The Chinese mining industry basically is coal-oriented. Besides coal China is leading producer of gold and a few rare earth minerals. Coal forming patterns and various mining conditions are the basis of research works that are strengthening the multi-faceted phenomena in the current status of Chinese coal mining industry. Mining industries have made huge contributions to China’s socio-economic development and the current mining practices in the country deal with the interests and concerns of local communities thereby reflecting high rate of economic growth. Coal consumption in the country has increased to meet escalating demand for industrial production and also for power generation. However, China is still importing coal to meet its high demand.
The pot pourri of papers in the special issue of the Journal provide comprehensive research works through field works and present the importance of various mining areas. Hopefully, this special issue should provide an insight and some food for thought for the discerning readers of the Journal.Read more
As the scale of open pit mining and mining intensity have increased continuously over time, the stability of high and steep side slopes have become a key issue that must be addressed in open pit mines. A number of cases have shown that high and steep side slopes with bedded structures are highly susceptible to failure, and these failures may lead to significant damage and destruction. In this work, indoor modelling experiments were performed to study slip-buckling failures in high and steep side slopes set along the bedding plane of layered rocks. Here, experimental similarity criteria were derived according to similarity principles to produce an accurate match with the subject of this study and to select similarity constants. River sand, plaster, and barite were selected as equivalent materials in this experiment, and matching tests were performed. Fuzzy comprehensive evaluation was used to determine the optimal matching scheme on the basis of prototype similarity and physicomechanical parameters including density, compressive strength, elastic modulus, and Poisson’s ratio. The model was filled and constructed through layered filling and tamping, and observation points were installed throughout the model. Based on the subject selected for this study and dynamic excavation processes in mining simulations, we observed deformations of the model that occurred during excavation and the application of a load by a hydraulic servo loading system set on the top of the model. Through analyses of the results, it was found that rocks on the upper part of the slope slipped along the bedding, while slip-buckling failure occurred at the foot of the slope. Finally, the most dangerous slippage surface was identified as a composite surface with flat and arced surfaces.
Keywords: Side slopes along rock layers, matching of equivalent materials, loading system, similitude model experiment
This research intends to obtain the pressure relief angle of protective scope through research and study of the protective scope and effects after mining of coal seam No. 2 as the protective seam of coal seam No. 5 in mining area No. 23 of Jinzhushan Mining Co., Ltd. CBM flow attenuation coefficients of taps within protective area are reduced from 0.016 and 0.015 d-1 before mining to 0.008 and 0.011 d-1; and average CBM extraction amount in seven days is raised by two to three times. This research provides scientific basis for mining of protective seams for the mine.
Keywords: Protective seam, pressure relief angle, attenuation coefficient, CBM flow
In order to study the change features of infrasonic waves in coal sample loading, we collect coal samples from the research area, conduct both lab test and theoretic analysis, and based on filtered and de-noised signals, establish the characteristic parameter of infrasonic waves – relative energy, and analyze the changes in the energy parameter of infrasonic waves in the loading process. The analysis shows: in the loading process, the energy of infrasonic waves changes in stages, including the slow increase, rapid increase towards the peak and slow decrease stages, which are consistent with the deformation stages of coal samples, and when the coal samples enter the plastic deformation stage from the elastic deformation stage, the infrasonic waves show an obvious abnormal change. Therefore, we can predict the deformation and failures of coal samples according to the changes in the energy of infrasonic waves. At the same time, due to advantages like non-coupled contact and small attenuation, the infrasonic wave prediction method is very useful in the coal sample failure prediction. This is of great significance to improving the accuracy of coal sample failure prediction and reducing coal mine accidents.
Keywords: Infrasonic waves, relative energy, prediction of coal sample failures, precursor characteristics, analytical method
The iron tower of transmission lines and its foundation are often confronted with settlement, inclination, displacement, distortion, etc. caused by surface movement and deformation. The double corridor project takes advantage of the layout of working surface, basically the regular time and the slowness of surface movement and deformation. Combined with geological information and mining conditions, the project chooses to construct new corridors in stable goafs which have been moved and deformed by coal mining. Through detecting tower deformation and mastering its trend, the new corridor will be built as soon as the deformation degree reaches the early warning value (the deflection of tangent tower reaches 0.3% while that of angle tower reaches 0.7%). The old corridor is then transformed into a double-corridor project. This project provides new ideas for transmission lines construction in mining areas by solving the problems in rerouting and high cost.
Keywords: Coal mining area, electric transmission lines, geological defects, management, double corridor project
In order to obtain the relationship between powder input, rotation rate, capacity of powder exhaust, power consumption, vibrational disturbance during normal operation of a spiral pipe, experiments of powder transport with different powder inputs (88-91, 133-137, 176-182g/s) and rotation rates (240, 300, 360, 420, 480, 540, 600rpm) are carried out. The results show that with the powder input remaining constant and the rotation rate increasing, the amount of powder residue obeys an exponential distribution and decreases gradually, and that the power consumption and vibration acceleration increase linearly. The results indicate that: (1) the capacity of powder exhaust is positively related to the rotation rate and (2) the higher the rotation rate is, the lower will be the marginal increment of powder exhaust. Through comparison of the images captured by a high-speed camera, the powder being transported falls within two flow regimes: (1) depositing and moving axially, and; (2) being stirred and moved spirally. Based on the comparison of the curves of powder residue, power consumption and vibration acceleration, a conclusion is drawn that the rotation rate of the spiral drill pipe in soft coal bed shall be controlled strictly and shall be neither too high nor too low.
Keywords: Spiral drill pipe, powder transport, flow regime, vibrational disturbance, drilling parameter
The permian Tiaohu formation in Santanghu basin is a rare tight tuff oil reservoir containing sedimentary organic matters. With medium-high porosity and ultra-low permeability, the oil reservoir is not connected between wells. In the light of the difficulty in reservoir development, large-scale volumetric fracturing was adopted on horizontal wells. Because of the poor physical properties, however, the fracturing fails to achieve substantial improvement of pore connectivity. The transformation effect is far from desirable, as the high initial production is followed by a rapid decline in yield. In order to effectively develop the tight tuff oil reservoir, the authors analyzed the geological mechanism of tuff tight oil, and adopted the water injection and huff-andpuff (WI-HnP) in the light of lab experiments and field tests. The method maximizes the comprehensive benefits of the exploration and development, and sheds new light on deepening the utilization of tight tuff oil reservoirs.
Keywords: Tight tuff, Santanghu basin, geological mechanism, water injection and huff-and-puff (WI-HnP)
Ranging from geological, hydrological to geographical conditions, the influencing factors of the stability of highsteep mining slope involve lots of unascertained information which is difficult to analyze and judge with simple methods. Based on engineering analogy, this paper analyzes the stability of high-steep mining slope by clustering and unascertained measuring method. The clustering center of the various influencing factors of the stability of high-steep mining slope was pinpointed through dynamic clustering, with a large number of historical data as training samples. After using the unascertained measure to evaluate the numerous unascertained information, the authors put forward a new method for stability analysis of high-steep slope mine. The results show that the proposed algorithm can predict the steady state of high-steep mining slope with a hit rate above 90%. All in all, this research sheds new light on rational and rapid analysis of high-steep slope stability.
Keywords: High-steep mining slope; stability analysis; clustering; unascertained method
The influence of mining area on the ‘ground surface’ is mainly divided into three categories: the movement and deformation of vertical direction (subsidence, inclination, curvature), the movement and deformation of horizontal direction (horizontal movement, stretching and compression) and the shear deformation of surface plane, which are mainly reflected by discontinuity deformations including surface cracks, collapse pits, subsidence troughs, etc. These kinds of deformation directly act on the iron tower foundation of transmission lines, causing varying degrees of damage on iron tower foundation, such as sink, tilt, displacement, distortion, etc. and thus influence safety of the iron tower and the stable operation of the entire transmission lines. Therefore, this paper reviews the actual situation of the mining area, compares the features of different foundations, and proposes a method of applying the independent big slab foundation. This foundation can resist uneven settlement in a mining depth to thickness ratio of 90 to 150, and adjust anchor bolt to assist for processing surface uneven settlement and deformation. In this way, the risks of geological hazards in the meaning area could be eliminated significantly.
Keywords: Geological hazard, independent big slab foundation, mining area, mining depth to thickness ratio, the deformation discontinuity
This paper determines the mineral composition and analyzes the brittlenessof Lower Cambrian Niutitang formation shale in Northwest Hunan using XRD technology. The results show that Niutitang formation shale in Northwest Hunan has rather complicated composition, mainly consisting of quartz and clay minerals. The average content of quartz is 41.40%~60.81%, and the average content of clay minerals is 21.43%~26.40%. Calcite, plagioclase, dolomite, pyrite, potassium feldspar and other minerals are also commonly found in the samples. The brittle minerals of Niutitang formation shale are featured by rich species, high content (greater than 40% in average) and large brittleness index (higher than 50% in average). Compared to the shales in different regions both at home and abroad, Niutitang formation shale in Northwest Hunan has better fracability.
Keywords: Shale; components of rock and mineral; brittleness; Niutitang formation; Lower Cambrian; northwest Hunan