Methane risk assessment in underground mines by means of a survey by the panel of experts (SOPE)
The purpose of the paper was to develop a method of methane risk assessment in order to fulfil the technical-organizational and legal requirements for occupational risk assessment in mines. Methane hazard and associated risks of the effects of ignition and/or explosion of methane is one of the most severe natural hazards.
Heuristic methodology based on the Delphi approach and a group survey by a panel of experts, which was named SOPE, was used to assess the magnitude of methane risk. The adopted tools for assessing the current state of methane risk factors and their possible accident consequences were targeted surveys, with the participation of experts representing, mainly, engineering-technical personnel of mine ventilation service. The objectivity and independence of the judgment of the experts was checked by determining indicators of the degree of the experts’ unanimity, indicators of their competence as well as indicators of the validity of their evaluations. The subject matter of the study of methane hazard were five longwall areas of the "A-Z" twin-mine (after the merge of two mines: Mine A and Mine Z), three longwalls operated towards plant A and two longwalls operated towards plant Z. For the assessment of each area of the mine, a Methane Risk Assessment Questionnaire consisting of 4 assessment cards, was used. The cards included four areas of the studied risk factors, i.e. factors shaping the methane hazard (17 factors), the activity of the methane ignition initiators (19 factors), detection and prevention of methane risk (16 factors) and possible human and material losses (13 factors).
The evaluation of 65 factors affecting the causes and consequences of the methane risk in the exploitation area under analysis, was conducted in accordance with the procedure of the adopted method, based on the proposed algorithm. Assessments by experts were used to calculate the indicators of the magnitude of methane hazard for each group of factors separately.
A practical example of the application of this method is incorporated in chapter four of this paper, which also discusses the results of the conducted research.
The obtained values of the indicators of methane risk assessment and analysis of their changes showed that the proposed method can be an important element in the design and construction of a modern methane safety system in coal mines. It provides the possibility of controlling this risk and enables the minimization of its consequences in accordance with the criteria of their acceptance, adopted in this paper. The method does not replace the currently used methods of methane risk assessment, but complements them in a significant and modern way.