A METHOD AND AN APPARATUS FOR THE MEASUREMENT OF THE VOLUME OF ROCK CHAMBERS

Abstract: A laser (10) is arranged to emit a laser beam (12') in the lengthwise extension of the rock chamber, said beam being deflected by means if a pentagon prism (14) which is arranged in such a manner that the beam (12) will be deflected at right angles. The deflected beam (16) is incident on the rock chamber wall (18) in an impact point (20). A theodolite (22) is positioned at a determined place in the rock chamber and is set to determine the position of the impact point (20). The prism is rotated and the positions of the impact points resulting therefrom are determined. On the basis of the knowledge gained regarding the positions of the impact points an estimation of the area of the vertical plane delimited by these points is made. A number of area-determination operations are made in a corresponding manner, the values of said area-determination operations forming the basis of the estimation of the volume of the rock chamber.

Description: A Method and an Apparatus for the Measurement of the Volume of Rock Chambers The subject invention concerns a method and an apparatus for the determination of the volume of rock chambers. The apparatus is designed to be used to establish the exact volume of the rock chamber as the blasting is progressing. The intended purpose of the blasted rock chamber may be as a subterranean storage room, a bomb shelter or a tunnel. When blasting rock chambers it is in the interest of the firm carrying out the blasting that the resulting rock chamber agrees in volume as nearly as possible to the volume ordered. It is expensive to blast away too large quantities of rock which must be disposed of. For this reason it is important that the volume of the rock chamber can be exactly determined as the blasting of the chamber is progressing. In US PS 3950096 is described a device designed to estab¬ lish the cross-sectional area of tunnels. This device comprises a carriage which is movable on rails in a blasted tunnel and which carries optical measuring means on its platform. The measuring means comprises a laser which emits a laser beam in the transverse direction of the tunnel. The light beams from the illuminated point on the rock chamber wall are reflected to an optical instrument and is refracted by means of a lens to a point the distance of which from the longitudinal axis of the tunnel is measured automatically. This distance is propor¬ tional to the distance between the longitudinal tunnel axis and the tunnel wall and in this manner it becomes possible to establish the distance. However, this method suffers from a number of disadvantages. The measured value is but a proportional part of the sought-after value, with the result that all errors and uncertainties of the read- -off values are enlarged by several times. The measurements are per¬ formed automatically, which means that no regard is paid to whether or not the read-off measuring point is positioned in a representative part of the profile of the area. For instance, the measuring point might be positioned on a protruding rock formation. The unreliability of the measuring results thus is considerable. This prior-art device obviously is intended to establish the area of the tunnel, not its volume, since it is not designed to coor¬ dinate a number of area-determination values to establish the volume of the rock chamber. Such coordination may be obtained only after the de- termination of the distance between various parallel measuring planes. In addition, the device is difficult to use, since it cannot be driven into the tunnel until after completion of the blasting of the tunnel when the rail is deposited. It is obvious therefore, that this device is not intended for the continuous measurement of the volume of the rock chamber while the work of blasting the latter is still in progress. One purpose of the subject invention is to provide a method for the exact measurement of the volume of a rock chamber as the blas¬ ting of the latter is progressing. A further purpose of the invention is to provide a simple and inexpensive apparatus for performing the method. The characterizing features of the method in accordance with the invention appear above all from claim 1. The apparatus in accor¬ dance with the invention is characterized primarily by the features appearing in claim 5. Further characteristics of the invention appear from the dependent claims. The invention will be decribed in closer detail in the following with reference to the accomapny ng drawings, wherein Fig. 1 is an overall perspective view of the apparatus in accordance with the invention, and Fig. 2 is a diagram illustrating ray paths an sight lines for performing the measuring method in accordance with the invention. The apparatus in accordance with the invention comprises a source of light which in the embodiment illustrated is a laser 10 emit¬ ting a laser beam 12. The laser 10 is positioned at the mouth of a rock chamber the blasting of which is in progress and the laser beam 12 is directed essentially in the lengthwise direction of the rock chamber. An optical deflecting member in the form of a prism is positioned in the interior of the rock chamber and in such a position that it is struck by the aser beam 12. The beam is deflected at righ angles and the deflected beam 16 strikes the rock chamber wall 18 and illuminates a spot 20 on the latter. An optical instrument in the form of a theodolite 22 is provided in the rock chamber laterally of the laser beam 12. The theodo¬ lite 22 is of a conventional kind and well known from the land sur¬ veying technology. The prism 14 preferably is a pentagon prism which is ar¬ ranged in such a manner that the deflected beam 16 will always be directed in a plane which extends at right angles to the beam 12 which is incident on the prism. The prism 14 is rotationally mounted in such a manner as to ensure that the deflected laser beam 16 may be directed in various directions in this plane which is perpendicular also to the main extension of the rock chamber. The rotation of the prism is effec¬ ted by means of a remote-controlled motor which preferably is operated by infrared light. Radio-control of the motor would mean a safety risk because of the presence of the blasting equipment inside the rock cham- be.r. The remote-control equipment preferably is operated by the person carrying out the measurements with the aid of the theodolite. The measurements are effected in the following manner. The theodolite 22 is positioned inside the rock chamber at an arbitrary point Pi the coordinates of which are determined exactly. The prism 14 is positioned in the ray path at a point P2 (see Fig. 2) the coor¬ dinates of which are likewise determined with great accuracy. The theo¬ dolite is set to measure the angle - * between a line 24 which extends in parallel with the non-refracted laser beam 12 and a sight line 26 which extends from the theodolite 22 to the impact point 20 of the deflected beam 16 on the rock chamber wall 18. The line 24 wall always extend perpendicularly to the plane in which the deflected beam 16 may occur. The coordinates of the impact point 20 may now be estimated in a simple manner by using well-known trigonometrical relations and on the basis of the knowledge gained of the coordinates for the measured points Pi and P2 and the read-off angle O . In the case of the simple situation shown in Fig. 1 the latter comprises only one horison- tal component but in the general case this angle will also comprise a vertical component. The area of the plane to be measured and which is perpendicular to the laser beam 12, is determined by turning the prism 14 little by little, so that the deflected beam 16 is directed against a number of points on the rock wall 18 in this plane. The coor¬ dinates of these impact points are determined with the aid of the theo¬ dolite 22 in the manner described above. On the basis of the knowledge gained of the coordinates of the impact points a fairly accurate appro¬ ximation may be made regarding the cross-sectional area of the opening of the rock chamber at the position of the prism 14. When a cross-sectional area has been established in the manner indicated, the prism 14 is moved to a point P*2, which is positioned further into the interior of the rock chamber and still in the ray path of the laser beam 12. The coordinates of point '2 are determined. The beam reaches the prism 14 and is directed in the form of a deflected ray 16' (beam) towards an impact point 20' on the rock wall 18. The area of the plane through point P' is determined 1n the manner described in the aforegoing. The coordinates of points P2 and P*2 being know, it becomes easy to determine the distance between the points and thus also the planes. Thereafter the volume of the volumetric element which is delimited by the two planes may easily be determined. The wall between them is regarded as being even. When the area of the second plane is to be determined there is a choice between either allowing the theodolite to remain at its original location Pi or moving it, should this be considered desir¬ able or necessary. By determining the volume of the volumetric element at the pace of the gradual and successive excavating of the rock chamber through blasting it becomes possible to obtain an accurate and exact value of the total volume of the rock chamber during the entire blasting process, which makes it possible to check continuously the size of the rock chamber during the blasting process, ensuring that no more rock material is blast away than was intended originally. One advantage inherent in the subject invention is that the measurement is effected manually, which means that also the choice of measuring points may be made manually. The measuring points are chosen so as to be representative of the cross-sectional outline, that is, minor projections, localized depressions, etcetera are avoided. This adds to the accuracy of the area calculations. Computer equipment (not shown) preferably is used in combination with the apparatus in accordance with the invention to process the measured values of the horizontal and vertical angles. The embodiment of the invention described in the aforegoing is to be regarded as one example only and a variety of other embodi¬ ments are possible within the scope of the appended claims. It is like¬ wise possible to determine volumes with the aid of the method according to the invention in tunnel bends or in locations where the setting of the laser 10 must be altered between measurements and thus the area- -determined planes will no be parallel. In these cases it is necessary to take into consideration the angle between the two planes. However, this angle is easy to determine because the coordinates of the impact points are known.

Claims: C l a i m s 1. A method of determining the volume of rock chambers, c h a r a c te r i z e d by directing a beam of light, preferably a laser beam (12) essentially in the lengthwise direction of the rock chamber, with the aid of an optical deflecting element (14) deflecting the beam of light in a first plane which extends at right angles to the non-refracted beam of light (12) so that the deflected beam of light (16) illuminates the wall (18) of the rock chamber in a first point (20), determining the position of this point through the readings from an optical instrument, such as a theodolite (22), deflecting the beam of light (12) in a further number of directions in the same first plane to illuminate a number of points on the wall (18) of the rock chamber, determining the positions of these points in the same manner as in the case of the first point on the basis of the knowledge gained of the positions of these points, estimating the area of the first plane, determined by these prints, determining in a corresponding manner the area of a second plane, which is positioned at a predetermined distance from the first plane, on the basis of the knowledge obtained of the areas of the two planes and the distance between them, making an estimation to determine the volume of the volumetric element, which is delimited by said two planes, and determining the total volume of the rock chamber with the aid of repeated determinations of volumetric elements at the pace of the excavation of the rock chamber through blasting. 2. A method as claimed in claim ^ c h a r a c t e r i¬ z e d therein that the beam of light (12) which is utilized to deter¬ mine the area of the planes remains at the same setting for area deter¬ mination of the various planes. 3. A method as claimed in claim 1 and 2, c h a r a c t e- r i z e d therein that the points the positions of which are deter¬ mined to estimate to area of a plane are chosen visually, only such points being chosen as are representative of the profile outline that determines the area of the plane. 4. A method as claimed in any one of the preceding claims, c h a r a c t e r i z e d therein that the position determinations of the measurement points are carried out in such a manner that the impact point of the deflected beam of light (16) on the rock wall is read with the aid of the theodolite (22), and that an angle (oi ) is measured between a line (24) which is parallel with the beam of light (12) and a sight line (26, 26') between the theodolite (22) and the illuminated point (20, 20') on the rock wall (18). 5. An apparatus for performing the method in accordance with claim 1 for the determination of the volume of a rock chamber, c h a¬ r a c t e r i z e d therein that a source of light (10) is arranged to emit a beam of light, preferably a laser beam (12), against an optical deflecting element (14) which is mounted at a determined place (P2) in the rock chamber, that the deflecting element (14) is arrang¬ ed to deflect the beam of light (12) at right angles to ensure that it illuminates an impact point (20, 20') on the rock wall (18), that an optical instrument, such as a theodolite (22), which is positioned at a determined place (P ) in the rock chamber is arranged to establish the impact point (20, 20') of the deflected beam (16, 16') on the rock chamber wall (18) and that the element (14) arranged to deflect the beam of light (12) is arbitrarily rotatable to deflect the beam of light in the rock chamber in a transverse plane which is perpendicular to the direction of the non-refracted beam of light, and is arranged to determine where the impact points (20, 20') of the deflected beam of light (16, 16') will occur on the wall (18) of the rock chamber. 6. An apparatus as claimed in claim 5, c h a r a c t e- r i z e d therein that the light-beam deflecting element is a pen¬ tagon prism (14). 7. An apparatus as claimed in claim 5 or 6, c a r a- t e r i z e d therein that the light-deflecting element (14) is remote-controlled to perform rotary movements and in that said remote control is effected with the aid of infrared light.

Inventors: CARLSSON HAOKAN, CARLSSON, HAOKAN
Applicants: CARLSSON HAOKAN, CARLSSON, HAOKAN
Application year: 1985
Main classification: G01C7
IPC codes: G01C7