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2017 Vol. 2, No. 3

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Current status and progress on the application of key stratum theory in mining subsidence
Chen Chao, Hu Zhenqi
2017, 2(3): 209-218.
Abstract(811) PDF(292)
Abstract:
The generation background,development process and application status of the key stratum（KS）theory were described,then the necessity of the application of KS theory in mining subsidence was analyzed.The Current status and progress on the application of KS theory in mining subsidence,such as the impact of KS on surface subsidence,subsidence prediction,mining-induced crack,surface subsidence reduction and goaf stability,were introduced in detail.The analysis indicates that it is helpful to study on dynamic process of surface subsidence formation mechanism of mining-induced crack,the accuracy of subsidence prediction and surface subsidence reduction effects may be improved in the application of KS theory in mining subsidence.The limitations of present literature were investigated,and the areas for further study in the future were proposed.
The scientific and technical problems and solutions on shallow ground-source heat pump system
Xu Shengheng, Zhou Tao, Sun Haizhou, Zeng Yifan, Liu Shouqiang, Wang Xiaolong, Wu Qiang
2017, 2(3): 219-227.
Abstract(924) PDF(233)
Abstract:
This paper discusses the concept and principle of shallow ground-source heat pump system（SGHPS）and studies the purpose and significance of its development.We analyze the key scientific and technical problems on SGHPS,including pump injection problem,the temperature field of ground heat exchanger system under variable working condition,the influence of main parameters on the heat transfer effect.We also put forward some valuable solutions and rational suggestions to improve the level of science and technology according to the characteristics of SGHPS,which would promote the development of the shallow ground to heat pump industry.
GPR data noise attenuation based on the Shearlet transform
Zheng Jing, Yu Ke, Wang Pengyue, Jiang Shuqi, Teng Xingzhi
2017, 2(3): 228-234.
Abstract(813) PDF(214)
Abstract:
When using ground penetrating radar(GPR)to detect the underground target distribution,valid signal in receiving data tend to be susceptible to noise and the interference of air-ground waves,which will affect the accuracy of target recognition and increase the difficulty of target recognitionThe successful application of Shearlet transform in image and seismic data shows its superiority for denoising processWhen using the Shearlet transform to reduce the noise of the data,the choice of threshold has a great influence on the denoising effectIn order to improve the denoising effect for radar data,a novel denosing method combining singular value decomposition(SVD)method for suppression of random noise to enhance the reflection signal caused by underground targetsThe method is applied to process was proposed the simulation and field datasets,and the experimental results show that the method is effective
Modeling test of deep buried tunnel in soft and broken rock based on non-contact monitoring methods
Sun Xiaoming, Han Qiang, Miao Chengyu, Yuan Shuai, Miao Peiyang, Lu Hao
2017, 2(3): 235-242.
Abstract(579) PDF(260)
Abstract:
A physical modelling test was carried out based on soft and broken surrounding rock tunnel.The formation and development process of temperature and displacement field were observed by two means of non-contact monitoring methods.The infrared thermal imager and the high-precision displacement monitoring system,the failure mechanism of the model was analyzed.Through the thermal imager,the excavation damage zone(EDZ)turned up in a low-temperature state along with the penetration of the full face excavation.By observing the temperature-time curves of the monitoring points in and out of EDZ,the temperature variation regularity in different area of the model emerged along the test process.The formation mechanism of the cracks which leaded to the destruction of the model was confirmed by the displacement nephogram and vector diagrams provided by the non-contact displacement monitoring.The formation and extension of the cracks connected EDZ and the roof collaps.The failure mechanism was analyzed reasonably by the combination of these two monitoring methods.
Experimental investigation on dynamic fracture toughness of offset crack material using caustic method
Li Qing, Cao Huaijian, Yang Mingze, Guo Yang, Xue Yaodong, Yu Qiang
2017, 2(3): 243-250.
Abstract(751) PDF(195)
Abstract:
The dynamic fracture behavior of notched semi-circular bending(NSCB)subjected to hammer impact loading was studied by using caustics experimental method.The results show that the shear stress at the crack tip increased with the offset distance increased,and correspondingly,the crack changed from mode I to mixed mode I-II,the time from impact force loaded to crack initiation also increased,moreover,the crack deflecting angle became more fluctuating with crack propagation;the crack velocity increased rapidly under dynamic load until it reached a certain value with continual fluctuation,with the ratio of crack vertical displacement to the total vertical length λ＞0.8,the crack velocity sharply decreased because of the effect of the local compressive stress around the hammer;as the offset distance increased,the initial fracture toughness KIC decreased,whereas KIIC increased;while the dynamic propagation toughness increased gradually with crack propagation.
Analysis of reasonable position layout of lower and large thickness coal seam
Meng Hao, Jia Shangwei, Cheng Zhanbo
2017, 2(3): 251-259.
Abstract(590) PDF(83)
Abstract:
In the near distance multi coal seam mining,special underground pressure of the lower coal seam appears affected by the mining of upper coal seam.How to arrange the lower seam roadway safely and effectively is not only the key to ensure the safety and efficiency of the mining working face,but also the core of improving the benefits of coal mines.On the basis of the problem of large thickness coal seam mining gateway layout under the coal pillar of upper coal seam in Tashan coal mine,through theoretical analysis,laboratory tests and numerical simulation this paper studies the reasonable layout position of the lower coal seam and draws the following conclusions.Various physical and mechanical parameters of the rock mass of the roadway surrounding rocks are obtained by the mechanical tests providing powerful data support for the theoretical analysis and numerical simulation of the paper;Using the theory analysis and numerical simulation methods,we study the distribution law of the non-uniform stress in the coal and rock mass under residual coal pillar loading;Through the analysis of reasonable layout of the lower coal seam,the layout of the No.3-5 special thick coal seam is determined by the way of inner fault distance 25m.
Numerical inversion simulation of coal and rock under uniaxial compression failure in PFC2D
Zhou Tianbai, Yang Xiaobin, Han Xinxing
2017, 2(3): 260-266.
Abstract(794) PDF(299)
Abstract:
Coal is a natural inhomogeneous and discontinuous rock,which is very difficult to obtain repeatability test results through the experiment method.This paper based on discrete element software PFC2D and obtained coal deformation damage control parameters by numerical inversion method,and simulated the deformation and failure process of coal rock under uniaxial compression by software.In terms of comparing the results of numerical simulation and laboratory test,the numerical inversion method is proven a useful method to study deformation and destruction of natural material.The numerical simulation results can provide theoretical and data basis for engineering practices.
Straightness measurement algorithm based on machine vision for coal longwall face
Liu Pengkun, Wang Cong
2017, 2(3): 267-273.
Abstract(766) PDF(250)
Abstract:
In the mining process of fully mechanized coal face with few hundred meters,long,narrow and undulating curved,face straightness is a non-visual measurement of large moving target.Studying the trapezoidal windows,grayscale,recognition and feature search vision algorithms as real-time measuring form of scraper conveyor,the straightness of local coordinate system is established with measurement of structure light pixel value to a straightness deviation from set.By chain-transfer algorithm,the face layout of multiple local straightness with camera coordinate system is transformed to global coordinate system with matrices and translation vector,as the conveyor section is the face of straightness measurement markers.Experiments show that visual inspection achieves accuracy of ±50mm for the whole face straightness,it meets requirements of highly effective shearer running along straight face.
The selective harmonic elimination based optimal fundamental frequency modulation for multilevel converter
Yang Kehu, Zhang Jianjun, Wang Yubo, Li Xiangyu
2017, 2(3): 274-280.
Abstract(775) PDF(229)
Abstract:
The selective harmonic elimination(SHE) based staircase modulation is a commonly used fundamental frequency modulation strategy for multilevel converters.However,the solutions to the staircase SHE equations cannot cover the full range of modulation index,which limits the applications of this modulation method.In order to solve this problem,this paper extends the staircase switching pattern to the general switching patterns,in which,the Groebner bases method is used to solve the SHE equations,and the achievable range of modulation index and the complete solutions for each switching patterns are obtained.By evaluating the total harmonic distortion,the optimal switching pattern and the corresponding optimal switching angles can be identified for the modulation indices in full range.Experiment results verify the correctness of the proposed method.
Recognition method of low-resolution coal-rock images based on curvelet transform
Wu Yunxia, Zhang Hong
2017, 2(3): 281-288.
Abstract(631) PDF(274)
Abstract:
Considering the limitations of wavelet in image representation—that it is only optimal in representing point singularities and difficult to extract curve features of coal and rock images,a new recognition method for low-resolution coal-rock images based on curvelet transform was proposed.The method used curvelet transform to decompose images into curvelet coefficients in different scales.Then,PCA was applied to obtain a lower dimensional representation that was put into a k-NN classifier. Finally,the final recognition result was obtained via weighted fusion of classification results.Experimental results showed that the features extracted by curvelet decomposition could effectively express the curve features of coal-rock images.Compared with several other existing methods,the proposed method had higher recognition accuracy rate,with the average recognition rate reaching 95.0%.Under the condition of low image resolution can it also get high recognition rate and meet the real-time requirements of coal-rock recognition.
Structure design and simulation study on the internal flow field of the negative-pressure remover
Zhai Guodong, Cheng Jiachun, Li Yaozong, Meng Lili, Wu Fei, Xu Chen
2017, 2(3): 289-293.
Abstract(659) PDF(257)
Abstract:
To solve the problem of the high concentration of coal dust when the coal is drawn from the hydraulic support,we designed a negative-pressure remover which was installed on the hydraulic support tail beam;determined the installation position combining with the parameters of the hydraulic support and got the biggest size of the negative-pressure remover;we chose different diameters of the ejecting cone with the laboratory test conditions and built up and mesh the 3D models of the negative-pressure remover;we used the Fluent-analysis software to simulate the models with different jet flowing velocities and got the best combining parameters of the jet flowing velocity and ejecting cone diameter,which provides some basis for the next optimization for the negative-pressure remover.
Adsorption characteristics of metal ions on kaolinite
Zhang Zhijun, Li Ya, nan, Tong Zhenyang, Nong Haitao
2017, 2(3): 294-300.
Abstract(905) PDF(292)
Abstract:
The adsorption of negative charge on kaolinite particles surface is the main reason that causes coal slime water settle difficult.By studing adsorption dynamics of Ca2+,Mg2+,K+ and Na+ on kaolinite,adsorption tests of single kind of ions on kaolinite,competitive adsorption in two kinds of ions and four kinds of ions were carried out.The concentrations of metal ions in different conditions were measured using ion chromatography,and then adsorption amount of metal ions on kaolinite were calculated.The result shows that the adsorption amount of metal ions on kaolinite is increasing until the adsorption reached equilibrium after 90 minutes,the order of adsorption amount of single kind of metal ions on kaolinite is Ca2+>Mg2+>K+>Na+,and the competitive adsorption in two kinds of ions and four kinds of ions also agree with this rule.This study will provide a theoretical basis for water chemistry regulation technology of coal slime water flocculation and sedimentation treatment technology.
Study on mineralogy of hydromagnesite from Bangor Lake in Tibet,China
Tian Haishan, Sun Zhiming, Liu Lixin, Jia Mengzi, Zheng Shuilin
2017, 2(3): 301-306.
Abstract(792) PDF(474)
Abstract:
In order to study the morphology,chemical composition,symbiotic relationship among major minerals and the typical embedding characteristics of the hydromagnesite from Bangor Lake in Tibet,polarizing microscope,scanning electron microscope,transmission electron microscope,electron probe and MLA mineral analysis system were used.The results indicate that the hydromagnesite is cryptocrystalline aggregate which consists of small crystal particles.The single crystal which has characteristic striation on the (001)is monoclinic plate-like.The hydromagnesite crystal usually grow into layered polysynthetic twin and contact twin along (100).Aragonite,dolomite and other carbonate minerals are often associated with hydromagnesite in disseminated symbiotic relationship in raw ores.It might be difficult to use physical mineral processing to get rid of them.

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