Journal of Mining and Safety Engineering

Failure Mechanism and Control Measure of Roadway Deformation with Fractured Surrounding Rock in Deep Mine

FANG Xin-Qiu, ZHAO Jun-Jie, HONG Mu-Yin

2012, 29(1): 1-7.

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To solve the support problem of fractured surrounding rock roadway in deep mine，based on the geological conditions of west track haulage roadway in Xuehu coal mine，we established the mechanical model of roadway floor heave，and studied the failure characteristics and influence factors of the surrounding rock in this paper．The results show that the fractured surrounding rocks around two sides of the roadway have natural pressure relief effect which can delay the formation of floor heave．With the compaction of surrounding rocks in the two sides，the stress continues to transfer toward the floor which then initiates the floor heave．Hereby，the secondary support technology is proposed to control the roadway deformation with fractured surrounding rock in deep mine，that is to say，the U-steel yieldable support is adopt as the first support，while the bolt-grouting and bolt-beam-net-anchor cable support are adopt as the second support．The greatest characteristic of the technique is altered from the lagging grouting to timely grouting，which provides a platform for exerting the anchorage effect of bolt，and the support efficiency is improved greatly．The final support parameters are determined by numerical simulation optimization，and have applied to the field industrial test．The observation results show that the roadway deformation is controlled effectively，and has obtained great social and economic benefits．

Research on Floor Heave Mechanism of Thick Seam Roadway in Wuyang Coal Mine and Its Control

YANG Ben-Sheng, GENG Xue-Liang, SUN Li-Hui, SONG Xian-Zhong, ZHANG Li

2012, 29(1): 8-13.

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In view of the frequent large deformation failures of the extraction roadway floor in thick seam 76#-2 in Wuyang mine，we proposed the prevention concept of medium and deep strengthening in thick seam roadway to control floor heave，through studying on the mechanism and control method of the floor heave in thick seam roadway．Additionally，the effects to the floor under different supporting ways were simulated by FLAC3D software. The results show that the floor deformation without supporting is 1.3~1.6 m，but the floor damage zone will be extended gradually under the mining stress disturbance．The floor plastic zone will be reduced correspondingly by the support of anchor coupled with the grouting，but the maximum value of floor deformation amount to 0.7~1.0 m when influenced by mining stress，and the roadway still can’t meet the production needs．By using the combined support of a branch of high-strength anchors coupled with concrete block and grouting，the plastic zone in floor surrounding rock will be reduced significantly，and the floor heave is only 0.24~0.38 m，which has met the requirements to control the floor deformation．Through the engineering tests of the combined support technique，the result shows that the two sides’displacement and floor heave of the roadway are 226 mm and 283 mm，which are reduced by 56.5% and 83.4%，respectively．Thus，the large-scale deformation of roadway floor in thick seam has been controlled effectively．

Prevention of Coal Roadway Roof Accidents Based on Geological Forecast Technology

WANG Qi，LI Shu-cai，LI Wei-teng，et al

2012, 29(1): 14-20.

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By the summary and analysis of the reasons and mechanism of mine roadway roof accidents，we find that the lack of geological information，the corresponding early warning mechanism and reasonable solutions are the main reasons for roof accidents during coal roadway drilling and supporting．Additionally，it has been proved that applying the advanced geological forecasting technology to prevent roof accidents is feasible．After summarizing several roof fall accidents of coal roadway in Juye mine area，it indicates that it is necessary to establish reasonable early warning mechanism of roof fall accident and design the corresponding prearranged support scheme．Thus，the prearranged support scheme and control method of roof accident are proposed based on advanced geological forecasting．The guidelines of the method in regular sequence are prior geological analysis，following geophysical prospecting，drilling to check，matched supporting plan designing and monitoring to feed back．Meanwhile，the repeated deduction and mutual correction between different predictionparts are quite important for the method．This method has been successfully applied to prevent several roof fall accidents，and one of the cases is analyzed in depth，which shows that the method has an ideal forecasting effect．The supporting plan with anchor beam can control roadway deformation in fault zone effectively，prevent roof collapse accidents，and get great economical benefits to feed back．And repeated deduction and mutual correction between prediction parts were important for the method．This method was successfully applied to prevent some roof fall accidents， and one of the cases was analyzed in depth．The case analysis showed that the method had an ideal forecasting effect．The supporting plan with anchor beam was good for controlling roadway deformation and preventing roof collapse accidents in fault zone，and it was economical．

Coal Wall Stability of Fully Mechanized Working Face with Great Mining Height in “Three Soft” Coal Seam and Its Control Technology

YUAN Yong, TU Shi-Hao, MA Xiao-Tao, SUN Lu-Lu, BAI Qing-Sheng

2012, 29(1): 21-25.

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To effectively control the coal wall stability of fully mechanized working face in “three soft” coal seam，we measured the characteristics of coal wall falling at NO.7₂19 fully mechanized face with great mining height in Xutuan Coal Mine of Huaibei Mining Group，built the mechanical model for stability analysis of wedge sliding object in coal wall，and analyzed the key effect factors of the sliding object stability．The results show that the coal wall falling in fully mechanized face with great mining height in “three soft” seam occurs mainly in wedge sliding type in the upper part of coal wall，and the stability coefficient of wedge sliding object (K) is proportional to C，P_h and μ， and inversely proportinal to W₀ and θ．By adopting technical measures of increasing the support resistance，controlling end face roof fall, strengthening coal wall，correctly using guard plate，appropriately increasing the advancing speed，et al，the coal wall stability of NO.7₂19 face has been effectively controlled．

Structure Forms of Basic Roof and Reasonable Supporting Parameters in Ends of Fully- Mechanized Top Caving Face

YANG Pei-Ju, LIU Chang-You

2012, 29(1): 26-32.

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The determination of face-end hydraulic support resistance is the key to support design and selection．Therefore，theoretical analyses were carried out in this paper to study the collapse of overburden，movenment rules of basic roof structure，and determination method of resonable supporting parameters in the face-end area．The results show that the basic roof can be the fractured or caving rock stratum in the face-end area．The sinking motion of the arc triangular pieces in the fractured zone is the same with the voussoir beam in the middle of the face，while the arc triangular pieces in the caving zone can be regarded as the cantilever beam which is only supported by coal wall and loaded by overburden pressure，or forms the similar voussoir beam structure hinged with the frontal and posterior arc triangular plates mutually．Different triangular plate structures of main roof result in different pressure behavior，that is，the pressure behavior of main roof is obvious in the voussoir beam structure，and the dynamic load coefficient is large，while the similar voussoir beam hinged by triangular plate structures results in less pressure behavior and smaller dynamic load coefficient．In the action relation between the support and surrounding rock in the face-end，the working conditions of support include three types：given deformation state，limited deformation state，and given loading state．Meanwhile，the reasonable supporting strength of face-end support under different conditons can be estimated by the corresponding voussoir beam，cantilever beam，and the similar voussoir beam hinged by triangular plate structures in the face-end area，respectively．

Support Technology of High Resistant and Yielding Property for Deep Roadway Under Dynamic Pressure

ZHANG Zhi-Kang, WANG Lian-Guo, DAN Ren-Liang，et al

2012, 29(1): 33-37.

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To solve the technological problems of deep roadway support，in view of the specific geological and technical conditions in dip roadway of No.10 District in Caocun Coal Mine，the in-situ stress was measured，and the roadway support form and parameters under dynamic pressure were designed and optimized with the use of roadway support expert system software．Then，the new support system of high resistant and yielding property was established，which uses the high-strength yielding bolt and ribbed anchor as core，and the underground industrial tests and ground pressure monitoring were carried out．The results show that the support system with high-strength yielding bolt and ribbed anchor，which is based on the in-situ stress measurement，can increase the overall capacity of support structure，and control the deformation of surrounding rock effectively．Thus，the intended effect of support design is reached，which ensures the stability and normal use of the deep roadway under dynamic pressure．

Key Construction Technology of Vertical Feeding Bore Hole for Solid Materials in Backfilling Coal Mining

Ju-Feng, ZHANG Ji-Xiong, AN Bai-Fu

2012, 29(1): 38-43.

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To increase the construction speed and hole quality of vertical feeding bore hole for solid materials in backfilling coal mining，based on analyzing the structure characteristcis of vertical feeding system，we analyzed the technological difficulties in drilling of vertical feeding system，and studied a set of construction techniques including the job practice，the pipeline installation，the method of inclination surveyor，et al．The results show that when using the technology which covers multistage drilling and chambering method，heavy crane or frame crane and float panel sinking method，and a variety of lateral deformation methods，the construction quality of vertical feeding system can be guaranteed．The technology has been successfully applied to a coal mine in China，while the bore hole driving speed can be reached to about 6 m/d，and the verticality is 1‰．

Simulation Experiment of Embedded Fiber Bragg Grating Monitoring in Rock Deformation Through Borehole

CHAI Jing, QIU Biao, LI Yi, ZHU Lei

2012, 29(1): 44-47.

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To explore the rock deformation in coal mine by the monitoring of embedded fiber Bragg grating (FBG) through deep borehole，an experimental physical simulation model was built for simulating the strata compression and subsidence process．Additionally，a prefabricate concrete bar with three embedded FBG sensors was designed to simulate deep borehole，and was placed in the physical model．The deformation of the prefabricate concrete bar during strata compression and subsidence processes was measured by the wavelength changes of FBG sensors，and was compared to the strain changes monitored by a resistance strain gauge located on the prefabricate concrete bar at the same location．The test results show that the FBG monitoring system has the advantages of high sensitive，reliable and stable，etc，and can realize the real-time monitoring of rock deformation. It is proved that the FBG monitoring system is an efficient method for measuring and understanding deformation of deep rock strata through a surface borehole．

Research on Creep Supporting Effect of Deep Strip Pillar

CHEN Shao-Jie, GUO Wei-Jia, CHENG Guo-Qiang，et al

2012, 29(1): 48-53.

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To study the creep supporting effect of deep strip pillar，the creep test of upper No.3 coal seam in Daizhuang Coal Mine is carried out．Based on the experiment results，the creep supporting effect of deep coal pillar was analyzed by using LS-DYNA software．The results show that the circumferential initial creep stress of the coal/rock sample is 3.061 MPa，which is far below the axial initial creep stress of 7.020 MPa．In addition，the creep strength and creep coefficient are 9.327 MPa and 0.647，respectively．Combined with the test results，the creep supporting effect of deep strip pillar can be simulated excellently by LS-DYNA software．The stress and deformation in simulated strip pillar show evident rheological properties．The situation of the pillar still changes greatly after the extraction of coal face．Under the effect of the overlying strata，the deformation of coal pillar is unchanged after15 ~ 16 months，and can keep stability for a long time.

Reasonable Width Calculation and Analysis of Artificial Pillar in Deep Mining

WANG Xiao-Jun, FENG Xiao, YANG Tao-Bo, ZHAO Kang, ZHAO Kui

2012, 29(1): 54-59.

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To design the geometric parameters of artificial pillar for deep mining，a new formula is developed to calculate the reasonable width of artificial pillar．Considering high-stress and large-disturbance in deep mining，the bearing mechanism of artificial pillar is clarified based on P’s theory．Through deduced formulas，mining span and mining depth are determined as the main factors affecting the reasonable width of artificial pillar，and the influence degrees of the factors are also calculated．The results indicate that the influence of mining span on the width of artificial pillar is greater than that of mining depth．The reasonable width of artificial pillar is calculated for deep mining in accordance with the engineering practice of one gold mine，and the rationality of formula and the influence degree of key factors are validated through field test．

Deformation Monitoring and Optimal Control During Chamber Construction in Broken Station of Jinchuan No.3 Mine

LIU Zeng-Hui, GAO Qian, YAO Wei-Xin, JIN Xue-Qi

2012, 29(1): 60-66.

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To effectively control the deformation of rocks in the large section chamber of broken station in Jinchuan No.3 Mine，we monitored the deformation of surrounding rocks and analyzed the factors affecting such deformation，indicating that the rock mass is characterized by a low critical creep stress，a broken sheardilatation creep，and a long duration of deformation．Aiming at these deformation characteristics，we adopt the principle of “yield through leaving space and strengthening support” and put forward a comprehensive evaluation index．We also proposed an orthogonal numerical simulation test program among the three factors，designed four levels through the comprehensive evaluation index analysis，and determined a reasonable amount of yield displacement in which the gross distortion of the chamber is 90 mm，the initial lining to yield deformation is 0，and the twain support to yield deformation is 50 mm．For the safety assessment and the long term stability prediction of broken surrounding rocks，we use FBG sensors to monitor the rock deformation．

Experimental Study on the Correlation Between Stress and P-Wave Velocity for Burst Tendency Coal-Rock Samples

GONG Si-Yuan, DOU Lin-Ming, XU Xiao-Ju,et al

2012, 29(1): 67-71.

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To explore the mechanism of rockburst，we established the experimental model between stress and P-wave velocity for burst tendency coal and rock samples from deep coal mine under the uniaxial loadings，and analyzed the parameters of the derived model．The results show that：1) the P wave velocity in rock sample changes more sensitively than that in coal sample under loadings，which means the P wave velocity in rock sample changes more quicker with the increase of stress；2) the velocity gradient of the sample is usually high at the elastic stage and then begins to level out at the plastic stage under the uniaxial loading，which shows that a power function is exist between the P-wave velocity and stress．The calculated correlation coefficients to measured value show that the experimental model has high fitness，and can be well used to describe the stress distribution and identify the risk level of rockburst in mines．

Studies on Establishment and Application of Microseismic Monitoring System in Hongtoushan Copper Mine

LIU Jian-Po, SHI Chang-Yan, LI Yuan-Hui,et al

2012, 29(1): 72-77.

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In this paper，in view of the serious conditions of ground pressure (rock burst，etc) appeared in Hongtoushan copper mine，we established a microseismic monitoring system in the mine，and analyzed the relationship between the microseismic activities and mining operation，and the spatial distribution of microseismic events，applied the energy index and apparent volume to forecast the occurrence of large scale rock fracturing．The location results using manual fixed-point blasting show that the location error of microseismic monitoring system is less than 10m，which suggests that the system can reach the requirement for ground pressure disaster monitoring in mine．Microseismic activities can be divided into two quiet periods and three active periods．There exits the incubation and early-warming periods before the large scale rock fracturing．The quick drop of energy index and the continuous increase of apparent volume can be used as the precursory characteristics of rock burst and large scale rock fracturing．Through the cloud charts of energy index and displacement，the potential danger areas of ground pressure disasters can be judged，which can be used to guide the safety management and ensure safety production in deep mine．

Study on Rock Burst Forecasting Prediction in A Deep Mine

LIU Xiao-Hui, WU Ai-Xiang, WANG Chun-Lai,et al

2012, 29(1): 78-83.

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In this paper，according to the microseismic monitoring information in a deep mine，the principle of seismology was adopted to make a quantization calculation of microseismic parameters，combined with the rock burst records in underground，the response pattern between the ground pressure activities and temporal-spatial variation of microseismic parameters was further studied．The results show that the spatial variation of microseismic parameters in a time domain reflects the stress distribution in rock mass，which can provide basis to identify the rock burst danger areas．The temporal variation of parameters in a certain area is closely related with the rock failure process，and the abnormal changes of microseismic parameters with time such as sharp increasing，quickly decreasing can characterize the different deformation stages of rock mass．Based on the research results，the point at which the seismic hardening process of rock mass ends and the strain softening process begins can be used as the pre-warning point of rock burst．Finally，a general prediction model for rock burst in the mine is constructed，and has shown good effects in practice，which also provides reference significance for rock burst prediction in similar mines．

Numerical Modeling of Rock Fracture Mechanism Under Disc Cutters and Associated Cutter Spacing Optimization

LIANG Zheng-Zhao, YU Yue, TANG Shi-Bin, LIU Hong-Yuan, TANG Chun-An

2012, 29(1): 84-89.

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In this paper，a numerical code of RFPA was applied to simulate the rock fracture mechanism under disc cutters of TBM．The fracture processes of rock specimens with confining pressure subjected to a single cutter，double cutters and three cutters were investigated respectively，and the cutter spacing was optimized under the action of multi-cutters．The results show that the whole fracture process under the action of single cutter has four stages: powder formation，crack nucleation，side crack initiation and propagation，and chip formation，and the rock fracture is dominated by tensile stress，accompanied by shear stress and compressive stress，etc．Under the confining pressure，the cracks parallel to confining pressure are easier to initiation and propagation，and more beneficial to the coalescence of side crack．Moreover，obvious synergistic effect is found between the neighboring cutters，and with the increase of cutter spacing，the specific energy consumed to rock fracturing increases in the beginning stages，and will decrease，when the spacing is beyond a critical value．The simulation results agree well with experimental ones，and will be beneficial to TBM design and disc cutter arrangement.

Research on Overlying Strata and Surface Movement Rule in Repeated Mining

LUAN Yuan-Zhong, LI Jing-Tao, LIU Na, LIU Yang, LUAN Heng-Xuan, MA De-Peng

2012, 29(1): 90-94.

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In view of the problems of repeated mining in both the upper and lower No.3 coal seams in one mine under the Weishan Lake，Shandong Province，we measured the ground movement and deformation values of lake area with GPS-RTK technology，monitored the heights of water flowing fractured zone in the mining of both upper and lower No.3 coal seams using the technology of double-head water-stopped machine of upward drill holes under the well，and established the fitted function of surface subsidence and horizontal movement．Moreover，the functional equation of intermediate layer and strata movement boundary in the repeated mining of upper and lower No.3 seams was set up by use of FLAC3D，which reveals the characteristics of surface movement and strata deformation in repeated mining of upper and lower No.3 seams in south Shandong mining area．The study is significant for the safety mining under water，and has a certain reference value for the mining areas with the similar geological and mining conditions．

Rock Expansion Boundary Anti-Permeability Strength and Its Application in the Coal Mine Floor Water Inrush Evaluation

DUAN Hong-Fei, JIANG Zhen-Quan, WANG Yi-Dong

2012, 29(1): 95-100.

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To solve the difficulties in coal mine floor water inrush evaluation，on the basis of the servo-controlled permeability test of rock in the complete stress-strain process，we proposed the concept of rock expansion boundary anti-permeability strength，and established a theoretical evaluation model of floor water inrush．In the model，several factors，such as the floor aquifuge effective thickness，lithology，rock mass integrity，and expansion boundary anti-permeability strength were considered，and the taking values of all factors were described in detail．Taking the No.17 coal seam and 2702 working face in Yangcun coal mine，Yanzhou mining group as an example，it proves that the evaluation model based on the expansive boundary anti-permeability strength is feasible to evaluate the coal mine floor water inrush．

Determination on Reasonable Malposition of Combined Mining in Close-Distance Coal Seams

YANG Wei, LIU Chang-You, HUANG Bing-Xiang

2012, 29(1): 101-105.

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Under the condition of combined mining in close-distance coal seams in Shigejie coal mine，to avoid the influence of roof periodic weighting on the lower coal seam during the mining process of upper seam，or the interaction of synchronized weightings between the upper and lower seams，we gives the selective method of determining the reasonable malposition in combined mining in this paper，by using the theories of semi-infinite elastic and underground pressure，and the field measurement data．The results show that：1) firstly，the malposition distance can be determined initially according to the mine geology and physical mechanical properties；2) then，the malposition should be modified after the theoretical analysis or field measurement of stress distribution zone between layers；3) finally，the reasonable malposition is determined ultimately by the examination of the field practice．According to the analysis results，selecting the sum of initial malposition and horizontal range value of the main stress effect zone between layers as the reasonable malposition distance in close-distance coal seams，can make the lower seam avoid bearing the continuous high stress from the upper seam．

Research on Dynamic Characteristics of Hydraulic Fracturing in Coal Body Containing Gas

LIN Bai-Quan, MENG Jie, NING Jun

2012, 29(1): 106-110.

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To study the hydraulic fracturing mechanism and its dynamic characteristics，taking 12th mine of Pingdingshan Coal Group as example，a related mathematic model was built，and the dynamic characteristics of fracture initiation and extension were gained in the progress of hydraulic fracturing by numerical simulation and field test，which is described as: stress cumulating →micro-cracks steadily developing →partially destroyed area forming →partially destroyed area extension and coalescence →cracks unsteadily developing．Combined with the analysis of onsite measured data and influencing factors of hydraulic fracturing dynamic changes of coal body containing gas，the coupling model which is composed of coal seam depth，gas pressure and hydraulic fracturing pressure is fitted．The results have an important significance to the field practice．

Gas Extraction Optimum Design of Layer-Through Borehole in Adjacent Seam Based on CFD Simulation

QIN Wei, XU Jia-Lin, WU Ren-Lun, HU Guo-Zhong, WANG Zhong-Wei, TIAN Gen-Wan

2012, 29(1): 111-117.

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Taking the fully mechanized caving face 15101 in Xindadi coal mine，Shanxi province as the research object，we have studied the strata movement rules of the face and the characteristics of pressure-relief gas drainage in adjacent seam，determined the arrangement principle of layer-through boreholes in face 15101．In addition，6 optimization schemes were proposed，and the associated numerical simulations were conducted by using FLUENT．According to simulation results，the optimal arrangement parameters of layer-through boreholes in adjacent seam were determined finally．The results show that the vertical height of final hole to the floor of 15# coal seam is 50 m，and the horizontal distance of final hole is 20 m deep into the face．After the parameter optimization，the gas extraction of adjacent seam in face 15101 has obtained a favorable effect，and the average gas extraction quantity is up to 51.8 m3/min．

Effect of Igneous Intrusion on Adsorption Characteristics of Coal to Gas

JIANG Jing-Yu, CHENG Yuan-Ping, WANG Hai-Feng,et al

2012, 29(1): 118-123.

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In this paper，to study the effect of igneous intrusion on adsorption characteristics of coal to gas，taking 11 samples of No.10 coal seam in Wolonghu coalfield as research object，we compares and analyzes the relationship between the multivariate physical properties of coals and the distances from coal samples to igneous rocks，by synthetically using the methods of industrial analysis，CH4 isothermal adsorption experiments，BET surface area calculated by liquid nitrogen adsorption method，and micro-pores measured by CO2 adsorption method．The results show that the thermal evolution area of magmatic is about 60 m．When approaching the igneous rocks，the vitrinite reflectance (Rm) increases from 2.74% to 5.03%，the volatile matter decreases from 16.04% to 6.85%，and the metamorphic grade of coal increases．Meanwhile，the adsorption constant (a) increases first and then decreases，while the maximal adsorption constant (No.8 coal sample in thermal evolution area) is 59.02 m3/t，and the minimal value (No.1 sample in magmatic covering area) is 13.53 m3/t．In addition，there is good relativity among the distribution curves of adsorption constant，BET surface area，and micro-pore volume．Furthermore，the numerical values in thermal evolution area are higher than that in normal area，while the values in normal area are higher than that in magmatic covering area．Moreover，the adsorption ability of coal to gas is reduced because of the contact metamorphism of magmatic，however，duo to the igneous intrusion，the micro-pores of coal samples in thermal evolution area are more development，BET surface area is more larger，gas adsorption positions increase，and the adsorption ability of coal to gas is enhanced．

Numerical Simulation of Tail Roadway Change to Gas Flow Field in Goaf

WANG Kai, JIANG Shu-Guang, ZHANG Wei-Qing

2012, 29(1): 124-130.

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To study the influence of tail roadway configuration to the gas flow field in goaf，we established the mathematical-physical model of working face and goaf with tail roadway according to the roadway layout in N1-2 Face．Combined with the influence of periodic weighting on the porosity of falling objects in goaf，we analyzed the step change of porosity according to the step of periodic weighting，and calculated the size of the segment permeability reasonably．Meanwhile，according to percolation theory of the gas flow in porous media，we compared the simulation results of three turbulence models in FLUENT to the measured results，and selected the Realizable k-ε model to simulate the air leakage field and gas concentration field under different conditions．The simulation results and field effects shows that when comparing the distribution simulation results of gas field with the measured gas concentration under the conditions of uniform penetration and sub-permeability respectively，the simulation results of sub-permeability are closer to the measured values．Influenced by the changes of gas concentration gradient and permeability in goaf，the greater the air flow distribution，the smaller the air leakage on the upper corner of tail roadway，and the smaller the step distance of tail roadway，the lower the gas concentration around the face．Comprehensively considered the amount of construction on tail roadway and the air volume distribution on air-return way，the best effect can be achieved when the step distance of tail roadway is 50 m and the air volume takes up 2/3 of the total intake airflow．Combined with the factors of step distance of tail roadway，distribution and regulation of air volume，periodic weightings，et al，a comprehensive measure has been developed to improve the utilization of the tail roadway，which has effectively solved the fluctuation and overrun situation of gas in upper corner and air-return way of fully mechanized caving face with tail roadway configuration．

The Relationship Between ‘U+I’ Ventilation System of Fully Mechanized Top Coal Caving Face and Coal Spontaneous Combustion

ZHOU Fu-Bao, LIU Yu-Sheng, LIU Ying-Ke

2012, 29(1): 131-134.

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In this paper，the ‘U+I’ ventilation system’s characteristics of fully mechanized top coal caving face have been analyzed and the air distribution formula of each roadway deduced．In addition，gas drainage efficiency of the ‘U+I’ ventilation system was investigated when the elevated lane was both blocked and unobstructed．And more specifically，the differences of the oxygen concentration field in the goaf caused by the elevated lane’s state of the ‘U+I’ ventilation system were studied with numerical simulation method and by combining the mine fire case dated April 8，2005 at the working face 5344 of Wulan Coal Mine，Shenhua-Ningxia Coal Industry Group．The research shows that if the elevated lane is blocked，the gas drainage efficiency would become lower and gas concentration at upper corner of working face would become higher．Besides，the oxidization and heat accumulation zone would be expected to be larger than before and nearer to the working face in the exhaust section．The results achieved may serve as a guidance to solve gas overrunning problem at work face and prevent coal spontaneous combustion in the goaf．

Prediction Model of Gas Concentration Around Working Face Using Multivariate Time Series

DONG Ding-Wen, LI Shu-Gang, CHANG Xin-Tan,et al

2012, 29(1): 135-139.

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For the purpose to achieve more accurate prediction of gas concentration around working face through effective analysis of gas measuring data in mines，based on Bayesian network method，chaotic phase space reconstructive technology，and Gaussian process regression model，we studied the prediction method for gas concentration by time series analysis in this paper．By applying Bayesian network method，the sample data sets which have strong relative features with gas concentration around face in time series were extracted to construct the prediction model of multivariate time series．Additionally，the sample space of gas concentration in multivariate time series was reconstructed by using chaotic phase space reconstructive technology．Furthermore，the gas concentration prediction around the face was carried out by using Gaussian process regression model，namely，the prediction values and the corresponding confidence intervals were used to describe the dynamic variation of gas concentration around the face．The case study shows that the prediction results of this method have much higher accuracy than that of univariate method，and the prediction interval is optimal in the same confidence level，which means it can better reflect the dynamic variation of gas concentration around the working face．

Research on the Influence of Airway Sensitivity on the Airflow Stability of Mine Ventilation System

JIA Ting-Gui, WANG Shu-Gang, QU Guo-Na,et al

2012, 29(1): 140-143.

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To definite the high sensitive airway which affects the airflow stability of main airway and stable operation of main fan in mine ventilation system，the multiple regression analysis method is applied to recognize the high sensitive airway in mine ventilation network，while the optimum regression equation between the air quantity (Qj) of main airway and independent value of ventilation resistance (Ri) in each airway is established，and the results are verified by network calculation．The comparison shows that the multiple regression results are consistent well with the test results，which means the airway sensitivity is an embodiment of the structure property of ventilation network，and is independent of the airflow resistance．Meanwhile，the change of high sensitive airway is the key to affect the airflow stability in mine ventilation system．Moreover，using the multiple regression analysis can avoid the difficulties in derivation of airflow directional discriminant in the traditional diagonal structure analysis，and can give qualitative analysis and evaluation on the airflow stabilities of other airways in mine．

Reconstruction of Gas Distribution Field in Working Face Based on Measured Data

DONG Hai-Bo, TONG Min-Ming, ZHANG Li-ping,et al

2012, 29(1): 144-150.

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To study the gas distribution law，find the gas accumulation location and prevent gas outburst in stope，we studied a reconstruction technology of gas distribution field in a woking face．By analyzing the gas concentration distribution in the coal face，the expansion principles on the measurement data of gas concentration were given．Meanwhile，three interpolation methods for the reconstruction of gas distribution field were compared，where the bicubic interpolation method can better reflect the gas distribution in the face．Hereby，a field reconstruction method of the bicubic extrapolation data based on binomial fitting of least-squares was presented．Finally，the influence of reducing measuring points on the reconstruction field of gas distribution was discussed，and then the installation principle of the gas monitor was given to reconstruct the gas distribution field better．The results show that this reconstruction method can present an accurate distribution of gas distribution in stope，and is also reliable when the measurement data is reduced．

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