矿业科学学报

Improved GM(1,1)model based on predicted residual in mining area with non-linear subsidence and its application

Yan Yueguan

2020, 5(5): 475-481. doi: 10.19606/j.cnki.jmst.2020.05.001

Abstract(386) PDF(101)

Abstract:
In mining areas,the surface movement and deformation are related to the safety of production
and the safety of ground buildings(structures). It is of great practical significance to regularly monitor and predict the surface movement and deformation in mining areas. Due to the long duration of surface subsidence in the mining areas,the observation data has the characteristics of long time series and nonlinear change,so there are some problems such as difficulty in the selection of modeling data interval and low prediction accuracy of GM(1,1). In view of the above problems,this paper establishes an improved GM(1,1)model based on the residual weighted correction,and puts forward the method of interval selection of modeling data, prediction process and evaluation standard of model accuracy. It is verified by an example that the prediction accuracy of GM(1,1)model is better than that of GM(1,1) model,and the method of interval selection of modeling data from stage to tail can improve the prediction accuracy.

Analysis of spatial and temporal distribution laws of mine earthquake induced by thrust fault coal bumps under mining disturbance

Ren Zheng, Jiang Yaodong

2020, 5(5): 482-489. doi: 10.19606/j.cnki.jmst.2020.05.002

Abstract(505) PDF(81)

Abstract:
In order to analyze the spatial and temporal distribution laws of mine earthquake induced by thrust fault coal-bump under mining disturbance,according to the power distribution law of G-R seismic activity,combined with the in-situ monitoring micro-seismic data and numerical simulation method,the frequency and energy release levels of high-magnitude events in underground mine earthquake activities are analyzed by b value and seismic moment M 0 . The results show that:the distribution law of underground micro-seismic activity is similar to the seismic distribution law of the crust. The activity of microseismic events is related to the b value. The smaller the b-value is,the higher the frequency of highmagnitude mine shock event in the entire mine shock events,and the more serious the impact on the working face. The analysis finds that the b value is affected by the in-situ stress,mining disturbance,and fault properties. Specifically:increasing the maximum and minimum principal stress difference,mining rate,fault throw or decreasing fault dip angle will reduce b value,resulting in high activity of micro-seismic activity,inducing coal-bump,and threatening the safe mining. There is obvious difference in the spatial distribution of thrust fault seismic moment M 0 . Under the influence of mining disturbance,the seismic moment in the upper area of the fault is relatively large. As the working face is approached,the overall value of the seismic moment is continuously increasing,and the area of high peak seismic moment is continuously expanding from top to bottom. The increase of the seismic moment value on the fault means that the level of releasable energy continues to increase,and the corresponding disturbance to the working face will be more intense,further increasing the risk of coal bumps.

Study on the dynamic propagation and numerical simulation of mode Ⅰ and mixed mode Ⅰ-Ⅱ cracks in PMMA specimens with unilateral semicircular holes

Li Chengxiao

2020, 5(5): 490-501. doi: 10.19606/j.cnki.jmst.2020.05.003

Abstract(404) PDF(56)

Abstract:
A new approach is provided to study the growth problems of mode Ⅰand modeⅠ-Ⅱmixed cracks,Split Hopkinson Pressure Bar(SHPB)is used to impact the PMMA USH(Unilateral semicircular hole)specimen containing precast crack. Results of mode Ⅰ cracks and mode Ⅰ-Ⅱmixed cracks are obtained. At the same time,dynamic caustics experiment is used to study the time history of crack growth and the change law of dynamic stress intensity factor at the crack growth tip. Numerical simulation of the test process is performed by using ABAQUS software to study its expansion path. The results show that the mode I and modeⅠ-Ⅱmixed crack trajectories obtained through experiments and the results of numerical simulation are basically similar,which proves the feasibility of using numerical methods to simulate the crack propagation. During the propagation of two types of cracks,the crack tip will be stopped for some time,but they will eventually move towards the central axis of the test piece. Using SHPB test and dynamic caustics experiment with a Unilateral semicircular hole specimen
can effectively obtain the mode Ⅰand modeⅠ-Ⅱmixed cracks,providing ideas for subsequent researches on crack propagation.

Experimental research on dynamic mechanics of early age concrete

Li Shenglin

2020, 5(5): 502-510. doi: 10.19606/j.cnki.jmst.2020.05.004

Abstract(383) PDF(54)

Abstract:
The single and double impact experiments were carried out on C20 and C40 concrete at five different ages using a 75 mm SHPB experimental device. The mechanical properties of early age concrete under impact loading were systematically studied from two aspects,namely curing age and strain rate. The results of
single impact test show that,on the one hand,the dynamic compressive strength of concrete under the same strain rate is logarithmically related to curing age,while the peak strain of concrete decreases with the increase of impact age. On the other hand,the uniaxial compressive strength at each curing age is in power relationship with the strain rate,and peak strain increases with the increase of strain rate. After the first impact,the concrete specimens are cured to the standard age,and then the second impact test in which the strain rates are the same is carried out to test the mechanical properties of concrete. The results of repeated impact tests show that when the first impact age is less than 3 days,the deformation ability of concrete decreases after reaching the stable age,but increases when impact age is more than 5 days. If the strain rate of the first impact test exceeds 25 s-1,the dynamic compressive strength will decrease with the increase of the first impact strain rate,and the later the age of the impact,the greater the reduction. Combined with the experimental results of C20 and C40 concrete,it is concluded that the lower the grade of concrete,the more its mechanical property is affected by strain rate and impact age.

Squeezing deformation mechanism and control technology of roadway between two goafs

Li Yongliang

2020, 5(5): 511-518. doi: 10.19606/j.cnki.jmst.2020.05.005

Abstract(488) PDF(42)

Abstract:
In order to solve the problem of large squeezing deformation control of roadway between two goafs,the panel track-roadway between two goafs in Fenghui coal mine is taken as the engineering background,and the methods of on-site monitoring,theoretical calculation and numerical simulation are comprehensively used. The deformation characteristics of the roadway,the characteristics of the overlying strata structure,the plastic failure modes and stress environment of the surrounding rock under different mining conditions are studied. The squeezing deformation mechanism of the roadway between two goafs is revealed. A combined support design of anchoring and grouting with “strengthening key parts and grouting modified surrounding rock” as the core is proposed. The on-site monitoring results show that the new support design has good control effect on the squeezing deformation of the roadway between two goafs,which can provide reference for the surrounding rock control under similar conditions.

Failure analysis and control of retained roadway at working face under protection coal pillar of the faults

Li Chen

2020, 5(5): 519-527. doi: 10.19606/j.cnki.jmst.2020.05.006

Abstract(363) PDF(53)

Abstract:
Aiming at the severe damage at retained roadway of coal seam 4-2 working face in Buertai coal mine,which is under 2-2 coal seam protection coal pillar of the faults,the failure characteristics and disaster mechanism of retained roadway under the protection coal pillar of faults were studied by means of field measurement, theoretical analysis and numerical simulation. Researches show that:①The deformation and failure of retained roadway are obviously regional,which is obviously more severe under the protection coal pillars of the faults;②Multiple mining operations result in different superposition and unloading of vertical and horizontal stresses,the maximum vertical stress being 1. 8 times of that under the protection coal pillar of the faults. ③After repeated mining,plastic zone of retained roadway under the coal pillar is 2 ~3 m,while it is about1 ~1. 5 m under the goaf. The measures of hydraulic fracturing and anchor cables support are put forward,which has been proved effective

Study on dynamic and static load stability of coal wall and scale effect of mining height in large cutting height working face

Fan Zhizhong

2020, 5(5): 528-535. doi: 10.19606/j.cnki.jmst.2020.05.007

Abstract(386) PDF(51)

Abstract:
Based on the theoretical analysis,numerical simulation and laboratory test,the instability mechanism and characteristics of the coal wall under the action of dynamic load are studied. A PFC 2D biaxial compression numerical test model is established,and the fracture is planted in the model to study the scale effect of coal body and coal sample under static load. It is concluded that the number,continuity and distribution of natural defects in coal seam have obvious influence on size effect. The larger the sample is,the lower the strength is,and the change trend is logarithmic curve. Further,the mechanical properties of coal samples under static and dynamic loads are studied by Hopkinson test. It is considered that there is a good consistency between the peak strength obtained from dynamic load test and the stability of coal wall,which reflects the influence of fine joint structure and defects on coal wall stability under the influence of mining. Taking Yangquan mining area as an example,the dynamic and static peak strength of coal samples No. 15 from mine No. 1,mine No. 2,mine No. 5 and Xinjing mine are
compared with the actual height of coal wall stability. It is concluded that the dynamic peak strength of coal sample can better reflect the influence degree of mining stress. on the stability of coal wall,which provides a theoretical basis for the definition of scientific mining height under strong disturbance.

Partial discharge characteristics of IGBT module in mine frequency converter under step pulse

Wang Yanwen

2020, 5(5): 536-545. doi: 10.19606/j.cnki.jmst.2020.05.008

Abstract(528) PDF(60)

Abstract:
The partial discharge occurs in IGBT device module of mine equipment. which leads to the breakdown of insulation and burns the device. In this paper the causes and characteristics of pd in IGBT module were studied. Therefore,based on the research of material structure,the partial discharge process model for the internal circuit of IGBT device module in coal mine equipment,which is under ultra-high slope pulse square wave, is innovatively proposed and verified by experiments. Then, the partial discharge characteristics of the device module under monopulse or repeated pulses are tested by the experimental platform,and the influence of the pulse rise time and pulse width on the partial discharge of the internal circuit of the device module is analyzed. According to the experiment results of partial discharge under a single pulse,the prediction formula for predicting and calculating the partial discharge initial voltage is innovatively proposed and verified. A certain reference for the insulation design and performance conditions of IGBT device modules in mine equipment is provided.

Modeling and control of series resonant three-port DC/ DC converter based on generalized state space averaging method

Hong Jun

2020, 5(5): 546-555. doi: 10.19606/j.cnki.jmst.2020.05.009

Abstract(487) PDF(71)

Abstract:
The modeling method of the three-port bidirectional DC/ DC converter is mainly for the circuit structure in which the resonant tank is a single inductor,and the topology modeling of the resonant tank for the LC resonance is in lack. This paper uses a generalized state space averaging method to model the series resonant three-port DC/ DC converter,and studies the system*s working mode,dynamic modeling process and control strategy. By building the simulation model in MATLAB/ Simulink,the power flow in different working modes is simulated and verified. The results show that the control strategy designed by the modeling method can achieve good system dynamic response characteristics.

Research on the strength and toughness of ZTA p/Fe45 composites

Wang Yue

2020, 5(5): 556-563. doi: 10.19606/j.cnki.jmst.2020.05.010

Abstract(318) PDF(68)

Abstract:
The strength and toughness of materials are closely related to the wear resistance of materials. In this paper,the strength and toughness and fracture mechanism of zirconia toughened alumina ceramic particles ( ZTA p ) reinforced metal matrix composites were studied to provide reference for improving the wear resistance of ZTA p reinforced metal matrix composites. Firstly, ZTA p / Fe45 composites with different particle sizes and different volume fractions were prepared by vacuum sintering technology. The tensile properties,bending properties and impact toughness of the composites were measured. The fractures of the composites were observed by scanning electron microscope(SEM)to analyze the fracture mechanism of the composites. The results show that the addition of ZTA p reduces the strength of the composites,but increases the toughness of the composites. As the volume fraction of ZTA p increases,the flexural strength of the composites decreases gradually. The impact toughness of the composites first increases and then decreases with the increase of ZTA p size. The impact toughness of
ZTA p / Fe45 composites with particle sizes of 2. 0 mm and 2. 5 mm(F14 and F12)is higher than that of Fe45 matrix. The fracture of ZTA p / Fe45 composites is brittle fracture,in which the fracture mechanism of Fe45 matrix is cleavage fracture. ZTA p mainly have two failure forms,namely particle fracture and particle debonding and pulling out.

Preparation and dye removal performance of MnFe 204@diatomite composite

Song Junying

2020, 5(5): 564-574. doi: 10.19606/j.cnki.jmst.2020.05.011

Abstract(384) PDF(52)

Abstract:
Massive discharge of dyes by industries into environment has posed a threat to aquatic organisms and human health. In order to reduce dye pollution,a MnFe 2 O4 @ diatomite composite adsorbent (MnFe 2O4 @ DE)with excellent removal effect of malachite green(MG)in wastewater and simple preparation method was prepared in this study. A variety of characterization methods were used to analyze structural properties of the composite and its adsorption effect on MG was also systematically studied. The results showed that the MnFe 2O4 nanoparticles were well distributed on the surface of diatomite. Compared to two monomer materials,the specific surface area(112. 1m2/g)and pore volume(0. 24cm3/g)of the composite increased significantly. The as-synthesized composite exhibited enhanced ad- sorption behavior to MG,and its maximum adsorption capacity could reach 25. 70mg/g,which was up to around 1. 89 and 1. 13 times as much as that of diatomite(DE)and MnFe 2O4respectively. The adsorption process was spontaneous and endothermic,which was consistent with pseudo-second-order kinetic model and Langmuir model. And MnFe 2O4 @ DE also showed good reusability. After 4 times of reuse,composite still had 87. 56% removal effect on MG. Therefore,MnFe 2O4 @ DE has good application potential in dye pollution control.

Analysis of the source of DOM in underground reservoir of coal mine

Han Jiaming

2020, 5(5): 575-583. doi: 10.19606/j.cnki.jmst.2020.05.012

Abstract(454) PDF(83)

Abstract:
For an in-depth understanding of the change process of　dissolved organic matter(DOM)in water environment of coal mine underground reservoir, this study used the three dimensional fluorescence spectrum(EEMs),combined with PARAFAC model,to analyze changes and components of the DOM in inflows and outflows in Daliuta coal mine underground reservoir. The principal component analysis(pca)was used to analyze the main factors by which the water body of the DOM was influenced. The results showed that the coal mine underground reservoir had a certain purification effect,and the TOC and UV 254 of DOM were significantly reduced at the outlet water. The DOM in the water body of underground reservoir can be divided into four components:uv-like fulvic acid(240 nm/380 nm),
protein-like tryptophan(275 nm/330 nm),uv-like fulvic acid(255 nm/380 nm)and visible fulvic acid (265 nm,355 nm/380 nm). Through principal component analysis and the analysis of f 470/520 ,HIX and BIX,the results showed that the source of DOM was a combination of endogenous input and terrestrial input,but with endogenous input as the main feature. The treatment of endogenous pollution should be considered in the operation and management of underground reservoirs.

First-principles study of properties nonmetals(C,N,S,P)doped anatase TiO2

Wang Guanyu

2020, 5(5): 584-591. doi: 10.19606/j.cnki.jmst.2020.05.013

Abstract(372) PDF(78)

Abstract:
Anatase TiO 2 semiconductor cell and TiO 1. 875 X 0. 125 ( 2×1×1)( X is C,N,S,P)with the replacement of O with C,N,S,P atom were produced by Materials studio software. Energy band structure,density of state(DOS)and optical properties were analysed by Castep software package based on density functional theory(DFT). The results showed that nonmetal doping led to the width of gap decreased to 0. 57 eV ( TiO 1. 875 C 0. 125 ), 1. 93 eV ( TiO 1. 875 N 0. 125 ), 1. 30 eV ( TiO 1. 875 S 0. 125 ) and 0. 21 eV (TiO 1. 875 P 0. 125 )and their adsoption band edge had different degree of red shifts toward the long wave-
length(TiO 1. 875 P 0. 125 > T iO 1. 875 C 0. 125 > TiO 1. 875 S 0. 125 > TiO 1. 875 N 0. 125 ). Nonmetal doping narrowed the band gap width and made the energy band denser. Valence band and condiction band of C and P doping both moved to the low energy area,in addition,the conduction band of N and S doping moved to the low energy area but valence band hardly moved. Different numbers of impurity energy levels were generated in different state of band gap due to the hybridization and coupling between C-2p,N-2p,S-2p,P-3p,O-2p and Ti-3d. The impurity energy levels generated new visible-light adsoption areas,catching elec-
trons from valence band and inhibiting electronic/ hole combination,which enhanced the photocatalytic activity. Above all,C,P doped anatase TiO 2 have narrower band width, narrower band gap, wider redshift and higher photocatalytic activity under visible-light.

Research Group of “University Innovation Research” of China University of Mining & Technology-Beijing and Wuhan University. Strategic thinking of giving full play to the role of university in national innovation system

2020, 5(5): 592-600. doi: 10.19606/j.cnki.jmst.2020.05.014

Abstract(251) PDF(118)

Abstract:
As an important part of the national innovation system, university plays a key role in promoting the innovation driven development strategy of China and building a country strong in science and technology in the world. University is the main place of training innovative and entrepreneurial talents,the important source of basic research and original innovation,and the important shaper of innovative culture and scientific spirit. At the same time,the university also accelerates the transformation of scientific and technological achievements through collaborative innovation with industry,and promotes the construction of an open national innovation system by participating in global cooperation of scientific and technological innovation. In the new era,university should give full play to the five-dimensional innovation function and promote the governance ability of national innovation system. This paper holds that we should reform the talent training mode of university,strengthen the construction of university's advantageous basic disciplines,plant the university’s innovative cultural gene and promote the scientific
spirit,deepen the innovation interaction and benefit coordination between universities and industries centered on high-quality economic development,and strengthen the cooperation and exchange of scientific and technological innovation with world-class universities and institutions.

2020 Vol. 5, No. 5