WO2008049170A1

WO2008049170A1 - Mine communication system

Info

Publication number: WO2008049170A1
Application number: PCT/AU2007/001632
Authority: WO
Inventors: Barend Jacobus Pienaar
Original assignee: Cmte Development Limited
Priority date: 2006-10-26
Filing date: 2007-10-26
Publication date: 2008-05-02
Also published as: CL2007003090A1

Abstract

An underground mine communication system using underground mesh nodes (4 and 5) connected by mesh communication paths (6) which are typically conventional wire line or line of sight wireless communication paths, is connected to a number of higher level receiver stations (7) in locations corresponding to the nodes (4) by way of through the ground wireless communication. The through the ground wireless communication may be implemented by way of magnetic loop antennae at corresponding locations (4) and (7) or by way of earth current antennae. The system provides numerous redundant pathways in the mesh, allowing communication to continue even when various mesh communication paths (6) are disrupted or destroyed by emergency situations.

Description

MINE COMMUNICATION SYSTEM

FIELD OF THE INVENTION

This invention relates to a mine communication system and has been devised particularly, though not solely, for emergency communications in underground mines. BACKGROUND OF THE INVENTION

There is a fast growing call for underground two-way wireless communication.

This is due to recent tragic accidents which may have been avoided if reasonable bi¬

directional underground communications were possible. However, through the ground wireless communication is difficult and complex to achieve, particularly when the specification calls for portable "Walkie Talkie" style equipment. The state of the art has not yet effectively achieved this.

Until fairly recently the most effective underground communications has been by way of a wire line telephone. This evolved into single wire communication telephones (SWT) using the ground as a return path. Usual UHF and VHF radios are limited to line of sight and severe distance attenuation due to wave guide and skin effects on electromagnetic waves underground. Very high powers are required to get any degree of ground penetration using an EM wave. Rescue teams use HF walkie-talkies (27 or 49MHz) which may penetrate a few meters into the rock but also remain very limited in their use underground. Low frequencies are attenuated less than high frequencies. It has

been found that the ground wave component of long wave broadcast (~200 kHz) can be

detected at considerable depths. However transmitting a similar signal from underground would require a very long antenna (about 800 meters) and considerable power.

Thus there are a multitude of unidirectional devices available which provide effective communications when all is going well and operations are normal. These range from underground mesh networked systems to underground pager type systems

and various other VLF leaky feeder systems. However when an emergency event occurs

such as a roof collapse or a fire, the integrity of the communication infrastructure may be

severely compromised to the extent that it no longer works. This is just the type of

situation in which personnel will need reliable communications with the surface and will

also need to be able to provide feedback on their geographical positions so that a rescue

may be planned or an escape route found.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an underground mine communication

system including a plurality of underground mesh nodes forming an underground

communication mesh with mesh communication paths therebetween, and a plurality of

higher level receiver stations in locations corresponding to some or all of the

underground mesh nodes, wherein each higher level receiver station communicates with

the corresponding underground mesh node by way of through the ground wireless

communication.

Preferably, the through the ground wireless communication is achieved by use of a

magnetic loop.

Alternatively, the through the ground wireless communication is achieved by an

earth current antenna.

In one form of the invention the higher level receiver stations are located on the

surface above the mine.

Preferably, the mesh communications paths between underground mesh nodes are

formed by conventional wire line or line of sight wireless communication.

Preferably, the higher level receiver stations are part of a fully connected wired or

wireless network. Preferably, the higher level receiver stations are each located substantially vertically above the corresponding underground mesh node.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described, by way of example only, with reference to the accompanying drawing which is a diagrammatic perspective representation of an emergency mine communication system according to the invention.

DETAILED DESCRIPTION

In an emergency condition there is a need to implement a practical bi-directional "through the ground" communication technology. The two practical options available for effective through ground communications are namely the use of a magnetic loop which radiates very little E wave energy or an earth current antenna. Both have been shown to provide effective through the ground communications using the current state of the art technology. The magnetic loop is also effective in providing locational information because of the highly directional nature of the magnetic radiation from a loop.

The present invention combines an underground wired or wireless fully connected network with magnetic underground to surface communication links. This provides enhanced redundancy hence giving the system a much greater reliability in unforeseeable emergency situations. Under normal operations the fully connected

(infrastructure) network will provide high speed communications to support production but when the network is compromised it will revert to a (necessarily) slower redundant uplink, sidelink or simply through the collapsed area, to complete the critical path.

To this end, in a typical mine divided into underground blocks such as 1 by way of roadways such as 2 or 3 a plurality of underground mesh nodes 4 and 5 are provided at strategic points throughout the mine in the area or at the level where mining is being undertaken.

The underground mesh nodes 4 and 5 form part of an underground communication mesh with mesh communication paths 6 between the nodes. The mesh communication paths may be formed by any known technique but are typically either conventional wire line communication paths or line of sight wireless communication by UHF or VHF radios.

At a higher level within the mine, or preferably on the surface of the mine a plurality of higher level receiver stations 7 are provided in locations corresponding to some or all of the underground mesh nodes. In the accompanying drawing, receiver stations 7 are shown in locations substantially vertically above the underground mesh nodes 4 but it will be recognised that the underground communication mesh may incorporate additional stand alone mesh nodes such as that shown at 5, typically in non- critical areas of the mine. The surface receiver stations 7 communicate with the corresponding underground mesh nodes 4 by way of through the ground wireless communication, typically by magnetic carrier uplinks 8.

The surface transceivers can themselves be part of a fully connected wired or wireless network to further increase redundancy in the system. In the event of an emergency, particularly where part of the mine collapses rendering some of the mesh communication paths 6 inoperable, communication can typically be achieved at the underground level of the mine via remaining mesh communication paths 6 to one or more mesh nodes 4 in undamaged portions of the mine. This mesh node 4 can then communicate via the magnetic carrier uplink 8 to the surface transceiver 7 in the corresponding position above the mesh node and from there into the fully connected wired or wireless network on the surface of the mine.

Because there are many mesh communication paths 6 and a significant number of magnetic carrier uplinks 8 the system has a high degree of built-in redundancy and is able to cope with communication failures along a large number of the mesh communication paths while retaining full communication through to the surface of the mine or to a higher level of the mine unaffected by the emergency.

Claims

CLAIMS:-

1. An underground mine communication system including a plurality of underground mesh nodes forming an underground communication mesh with mesh communication paths therebetween, and a plurality of higher level receiver stations in locations corresponding to some or all of the underground mesh nodes, wherein each higher level receiver station communicates with the corresponding underground mesh node by way of through the ground wireless communication.

2. An underground mine communication system as claimed in claim 1 wherein the _ through the ground wireless communication is achieved by use of a magnetic loop antennae at both the underground mesh node and the corresponding higher level receiver station.

3. An underground mine communication system as claimed in claim 1, wherein the through the ground wireless communication is achieved by earth current antennae at both the underground mesh node and the corresponding higher level receiver station.

4. An underground mine communication system as claimed in any one of the preceding claims wherein the higher level receiver stations are each located substantially vertically above the corresponding underground mesh node.

5. An underground mine communication system as claimed in any one of the preceding claims wherein the higher level receiver stations are located on the surface above the mine.

6. An underground mine communication system as claimed in any one of the preceding claims wherein the mesh communications paths between underground mesh nodes are formed by conventional wire line or line of sight wireless communication.

7. An underground mine communication system as claimed in any one of the preceding claims wherein the higher level receiver stations are part of a fully connected wired or wireless network.