矿业科学学报

Analysis of uplift bearing capacity for slope crest foundation of power transmission line in slopes terrain

Han Yangchun, Cheng Jiulong

2019, 4(2): 95-101.

Abstract(584) PDF(142)

Abstract:
Abstract:The slope crest foundation is a common type of foundation which is often used in power transmission line through the slopes terrain , the study on the uplift bearing capacity of this foundation is still at the initial stage in China.Firstly , the parameter inversion of rock mass mechanics parameters were inversed by FLAC " based on the results of in-situ test on the flat ground in Anhui.Secondly, 138 numerical simulations of slope crest foundation were calculated according to the different distances between slope shoulder and foundation edge , foundation depths and slope angles by using the inversion parameters.And it is concluded that the failure modes of the slope crest foundation can be divided into the shallow buried mode and the deep buried mode by comparing the vertical and horizontal displacement nephogram and the plastic zone distribution of the simulation results.Meanwhile , based on the analysis of the decay rate of ultimate uplift load, it is summarized that the uplift bearing capacity of slope crest foundation increased with the increase of the distance between slope shoulder and foundation edge and foundation depth , but decreased with the increase of slope angle.The concept of minimum safe top distance of slope foundation is proposed to provide scientific basis and reference for design and construction of transmission line slope foundation.

Numerical simulation analysis of mine pressure distribution of shallow coal seam by truncated short wall beam theory

An Bo, Zheng Xiaohui, Zhu Chun, Zhao Junzheng, Tao Zhigang, He Manchao

2019, 4(2): 102-111.

Abstract(515) PDF(127)

Abstract:

Based on the theory of“cutting short-wall beam”, the automatic cutting-in coal-free pillar mining technology for roof-cutting pressure relief is widely used in engineering practice.However,due to the limitation of the numerical modeling of large deformation materials , the numerical simulation analysis of mine pressure distribution based on theory of truncated short wall beam has not been studied. in the paper, the numerical simulation model of NPR bolt/ cable is established at the first based on the constant resistance mechanical mechanism of the NPR bolt/cable in the supporting process ,achieving the goal of numerical and programmed calculation of large deformation materials . 'Then, based on the background of Hecaogou No.2 coal mine engineering, mine pressure in longwall mining is continuously monitored on-site.Finally , the numerical simulations and comparative analysis of mine pressure distribution by applying theory of truncated short wall beam on 1105 working face were made through FLAC3 program.The paper reveals the different characteristics of the distribution of abutment pressure under traditional technology and the working face of theory of truncated short wall beam , and this lays a theoretical foundation for the study of stress field distribution and the rule of temporal and spatial variation of rock mass structure using theory of truncated short wall beam.

Study on the influence of length-diameter ratio on the mechanical characteristics of cracks at the end of linear charges

Li Qing, Zhang Suixi, Wan Minghua, Guo Yang, Xu Wenlong, Feng Dandan

2019, 4(2): 112-119.

Abstract(470) PDF(105)

Abstract:
Dynamic caustic experimental method and numerical simulation method were used to study the crack propagation rules and the tension/compression damage zone at the end of boreholes in the planar model.The results show that the effect of different length-diameter ratios on the crack propagation was significant. As the length-diameter ratio increasing , the crack propagation lengths increased and the expansion angles decreased.When the length-diameter ratio was 5/5 ,the crack propagation angle was about 90°.When the length-diameter ratio increased to be 20(30/1.5) , the crack propagation angles decreased to be 40°.As the length-diameter ratios increased again , the crack propagation angled didn 't change any more.The numerical results are in good agreement with the experimental results , and Numerical simulation shows that small area of compression damage area formed in the area of the column hole , and“X"type tensile damage zone formed at the end of the hole , which lead to the formation of explosive crack easily at the end of the borehole.The radius of the tensile damage zone was approximately 5 times the radius of the compression zone around the borehole.

Experimental study on mechanical properties of frozen soil in deep soil of Wanfu coal mine

Dai Huadong, Wang Qingcheng

2019, 4(2): 120-126.

Abstract(512) PDF(160)

Abstract:
Aiming at the problems of inadequate basic theory and lack of engineering experience in the construction of deep surface soil in Wanfu CoalMine, it is required to collect the soil samples of the Wanfu deep well and to carry out the testing and analysis of the mechanical properties of the frozen soil.The results indicated :At the freezing temperalure designed in this experiment, the uniaxial compressive strength , triaxial compressive strength , creep stress , and frost-heaving force of the frozen soil samples all show an increasing trend with the decrease of the freezing temperature.At the same time , the creep performance of frozen soil in the deep surface soil layer is particularly obvious.The influence of water content and sampling depth on the design of frozen wall can not be ignored.Therefore , according to the data of the single axis compression test , the three axis compressive strength test , the uniaxial creep test and the frost heave test , the multiple regression analysis is carried out ,comprehensive consideration of the effects of freezing temperature , moisture content and sampling depth on the mechanical properties of frozen soil specimens ,the mathematical models possess high degree of fit and good correlation.It provides technical support for the design of the frozen wall of deep surface layer and the determination of mechanical parameters under different geological conditions.

Study on the suspended properties of gangue particles with high concentration of gangue and fly ash

Yang Jie, Wu Jilong, Jin Junyu

2019, 4(2): 127-132.

Abstract(438) PDF(126)

Abstract:
This paper focus on the Xinyang coal gangue fly ash high concentration backfill slurry characteristics. The mechanic model was established to research the coal gangue suspension within the high concentration slurry and theoretical analysis was carried out to study the potential influence factors to the coal gangue suspension.The results show the most significant method to enhance the coal gangue suspension is to improve plastic viscosity and yield stress of the high concentration slurry.The suspending agent that employed in the slurry configuration is to enhance the slurry plastic viscosity , resulting in improving the coal gangue suspension characteristic and decreasing the coal gangue fall downward speed.'The results reveal that the excessive amount of additive less the fluidity of the slurry , increase the slurry pipe transportation resistance.Coal gangue remains suspension characteristic in Xinyang high concentration slurry when the slurry viscosity range from 3.24 to 3.40 Pa · s while the slurry yield stress is between 107.9 to 111.9 Pa.At this level of rheology characteristics , the slurry is adequate to transport.

Engineering cases and deviatoric stress distributions under trapezoidal load in coal pillar floor

Lan Shizhong, Xie Shengrong, Suo Haixiang, Zhang Tao

2019, 4(2): 133-143.

Abstract(606) PDF(71)

Abstract:
A mechanical model of the deviatoric stress distribution of the floor under the trapezoidal load was established , and the maximum principal stress formula of the floor under coal pillar was derived, and the response characteristics of the deviatoric stress field of the floor under the different load spans and the asymmetry coefficient were obtained.With the decrease of the load spans, the deviatoric stress value of the floor was decreased ,and the degree of asymmetry of the high deviatoric stress concentration area in the two sides of the floor was weakened , and eventually there was convergencing to form a contimuous high deviatoric stress area shaped like“apple”".When l<入≤4, the distribution is asymmetry saddlle type consistent with the load level.With the increase of 入 value , the asymmetry was increased,and the growth rate of the high load side was significantly higher than that of the low load side.The minimum value increased linearly , and its position is shifted to the low load side.When the load span was 35 m,with the increase of depth , the asymmetric trend of the deviatoric stress became slow , while there was a relatively obvious low deviatoric stress area in a certain range of the floor , which could be used as the ideal area of roadway layout.Combined with the geological conditions and mechanical analysis of Xinyang coal mine , the Xin No 102 material roadway was arranged at x= 15 m, and the supporting scheme of the high prestress and intensive bolt ( cable) was determined.We carried out the field tests and achieved good control effects. These provide theoretical basis and technical reference for the roadway layout and control of surrounding rock in the lower seam of close distance coal seams.

Experimental study on agglomeration of submicron mineral dust in vortex generator

Zhang Jiangshi, Wang Yameng

2019, 4(2): 144-151.

Abstract(474) PDF(122)

Abstract:
The effects of vortex generating agglomeration device, vortex spacing and inlet velocity of dust-bearing gas flow on the agglomeration of submicron mineral dust in vortex generator were studied by simulations and experiments to explore the agglomeration laws of submicron mineral dust. The particle trajectory was changed by the vortex generating agglomeration device in numerical simulation,and the turbulent intensity and vorticity of the agglomeration zone could be increased by decreasing the vortex spacing and increasing the inlet velocity of dust-bearing gas flow ,resulting in the particle trajectory become more disordered.The experimental results show that the vortex generating agglomeration device can promote agglomeration , and the agglomeration efficiency of submicron mineral dust increases with the increase of inlet velocity of dust-bearing gas flow and decreases with the increase of vortex spacing.

Broken bar identification of double squirrel cage motor rotor

Wang Yanwen, Guo Lin, Zhao Feng, Yang Xiaozhou

2019, 4(2): 152-161.

Abstract(547) PDF(117)

Abstract:
The multi loop model of the independent end ring double squirrel cage motor with the skin effect was established by using the layered method and multiloop method in this paper.Based on the model ,the time-frequency characteristics of the stator current in the starting process of the unloaded shearer uncovered in broken bars situations were investigated.The synchro extracting short-time Fourier transform was used to analyze of the time-frequency of the starting current.For broken bar identification , the amplitude-frequency angle was defined in the amplitude-frequency plane , and the time-frequency angle was defined in the time-frequency plane.The simulation results show that the amplitude-frequency angle can be used to distinguish whether the fault belongs to the upper cage or the lower cage ,and the time-frequency angle can be used to roughly determine the number of broken bars.

Disinfection effects induced by graphene-based photocatalytic composites under solar light illumination

Zhang Wanzhong, Yao Dengke, Cheng Shenhang, Yu Caihong, Sun Zhiming, Zheng S huilin

2019, 4(2): 162-169.

Abstract(494) PDF(117)

Abstract:
ZnO/graphene and ZnO/stellerite composite photocatalysts were prepared through a facile hydrothermal-calcination processing with zinc acetate , urea , natural stellerite and graphene.The composition , morphology , specific surface area ,pore size distribution and light absorption properties of prepared composites were characterized by scanning electron microscopy(SEM), X-ray diffraction (XRD ) ,nitrogen adsorption/desorption and UV-visible diffused reflectance spectroscopy (UV-vis DRS ). It was found that the prepared photocatalysts ZnO/stellerite and ZnO/ graphene had wurtzite ZnO phase morphology with ZnO paticle sizes of 22.42 nm and 15.72 nm.SHEr of composites were 16.54 m'/g and 35.55 m'/g respectively.3D structure between ZnO and graphene resulted in the response to visible light region , reduced recombination of free charges , and enhanced interface charge transfer.'The disinfection action towards Staphylococcus aureus ( S.aureus)under solar light showed that the optimal amount of ZnO/graphene was 100 mg/L.ZnO/graphene exhibited significantly enhanced photocatalytic
disinfection efficiency than ZnO/stellerite powders , and disinfection rate up to 1.17 h'is 1.31 times that of ZnO/stellerite composite.

Pollution characteristics and source analysis of polycyclic aromatic hydrocarbons in soil of coal fired power plant

Zou Yiping, Lou Manjun, Yao Linying, He Haibin, Zhao Shenwei, Jia Jianli

2019, 4(2): 170-178.

Abstract(452) PDF(83)

Abstract:
In this study, 16 kinds of priority PAHs listed by US Environmental Protection Agency
(USEPA) were selected as research objects.Ten soil samples collected from a coal fired power plant in southwest of China were analyzed by gas chromatography-mass spectrometry (CC-MS) to determine the contents of PAHs.Based on the analysis of the characteristics of PAHs and its variation , the source of soil PAHs in coal fired power plant was determined by the method of pollutant source analysis. 'The results showed that 16 PAHs were detected in the soil of the plant , and the contents of 16 PAHs were 4706~12 175 ug/kg.Average content of PAHs were 7 436 ug/kg.Compared with other regions in China and abroad , the PAHs in the soil of the power plant are seriously polluted.The content of PAHs

Research on separation mechanism of liquid-solid fluidized bed separator

Sun Mingyang, Wei Lubin, Li Yang, Xue Hongchao, Yu Chuanbing

2019, 4(2): 179-186.

Abstract(403) PDF(122)

Abstract:
Separation mechanism of liquid-solid fluidized bed separator (LSFBS) was studied by using theoretical analysis and experimental researches.Characteristics of autogenous medium fluidized bed in LSFBS were analyzed and the influence of autogenous medium size on the separation performance of ISFBS was studied , taking quartz particles of various sizes as autogenous medium.According to the separation results ,a better segregation could be achieved by using finer autogenous medium.Particularly , the optimum of Evalue of 0.15~0.2 mm quartz was 0.053 while that of 0.25~0.45 mm quartz increased to 0.095.Finally , the influence of size distribution of feed and operating conditions on the separation efficiency was analyzed.Reducing feed size range and enlarging lower-size limit of feed could improve the device performance.Under a certain bed pressure ,a smaller upward current velocity could generate a higher solid volume fraction and bed effective density.A smaller upward curent velocity could also decrease the influence of size and shape on the movement of particles.All of these changes could induce a better separation performance for LSFBS.

Research on the optimization of coal mine safety production management system

Song Xi, Ding Wenmei, Ning Yuncai, Zhang Yong

2019, 4(2): 187-194.

Abstract(456) PDF(66)

Abstract:
Taking a coal mine in Shaanxi province as an example , this paper made an optimization study of its existing safe production management system.In full field investigation , the paper investigated the current situation of the safe production management system of the coal mine , and summarized the existing problems and analyzed the reasons for the formation of the problems.Based on the theory of scientific safety management and above problems , the optimization principles and goals of the safe production management system were clarified , and the corresponding optimization plan was put forward.The optimal design of the new safety requirements for the existing safe production management information system was proposed.A more complete supervision and inspection system was established , and a more scientific assessment process and evaluation system was developed. Finally , this optimization scheme was applied and verified in practice , and found that accident incidence was reduced significantly , and economic and social benefits were significant improved.

2019 Vol. 4, No. 2