US-12624937-B2 - Method of managing a blast system

US12624937B2US 12624937 B2US12624937 B2US 12624937B2US-12624937-B2

Abstract

A blasting system ( 10 ) wherein a test through-the-earth signal of predetermined strength is sent from a defined position and the strength of the signal, as received at each of a plurality of locations ( 24 ) within a blast site, is measured thereby to enable an operative zone ( 56 ) to be defined wherein at any location within the operative zone a fire command through-the-earth magnetic signal, of such predetermined strength, transmitted from the defined position, as received at such location, will have a strength above a threshold signal strength.

Inventors

Abraham Johannes Liebenberg
Tielman Christiaan Meyer

Assignees

DETNET SOUTH AFRICA (PTY) LTD

Dates

Publication Date: 20260512
Application Date: 20230901
Priority Date: 20220905

Claims (7)

1 . A method of managing a blasting system at a site which includes the steps of: deploying an antenna at a predetermined position at the site, determining original positional data of the antenna's said predetermined position, logging said original positional data, transmitting a through-the-earth magnetic signal of a predetermined signal strength from the antenna, 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 received at the location, using the positional data of the locations 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, again deploying the antenna at said predetermined position at the site, determining a current positional data of the again deployed antenna, comparing the current positional data of the antenna to said original positional data, and only if the current positional data and said original positional data correlate, 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.
2 . A method according to claim 1 wherein at each of the plurality of spaced apart locations use is 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.
3 . A method according to claim 2 wherein the measure of the strength of the received magnetic signal and, optionally, the positional data of the location of the MFSM are stored in a memory module of the MFSM.
4 . A method according to claim 3 wherein the positional data, for acceptable received signal strength, is used to define a geographical boundary of an operative zone within which detonator assemblies can be reliably deployed.
5 . A method according to claim 4 wherein at least one tagger is used to scan each MFSM thereby to read, and then to store in the tagger, the respective positional data of the location of that MFSM.
6 . A method according to claim 5 which includes the step of transferring the stored positional data from the tagger to a processor at a data collection point which is configured to use the positional data and the measures of the received signal strength thereby to define the operative zone.
7 . A method according to claim 1 which includes the steps of tagging a detonator assembly only if the intended deployment position of the detonator assembly is situated within the operative zone and, thereafter, of deploying the tagged detonator assembly at such deployment position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national phase entry of PCT/ZA2023/050053, filed on Sep. 1, 2023, which claims priority to South African Application Number 2022/09857, filed on Sep. 5, 2022, the entire contents of both of which are fully incorporated herein by reference. 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. An object of the invention is to address at least to some extent the aforementioned situation. SUMMARY OF THE INVENTION The invention 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 at least one tagger to scan each MFSM thereby to read and then store in the tagger the respective positional data of the location of that MFSM. Any suitable technique may be used to obtain the positional data. In one form of the invention the tagger is used to s