This study focused on developing a risk assessment method for explosion at a coal reclaim tunnel (CRT) facility. The method was developed based on an analytical hierarchy process (AHP), which is an expert system that quantifies the factors of explosion incidents, based on events and hierarchies. In this paper, the proposed model was modification from original AHP model, specifically modifying the structure from ''alternative's results'' to ''total risk-rating's results''. The total risk-rating is obtained by summing up risk-rating of each factor, where the risk-rating is a multiplication product of the risk value by the AHP weighted value. To support decision-making using the expert system, data on the real conditions of the CRT were collected and analyzed. A physical modeling of the CRT with laboratory-scale experiments was carried out to show the impact of a ventilation system in CRT on diluting the methane gas and coal dust, in order to support the quantification of AHP risk value. The criteria to evaluate the risk of explosion was constructed from six components that are: fuel, oxygen, ignition, confinement, dispersion, and monitoring system. Those components had fifty-two factors that serve as sub-components (root causes). The main causes of explosion in CRT were found to be: mechanical ventilation failure and abnormal ventilation, breakdown of monitoring system, and coal spontaneous-combustion. Assessments of two CRT facilities at Mine A and Mine B were carried out as a case study in order to check the reliability of the developed AHP method. The results showed that the risk rating of Mine A was classified as high and Mine B was classified as medium, which is in a good agreement with the site conditions.

No abstract

The new comprehensive fire and explosion risk assessment of coal reclaim tunnel (CRT), by applying Monte Carlo simulation to address the probability distribution of risk fire and explosion factor, and the risk matrix analysis as a method to classify the total risk rating obtained from Monte Carlo simulation, has been proposed in the present research. Two CRT facilities, that is A and B, which differentiate by the locations have been analyzed using the proposed method. The result shows that CRT A is classified as extreme risk level, and CRT B is divided into two groups, which classified as high-risk level with cumulative probability of 81.73% and as moderate risk level with cumulative probability of 18.27%. Because they situated on the extreme risk and high-risk level, the risks are classified in unacceptable risk level. After simulating with several preventive actions, the result shows that the risks have been lowered into acceptable risk level, with a 100% probability of moderate-risk level. A sensitivity analysis for the CRT A and B reveals that among 49 factors identified, the 4 (four) most influential factors for the fire and explosion risk are the ventilation system, the oxygen concentration, a coal spontaneous combustion, and the monitoring facilities.

Potential hazards that often occur in underground tunnels are dangerous and toxic gases, one of which is carbon monoxide (CO) which can be found in underground tunnels for example as a result of imperfect detonation on work surfaces. CO gas is very poisonous so it can cause death. This study aims to determine the spread of CO gas when diluting with tunnel ventilation in the horizontal front. This research was conducted on a physical model of the laboratory with a ratio of 1:10 compared to the actual tunnel, that is at the cross section of the model in the laboratory 40 cm x 40 cm. The effectiveness of dilution or dilution is indicated by the value of the diffusion coefficient, where the greater the diffusion coefficient, the more diffused the CO gas concentration, so the faster the CO gas concentration decreases. The parameters of the test conditions are the ratio of the duct to face distance (L/D) and the Reynolds number (Re) which shows the variation of air velocity in the tunnel work surface. Test results from the distribution of CO gas showed the influence of the configuration of the forcing duct and exhausting duct distances on the working front to the CO gas dilution. In this study also found the influence of Reynolds numbers on the value of the diffusion coefficient, that the greater the value of Re, the greater the value of E.