Method for determining the position of a cutting device in the ground using a mobile carriage

Abstract

An excavator machine that includes components such as: a suspended casing having a top end and a bottom end; at least one cable that extends above the casing, where the cable is under tension and has a bottom end that is fastened to the top end of the casing; and a cutter device that is arranged at the bottom end of the casing. The excavator machine further includes: a carriage that is mounted to slide along the cable; a device for moving the carriage along the cable; and a locator device for determining the three-dimensional position of the carriage.

Claims

1. An excavator machine comprising: a suspended casing having a top end and a bottom end; at least one cable extending above the casing, said cable being under tension and having a bottom end fastened to the top end of the casing; a cutter device arranged at the bottom end of the casing; wherein the excavator machine further comprises: a carriage that is mounted to slide along the cable; a device for moving the carriage along the cable; and a locator device for determining a three-dimensional position of the carriage.

2. The excavator machine according to claim 1, further comprising: a guide device for preventing the carriage from pivoting about the cable as the carriage moves along said cable.

3. The excavator machine according to claim 2, wherein the casing is fastened to the bottom end of a first cable and to the bottom end of a second cable, wherein the carriage is mounted to slide along the first cable, and wherein the guide device comprises at least one arm secured to the carriage and co-operating at least with the second cable.

4. The excavator machine according to claim 3, wherein the arm has a distal end that co-operates with the second cable.

5. The excavator machine according to claim 4, further comprising: an extractor pipe for extracting cuttings, wherein the extractor pipe extends above the casing, and wherein the arm is curved so as to be spaced apart from the extractor pipe.

6. The excavator machine according to claim 1, wherein the locator device includes at least one device for measuring a tilt of the carriage, wherein the at least one device for measuring the tilt is arranged in the carriage.

7. The excavator machine according to claim 6, wherein the locator device has first and second devices for measuring the tilt of the carriage, wherein the first and second devices for measuring the tilt are arranged to measure tilt angles in two mutually perpendicular vertical planes.

8. The excavator machine according to claim 6, wherein the locator device further comprises a device for measuring an angle of rotation of the carriage in a plane substantially perpendicular to the cable.

9. The excavator machine according to claim 1, wherein the carriage has a memory for storing data measured by the locator device during a movement of the carriage.

10. The excavator machine according to claim 1, wherein the locator device further comprises a device for determining a length of a movement of the carriage along said cable.

11. The excavator machine according to claim 1, wherein the device for moving the carriage comprises a connection cable fastened to the carriage.

12. The excavator machine according to claim 1, wherein the device for moving the carriage is configured so that the downward and/or upward speed of the carriage along the cable is controlled.

13. The excavator machine according to claim 1, further comprising: a device for determining a position of the casing from measurement data taken by the locator device during a movement of the carriage along the cable.

14. The excavator machine according to claim 13, wherein the casing includes an inclinometer enabling a tilt of the casing to be measured relative to vertical, and wherein the excavator machine also comprises a device for determining a position of the cutter device from the position, a length, and the tilt of the casing.

15. The excavator machine according to claim 1, further comprising: a guide assembly arranged at a ground surface to hold stationary in a horizontal plane a zone of the cable that lies in said plane while the casing is being lowered, said guide assembly serving, at least at the instants that measurements are taken, to define at least one fixed reference position in three-dimensional relationship with the bottom end of the cable.

16. A method of boring into soil, the method comprising: providing an excavator machine according to claim 1; performing a boring step by causing the casing to penetrate into the soil; performing a step of moving the carriage along the cable, during which step three-dimensional positions of the carriage are measured at different measurement points; and determining a position of the casing in the soil from the three-dimensional position measurements of the carriage.

17. The method according to claim 16, wherein the carriage is held stationary at each measurement point.

18. The method according to claim 16, wherein a tilt of the casing is measured and a position of the cutter device in the soil is determined from the position of the casing and the tilt of the casing.

19. The method according to claim 16, wherein the cable is held stationary prior to performing the step of moving the carriage, and wherein a plurality of steps of moving the carriage are performed during the boring step so as to determine a plurality of positions of the casing in the soil and so as to obtain a real path followed by the casing in the soil.

20. The boring method according to claim 19, wherein the real path followed is compared with a path that is predetermined for the casing in the soil, and the positioning of the casing is corrected during the boring step in order to minimize an offset between the real path and the path that is predetermined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention can be better understood on reading the following description of an embodiment given by way of non-limiting example and with reference to the accompanying drawings, in which:

(2) FIG. 1 is an overall view of the excavator machine of the invention while boring;

(3) FIG. 2 is a plan view of guide means for placing in a horizontal plane at the surface facing the trench;

(4) FIG. 3 shows the beginning of the boring operation, the casing being shown in front view, in a plane orthogonal to the thickness of the trench, the casing being oriented vertically;

(5) FIG. 4 is a side view of the FIG. 3 casing;

(6) FIG. 5 shows the casing held stationary at great depth in front view, in a vertical plane orthogonal to the thickness of the trench, the path followed by the casing having deflected away from the vertical in a direction X parallel to the width of the trench;

(7) FIG. 6 is a side view of the FIG. 5 casing showing the deflection of the path followed by the casing relative to the vertical in a direction Y parallel to the thickness of the trench;

(8) FIGS. 7A to 7D show the position of one of the cables of the casing of FIGS. 5 and 6 in horizontal planes situated at different depths at which the position of the carriage is determined;

(9) FIG. 8 shows the movement of the carriage along the axis X between two successive measurements;

(10) FIG. 9 shows the movement of the carriage along the axis Y between two successive measurements;

(11) FIG. 10 is a detail view of the carriage; and

(12) FIG. 11 is a diagram showing the mathematical processing of the signals used for determining the position of the cutter device of the casing in the ground.

DETAILED DESCRIPTION OF THE INVENTION

(13) FIG. 1 shows an excavator machine 10 in accordance with the present invention while boring a trench T in soil S adjacent to a screen E already in place in the soil.

(14) In the description below, the term thickness designates the short dimension of the trench T considered in a horizontal plane, and the term width designates the long dimension of the trench T considered in a horizontal plane. The term depth designates the height of trench considered in a vertical direction.

(15) Finally, the description refers to an orthogonal reference frame X, Y, Z, where X is an axis parallel to the width of the trench, Y is an axis parallel to the thickness of the trench, and Z is a downwardly-oriented vertical axis.

(16) In this example, the excavator machine 10 is a hydraulic cutter. The excavator machine comprises a suspended casing 12 having a top end 14 and a bottom end 16.

(17) The casing extends in a longitudinal direction DL and presents a length L.

(18) A cutter device 18, having rotary drums 20, is fastened to the bottom end 16 of the casing 12.

(19) In conventional manner, the casing 12 is suspended from a hoist 22. For this purpose, in this non-limiting example, the excavator machine has first, second, third, and fourth carrier cables referenced 30, 32, 34, and 36. Each cable has a bottom end 30a, 32a, 34a, or 36a that is fastened to the top end 14 of the casing. The fastener points of the cables 30, 32, 34, and 36 to the top portion of the casing are referenced A, B, C, and D. In known manner, the top ends of the cables are mounted on one or more drums carried by the hoist 22.

(20) The cables are carrier cables in the sense that they carry the casing 12. It should be understood that the cables are tensioned by the action of the weight of the casing. It should also be understood that the cables extend above the casing 12.

(21) The excavator machine 10 also has a pipe 13 for extracting cuttings, which pipe extends above the casing, being connected to the top end 14 of the casing. As can be seen in FIG. 1, the carrier cables 30, 32, 34, and 36 are arranged around the pipe 13 for extracting cuttings and they extend substantially parallel thereto.

(22) In accordance with the present invention, the excavator machine 10 has a carriage 50 that is mounted to slide along the first cable 30. As explained above, the carriage 50 can also be configured to slide along any of the other three cables 32, 34, and 36.

(23) The carriage 50, shown in FIG. 10, comprises a body 52 having three wheels 54 fastened thereto that enable the carriage 50 to slide along said cable 30. The wheels 54 are arranged on opposite sides of the cable so as to clamp onto it, thereby enabling the carriage 50 to slide along the cable.

(24) In this example, the movement of the carriage 50 along the first cable 30 is driven by a device comprising a connection cable 60 connected to the body 52 and also to a drum 62 at the surface. Although the carriage can move down along the cable under the action of its own weight, its downward speed is nevertheless controlled by the action of the drum 62.

(25) The drum 62 also has a function of raising the carriage 50 at controlled speed.

(26) In order to avoid the carriage 50 pivoting about the cable 30 while it is moving, a guide device 56 is provided that comprises an arm 56 that is secured perpendicularly to the body 52, and that co-operates with another cable, specifically the cable 34 in this example. The first and second cables are situated in the same half-thickness of the casing, but not in the same half-width of the casing.

(27) The arm 56 has a distal end 56a co-operating with the second cable. In this example, the distal end 56a has two rollers 58 with axes of rotation that are substantially parallel to the arm and serving to minimize friction between the arm and the second cable 34.

(28) In the example shown in FIG. 1, the arm 56 is curved so as to be spaced apart from the extraction pipe 13. This serves to avoid any risk of the arm coming into contact with the extraction pipe, which would impede or block movement of the carriage.

(29) In this embodiment, the excavator machine 10 also has guide means 70 for guiding the first, second, third, and fourth cables 30, 32, 34, and 36. These guide means 70 are constituted by cross-bars 72 holding four guide rings 74 in position for guiding the cables. As can be seen in FIG. 3, the guide means 70 are positioned at the surface and their function is to hold in position in a horizontal plane Q the zones of the cables that are located in the horizontal plane Q.

(30) During the boring operation, as described below, the guide means are fastened relative to the ground so that the carrier cables remain fixed in position in the horizontal plane Q. The guide rings 74 could naturally be of some other shape, defining four fixed reference positions referred to as A.sup.0, B.sup.0, C.sup.0, and D.sup.0. The positions of the rings preferably coincide with the positions of the fastener points A, B, C, and D when the top end of the casing is situated substantially in the horizontal plane Q.

(31) It can be understood that the guide means ensure that the reference points A.sup.0, B.sup.0, C.sup.0, and D.sup.0 do not depend on any movements or deflections of the casing 12.

(32) As mentioned above, an object of the invention is to determine the position of the cutter device in the soil during the boring step. For this purpose, the position of the casing 12 in the soil is initially determined, and more particularly the position of the top portion of said casing is determined. For this purpose, at least the difference between the fastener point A of the first cable 30 relative to the fixed reference point A.sup.0 is measured.

(33) In order to determine more precisely the position of the top portion of the casing, it is preferable also to measure the departures of the fastener points B, C, and D of the other cables relative to the associated fixed reference positions B.sup.0, C.sup.0, and D.sup.0.

(34) In accordance with the invention, the difference between the fastener point A of the first cable relative to the fixed reference point A.sup.0 is determined by moving the carriage 50 along the cable between the reference position A.sup.0 and the fastener point A. This movement may be downward movement along the cable or it may be upward movement.

(35) During the step of moving the carriage 50 along the first cable 50, the three-dimensional position of the carriage 50 is measured periodically with the help of a locator device. During the movement step, the first cable is held stationary. For this purpose, in this example, downward movement of the casing 12 is stopped.

(36) It can thus be understood that the first cable is stationary while the carriage 50 is moving and taking measurements.

(37) With reference to FIGS. 5 and 6, it can be understood that at an instant t, when a three-dimensional position measurement is performed, the position of the carriage 50 on the first cable 30 is written A.sup.i, where i is an integer in the range 1 to N. In this example, N measurements of the three-dimensional position of the carriage are thus taken. The N positions of the carriage, at which measurements are taken, are referred to as measurement points and they are distributed along the first cable. Consequently, the measurement point A.sup.N preferably coincides with the fastener point A, or is at least situated in the immediate vicinity of said fastener point. The carriage 50 is preferably stopped at each measurement point A.sup.i so that the carriage is not moving while the measurement is being taken, thus making it possible to obtain measurement values that are more accurate.

(38) The locator device comprises firstly first and second tilt measurement devices 80 and 82 arranged in the carriage 50 and suitable for measuring tilt angles in two mutually perpendicular vertical planes. These tilt measurement devices, specifically inclinometers, serve to measure: a tilt angle relative to the vertical, this angle corresponding to a rotation of the carriage 50 about the axis Y, as shown in FIG. 5; and a tilt angle relative to the vertical, this angle corresponding to a rotation of the carriage 50 about the axis X, as shown in FIG. 6.

(39) When the casing is purely vertical, it can be understood that the carrier cables are likewise vertical, and that as a result the tilt angles and are zero.

(40) It can also be understood that when the casing deflects from its vertical path, the carrier cables tend to tilt and to curve, as shown in FIGS. 1, 5, and 6, thereby having the effect that the casing tilts relative to the vertical direction. Under such circumstances, at least one of the angles and is non-zero.

(41) The values of the tilt angles and as measured at a point A.sup.i are written .sup.i and .sup.i. Thus, at each measurement point A.sup.i, with the carriage preferably being stopped, the angles .sup.i and .sup.i are measured. The tilt angles .sup.i and .sup.i, where i=1 . . . N as measured during the movement of the carriage are stored, in this example, in a memory 51 arranged in the carriage 50.

(42) The locator device comprises secondly a device 84 for determining the length l of the movement of the carriage along the first cable 30. This length l corresponds to the length l of the connection cable 60 that has been unwound from the drum 62. The device 84 naturally enables an infinitesimal movement l.sup.i of the carriage 50 to be measured between two successive measurement points A.sup.i-1 and A.sup.i. The value of the movement l.sup.i may be selected as being a constant value l determined by the drum 62. In a variant, the movement l.sup.i is measured by means on board the carriage.

(43) In this example, the travel speed of the carriage is controlled. It is preferable for the speed at which the carriage moves up or down to be constant, and to lie in the range 1 meter per second (m/s) to 10 m/s.

(44) In the variant shown, the locator device also has a device 86 for measuring the angle of rotation .sup.i of the carriage 50 in a substantially orthogonal plane perpendicular to the cable, relative to a reference angular position .sup.0. In this example, the angle of rotation is measured in a horizontal plane. Because of the presence of the arm 56, the angle of rotation corresponds to the twist angle of the cable relative to a straight line passing through the reference points A.sup.0 and B.sup.0. The angle of rotation .sup.i is preferably measured at each measurement point A.sup.i, and in particular at the final position A.sup.N in order to obtain an estimate of the rotation of the top portion of the casing relative to the reference straight line passing through the reference positions A.sup.0 and B.sup.0. The angles of rotation .sup.i are stored in the memory S1 of the carriage.

(45) With reference now to FIGS. 8 and 9, it can be understood that the values .sup.i and .sup.i, .sup.i, and l.sup.i enable infinitesimal movements X.sub.A.sup.i and Y.sub.A.sup.i to be determined along the axes X and Y by trigonometric calculation. These movements X.sub.A.sup.i and Y.sub.A.sup.i are also shown in FIGS. 7A to 7D which are horizontal section views showing a few of the measurement points A.sup.1, A.sup.i, and A.sup.N of the carriage 50 at which the three-dimensional position of the carriage is measured.

(46) In another advantageous aspect of the invention, the excavator machine also has a device 90 for determining the position of the casing 12 from the measurement data, i.e. the values .sup.i, .sup.i, and .sup.i taken by the first and second tilt measurement devices 80, 82 of the locator device and by the device 86 for measuring the twist of the cables during the movement of the carriage along the first cable 30.

(47) In this example, the device 90 has mathematical processor means enabling the above-mentioned movements X.sub.A.sup.i and Y.sub.A.sup.i to be calculated and then by an integral calculus enabling the movement values X.sub.A and Y.sub.A of the point A along the axes X and Y to be determined relative to the fixed reference position A.sup.0.

(48) The position of the casing 12, and more particularly the position of its top portion 14, is determined from the movement values X.sub.A and Y.sub.A, and the depth of the point A can be determined for example from the length of the first cable 30 that has been unwound or with the help of some other type of depth measuring instrument secured to the casing.

(49) The number of measurement points N is selected to be large enough to obtain a result that is accurate, it being understood that the value N may depend on the depth that has been reached by the casing. As non-limiting examples, N may be selected so as to take a measurement once every 0.20 m, 0.5 m, 1 m, or 2 m along the cable.

(50) For this purpose, measurements are preferably taken at fixed time intervals, with the carriage being moved at constant speed.

(51) In order to improve the accuracy of measurements, it is possible to increase the number N of measurement points by taking measurements both while lowering the carriage and also while raising it. It is also possible to perform these steps by causing the carriage 50 to slide along other cables, in order to determine the positions of the points B, C, and D.

(52) In another advantageous aspect of the invention, the excavator machine also has a device 92 for determining the position of the cutter device 18 in the ground, on the basis of the position of the casing, and more particularly on the basis of the position of the top portion of the casing 12. The position of the cutter device 18 is also determined from the length (or height) L of the casing and from its tilt relative to the vertical.

(53) The tilt of the casing 12 is measured using an inclinometer 100 arranged in the casing 12 and measuring a first tilt angle relative to the vertical, as shown in FIG. 5, and a second tilt angle relative to the vertical, as shown in FIG. 6. The first and second tilt angles are measured in two vertical planes that are mutually orthogonal.

(54) The position of the cutter device 18 relative to the points A, B, C, and D is known, so knowledge of the positions of the points A, B, C, and D of and the tilt of the casing makes it possible to calculate, for example, the position of a middle point W situated between the leading edges of the rotary drums.

(55) In order to improve measurement accuracy, account is also taken of the angle of rotation of the top portion of the casing 12.

(56) In FIG. 11, the mathematical processing of the information delivered by the various above-mentioned measurement devices is shown diagrammatically and serves to calculate the position of the middle point W of the cutter device.

(57) The device 90 for determining the position of the casing 12 receives the values .sup.i and .sup.i, and also .sup.i as measured during the movement of the carriage by the inclinometers arranged in the carriage, and l.sup.i as measured by the device 84 for determining the distance the carriage has moved along the first cable 30. The device 90 calculates the coordinates of the points A, B, C, and D. In order to determine the position of the cutter device, the device 92 receives the coordinates of at least one fastener point A, together with the values of the first and second casing tilt angles and as provided by the inclinometer 100 secured to the casing. The device 92 then provides the coordinates of the middle point W.

(58) During boring, several steps are performed of moving the carriage with the casing 12 at different depths for the purpose of determining a plurality of positions of the casing and of the cutter device, thus making it possible to obtain the real path followed by the casing, and by the cutter device, in the soil S.

(59) Comparing the real path followed with the (desired) path predetermined for the casing, makes it possible to determine the offset or the deflection of the path followed by the casing. This offset can be minimized during boring by actuating path corrector means, e.g. hydraulic pads 110 arranged on the faces of the casing. These pads 110 bear against the walls of the trend, thereby enabling the tilt of the casing to be modified, and thus enabling its path to be modified.