CA2468576A1

CA2468576A1 - A blast movement monitor and method for determining the movement of a blast movement monitor and associated rock as a result of blasting operations

Info

Publication number: CA2468576A1
Application number: CA 2468576
Authority: CA
Inventors: David Mario La Rose; Darren Mark Thornton; Michael Wortley
Original assignee: University of Queensland UQ
Current assignee: Leica Geosystems Pty Ltd
Priority date: 2003-05-27
Filing date: 2004-05-27
Publication date: 2004-11-27
Anticipated expiration: 2024-05-27
Also published as: CA2749631A1; CA2749631C; CA2468576C

Abstract

A method for measuring the movement of boundaries between different portions of a heterogeneous rock body is disclosed. The method comprises placing a plurality of blast movement monitors 109 in a rock body prior to blasting and noting the position of each blast movement monitor. The rock body is then blasted to break it up into a plurality of pieces. Thereafter the position of the blast movement monitors 109 is located and based on this the boundaries of rock portions can be adjusted to account for the blast. This leads to a more accurate reporting of different ore bodies to the appropriate processor in a heterogeneous rock body. An apparatus for carrying out the method is also disclosed. The apparatus comprises broadly a said monitor 109 and a receiver. The monitor 1 comprises a transmitter 109 received within a casing 111 that in turn is received within a housing 126. Further the casing 111 can move within the housing 126 and self right so that it always transmits its signal in an upright direction.

Claims

1. A method for determining the movement of a blast movement monitor placed within a body of rock as a result of blasting of the rock, the method comprising:
placing at least one movement monitor in the rock body and noting its position;
blasting the rock body in the usual fashion to break up the rock body into a plurality of rock pieces; and locating the position of at least one placed movement monitor by analysing a signal passed between the monitor and an external communication device to determine the post blast position of the monitor at least in a plane parallel to the ground;
whereby to measure the movement of the monitors by comparison of pre and post blast positions as a result of the blasting.

2. A method according to claim 1, wherein the signal is an electro-magnetic signal having a specific frequency and the step of locating at least one movement monitor comprises locating the position of the monitor in three dimensional space.

3. A method according to claim 1, wherein the signal that is measured is the magnetic field component of an electro-magnetic field and the frequency of the signal is in the range of 10-200 kHz.

4. A method according to claim 1, wherein the signal is a low frequency signal in the range of 20-100 kHz.

5. A method according to claim 1, wherein the movement monitor includes a transmitter for transmitting the signal and wherein the external communication device also includes a detector for detecting the signal from the transmitter.

6. A method according to claim 5, wherein the detector senses the magnetic component of the electro-magnetic field generated by the transmitter and also the strength of the magnetic field at that particular point.

7. A method according to claim 5, wherein each movement monitor has means for enabling the transmitter to orientate in a certain direction after the blast so that all monitors are consistent in the direction in which they emit their signal.

8. A method according to claim 7, wherein the orientating means comprises self righting means wherein the transmitter in each monitor is able to return to an upright position after the blast so as to transmit its signal in a substantially vertically upward direction.

9. A method according to claim 8, wherein the transmitter is received within a casing which in turn is housed within a housing with the casing being movable relative to the housing wherein the self righting means comprises forming the casing and transmitter with an asymmetric weight distribution with a centre of mass positioned directly beneath the centre of the monitor so as to cause the monitor to revert to its upright position if it is disturbed during the mining operation.

10. A method according to claim 1, wherein a plurality of said movement monitors are placed within the rock body spaced apart from each other within the rock body and wherein the monitors are positioned 0 to 15 m beneath the surface of the rock body.

11. A method according to claim 10, wherein each monitor is positioned 1 to 10 m beneath the surface of the rock body, and wherein the monitors are received within drill holes within the rock.

12. A method according to claim 1, wherein the detector is used to locate the XY
position of the monitor on the surface of the broken rock on an imaginary XY
plane by locating the point on the surface of the muck pile where the magnetic field signal is at its greatest.

13. A method according to claim 12, wherein the vertical depth of the monitor within the muck pile can be gauged by measuring the strength of the magnetic field at the point on the surface where the magnetic field signal is at its greatest.

14. A method according to claim 12, wherein the vertical depth of the monitor within the muck pile can be gauged by measuring the angle of the magnetic field sensed by the detector.

15. A blast movement monitor for measuring the movement of rock within a rock body as a result of a blasting operation, the monitor comprising:
a monitor body defining an interior space;
an internal communicating device that is received within the interior space of the monitor body for either transmitting a signal outwardly to an external communication device or being able to detect a signal transmitted inwardly by the external communication device; and a housing having an internal surface defining an interior chamber within which the monitor body is received, the monitor body being capable of movement relative to the housing within the housing.

16. A blast movement monitor according to claim 15, wherein the internal communicating device transmits a signal outwardly rather than receiving a signal inwardly and includes a transmitter for transmitting said signal.

17. A blast movement monitor according to claim 15, wherein the transmitter transmits an electro-magnetic field signal at a particular frequency, and wherein the transmitter comprises an electric coil coupled to an electrical supply through which electrical current can be passed to generate an electro-magnetic field.

18. A blast movement monitor according to claim 15, wherein the monitor body comprises a casing made of a non conductive material such as plastics material that is configured such that it can be moved in all directions across the internal surface of the housing.

19. A blast movement monitor according to claim 18, wherein the casing has a curved surface and the internal surface of the housing has a complementary curved shape such that the casing can slide over the internal surface of the housing.

20. A blast movement monitor according to claim 18, wherein the housing contains a liquid intermediate the casing and the internal surface housing to lubricate movement of the casing relative to the housing.

21. A blast movement monitor according to claim 18, wherein the casing in turn comprises two casing hemispheres that are releasably attached to each other, and further includes fastening elements for securely attaching the two hemispheres to each other.

22. A blast movement monitor according to claim 18, wherein the housing comprises two parts releasably attached to each other to enable the housing to be opened up when required to provide access to the casing, and further including fastening elements for securely attaching the two housing parts together and is also made of a plastics material.

23. A blast movement monitor according to claim 15, further including a cover within which the housing is received.

24. A blast movement monitor according to claim 23, wherein the cover is spaced outwardly away from the external surface of the housing and a padding material is placed between the cover and the housing.

25. A blast movement monitor according to claim 24, wherein the cover is made of plastics material and has a circular cylindrical configuration.

26. An apparatus for measuring the movement of at least one blast movement monitor within a rock body, comprising:
at least one blast movement monitor as claimed in any one of claims 14 to 25;
and an external communication device for communicating with the blast movement monitor.

27. A blast movement monitor according to claim 26, wherein each monitor includes a transmitter for transmitting signals outwardly and the external communication device is a detector for detecting signals from a transmitter in the blast movement monitor.

28. A blast movement monitor according to claim 27, wherein the detector comprises a magnetic field detector in the form of a magnetic coil tuned to the same frequency as the monitor.

29. A blast movement monitor according to claim 28, wherein the detector further includes an amplifier operatively coupled to the detector.

30. A blast movement monitor according to claim 2, wherein the detector is hand held and is carried by an operator moving across the surface of the blasted rock body.

31. A method of measuring the movement of boundaries between different portions of a heterogeneous rock body as a result of a blast, the method comprising the following steps:
placing at least one blast movement monitor as claimed in any one of claims 15 to 25 in a rock body prior to blasting and noting the position of each blast movement monitor;
blasting the rock body to break up the rock body into a plurality of rock pieces;
locating the position of at least one blast movement monitor as a result of the blast;
measuring the movement of the rock in the region of at least one blast movement monitor due to the blast; and adjusting the position of the boundaries between different rock portions in response to the measured movement of rock to compensate for movement caused by the blast.

32. A method according to claim 31, further including the step of providing a map of the boundaries of the different rock portions within the rock body prior to said step of adjusting the position of the boundaries.

33. A method according to claim 32, wherein the step of placing comprises placing a plurality of said blast movement monitors in holes in the rock body spaced apart from each other.

34. A method according to claim 31, wherein the blast movement monitors are placed in holes that are drilled in the rock body and the holes are spaced apart from each other and the explosives holes.

35. A method according to claim 31, wherein the step of locating includes locating the position of at least 75% of the placed monitors.

36. A method according to claim 31, wherein the boundaries of the rock body delineate rock portions that are a recoverable ore polygon and waste.

37. A method according to claim 36, wherein the rock body comprises a rock portion that is a polygon of high grade gold ore received within a large body of host waste rock.

38. A method according to claim 31, wherein the boundaries of the rock body delineate rock portions that are high grade ore, low grade ore and waste.

39. A method according to claim 38, wherein the high grade ore comprises polygons of gold ore having a grade of about 5-7 g/t and also low grade polygons of gold ore of about 1-3 g/t that need to be recovered separately from the high grade ore.

40. A method according to claim 31, wherein the boundaries of the rock body delineate rock portions that are sulphide ores, oxide ores and/or supergene ores.

41. A method according to claim 31, wherein at least some of the blast movement monitors are placed in positions in the rock body that are on or are proximate to a boundary between different rock portions within the rock body.

42. A method according to claim 31, wherein the step of adjusting the position of the boundaries between the rock portions includes adjusting each said boundary based on a distance weighted average movement of one or more monitors as a result of the blast.

43. A method according to claim 42, wherein the step based on movement of a plurality of monitors located on the boundary or in proximity to the blast monitor.

44. A method according to claim 31, wherein the method further includes building up an adjusted three dimensional map of the boundaries of the different rock portions based on the measured movement of the blast movement monitors as a result of the blast.