Methods, systems and devices for monitoring movement of rock in a mine

Abstract

A method for monitoring depth of a cave front in a cave-type mine. The method includes: providing a stationary reader device and mobile marker devices, each of the marker devices adapted to (i) emit an electromagnetic signal, (ii) detect strength of the signal emitted by another of the marker devices, and (iii) wirelessly transmit information related to the detected signal via the other marker devices to the stationary reader device; drilling a hole into a rock region of a mine, installing the mobile marker devices at sequential known depths within the hole; monitoring the reader device to detect a decrease in the strength of a signal emitted by a first marker device by a second marker device; and in response to a decrease being detected by the second marker device, inferring the depth of the cave front to be between the known depths of the first and second marker devices.

Claims

1. A method for monitoring depth of a cave front in a cave-type mine, the method comprising acts of: providing a stationary reader device, providing a plurality of mobile marker devices, each of the plurality of marker devices adapted to (i) emit an electromagnetic signal, (ii) detect strength of the electromagnetic signal emitted by another of the plurality of mobile marker devices, and (iii) wirelessly transmit information related to the detected electromagnetic signal via another of the plurality of marker devices to the stationary reader device, drilling a downwardly orientated drill hole into a rock region of a mine, installing the plurality of mobile marker devices at sequential known depths within the drill hole, monitoring the reader device to detect a decrease in the strength of an electromagnetic signal emitted by a first of the plurality of mobile marker devices by a second of the plurality of mobile marker devices, in response to a decrease in the strength of an electromagnetic signal emitted by the first of the plurality of mobile marker devices being detected by the second of the plurality of mobile marker devices, inferring the depth of the cave front to be between the known depths of the first and second of the plurality of mobile marker devices.

2. The method of claim 1, wherein a decrease in strength of the electromagnetic signal is judged by comparing the strength of the electromagnetic signal before a caving process to the strength of the electromagnetic signal after the caving process.

3. The method of claim 2, wherein the caving process is blasting.

4. The method of claim 1, wherein the electromagnetic signal is a radio wave signal and/or the wireless transmission is by radio wave.

5. The method of claim 1, wherein the information is transmitted by a mesh networking protocol.

6. The method of claim 1, wherein each of the plurality of mobile marker devices comprises a housing adapted to physically protect the electronics contained therein from a mining activity.

7. The method of claim 6, wherein the mining activity is blasting, drilling, hammering, or digging.

8. The method of claim 1, wherein each of the marker devices is uniquely identifiable.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a diagrammatic cross section a cave-type of underground mine.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

(2) Reference is made to FIG. 1 which shows in diagrammatic cross section a cave-type of underground mine. A series of holes are drilled into the ore body, into which markers are installed at regular depths. Each marker is able to send and receive information by RF.

(3) Each marker is allocated a two-part identifying code, consisting of a subnet and a Marker ID. The subnet is associated with the hole into which the string of markers is inserted. The Marker ID is a sequential number, such that the markers along the hole have gradually increasing Marker IDs. All communications are initiated from a reader device that is accessible and serviceable by mine staff. The reader device is capable of communicating with a certain number of markers within range.

(4) In FIG. 1, a series of 4 vertically oriented drillholes is shown, with each having 12 marker devices disposed at regular intervals: marker 01 is the deepest, while marker 12 the most shallow.

(5) Each set of 12 markers in a single downhole defines a subnet. Thus, subnet 10 comprises markers 1 to 12. Subnet 20 comprises a second group of markers 1, 2, 3 . . . 12, and so on.

(6) FIG. 1 also shows 3 horizontally disposed Subnets (01, 02 and 03), with each Subnet having a number of RF detectors (01, 02, 03 . . . ). Each Subnet 01, 02 and 03 relays information to a reader device (reader 01, reader 02, and reader 03) via node 99.

(7) When ore is fragmented from the mine, the cave front propagates upwardly. In the process of fragmentation, the markers drop downwardly into the cave sequentially (marker 01 first, and marker 12 last).

(8) As an example of a typical set of communications, the method of identifying the best nodes to link Subnet 03 to Subnet 20 is now presented.

(9) To identify the best nodes to link to other Subnets, the system performs a Neighbour Discovery command on each marker in Subnet 03. A Neighbour Discovery command is focussed on the signal strengths between a specifically-addressed marker and all other markers within range of that marker. With the example scenario, the Neighbour Discovery command will therefore be repeated for each marker in Subnet 03. This data is collected and stored (in the Reader or in the computing equipment connected to the Reader) in order to decide on the routing for future communications.

(10) The markers in range (as detected by a Neighbour Discovery command) could be in the same subset or in other subnets.

(11) In order to communicate with another subnet, the system chooses a marker having strong communications with the other subnet. Take the example of the figure below. Suppose we want to communicate with markers in Subnet 20, from Subnet 03. Suppose that Subnet 03 markers 12, 11, 10 and 09 are all within range of markers from Subnet 20. Given their relative distances, suppose that Marker 11 has the strongest signal, when communicating with Subnet 20, Marker 12. Therefore, in future communications from Subnet 03 to 20, the routing information would be as follows: Origin: Subnet 03, Marker 99 Node Route Direction: Downstream Link from: Subnet 03, Marker 11 Link to: Subnet 20, Marker 12

(12) With this routing information, a Neighbour Discovery command can be issued to each marker in Subnet 20, via Subnet 03. This will provide the RF signal strength between for each pair of intercommunicating markers.

(13) The figure below shows a scenario whereby the system is used to measure the position of the cave front. Subnets 01, 02 and 03 are along a tunnel through the ore. From this tunnel, various holes are drilled into the ore (Subnets 10, 20, 30 and 40). Eventually, as material is extracted from the bottom of the mine, the whole area will gradually collapse and sink down. Therefore, the tunnel will become unsafe for humans. That is why readers cannot be placed at the start of 600 subnets 10, 20, 30 and 40. Communications to these subnets need to be made via Subnets 01, 02 and 03.

(14) The three subnets (01, 02 and 03) in the main tunnel are redundant for the following reasons: (i) To save battery power. Two Subnets can be put to Hibernate, using the Hibernate command. The Hibernate command makes the commanded subnet Hibernate for the period of time specified in the Hibernate command (say, 1 week). For example, Subnets 01 and 02 may be commanded to Hibernate, and Subnet 03 would then be used to communicate. This preserves the batteries in Subnets 01 and 02. The load on the batteries can be managed by later communicating on, say, Subnet 01, and putting Subnets 02 and 03 to Hibernate. (ii) Reliability. If, over time, markers fail (eg due to flat batteries), the remaining subnets can ensure that communications are still possible. Even if several markers have failed in all Subnets, the routing algorithm can allow communications to switch from Subnet to Subnet along its length.

(15) By using a combination of Ping commands and Neighbour Discovery commands, we can regularly check on the mine's caving progress. As the mine caves, the lower markers will start to move away from the rest of the subnet. As they move, their RF signal strength (as measured by the Neighbour Discovery command) will change, and reduce.

(16) Ping and Neighbour Discovery commands require a response from a particular marker. With a Ping command, the marker that must respond is the one that could not make contact with any markers further along the subnet, in the required direction. That marker constructs a packet of information and sends it back to the reader, using the same path as the outgoing command.

(17) The communication technique and data packet structure is the same as for the command, but the route will be the opposite, and the type of packet is Data instead of a command.

(18) It will be appreciated that in the description of exemplary embodiments of the invention, various features of the invention may be grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following this description are hereby expressly incorporated into this description, with each claim standing on its own as a separate embodiment of this invention.

(19) Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and from different embodiments, as would be understood by those in the art. For example, in the claims appended to this description, any of the claimed embodiments may be used in any combination.

(20) In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.