Prediction Indices

Outburst prediction indices( ACARP C 4034 Chapter 9)

Different indices are use in different countries to predict an outburst

Ettinger’s Sorption/ Desorption index : This index was developed initially by Ettinger (1953) as the means of classifying coal in terms of proneness to outburst. The gas emission index was based on the gas pressure build-up (P) in millimeters of Mercury (Hg) of coal enclosed in a pressure chamber of known dimensions. This was also reported by Lama & Bodziony (ACARP project C 4034, chapter 9, section 9.2.1) outburst scoping study.

Po-60 index: This index was developed as a follow up to P 0-30 index based on the work of Ettinger et al (1953).This method was mainly used in Belgian coal mines (Vandeloise, 1964). P 0-60 Index is used to estimate the liability of outburst in an advancing face. The value has been found to depend upon the depth of the borehole and the structure of coal ( ACARP C 4034 Chapter 9 Section 9.2.2).

Polish Desorbometer: This instrument was mainly used in Poland for defining outburst conditions in Anthracite mines with CO2 in the lower Silesian coal field basin (Kozlowski and Polak, 1978 a, b). Its application in Australian mines was also reported by Lama (ACARP project no C3079, chapter 13, page 573).

KT index: This index is a measure of the change in desorption rate of coal sample ( ACARP C 4034 Chapter 9 Section 9.2.4). The index KT was determined by Janas and Winter (1977) for Leichhardt Colliery, Gemini seam (Australia) as reported in ACARP C 4034.

P Express index: Developed by Paul,(1977), this method was used to determine KT index when the automatic equipment for KT determination was not developed ( ACARP C 4034 Chapter 9 Section 9.2.5).

Gas emission V index: The V index is the measure of the volume of gas in the early stages of desorption of coal sample under atmospheric pressure. This index was used in France Somnier (1960) ( ACARP C 4034 Chapter 9 Section 9.2.6).

Hargraves emission rate: Hargraves emission meter, measures gas emitted from the samples with virtually no back pressure (± 25mm H2O) in a tube coiled flat on a plate. This index has been widely used in several Australian coal mines, particularly at Metropolitan and other mines in the southern coal fields of NSW, and in some mines of Queensland ( ACARP C 4034 Chapter 9 Section 9.2.7).

Gas flow index G: This index has been used mainly in Russia, Ukraine, Czech Republic and other Eastern European countries. The method is based upon measurement of gas flow from bore holes drilled in the face ( ACARP C 4034 Chapter 9 Section 9.3).

Seam thickness variation index Mm: Seam thickness variation index is a measure of the tectonic stress which can cause local compression of the coal seam. Seam thickness variation index (Mm) was used in Bulgaria and Russia (ACARP C 4034 Chapter 9 Section 9.6).

V30 index : This is an index of the initial desorption rate which defines the amount of gas liberated in the first 30 seconds after the coal face has been blasted. It is a measure of the gas content of coal and the rate of gas emission based on the assumption that the firing pattern and the amount of explosive used remain the same. The underlying assumption is that the outbursts manifest themselves when the gas content exceeds 9 m3/t (Noak et al, 1983) ( ACARP C 4034 Chapter 9 Section 9.7).