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Goaf roadway poses a vital threat to coal mine safety and miner’s life. The scale of the goaf roadway volume is relatively small, therefore, the ordinary geophysical prospecting method can hardly detect it accurately. Also, the drilling method can rarely hit the target precisely. For the purpose of detecting the goaf roadway more precisely, a roadwayborehole transient electromagnetic method( TEM), belonging to a 2 D operating method with fixed source and dynamic reception device, was proposed. This method, by arranging a fixed transmission cable over the borehole and shifting a receiving probe along the borehole to implement three-component observation, realized a high-precision detection for the borehole radial geological anomalous bodies. The device, with more complex observation curve, had harder inversion difficulties. By analyzing the data characteristics adopting asynchronous parallel GPU plus CPU finite-different time-domain 3 D numerical simulation method, this paper presented a related sliding time window wave-field inverse transformation algorithm, combined the both advantages of time segmentation and full time wave-field transformation algorithm, to transform data with higher accuracy. By studying the characteristics of time-distance curve of 2 D transient electromagnetic virtual wave field data, a corresponding dynamic correction algorithm was derived. By adopting equivalent conductive plane method, initial velocity model was constructed. Ultimately, based on virtual acoustic medium hypothesis, the roadway-borehole TEM data pseudo-seismic inversion was realized by the means of conjugate gradient full-waveform inversion technique. The inversion results of 3 D numerical simulation, flume simulation experiment and coalmine on-site simulation data showed that it had acquired favorable effect in exploring small-scale anomalous body on the radial direction of the borehole. In order to test the practicability and availability of this operating method in detecting water-logged goaf roadway’s shape, characteristics and scale, the author’s research group has conducted an case study in Shanxi’s coal mine. The research showed that the roadway-borehole TEM detection method is a great combination to underground geophysical exploration technology and drilling technology, and to make them supplement to each other. It is an effective application in goaf roadway with water detection. [ABSTRACT FROM AUTHOR]

Long-term stockpiling of coal gangue would cause acidic pollution at surrounding area and heavy metal content to exceed the standard. The coal gangue was obtained from Yangquan coalmine in Shanxi to study the mechanism of the influence that coal gangue’s self-heating oxidation has on the leaching and release characteristics of acidic pollutants. The dynamic leaching experiments were carried out in an automatic temperature-controlled leaching system. The leaching rules of leaching solutions’ pH values, electrical conductivities (ECs), oxidation-reduction potentials (ORPs) and sulfate contents (SO2-4) were investigated at different temperatures. Also, the respective mineral components of coal gangue samples before and after the leaching operations were analyzed semi-quantitatively. The result shows that weathered coal gangue contains a great quantity of soluble sulfates, and the content of acidic components is greater than the sum of alkaline and argillaceous mineral components. The sulfate content of wetting solution exceeds the subsurface class - water index at the beginning of the experiment, so it can be regarded as highly mineralized water. Besides, the wetting solution assumes weak acidity and oxidation state, but the oxidizing property does not exceed the value of the general defined oxidizing soil (400 mV). As time goes on, however, the pH value will increase at first, then decrease and tend to be stable eventually. At t=3 h, the pH value reaches a maximum of about 7. 34-8. 03. The sulfate content and EC value will decrease sharply at first and then stabilize at around 2 500 mg/L and 2 mS/cm respectively, while the ORP will be fluctuating within the range of 325. 9 mV and 435. 2 mV. When temperature rises from 50 to 200 °C, the steady state pH value (pHs) of solution and the residual pyrite content in coal gangue will decrease at first and then increase, and pHs values are maintained less than 5. 79 at 150 °C to 200 °C. The sulfate and gypsum contents will increase at first and then decrease while the volatility of ORP will increase gradually as temperature increases, and the relative standard deviation (RSD) increases from 9. 54% to 10. 06%. The EC value is not significantly affected by temperature. All these indexes will obtain their extreme values at 150 °C, the extreme values of pHs, min and ORPmax are 4. 98 and 435. 2 mV, respectively, which present a strong acidity and strong oxidation state. Therefore, the oxidation of acid-generating substances in coal gangue can be divided into weathering oxidation and autothermal oxidation, which are mainly affected by the combination of ambient temperature, water content and degree of air contact. The acid pollution evolution process caused by the autothermal oxidation of coal gangue is determined by alkaline components, nitrous substances and acidic components produced by oxidation, also, the leaching release rate of three components gradually tend to be stable after long-term storage. This paper explains the mechanism of temperature’s influence on the acid production of pyrite oxidation in coal gangue, which could provide a research basis for forecasting the dynamic evolution of self-heated coal gangue hills’ acidic pollution caused by rainfall leaching and infiltrating. [ABSTRACT FROM AUTHOR]

To reflect the effect of confining pressure on the brittleness of the post-peak rock, the degradation angle of post-peak strength of the new parameter was presented. Based on the test data for mudstone of Shanxi in triaxial compression, the linear relationship between the degradation angle and the confining stress was founded. The law between the equivalent plastic shear strain and the degradation angle was presented, and the strain softening model of rock based on the degradation angle was set up. Fish function method within FLAC was used and the numerical code was developed. In numerical case study, the strain softening processes under variable confining pressure for mudstone of Shanxi were modeled. The simulating results accord with experimental data. Those show that the degradation angle is an effective parameter to reflect the effect of confining pressure on the brittleness of the post-peak rock; the model in this paper is reasonable and can be used to model the strain softening processes of post-peak strength rock. [ABSTRACT FROM AUTHOR]