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EP-4496978-B1 - METHOD OF MANAGING A BLASTING SYSTEM

EP4496978B1EP 4496978 B1EP4496978 B1EP 4496978B1EP-4496978-B1

Inventors

  • LIEBENBERG, ABRAHAM JOHANNES
  • MEYER, Tielman Christiaan

Dates

Publication Date
20260506
Application Date
20230901

Claims (7)

  1. A method of managing a blasting system (10) at a site (12) which includes the steps of transmitting a through-the-earth magnetic signal of a predetermined signal strength from an antenna (14) which is located at a predetermined position, at each of a plurality of spaced apart locations (24) at the site (12) obtaining positional data (51) of the location (24) and obtaining a measure of the strength of the through-the-earth magnetic signal received at the location (24), using the positional data (51) and the measures of the received signal strength to define an operative zone (56), at the site (12), within which operative zone (56) each of the measures of the received signal strength is above a threshold value (62), deploying a plurality of detonator assemblies (30) at spaced apart positions at the site (12), allowing a detonator assembly (30) to be tagged and thereby to be included in the blasting system (10) only if the position of the detonator assembly (30) is situated within the operative zone (56) and, in use, locating the antenna (14) at said predetermined position and transmitting from the antenna (14) to each tagged detonator assembly (30) a fire command signal which has a signal strength which is equal to or greater than said predetermined signal strength.
  2. A method according to claim 1 wherein at each of the plurality of spaced apart locations (24) use is made of at least one magnetic field strength meter (MFSM) (22) which includes a receiver (36) which is responsive to the received through-the-earth magnetic signal thereby to obtain a measure of the strength of that received signal at that location (24).
  3. A method according to claim 2 wherein the measure of the strength of the received magnetic signal and, optionally, the positional data (51) of the location (24) of the MFSM (22) are stored in a memory module (38) of the MFSM (22).
  4. A method according to claim 3 wherein the positional data (51), for acceptable received signal strength, is used to define a geographical boundary of an operative zone (56) within which detonator assemblies (30) can be reliably deployed.
  5. A method according to claim 4 wherein at least one tagger (32) is used to scan each MFSM (22) thereby to read, and then to store in the tagger, the respective positional data (51) of the location (24) of that MFSM (22).
  6. A method according to claim 5 which includes the step of transferring the stored positional data (51) from the tagger (32) to a processor (52) at a data collection point (54) which is configured to use the positional data (51) and the measures of the received signal strength thereby to define the operative zone (56).
  7. A method according to claim 1 which includes the steps of tagging a detonator assembly (30) only if the intended deployment position of the detonator assembly (30) is situated within the operative zone (56) and, thereafter, of deploying the tagged detonator assembly (30) at such deployment position.

Description

BACKGROUND OF THE INVENTION This invention relates to a method of managing a blasting system which is based on the use of through-the-earth magnetic signal transmission. A blasting system of the kind referred to typically includes a site which includes a plurality of spaced apart boreholes into which respective detonator assemblies are deployed after tagging, and a transmitter at the site for transmitting through-the-earth magnetic command signals via an antenna from a blast controller to the detonator assemblies. A field strength survey is conducted at the site, beforehand, by placing a plurality of magnetic field strength meters (MFSMs) at respective spaced apart locations at the site to measure the received signal strengths of a through-the-earth magnetic signal (a test signal) at the respective locations to determine a range of transmission of the antenna. As boreholes, for practical reasons, are often drilled before the field strength survey is conducted, workers at the site could inadvertently tag and load a detonator assembly into a borehole at which the received signal strength of the test signal is too low for reliable operation. A command signal from the blast controller might then not be received by that detonator assembly which may (inadvertently) have been included in a blast plan. As a result the detonator assembly might not receive a fire command signal and, in that event, will not be fired. This leads to a dangerous situation because a misfired detonator could be present at the time of excavation of a rock body in which the detonator assembly was placed and could detonate with a likelihood of causing injury to or death of personnel, and damage to equipment. WO 2022/073043 A1 describes a blasting system configured to ensure that the strength of a magnetic signal transmitted from a blast control centre at a particular location is not weak. WO 2022/073042 A1 contains a similar disclosure. These prior art documents do not address the situation in which a detonator assembly is positioned at a location at which the magnetic signal is too weak to be reliable. Under that condition a detonator, even if tagged, would not be responsive to a fire command and, in that event, there would be a misfire. An object of the invention is to address at least to some extent the aforementioned situation. SUMMARY OF THE INVENTION The invention as defined by claim 1 provides a method of managing a blasting system at a site which includes the steps of transmitting a through-the-earth magnetic signal of a predetermined signal strength from an antenna which is located at a predetermined position, at each of a plurality of spaced apart locations at the site obtaining positional data of the location and obtaining a measure of the strength of the through-the-earth magnetic signal as received at the location, using the positional data and the measures of the received signal strength to define an operative zone, at the site, within which operative zone each of the measures of the received signal strength is above a threshold value, deploying a plurality of detonator assemblies at spaced apart positions at the site, allowing a detonator assembly to be tagged and thereby to be included in the blasting system only if the position of the detonator assembly is situated within the operative zone and, in use, locating the antenna at said predetermined position and transmitting from the antenna to each tagged detonator assembly a fire command signal which has a signal strength which is equal to or greater than said predetermined signal strength. The through-the-earth magnetic signal may be sent from the antenna via a transmitter at a blast controller at the site. At each of the plurality of spaced apart locations use may be made of at least one magnetic field strength meter (MFSM) which includes a receiver which is responsive to the received through-the-earth magnetic signal thereby to obtain a measure of the strength of that received signal at that location. The measure of the strength of the received magnetic signal and, optionally, the positional data of the location of the MFSM may be stored in a memory module of the respective MFSM. The positional data (for acceptable received signal strength) is used to define a geographical boundary of the zone which, for the purposes of the invention, is an operative zone within which detonator assemblies can be reliably deployed. It is therefore convenient and useful to have the positional data of the relevant MFSMs transferred to memory in a tagger, or similar device, for easy access while establishing the blasting system. The MFSMs are preferably positioned at respective spaced apart locations at or near a boundary of the site. In one embodiment each MFSM includes a respective identifier which is stored in the memory module of the MFSM. The identifier may be linked to the measure of the strength of the received magnetic signal and the positional data. The method may extend to the use of a