duct 26 is intended to supply a central inflatable sleeve, and the gas supply duct 14 is intended to supply two inflatable sleeves adjacent to the central sleeve, the three sleeves being placed in the zone 15.

The probe 13 is also provided with a shoe 27 at its bottom end, in the operational configuration of the probe 13.

The adjacent inflatable sleeves are supplied with gas by means of ducts 16 and 17 that connect the gas supply duct 14 to the adjacent inflatable sleeves.

The pressure-measurement probe 13 is covered with the protection device 1 described above. The device comprises, on each side of the zone 15, two flexible element supports 301, 302, each support 301, 302 consisting of two semi-cylindrical half supports. The half supports comprise a half support body 801, 802 to which an annular element 501, 502 is fixed by means of screws 701, 702. Flexible elements 2, which are stainless steel blades folded at their ends, are disposed in the interstice delimited by the half support bodies 801, 802 and the annular elements 501, 502.

The flexible-element support 301 disposed at the top end of the protection device 1 of the probe 13, in the operational configuration of the probe 13, is able to move longitudinally between two stops 18, 19, the stop 18 being the called the external stop, and the stop 19 being called the internal stop. At rest, the half-support body 801 is held against the external stop 18 by means of a damper 20. The damper 20 is a polyurethane ring.

Likewise, at the bottom end of the probe protection device 13, in the operation configuration of the probe 13, the flexible-element support 302 is able to move longitudinally between two stops 21, 22 of the shoe 27, the stop 22 being called the external stop, and the stop being called the internal stop. At rest, the half-support body 802 is held against the external stop 22 by means of a damper 24. The damper 24 is a polyurethane ring.

FIG. 3, where the identical elements bear the same reference signs, illustrates the probe 13 during the pressure-measurement test. The central inflatable sleeve 23, and the inflatable sleeves 24, 25 adjacent to the central sleeve 23, are supplied with fluid and are therefore in the inflated state. For more clarity, the sleeves 23, 24, 25 are shown schematically. This expansion of the sleeves 23, 24, 25 causes a radial deformation of the flexible elements 2. The deformation simultaneously causes a longitudinal movement of the two supports 301, 302 in the direction of the internal stops 19, 21.

Thus the top 301 and bottom 302 flexible-element supports which, before the expansion of the sleeves 23, 24, 25, were in abutment on the external stops 18, 22, will bear on the internal stops 19, 21, when the sleeves 23, 24, 25 are inflated.

The radial deformation of the flexible elements 2 is also accompanied by withdrawal by sliding of the ends of the flexible elements 2 into the interstices delimited by the half-support bodies 801, 802 and the annular elements 501, 502. Thus, during the radial deformation, the curved ends of the flexible elements 2 slide in the interstices and move away from the bottom of the interstices, which reduces the inertia of the device 1.

Conversely, at the end of the pressure-measurement test, during the deflation of the sleeves 23, 24, 25, the radial deformation of the flexible elements 2 diminishes. The flexible-element supports 301, 302 regain their initial position against the external stops 18, 22 under the action of the dampers 20, 24. At the same time, the flexible elements 2 also regain their initial position by sliding of their ends in the interstices, the sliding taking place in the direction of the bottom of the interstices.

Even if FIGS. 2 and 3 show a protection device 1 comprising both a first compensation means comprising flexible elements 2 provided with curved ends disposed in interstices, and a second compensation means comprising dampers 20, 24 able damp longitudinal movements of the supports 301, 302, the protection device 1 may comprise only the first or second compensation means.

The device 1 according to the invention therefore effectively protects the probe 13, without impairing measurements during the pressure-measurement test, by virtue of the low resistance of the device 1 to the deformation of the probe 13.

Claims

1. Device (1) for protecting an elongate-shaped geotechnical or geophysical probe (13) and able to deform radially, characterised in that it comprises:

a plurality of elongate-shaped flexible elements (2), able to undergo radial deformation, in the operational configuration of the device (1),

means of longitudinal compensation for the radial deformation of the flexible elements (2), in the operational configuration of the device (1),

two flexible-element supports (301, 302), each accepting one end of the flexible elements (2), the supports (301, 302) being able to move longitudinally on the probe (13), so that the flexible elements (2) longitudinally protect the external part of the probe (13) lying between said supports (301, 302), in the operational configuration of the device (1).

2. Device (1) according to claim 1, characterised in that the means of longitudinal compensation for the radial deformation of the flexible elements (2) are formed by an interstice (11) in at least one of the flexible-element supports (301, 302) and by a curved end of the flexible elements (2), each end being disposed for reversible sliding in said interstice (11).

3. Device (1) according to claim 2, characterised in that the interstice (11) is delimited by two annular zones (5, 9) with different diameters.

4. Device (1) according to claim 2, characterised in that the means of longitudinal compensation for the radial deformation of the flexible elements also comprise at least one damper (20, 24) intended to damp longitudinal movements of at least one of the flexible-element supports (301, 302), in the operational configuration of the device (1).

5. Device (1) according to claim 1, characterised in that the flexible elements (2) are fixed to the flexible-element supports (301, 302), and in that the means of longitudinal compensation for the radial deformation of the flexible elements comprise at least one damper (20, 24) intended to damp longitudinal movements of at least one of the flexible-element supports (301, 302), in the operational configuration of the device (1).

6. Device (1) according to claim 4, characterised in that the dampers (20, 24) are elastic rings.

7. Device (1) according to claim 1, characterised in that the flexible-element supports (301, 302) are cylindrical in shape and comprise a plurality of cylindrical portions assembled together.

8. Device (1) according to claim 1, characterised in that the flexible elements (2) are steel blades.

9. Geotechnical or geophysical probe (13), characterised in that it is covered with a protection device (1) according to claim 4.

10. Probe (13) according to claim 9, characterised in that it is of the type comprising three inflatable sleeves (23, 24, 25) aligned along the longitudinal axis of the probe (13).

11. Probe (13) according to claim 10, characterised in that the flexible-element supports (301, 302) are disposed on each side of the assembly formed by the three inflatable sleeves (23, 24, 25).

12. Probe (13) according to claim 9, characterised in that each flexible-element support (301, 302) is able to be moved longitudinally between two stops (18, 19, 21, 22) of the probe (13), the movement being damped by the damper (20, 24).

13. Device (1) according to claim 2, characterised in that the means of longitudinal compensation for the radial deformation of the flexible elements also comprise at least one damper (20, 24) intended to damp longitudinal movements of at least one of the flexible-element supports (301, 302), in the operational configuration of the device (1).

14. Device (1) according to claim 5, characterised in that the dampers (20, 24) are elastic rings.

15. Device (1) according to claim 4, characterised in that the dampers (20, 24) are elastic rings.

16. Geotechnical or geophysical probe (13), characterised in that it is covered with a protection device (1) according to claim 1.

17. Probe (13) according to claim 16, characterised in that it is of the type comprising three inflatable sleeves (23, 24, 25) aligned along the longitudinal axis of the probe (13).

18. Geotechnical or geophysical probe (13), characterised in that it is covered with a protection device (1) according to claim 5.

19. Probe (13) according to claim 18, characterised in that each flexible-element support (301, 302) is able to be moved longitudinally between two stops (18, 19, 21, 22) of the probe (13), the movement being damped by the damper (20, 24).