Title

Detection of collapses and communicating with inaccessible areas in underground coal mines using WSN

Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Engineering Science

School

School of Engineering

First Advisor

Professor Daryoush Habibi

Second Advisor

Dr Iftekhar Ahmad

Abstract

Wireless sensor networks (WSN) are used in underground mines to monitor concentration of gases, temperature, and humidity. A WSN deployed in underground mines can also be used for localisation of miners and for detecting collapses. Underground coal mines consist of long and narrow tunnels, several hundred metres beneath the surface of earth. These tunnels can be several kilometres long, with the width and height of these tunnels being no more than a few metres. A WSN in underground coal mine is an example of a chain type wireless sensor network (CWSN). CWSNs are special types of WSNs in which sensor nodes are placed along an elongated geographical area with the nodes forming a chain topology. In CWSNs, their shape dictates network design. Unlike other large scale WSN, there is only one path for data transfer in CWSNs. Hence the probability of network getting broken in disjoint sections, due to node failures, is much higher in CWSNs compared to other large scale WSNs. Disjoint sections are two sections of the same network which are out of the communication range of each other. When the network is broken into two or more disjoint sections, the sink node loses connectivity with parts of the network and hence some areas are left unmonitored despite having functional sensor nodes.

In the first contribution chapter of this thesis, we design a distributed connectivity restoration algorithm for generic chain-type wireless sensor networks. We usemovable relay nodes to restore connectivity in the network. Our algorithm strivesto move a minimum number of relay nodes while only requiring local knowledge ofthe network. In the second contribution chapter, we consider the scenario of collapses occurring in underground coal mines. We design an algorithm for detecting collapses in chapter four. A collapse may leave parts of the mine inaccessible and unmonitored. A collapse will also break WSN into two or more disjoint sections which are physically separated by the collapse consisting of soil and rock. We investigate the propagation characteristics of EM waves through soil and rock. We determine the factors on which communication range of EM waves through soil depends on. We propose special movable relay nodes which use low frequency and high power transmitters to communicate through a collapsed area of the mine, restoring connectivity in the WSN. We design an algorithm to restore connectivity through collapsed areas of the underground mine tunnels using these special movable relay nodes. Communicating with inaccessible area of the mine will help locate miners which may be trapped in that section and will enable the network to monitor the inaccessible area of the mine.

LCSH Subject Headings

Wireless sensor networks.

Coal mines and mining -- Communication systems.

Access Note

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