BLASTING SYSTEM

Abstract

A blasting system which includes a number of roving GPS receivers, and associated taggers, which communicate with one another and with a control mechanism, and a reference GPS receiver which transmits RTCM corrective positional data which is stored at each roving GPS receiver to improve the accuracy of coordinate determinations for boreholes.

Claims

1. A blasting system which is established at a blast site, the blasting system including a control mechanism, a plurality of boreholes at the blast site, a base antenna positioned at a known reference location at the blast site, a reference GPS receiver, which includes a transmitter, in communication with the base antenna, and at least one roving GPS receiver, which is movable by an operator on the blast site, which receives positional data corrections from the transmitter at the reference GPS receiver and which is in communication with the control mechanism.

2. A blasting system according to claim 1 wherein the positional data corrections are RTCM corrections.

3. A blasting system according to claim 1 wherein the base antenna is positioned on a conductive base plate which is placed directly over the reference location and which is surrounded by a conductive collar (58).

4. A blasting system according to claim 1 which includes a respective tagger which is associated with each roving GPS receiver and wherein the corrected positional data for all of the boreholes is stored at each roving GPS receiver and at the control mechanism.

5. A blasting system according to claim 4 wherein the control mechanism is configured, in response to positional data corrections for each borehole, to calculate a timing delay for a detonator in such borehole.

6. A blasting system according to claim 5 wherein the respective tagger is configured to receive said timing delay from the control mechanism and to assign the timing delay to the denotator.

7. A blasting system according to claim 1 which includes a plurality of said roving GPS receivers and a plurality of taggers which are re- spectively associated with the roving GPS receivers, and wherein the roving GPS receivers are interactive with one another and with the control mechanism so that the data which is held in any tagger is identical to the data held in each other tagger, and in the control mechanism.

8. A blasting system according to claim 1 which includes a plurality of said roving GPS receivers and, a plurality of taggers, each tagger being associated with a roving GPS receiver and wherein said transmitter transmits to all the GPS receivers corrective positional data so that accurate positional data for each borehole is determined by the respective GPS receiver and wherein the positional data for all of the boreholes is stored in all of the taggers and in the control mechanism.

9. A blasting system according to claim 8 wherein the control mechanism is configured, in response to the said corrective positional data for a borehole, to calculate a timing delay for a detonator in such borehole.

10. A blasting system according to claim 9 wherein the respective tagger is configured to receive said timing delay from the control mechanism and to assign the timing delay to the detonator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention is further described by way of example with reference to the accompanying drawings in which:

[0028] FIG. 1 schematically depicts a blasting system established at a blast site in accordance with the principles of the invention, and

[0029] FIG. 2 depicts a base antenna used in the blasting system.

DESCRIPTION OF PREFERRED EMBODIMENT

[0030] FIG. 1 of the accompanying drawings schematically depicts a blasting system 10 according to the invention which is established at a blast site 12.

[0031] The blast site 12 typically extends over a large area and includes a large number of boreholes 14, possibly of the order of several thousand. As is known in the art each borehole 14 is loaded with explosive material and one or more detonators (not shown).

[0032] If the boreholes 14 are drilled by means of automated or autonomous drilling machines then the geographical position of each borehole, in terms of longitude and latitude coordinates, is automatically determined and is known with an acceptable degree of accuracy. Despite this it can be difficult for an operator using a tagger to establish where, on the blast site, the operator is i.e. to identify a borehole in the midst of a large number of boreholes, which may be closely spaced from one another.

[0033] In some instances automated drill rigs are not used. As a consequence a plan which accurately reflects the positions of the boreholes is not available.

[0034] If the blast site 12 extends over a large area then the curvature of the earth must be taken into account so that the position of each borehole can be accurately determined i.e. it is not acceptable to view the blast site as a planar or two-dimensional site.

[0035] In each instance in order to obtain accurate data relating to the position of each borehole 14 a differential GPS system is employed. Use is made of a base or reference antenna 20 which is positioned at a known location 22 on the blast site. Preferably the known location 22 is a borehole 24 selected from the plurality of boreholes 14. This however is not essential for a reference location 22 can be selected using other criteria. The use of a selected borehole 24 has the benefit that any offset or error arising in recording the position of the borehole 24 is mitigated as the positions of the remaining boreholes are determined using a reference system based on the positional data of the chosen borehole 24.

[0036] A number of roving GPS receivers 30, 30A, 30B etc. can be used at the blast site. Each roving GPS receiver is associated with a respective tagger 34 and is carried by a respective operator, not shown, who traverses the blast site 12. The taggers 34 can communicate with each other using transceivers and can also communicate with a reference GPS receiver 38 which is associated with the base antenna 20 and which is at the reference location 22. The reference GPS receiver 38 includes a transmitter 38(T) for the transmission of data.

[0037] The blasting system 10 also includes a control mechanism 40, positioned at any appropriate location, which includes a memory unit 42 and a communication facility 44.

[0038] If the boreholes 14 are drilled at precisely determined locations using, for example, automated drill rigs then the geographical coordinates (longitude and latitude) of each borehole are known with an acceptable degree of accuracy. That data is collected at the time of borehole drilling and when appropriate is stored in the memory unit 42.

[0039] A GPS receiver typically works with an accuracy of, say, ten meters. Apart therefrom, as noted hereinbefore, signals to the GPS receiver can be adversely affected by various physical factors. To address these aspects the invention makes use of a differential GPS approach in that the reference GPS receiver 38 is in communication with the base antenna 20 which is at the reference location 22. The coordinates of the reference location 22 are known and are stored in the memory unit 42.

[0040] As a roving GPS receiver 30, plus an associated tagger 34, traverses the blast site 12 the respective operator positions the GPS receiver 30 directly over a selected borehole and determines the GPS coordinates thereof. RTCM data from the reference GPS receiver 38 is transmitted continuously, or as required, to each roving GPS receiver and the correction factors transmitted in this way are applied in real time to correct the data in the GPS receiver 30 so that the coordinates e.g. the longitude and latitude positions of the borehole in question are determined with an acceptable degree of accuracy. Such determination (i.e. of the coordinates) is transmitted from the GPS receiver in question to the other roving GPS receivers and to the control mechanism 40. Thus, at all times, each GPS receiver and associated tagger carry the same information as the other roving GPS receivers and associated taggers, and that information is replicated at the control mechanism 40. At the control mechanism a processor, using known techniques, calculates the timing delays associated with the respective detonators which are to be placed in the respective boreholes 24. This makes it possible for the time delays to be calculated in real time as each borehole is processed in the aforementioned way i.e “added” to the systems. The time delays can thus immediately be assigned to the various denotators.

[0041] It is possible for a tagging plan generated at the control mechanism 40 to be downloaded to each roving GPS receiver and associated tagger. The tagger then determines the boreholes which are closest and the operator then assigns the calculated timing of delays to the respective detonators.

[0042] If accurate data relating to the positions of the boreholes is not available from the memory unit 42, for example if automated drill rigs were not used in the drilling of the boreholes 14, then each tagger may have the capability to create a location-accurate plan of the blast site. This is achieved when the operator walks to each borehole 14 and adds positional data of the borehole, corrected using RTCM factors from the reference GPS receiver 38, to the geographical plan. As indicated this data is transferred to all other taggers in the system and to the control mechanism 40.

[0043] Once all the boreholes have been tagged in the described manner the control mechanism calculates the timing delays for the respective detonators which are to be placed in the boreholes and this timing data is transmitted to each of the taggers. The detonators can then be programmed as appropriate and placed in the boreholes in order to implement the blasting system. As indicated though the time delay for each denotator can be calculated in real time, as each borehole is tagged, and then assigned to the detonator. This detonator would be programmed with accurately determined timing delays during the tagging sequence.

[0044] The antenna configuration shown in FIG. 2 reduces the ground area required to have an effective ground plane. The antenna 20 is primarily used when there is a space constraint e.g. during use of a mobile device. This cautionary step is taken to reduce the incidence of multipath propagations of signals. Use is made of a conductive structure 50 with a base plate 56 which preferably is placed directly over the selected borehole 24. The plate 56 is surrounded by a vertically extending collar 58 which partly surrounds the antenna 20. This arrangement has been found to be effective in simulating a larger ground plane and in eliminating the incidence of reflected signals onto the antenna.