Flow tracking in block caving mining

Abstract

The invention provides a method and system for monitoring the flow of ore in block cave mining operations by inserting an active magnetic beacon 1 into the ore body 12 and generating an alternating magnetic signal with the beacon 1 . The ore is monitored with a magnetometer ( 14, 15, 16, 17, 18 ) to detect the magnetic flux emitted by the beacon 1 thereby determining the position of the beacon. Successive recordings of the position of the magnetic beacon are taken as it moves along with the ore as it “caves”. In this way, the flow patterns of the ore may be revealed.

1 . A method of monitoring the flow of ore from an ore body during block caving mining operations, said method including the steps of:
 implanting a beacon in the ore body;   generating an magnetic signal with the beacon;   monitoring the magnetic field in the ore body area with a magnetometer to identify the signal from the beacon; and   calculating the origin of the signal at discrete intervals to determine the path of the beacon and derive the flow of the ore as it is mined.   
   
   
       2 . A method according to  claim 1  wherein the signal is generated by rotating a magnetic field having a polar axis, about a rotation axis perpendicular to said polar axis thereby to generate an alternating magnetic signal when monitored on the plane of rotation of the magnetic field. 
   
   
       3 . A method according to  claim 2  wherein the signal is monitored by the magnetometer along a remote monitoring axis, said monitoring axis and said rotation axis aligned generally parallel to one another and perpendicular to said plane of rotation such that the location of the beacon can be deduced as lying on a plane orthogonal to said monitoring axis and coincident with a point of peak signal strength monitored by said magnetometer. 
   
   
       4 . A method according to  claim 2  wherein the signal is monitored by the magnetometer on a remote monitoring plane, said monitoring plane and said rotation axis aligned generally parallel to one another and perpendicular to said plane of rotation such that the location of the beacon can be deduced as lying on an axis normal to said monitoring plane and coincident with a point of peak signal strength monitored by said magnetometer. 
   
   
       5 . A method according to  claim 4  wherein first and second signals are generated on respective first and second planes of rotation by rotating the magnetic field about respective first and second rotation axes and wherein said first and second rotation axes are generally orthogonal. 
   
   
       6 . A method according to  claim 5  wherein the first signal is monitored on said monitoring plane such that the location of the beacon can be deduced as the intersection between the plane orthogonal to said monitoring axis and coincident with a point of peak signal strength on said monitoring axis and, the axis normal to said monitoring plane and coincident with a point of peak signal strength on said monitoring plane. 
   
   
       7 . A method according to  claim 6  wherein said second rotation axis is gravitationally aligned to be generally vertical and said second rotation axis is substantially horizontal. 
   
   
       8 . A method according to  claim 7  wherein the monitoring axis is located in a vertical borehole adjacent the ore body. 
   
   
       9 . A method according to  claim 7  wherein the monitoring plane is located on the surface above the ore body. 
   
   
       10 . A method according to  claim 7  wherein the beacon is programmable to generate said first and second signals at distinct but generally sequential periods. 
   
   
       11 . (canceled) 
   
   
       12 . A method according to  claim 2  wherein the rotation axis is gravitationally aligned generally vertically. 
   
   
       13 . A method according to  claim 12  wherein the signal is monitored by a plurality of magnetometers each moveable along a respective vertical monitoring axis disposed substantially adjacent and surrounding the ore body. 
   
   
       14 . A method according to  claim 13  wherein each monitoring axis is disposed in a vertical borehole. 
   
   
       15 . A method according to  claim 13  wherein at least one magnetometer monitors the strength of the signal generated by the beacon along the respective monitoring axis such that the peak signal strength depth on the monitoring axis corresponds to the origin of said signal and the depth of the beacon can be deduced. 
   
   
       16 . A method according to  claim 13  wherein the position of the beacon on the horizontal plane is calculated by monitoring the relative timing of the alternating signal and calculating the phase angle between the monitoring axes with respect to the beacon. 
   
   
       17 . A method according to  claim 13  wherein each magnetometer is linked to a central control unit to record and compare data from the magnetometers. 
   
   
       18 . A method according to  claim 13  wherein the beacon is programmable to generate said signal at predetermined intervals and for predetermined periods. 
   
   
       19 . A method according to  claim 1  wherein the magnetic field is generated by a high magnetic moment rare earth bar magnet. 
   
   
       20 . A method according to  claim 1  wherein the magnetometer includes a super conducting quantum interference device (SQUID). 
   
   
       21 . A self-contained beacon for implanting into an ore body during block caving mining operations, said beacon including:
 a protective outer casing of a non-magnetic material; and   a magnetic field generator for generating an alternating magnetic signal.   
   
   
       22 . A beacon according to  claim 21  wherein the magnetic signal generator includes means for generating magnetic field having a polar axis, said magnetic field configured for rotation about an axis of rotation perpendicular to the polar axis of the magnet. 
   
   
       23 . A beacon according to  claim 21  wherein the means for generating a magnetic field includes a rare earth bar magnet. 
   
   
       24 - 25 . (canceled) 
   
   
       26 . A beacon according to  claim 21  wherein the magnetic signal generator is gimbal mounted within a housing. 
   
   
       27 . A beacon according to  claim 26  wherein the gimbal is biased to align the magnetic signal generator with a first predetermined axis. 
   
   
       28 . A beacon according to  claim 26  wherein the gimbal is gravitationally biased. 
   
   
       29 . A beacon according to  claim 26  wherein magnetic signal generator is located within a sphere within the cavity. 
   
   
       30 . A beacon according to  claim 29  wherein the cavity is generally spherical and has a diameter larger than the outside diameter of the sphere defining space for a damping fluid between the cavity and sphere. 
   
   
       31 - 32 . (canceled) 
   
   
       33 . A beacon according to  claim 27  wherein the magnetic signal generator is moveable between said first predetermined axis and an orthogonal second predetermined axis