IE63125B1

IE63125B1 - Pyrotechnic dynamic penetrometer

Info

Publication number: IE63125B1
Application number: IE430991A
Authority: IE
Inventors: Bernard Castagner
Original assignee: Bernard Castagner
Priority date: 1990-12-12
Filing date: 1991-12-11
Publication date: 1995-03-22
Also published as: IE914309A1; DZ1545A1; CS374291A3; AU677160B2; CN1063158A; BR9107271A; CN1030797C; WO1992010753A1; GR3015150T3; IL100296A; FR2670582B1; NO932161D0; IL100296A0; ATE114371T1; MA22362A1; CA2098091A1; NO932161L; OA09805A; JPH06503619A; FI932673A

Abstract

The dynamic pyrotechnical penetrometer determines soil characteristics by using the pressure created by a pyrotechnical gas generator to drive a probe rod (1) into the ground, with continuous detection and measurement of penetration. A standard probe rod mounted on a piston (2) containing a magnet (3) is placed in a solenoid-equipped amagnetic tube. A recoiling mass (4) which balances the amount of rod movement created by the gas from a pyrogenerator (5) contained in said recoiling mass, is then also placed in said tube. A unit for acquiring and processing the movement data of the standard rod calculates the resistance of the ground in response to the insertion of the rod.

Description

Pyrotechnic dynamic penetrometer The present invention relates to a system for examining soils and for measuring their characteristics. The two principal existing soil examination systems are examination by pressure measurement and examination by penetration measurement, in particular dynamic penetration measurement. The principle of dynamic penetration measurement is the determination of the kinetic energy necessary for driving in a probe of a certain height, the kinetic energy generally being created by the calibrated fall of a given mass.

Probings carried out with this system take up a lot of time and in these days of high labour costs, they are expensive.

Furthermore, most of these systems do not include an automatic written report of the characteristics of the soils, which would confer greater credibility on the examinations carried out.

The pyrotechnic dynamic penetration measurement ’ system which is the subject of the innovation in particular makes it possible to meet the following major requirements: speed of execution, reduction of costs and credibility of the measurement.

The system which is the subject of the present patent determines the characteristics of the soil by the continuously detected and measured driving of a standard probe rod into the soil. This driving-in is carried out by the use of the pressure created by a pyrotechnic gas generator.

The originality of the design of the system which is the subject of the present patent will emerge from its description, from the justification of the techniques used and from its operating diagram.

The important features of the system proposed by the invention are as follows: - The pressure created by a pyrotechnic gas generator in an ejection tube is used for driving a standard probe rod into the soil.

- The displacement of the rod in the ejection tube is detected continuously, in particular by the passage of a magnet, connected to the rod, through solenoids placed along the ejection tube.

- This displacement, which is the resultant of the acceleration created by the gas pressure on the rod and of the acceleration created by the resistance of the soil on this same rod is continuously computed by means of a pre-programmed electronic circuit.

- In the case of a light and portable system, use is made of the balancing of the quantities of movements by a vertical backward-moving mass, part of which preferably serves as an expansion chamber for the gases and as a guide for the standard rod.

The following description is purely illustrative and non-limitative, and must be read with reference to the appended drawings in which: - Figure 1 shows the simplest embodiment of the system which is the subject of the invention.

- Figure 2 shows a system more specially adapted to small-depth probings.

- Figures 3 and 4 show a system more specially adapted to larger-depth probings.

The basic system is shown diagrammatically in Figure 1.

The standard probe rod (1) is fixed to a piston (2) in which a magnet (3) is placed.

The backward-moving mass (4) balances the quantity of movement which will be transmitted to the stan30 dard rod (1) and to its piston (2).

It is equipped with a gas generator (5). The absorption of the recoil energy is ensured by gravity.

Without departing from the scope of the invention, it is possible to use another means of balancing the recoil forces, such as energy absorbers, the mass of the carrier or of the system.

The assembly of rod, piston, backward-moving mass and generator is placed in a recoil tube (7) manufactured from non-magnetic materials. The recoil tube (7) is equipped with solenoids (6) preferably placed concentric with the launch tube.

These solenoids (6) are connected to the data processing and electronic unit (9).

After ignition, the gas generator feeds gas into the expansion chamber (8) located between the piston (2) and its backward-moving mass (4), the pressure thus generated moves the standard rod (1) at speed. During the ejection of the rod, the passage of the magnet (3) through the various solenoids (6) generates electrical signals for which the time intervals between appearances are computed.

This allows computation of the speed and then of the acceleration of the. standard rod.

The law P(t) for pressure delivered by a given gas generator into the expansion chamber is known, either precisely because of a measurement, or to a good approximation (2 to 3%) because of the reproducibility of performance of the gas generator used.

The deceleration force due to the resistance of the soil to the driving-in of the standard rod is therefore knownϊ R(t) = S.P.(t) - m G(t) The computations are carried out either with an adapted logic circuit, or with an existing pre-programmed computer.

Without departing from the scope of the invention, it will be possible to use other systems for detecting a passage of this type, such as electromechanical contactors or photoelectric cells.

Similarly, without departing from the scope of the invention, it is possible to replace the passage detectors and a part of the data processing circuit by an accelerometer.

The standard rod may or may not be equipped with a point (10) whose maximum diameter is greater than that of the rod, depending on the type of measurement to be carried out.

. The system which is the subject of the present invention in its portable version and as used for lowdepth probings is shown diagrammatically in Figure 2.

The standard probe rod (1) is fixed to a piston (2) in which a magnet is placed.

The backward-moving mass (4) balances the quantity of movements which will be transmitted to the standard rod and to its piston. It is preferably constituted from a tube made from non-magnetic materials, for example a cylindrical tube closed at its upper end; the backward-moving mass thus serves as an ejection tube.

Before being driven in, the standard rod equipped with the piston is held in the backward-moving mass preferably by means of a deformable clip (15) but, without departing from the invention, it is possible to use another fixing system such as a ball spring, a plate spring...

The backward-moving mass (4) slides in a recoil tube (7) made from non-magnetic materials and preferably made from glass fibre composite with a thermohardening or thermoplastic matrix.

At its point of contact with the soil, the guidance tube is preferably provided with a support foot (17) equipped with a shock absorber (16) for the falling back of the backward-moving mass.

The solenoids (6) for detecting the passage of the magnet are preferably located around the guidance tube and connected to the electronic processing unit (9) .

The system can be independent and be simply equipped with a folding adjustable tripod (22).

This tripod can preferably be constituted from an assembly ring (18) for the three legs (19) whose length is adjustable by means, for example, of a lockable slider (20) and which bear on the soil by means of feet (21) which can have holes in them for, if appropriate, fixing the system to the soil.

The backward-moving mass preferably has the support of the breech (14) of the gas generator and of its initiation safety system (13) mounted on top of it.

The initiation of the gas generator is preferably by means of percussion but, without departing from the scope of the invention, it will be possible to use electrical initiation or initiation by laser beam.

The body of the gas generator is preferably made of thermoplastic, thermohardening, elastomer, cardboard or composite materials and its structure is preferably designed to open at low pressure out of its operating housing and to do this for safety reasons in the case of possible accidental ignition or of fire.

In order to facilitate loading and to ensure safety, the gas generator (5) is preferably placed in a housing (12) located in a movable breech (11).

The insertion of this movable breech (11) in its support (14) allows the gas generator to be placed in the operating position facing the inlet channel to the expansion chamber (8) and the arming of the initiation safety system (13) .

Without departing from the scope of the invention, it is possible to adapt other constructions of the piston-ejection function.

Figure 3 shows a variant specially adapted for deep probing carried out by means of a single standard rod or of several rods assembled as the probing progresses.

The ejection thrust function and the guidance function of the standard rod are not provided by a piston but, on the one hand, by the closed end of the hollow standard rod (1) carrying the point (10) whose maximum diameter is greater than that of the rod or whose maximum diameter is not greater than that of the rod and, on the other hand, by an axial tube along which the standard rod slides.

The standard probe rod (1) is equipped with a collar (25) which allows its driving into the soil to be limited in the case of excess energy with respect to the energy absorbed by the driving into the soil.

The magnets (3) are located in this collar (25). In this case, the solenoids are not concentric with the tube but located along the tube and the magnets are placed in a plane perpendicular to the movement of the rod.

The standard probe rod elides over a guide tube (27) which is connected, preferably by means of a chuck (26), to the backward-moving mass (4), the latter also forms a recoil guidance tube and is equipped with the expansion chamber (8) and the breech of the gas generator (5). without departing from the scope of the invention, the probe rod (1) can be inside the guide tube (27).

The recoil tube (7) comprises a bore (29) in its upper part.

The expansion chamber comprises one or more orifices (28) equipped or not equipped with a valve or with a shear membrane.

In fact, in the case of a blockage of the standard probe rod in the soil, it is necessary to evacuate the gases from the expansion chamber in order to limit the rising of the backward-moving mass.

This evacuation is preferably carried out by means of this bore (29) and of these orifices (28). They are placed in such a way that they only slightly degrade the performance of the gas generator.

The recoil tube (7) and the tubular part of the backward-moving mass have an opening (30) (Figure 4) to allow the loading of the standard rod (1) equipped with its guidance tube (27). This opening is closed during its operation either by a door (30) or by the rotation of the backward-moving mass in the guidance tube.

In the case of the presence of a door, the loading of the standard probe rod is carried out by opening the door (30) of the backward-moving mass. This door is equipped with a locking system (31) which, for safety reasons, is preferably linked with the firing safety device (15).

In the case of partial or difficult driving-in of the standard rod, it is easily possible either to withdraw it, or to complete its driving-in by using a second gas generator.

In order to withdraw the standard probe rod (1), it suffices to open the chuck (26); the guide tube (27) drops to the bottom of the standard rod and it is then possible to release the system and then extract the guide rod, where appropriate with the help of an extractor bearing on the collar (25).

It is also possible to add a second extension probe rod in order to deepen the probing by fixing it in the place of the collar after dismantling the guide tube.

Claims

1. Apparatus for examining and characterising a soil, comprising 4 - a recoil tube (7), 5 I - a probe rod (1) which is movable with respect to the recoil tube (7), 10 - a pyrotechnic generator, - detection means (6) comprising a plurality of component parts, - the probe rod (1) being arranged to be driven into the soil by the action of the pyrotechnic generator (5), - the detection means (6) being fixed to the recoil tube (7) 15 and each of its component parts detecting the passage of the probe rod (1) at its respective position in such a manner as to provide a measure of the movement of the probe rod during its driving-in. 20 2. Apparatus according to Claim 1, characterised in that the movement of the probe road (1) is detected by the passage of a magnet (3), connected to this rod, through solenoids (6) placed along the outer tube (7). 25 3. Apparatus according to Claim 1, characterised in that the movement of the probe rod (1) is detected by the passage of the latter in front of photoelectric cells or electromechanical contactors. 30 4. Apparatus according to one or more of the preceding claims, characterised in that the coordinates of the movements of the rod are entered into a computer (9), dedicated or not dedicated, programmed and initialised with the parameters of the apparatus, in order to obtain directly characteristics of the soil and to make them available for display or printing. 35 5. Apparatus according to one or more of the preceding claims, characterised in that the balancing of the quantity of movements - 9 transmitted to the probe rod is ensured by a backward-moving mass (4) located in the recoil tube (7), the kinetic energy of which is absorbed by use of the force of gravity.

2. 6. Apparatus according to Claim 5, characterised in that the backward-moving mass comprises the housing of the pyrotechnic generator (5).

3. 7. Apparatus according to Claim 5 or Claim 6, characterised in that the backward-moving mass serves as a guidance tube for the probe rod and as an expansion chamber for gases.

4. 8. Apparatus according to Claim 7, characterised in that the backward-moving mass has, at the level of the expansion chamber (8), one or more safety vents (28), and the recoil tube has a bore (29) to facilitate the extraction of gases in the case of premature blockage of the probe rod in the soil during its driving-in.

5. 9. Apparatus according to any of Claims 5 to 8, characterised by the use of a hollow probe rod (1) sliding along a removable guide tube (27) locked in the backward-moving mass (4) by a chuck (26) or by a fast fixing system.

6. 10. Apparatus according to one or more of the preceding claims, characterised in that the probe rod may be in several sections assembled by a locking joint as the probing operation proceeds.

7. 11. Apparatus according to one or more of the preceding claims, characterised in that the body of the generator is made of thermoplastic or composite materials and opens at low pressure out of its operating housing.

8. 12. Apparatus as defined in Claim 1 for examining and characterising a soil, substantially as described herein with reference to and as illustrated in the accompanying drawings.