Sudden Outbursts of Gas and Coal in Underground Coal Mines

The phenomenon of outbursts of gas, coal and rock is neither new nor isolated in its occurrence to a particular coal field. It has occurred in virtually all the major coal producing countries of the world.  In the last 150 years, as many as 30,000 outbursts have occurred in the world, some with very serious consequences.  This has forced mining leaders to develop an understanding of the phenomenon, and procedures to minimise the effect of outbursts or eliminate them completely. It is a complex phenomenon and occurs under a variety of conditions and even today it is not well understood.

For almost half a century now, there has been a fairly widely accepted view that reliable methods for the pre-diction of outbursts must be not only based upon long years of practical experience in mines, but also on scientific research and experimentation. As a consequence, an enormous amount of energy has been directed in this field in many countries of the world.

Two Categories

Research investigations and mining system development in regard to outbursts of gas, coal and rock can be divided into two main categories:

• Development of mining methods, safety procedures and equipment modifications which can help either reduce or eliminate the effect of outbursts particularly in regard to mine workers. 

• Basic research conducted in the laboratory and applied research conducted in underground mines to better understand the mechanisms, role of coal properties and the mining and geotechnical conditions that favour outbursts with the aim of developing methodologies that can change the conditions in-situ so that outbursts can be eliminated or their intensity and their effects reduced. 
• Development of mining methods, safety procedures and equipment modifications which can help either reduce or eliminate the effect of outbursts particularly in regard to mine workers. 
• Basic research conducted in the laboratory and applied research conducted in underground mines to better understand the mechanisms, role of coal properties and the mining and geotechnical conditions that favour outbursts with the aim of developing methodologies that can change the conditions in-situ so that outbursts can be eliminated or their intensity and their effects reduced.

Observations & Experiments

A very important part has been played by in-situ observations related to every phase of occurrence of an out-burst. Field observations have provided data to develop practical methodologies and to understand the role of geology in outbursts. In fact very careful observations of sites of early outbursts allowed development of con-cepts which are still valid more or less valid today.

Conducting experiments in-situ, however, presents many problems associated with methodology and the possi-ble unintentional initiation of an outburst.

Laboratory studies on the other hand have the advantage that a large number of factors can be varied and the tests are reproducible.

The integration of measurements and observations from both the field and the laboratory, and their application to improve underground practice have resulted in safer mining under outburst prone conditions.

International Symposium

An International Symposium-cum-Workshop on Management Control of High Gas Emissions and Outbursts in Underground Coal Mines was held in Wollongong in 1995.

Prior to and during the Symposium-cum-Workshop, a survey was conducted on the research needs of the Aus-tralian coal industry in regard to outbursting. The results of this survey are included in this report.

In spite of the great amount of work that has been done in Australia over the last 30 years or so and particularly in the last 15 years, this is still minuscule compared to the knowledge available in the world literature, particularly from Europe, Japan and China.

Other Areas Covered

No doubt, the conditions existing in different coal fields are quite different and so also are the methods for mining coal, but basic studies on outbursts e.g., mechanisms, properties of coal, role of gases, prediction tech-niques and control methods used in other countries are relevant for the Australian underground coal mining industry. It was therefore thought proper to extend this study to encompass all possible aspects of outbursts of gas and coal.

Different control methods have been used in different coal fields. So that readers can compare, information is presented on outburst from different countries and different coal fields around the world.

In Australia, the commonly accepted control method is gas drainage. This has been discussed in detail in a separate chapter.

The concept of this book developed when one of the authors, R. D. Lama, was invited by the Research Committee of the Australian Coal Association to prepare a Scoping Study and conduct research in the area of outbursts of gas and coal. Realising the enormity of the job, he invited J. Bodziony of the Strata Mechanics Research Institute, Polish Academy of Sciences, Kraków, to join him in this study. This book is thus based on the Scoping Study with some additions and modifications.

It is almost impossible to encompass everything that has been done, said, or written on this subject, especially when the understanding of the phenomenon is still not complete. In writing this book the needs of the Australian mining industry were kept in view. Because of this, certain topics such as theoretical studies on gas and rock bursts have not been included as these were thought to be not so relevant to the direct needs of industry, whilst a separate chapter on Investigations Prior to Opening a Deposit has been included.

The authors have attempted to cover other subjects directly applicable to the needs of industry as much as pos-sible within the constraints of space and time. However, enquiring minds will reach for the original publications referred in the text for greater details.