GB2109443A

GB2109443A - Boring in the ground

Info

Publication number: GB2109443A
Application number: GB08232108A
Authority: GB
Inventors: Wolfgang Schreiber
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1981-11-13
Filing date: 1982-11-10
Publication date: 1983-06-02
Also published as: DE3145129C1

Abstract

A method for determining the position and location of a device for producing a connecting boring in the ground between two vertical bores. This cross borer device having a front part 2 and rear part 3 moving in alternation, the operation of determining the position and location is carried out by incrementally adding together the vectors of movement of the cross borer. For this purpose the coordinate axes of the rear part 3 are determined by means of a starting part remaining in the starting hole of the crossbore. After the front part 2 bearing a boring head has moved forward the coordinate axes of the front part 2 are determined in relation to the rear part 3. The rear part 3 is then moved up into position, the situation and location being determined relative to the front part 2 and used in relation to the latter as a reference coordinate. <IMAGE>

Description

SPECIFICATION Method for determining the position and location of a device for boring a coneeting bore in the ground This invention relates to a method for determining the position (attitude or orientation) and location of a boring device for providing a connecting bore in the ground between two vertical bores (cross borer) and an apparatus for carrying out the method.

In order to mine from deep coal seems, for example, at depths of 5 km, modern methods sink two vertical bores at a spacing of 200 m for instance and with a diameter of about 60 cm into the coal-bearing seam. Between the two vertical bores a connecting bore is provided which passes through the coal seam and makes it possible for the coal to be subsequently mined by gasification.

In this method there is a problem in continuously determining the position and situation of the boring device (cross borer) for the production of the connecting bore between the two vertical bores so that the cross-connecting borer can be controlled as it moves through the seam.

Methods known from aerospace technology for determining the position and locating data cannot routinely be applied owing to the lack of precision and the impossibility of reorientating the cross borer, The difficulty is aggravated by the fact that the cross borer may be in motion for up to about 10 hours between vertical bores.

The use of a rotary platform, owing to the precession of a triaxially stabilized rotary platform, requires control mechanisms to be accurate to within about 0.1 50 over a period of 10 hours.

Optical verification of the path, although in principle enabling highly accurate measurements to be taken, cannot be used in this case because in the travel of the bores they may cave in or the direction of movement may have to be considerably changed.

A magnetic orientation system is possible as a supplement to an earth gravitation sensor for pitch and roll information by using the magnetic field of the earth or a superimposed magnetic field for the purpose of obtaining pitch and yaw information.

The geological formations, however, give reason to expect serious distortions from the ideal for the lines of force of the field. In addition, this method would only enable the location but not the position of the cross borer to be determined. The production of an electrical current path between the vertical bores and the connecting bores through the seam fails as a method owing to the impossibility of clearly distinguishing between the conductivity of coal and that of the surrounding material.

Acoustic location is also possible using geophones to locate the cross borer as a source of the sound. This method fails to provide any information on the position of the cross borer.

An object of this invention is to provide a method and apparatus for determining the position and orientation of a cross borer so that it can be used with the necessary accuracy for the production of a connecting bore between two vertica' bores.

According to this invention there is provided a method for determining the position and location of a cross boring device comprising at least a front part and a rear part moving alternately, and for the production of a connecting bore through the ground between two vertical bores, in which method determination of the position and location of the borer device is effected by incrementally adding together the movement vectors and wherein: a) the coordinate axes of the rear part is determined by a starting part which remains in the mouth of the bore hole; b) the coordinate axes of the front part are determined in relation to the rear part after the front part carrying the boring head has moved forward; c) the rear part is then moved into position, and location and position are determined by reference to the front part and used as reference coordinates.

The main advsntage of this invention is that with relatively short proven single parts available the method enables the cross borer to be controlled in such a way that wasted bores are not produced. The cross borer accurately reaches the second vertical main bore and can be recovered from it and used again.

The invention is described and explained in greater detail by reference to an example shown in the accompanying drawings. In the drawings: Figure 1 shows a cross borer apparatus, Figure 2 shows a first embodiment of the apparatus, and Figure 3 shows a second embodiment of the apparatus.

The principle of the present invention is first explained briefly and it is based on the addition of vectors in which, by incrementally adding up the motion vectors of the cross borer 1 (see Figure 1) defined information on the position and location can be obtained. The starting point is that the intersection points of the coal seam or any other formation with the vertical bores constitute known points in a system of coordinates. The cross borer 1 has to describe, between these two points, a series of lines depending on the geological conditions. This iine curve is represented by a finite number of vectors. The vectors are automatically determined by the cross borer 1 and the cross borer 1 therefore has at least two parts moving in alternation, the front part 2 and the rear part 3, which are interconnected via a measuring system explained in detail in the following.

The front part 2 carrys the boring head 4 with a damping device 5 being possibly provided between the front part 2 and the boring head 4.

The rear part 3 and the front part 2 are flexibly interconnected via a variable length structure 6.

The cross borer will therefore move forward with a worm-like motion and mechanical details of the parts provided for the purpose of moving the rear part 3 up into position after the front part 2 are not shown or described. The flexible structure 6 itself has only moderate frictional forces to overcome and protects the measuring device from hot gas and falling rock. The sequence of movements is as follows: After the cross borer 1 has worked into the seam (not shown in the drawing) the coordinate axes of the rear part 3 are determined using the starting part 7 remaining in the starting hole.

When the boring head 4 and thus the front part 2 has moved farther on the coordinate axes of the front part 2 are determined in relation to the rear part 3. After the rear part 3 has then been moved up into position, its position and location in relation to the front part 2 are determined and then used as a reference coordinate system.

It should be noted that it is only the measuring values that are to be recorded in each case. The processing, i.e. the conversion of the coordinates and the operation of determining the vectors, takes place in guidance apparatus situated on the ground surface and not forming part of this invention, although in principle, of course, this processing can also take place in the cross borer itself.

Figure 2 shows a first embodiment of an apparatus.

Six different measured values are required for the translatory movement and rotation of a body in a system of coordinates. In the application of this principle three paraxially adjusted lasers 8, 9 and 10 are mounted on one of the parts, i.e. on the front part 2 or on the rear part 3. The lasers illuminate a surface in a new system of coordinates on the other part 3. On this other part 3, e.g. the rear part, three sensors 11, 12 and 13 are provided opposite the lasers 8, 9 and 10 respectively and these may be of the chargecoupled type. These sensors are divided in a known manner into a four-quadrant form. From the length of the three laser beams and the thus subdivided image sensors 11, 12 and 1 3 the relationship between two systems of coordinates can be unambiguously ascertained.

Figure 3 shows a further constructional version.

In this case the length measurement is made by means of laser interferometry customary in the art of machine tools. The length measurement is relative and takes place continuously along a fixed axis. Even a slight displacement of the laser, interferometer or reflector leaves the result unaffected.

The two different coordinate systems to be brought into relationship with each other, i.e. the front part 2 and the rear part 3, are interconnected by six telescopic tubes 14, 15, 16, 17, 18 and 19 in the manner illustrated. The telescopic tubes 14 to 19 are connected to the parts 2 and 3 by universal ball joints, not shown in detail. Laser interferometers are mounted in the telescopic tubes 14 to 19. When the telescopic tubes move the laser interferometers axes are automatically adjusted. Only two length measurements are required in this apparatus. The accuracy obtainable with laser interferometers already available quarantees the required accuracy in the vectorial addition.

The redundant method of vectorial addition by the acoustic location of the borer 1 is not illustrated. The basis is that the drive of the borer 1 not shown in the drawing, can be switched on and off as required during the boring method, so that geophone chains mounted in the vertical bores can locate the cross borer 1 with sufficient accuracy by the propagation delay occurring in the medium through which it is moving. This method as such is already sufficiently well known from existing prior art and is theretore not explained in detail. In conjunction with the other methods and apparatus of the invention it is considered to be novel and inventive.

To supplement the method and apparatus already described the cross borer can be constructed from a number of parts with only one part being moved and the others remaining stationary. This renders the reference coordination system at least singly redundant whereby it is insensitive to the displacement of the surrounding medium.

The parts of the cross borer 1 may be driven individually or by a common drive system.

Additional gyro platforms in the front part 2 and rear part 3 may also be of use for the purpose of sensing short movements in the reference system which is required to remain motionless.

Finally, the direction can be reorientated by providing a rapid gyro platform between the starting part remaining in the vertical bore and rear part of the cross borer, so that the direction can be realigned. Although the position of the platform itself is then inexact, this is no problem, since accuracy in this respect is not necessary.

A source of sound in the target bore may be sensed for direction of the cross borer to provide yaw information. An earth gravitation sensor carried with the apparatus provides additional information on the roll and pitch condition of the cross borer. In addition to these systems the boring device itself can be equipped with a sensing system for determining the nature of the surrounding soil and its location. Suitable sensors for this purpose are those of the type mounted in the form of a rim around the boring head and measuring the hardness, so that the cross borer is controlled in such a way that it invariably operates in the zone between the seam and the bed. By image transmission the optical conditions of the surrounding material can be transmitted, for example by means of a "load-coupled" camera, to the surface to provide additional information for control decisions, Ultrasonic measurement of the thickness of the layer is a simple means for enabling the thickness of the seam to be determined, at least along the horizontal boring.

The guidance apparatus on the surface is briefly discussed, although it does not form part of the subject of the invention. This guidance apparatus, which is installed for example in a vehicle, operates on a regulating circuit between the sensing system and the actuating system. The measuring values obtained through the telemetric system are evaluated at this point and presented in such a way that an operator can obtain information for control purposes. In this system the guide apparatus gives the operator the sensation as if he were a pilot in the cross borer.

For this purpose a display of the vertical bores of the seam and also the position and location of the cross borer can be shown on a screen and in a system of coordinates, which may be threedimensional. The distribution of the different hardnesses around the boring head can also be illustrated visually. The image from the camera can be seen on a further screen. The operator is thus enabled to operate along the bed of the seam taking the direction of the target bore into account.

Under these conditions the telemetric and telecommand system must control the functions of switching the driving mechanism on and off and controlling the speed, adjusting the boring head, controlling the movement of the tructure, aligning the camera and operating the hardness sensors.

The data can be transmitted, for example, through a photoconductor cable.

The cross borer of the invention is thus not only of advantage for coal mining but may operate in any medium, so that it is universally usable.

Claims

1. Method for determining the position and location of a cross boring device comprising at least a front part and a rear part moving alternately, and for the production of a connecting bore through the ground between two vertical bores, in which method determination of the position and location of the borer device is effected by incrementally adding together the movement vectors and wherein: a) the coordinate axes of the rear part is determined by a starting part which remains in the mouth of the bore hole; b) the coordinate axes of the front part after the front part carrying the boring head has moved forward; c) the rear part is then moved into position, and location and position are determined by reference to the front part and used as reference coordinates.

2. Method in accordance with Claim 1, wherein the measured values are further processed in the guidance apparatus on the surface of the ground.

3. Method in accordance with Claim 1 or Claim 2, wherein vectorial addition is combined with an acoustic location process of the cross borer device.

4. Method in accordance with any one of Claims 1 to 3, wherein by means of a chain of geophones in the vertical bores the cross borer is further located acoustically using a propagation time delay method.

5. Method in accordance with any preceding claim, wherein the target bore is provided with a source of sound wherein the direction can be sensed by the cross borer device, roll and pitch of the cross borer device being determined by earth gravitational sensors.

6. Apparatus for carrying out the method of any preceding claim 1 to 3, wherein one part of the cross borer device has three paraxially adjusted lasers, the other part having three detectors positioned opposite the lasers, the detectors being subdivided into a four-quadrant form.

7. Apparatus for carrying out the method of any preceding Claim 1 to 3, comprising a control means for a boring device having at least two parts arranged in axial succession and in which the two parts of the cross borer are interconnected by six telescopic tubes in which laser interferometers are mounted, each of the two parts having three mounting points and the telescopic tubes being mounted thereon by universal joints.

8. Method for determining the position and location of a cross boring device substantially as herein described and as exemplified and illustrated.

9. Apparatus for a cross boring device and a cross boring device incorporating such apparatus as described herein with reference to Figure 1 or 2 or 3 of the drawings.