Determination of loading capacity index of a continuous miner in soft rock roadway and virtual test method

To improve the loading efficiency and reduce energy consumption of a continuous miner in soft rock roadway, a seven-arm star wheel designed with Gaussian fitting method was proposed, and a coal loading model of the continuous miner star wheel loading mechanism was reconstructed with EDEM software. The loading capacity of the seven-arm star wheel and the three-arm star wheel of the EML340 continuous miner at different working speeds were studied respectively. The scientific and reasonable identification index was formulated and the index evaluation system of loading star wheel was established. It has been found that the performance of the loading star wheel is a collection of various identification indicators, the coal returning mass reducing the loading efficiency and increasing unnecessary energy consumption, therefore, it is difficult to identify by a single index. Loading coal and rock by the star wheel is a process that consumes energy and pays attention to output, therefore, the identification index should include two kinds of efficiency parameters and energy parameters. Rake coal torque and loading specific energy consumption have reflected the degree of energy utilization, which can be comprehensively used for preliminary design of the star wheel. The performance parameters such as loading power and loading efficiency are reliable indicators for designing and performance evaluation of the star wheel. Based on the statistical analysis of the test data, compared with the three-arm star wheel of the EML340 continuous miner, the loading efficiency of the seven-arm star wheel has been significantly improved. The loading power for coal loading has been reduced by 46%. The feasibility of the Gaussian design method of loading star wheel has been verified.

Deployment of Continuous Miner in Under Ground Coal Mine – A Case Study of Sarpi Mine.

The continuous miner technology (CMT) is being adopted extensively in underground coal mines of India as Mass Production Technology (MPT). This technology potentially eliminates the two-unit operating, namely the drilling and blasting. This elimination helps for better strata control and avoids the drillers working in unsafe conditions, maybe under the loose coal roof. This CMT improves the quality of the coal extracted and increases the output per man shift (OMS) by reducing the deployment of face crew. It also reduces the accident as it is operated by remote and workforce exposure to faces is limited. The method also helps for better roof and side control, thus preventing side and roof fall danger. With the changing time now, continuous miners of different heights are available, which helps for optimum use of technology to mine out varying insitu height of coal seam. This paper discusses the performance of the CMT in the Sarpi mine and compares the technology available globally.

Experimental and Numerical Investigation of the Effect of Integration of a Flooded-Bed Scrubber into a Longwall Shearer on Airflow along a Coal Mine Longwall Face

Dust control is one of the most difficult challenges for underground coal mine operators, especially longwall mine operators. The most widely used dust control technologies at a longwall section are ventilation air and water sprays, whereas a continuous miner section has the added advantage of having a dust scrubber built into the continuous miner. To test the potential benefits of integrating a flooded-bed scrubber into a longwall shearer, the authors designed and built a dust scrubber system for a full-scale mock-up of a longwall shearer. The mock-up was installed in the longwall test gallery at the Pittsburgh Research Laboratory (PRL) for testing. Air quantity surveys were performed at different cross-sections of the test gallery at a fixed face-air quantity, but at different scrubber airflow rates to quantify the distribution of air in the test gallery. Subsequently, a computational fluid dynamics (CFD) model of the PRL test gallery was developed and validated. In this study, the effect of the flooded-bed scrubber on airflow pattern in the test gallery is investigated using the validated CFD model. This model can be used further to predict the dust capture efficiency of the scrubber and to develop new techniques to reduce dust concentration in longwall sections.

Design of remnant pillar in mechanized depillaring using continuous miner

Ribs and snooks are the critical natural support at the goaf edge in the mechanized depillaring operation of the bord and pillar mining system. The pillar extraction has been carried out by taking the slices and leaving ribs and snooks during the depillaring operation. Remnants are the remaining portion of the extracted pillar. The depillaring operation leads to an unsupported roof, and the immediate unsupported roof imposes its weight on the pillar (remnant) under extraction. The remnant’s purpose is to provide a necessary reaction to the overhang to restrict roof failure until the pillar’s final slice. The remnant’s stability during depillaring operation has been accessed in the study using three-dimensional numerical simulations. A scheme has also been proposed in the study to evaluate the factor of safety (FOS*) of the remnant pillar in the residual phase at different stages of slicing operation. A case of an Indian coal mine using the fish-bone method has been chosen for the study. A typical depillaring stage has been selected for the extraction of the pillar using the fish-bone method. The numerical simulation of the considered panel provides the vertical stress and yielding profile on the pillars at different stages of depillaring. The simulation results show the influence zone up to one pillar from the goaf edge. The immediate intact pillar shows considerable yielding of about 60% of the pillar area. The remnants have completely yielded during the slicing operation but provide a reaction to the immediate strata. The remnant should provide the reaction to the immediate roof till taking the final slice from the pillar. The remnant’s FOS* is calculated by taking the ratio of reaction offered by the remnant (numerical simulations) and the weight of the overhang (estimation). The area’s borehole section shows two layers of medium to coarse-grained sandstone as an immediate stratum. The weight of the immediate strata has been estimated in the study considering the immediate strata’s thickness. Two different scenarios of immediate strata thickness (i.e., 4.75 m and 9 m) have been considered in the study to evaluate the remnant’s FOS at different depillaring stages.

A new automated, safe, environmentally sustainable, and high extraction soft-rock underground mining method

SYNOPSIS Ore deposits are becoming more complex to mine as a result of the exhaustion of surface and other easily mined deposits. There is also increasing socio-political pressure to design more environmentally sound, sustainable, and safe mining practices. Wang and Ma designed a mining method for coal, similar to a modified drift and fill using a continuous miner to take sequential cuts (rooms) that are subsequently backfilled. The authors have modified the concept to make it more autonomous, safer, and less costly using highwall coal mining techniques, modified and adapted for underground applications. The method is more flexible than longwall mining and the percentage extraction would seem to be in the same range. In addition because of the backfilling, surface subsidence would not be a major issue and could be more effectively managed. Keywords: highwall mining, underground coal mining, backfilling, backfill face stability, continuous miner, safety.