معدن زغال سنگ طبس

In longwall mining, after extracting each slice from the coal seam and advancing the face, a severe stress concentration is formed in the vicinity of the roof and coalface due to the stress disturbance and also the caving of the immediate roof, which resulted in roof displacement, cracks propagation, and roof failure. Due to the caving of the immediate roof and the displacement of the overburden layers by face advancement, there is a possibility of propagating the fractures and instability of the roof in the coalface. The roof failure in a longwall face will bring adverse consequences such as the stoppage of mining operations, damage to equipment, injuries, and fatalities. In this research, the critical events that are effective on the roof failure in the E3 panel at the Tabas coal mine were identified, and the risk of roof failure was evaluated using the fuzzy event tree analysis approach through filling out the questionnaire by the mining experts and faculties. In this way, ten scenarios were examined to analyze the risk of roof failure by checking the roof failure or non-failure, and then the probability of critical events was calculated. Based on the results, the probabilities of roof failure in the fourth, tenth, and seventh scenarios are respectively 5.68, 4.21, and 1.70 percent, and the risk values in these three scenarios are respectively 28.42, 21.05, and 8.51. Therefore, the most critical scenario in this research is the fourth one, in which the preventive measures should be taken through the timely control of critical events to reduce or prevent the risk of roof failure.

Methane is one of the gases emitted from coal seams, which is released into atmosphere through ventilation operation. The emission of this gas causes environmental problems and losing of energy resources. According to previous studies, several billion cubic meters of methane annually are emitted from coal mines in the world. Currently, methane drainage operation is done in many coal mines in the world and the drainages methane was collected by special methods and transported by pipelines to the surface. This gas was used for power generation, sales, town gas and industrial use. Tabas mechanized coal mine extract by longwall mining. In this mine coal seam gas content was varied from 10 ton per cubic meters in depth of 100 m to 20 ton per cubic meters in depth of 600 m. This condition caused that methane drainage operation is done in this mine. The aim of this paper is feasibility study of methane drainage in Tabas coal mine for power generation. Therefore, by considering the investment and operating costs as well as the income from the sale of gas to the power plant, the results has been shown that methane drainage for power generation is economic. However, methane drainage operation in Tabas coal mine, in addition to its energy efficiency and methane production as a fuel, reduce greenhouse gas emission and outburst potential in this mine.

In parts of constructing east-west section of line7 Tehran subway, the excavating machine (EPB-TBM) passes from the top of the Abouzar’s wastewater conveyance tunnel with clear distance of 2.25 m. The FLAC 3D has been used to model this problem and find the deformations and forces of ground and linings. The modeling results showed that after excavating subway tunnel, lining of Abouzar tunnel will move upward due to the increasing plastic zones and stress relaxation. This rate of displacement induced the internal force more than allowable designed amount in concrete lining of Abouzar tunnel. Generally, excavating a tunnel near another tunnel may lead to significant interaction effects, which mainly depends on tunnels position relative to each other (parallel or cross), the distance between two tunnels, tunnel dimensions, lining rigidity, stress and boring environment condition as well as the method of tunnel boring. The interaction between adjacent tunnels have been investigated by different researchers using methods such as analytical and empirical, field observation, physical modeling and numerical modeling. In the current project, the tunnel of Tehran metro line7 passes with a distance of 2.25 meters from the top of the Abouzar tunnel. Because of the three-dimensional nature of the interaction problem between underground spaces, numerical modeling is an appropriate tool for the analysis of these complicated problems. Therefore, FLAC3D software has been used in order to investigate the interaction analysis. The purpose of modeling is to study stability of support system of Abouzar tunnel during tunnel excavation of Tehran metro line7. In this paper, the finite difference method (FDM) is used for modeling and solving the problem. FLAC 3D program which uses FDM was selected in order to study the interaction between the two tunnels, in construction stage. For this purpose, at first Abouzar tunnel modeled and excavated, then impact of stepwise excavating of line7 Tehran subway on lining system of Abouzar tunnel is investigated numerically. History of Internal forces, bending moments and structural displacement of Abouzar’s tunnel lining have been provided and studied. Engineering recommendations have been proposed in different-leveled intersecting tunnels. The results of the modeling showed that after excavation of metro tunnel, the support system of Abouzar tunnel will be uplifted because of increasing plastic zone and stress relaxation. This displacement causes internal forces in Abouzar tunnel lining which are more than allowed values.

Underground coal mining has always known as one of the most hazardous mining activities. The risk of possible incidents in these mines may cause the irreparable damages such as death or personal injury, damage and loss of equipment or interrupting the production process of mines. For this reason, the risk analysis has a very important role in underground coal mines. Hazards identification is the first step of a risk analysis process. In this research by using a combination of library efficiency and expert judgment, the most important hazards in lonwall coal mining have been identified. The prioritization of identified hazards is done by using fuzzy TOPSIS. For this aim the likelihood, severity and reaction was considering as a main criteria and vulnerability and detection as the sub criteria. The results show that the severity and reaction by weight of 0.416 and 0.293 respectively has the highest and lowest impact on the hazard ranking. The proposed model was used in Tabas longwall coal mine. Results show that the roof fall at the panel face and gates by similarity index of 0.832 and 0.823 is the most important known hazards. Also, the subsidence and flooding by similarity index of 0.492 and 0.482 has the minimum level of similarity index. To determine the sensitivity of the achieved ranking, a sensitivity analysis was conducted. The results show that the proposed model has no sensitivity to the weight of decision criteria.

With regard to the types of risks existing in tunnels, geotechnical risks play an important role in the selection of tunneling method and machine types. Also, in order to prevent some geological and geotechnical hazards during tunneling, selecting the most appropriate tunneling machine is very important. In this research study the main geotechnical hazards of tunneling by Roadheader with their common mitigation measures were specified. At present, three Roadheaders are excavating the three drifts of the Tabas coal mine in Iran. Hence, the above drifts were used in this research study. The risk assessment matrix method in these tunnels showed that there is a lower risk of tunneling by Roadheader than utilizing the drilling and blasting method. The determined geotechnical risk assessment also showed that the transverse cutter head is more suitable in comparison to a longitudinal cutter head for such tunnels. Then by using an instantaneous cutting rate model, the cutter head power of the Roadheader was determined. According to the model, a light weight Roadheader with a cutter head power of about 80-110 Kw and 40 ton weight are suitable. Finally, the four types of manufactured Roadheaders which their specifications were similar to the determined ones were selected.