Table of Content

15 July 2012, Volume 29 Issue 4

Previous Issue    Next Issue

Large Deformation Mechanism of Roadway Driving Along Goaf under Unstable Overlying Rock Strata

ZHANG Yuan, WAN Zhi-Jun, LI Fu-Chen

2012, 29(4):  451-458. 

Asbtract ( 5963 )   PDF (618KB) ( 4498 )  

Related Articles | Metrics

In order to grasp the large deformation mechanism of roadway driving along goaf under unstable overlying rock strata, the digital panoramic borehole camera system was adopted to observe the roof rock strata of the roadway driving along goaf. Count Fracture Numbers in a Basic Measuring Scale Method was proposed to undertake borehole fracture statistical analysis. According to the method, the fractures in the roof of the roadway driving along goaf were statistically analyzed; fractures distribution as well as the evolution law was also investigated. Observation results indicate that longitudinal fractures and transverse fractures are two major fracture forms in roof rock strata. As for the distribution, the longitudinal fractures are mainly found on the top of the roof strata in the roadway, while the transverse fractures distribute in the bottom of the roof strata along goaf. As the stabilization time of the overlying strata of the goaf went by, the longitudinal fractures gradually evolved into fracture zone, and the transverse fractures evolved into roof separation zone and radial dislocation. When the two forms of fracture cross together, a wide range of abnormal fracture zone would come into being very easily. The field observation confirms that the primary causes of the overlying strata deformation of the roadway driving along goaf are the fracture of the main roof, the rotating of the key block and its sinking and slippage. Therefore, in order to control the rotating and slippage of the key block after the fracture of the main roof will be a fundamental method to control the deformation of the roadway driving along goaf.

Stress distribution of coal pillar with gob-side entry driving in the process of excavation & mining

ZHENG Xi-Gui, YAO Zhi-Gang, ZHANG Nong

2012, 29(4):  459-465. 

Asbtract ( 7420 )   PDF (676KB) ( 5587 )  

Related Articles | Metrics

The stress distribution of coal pillar with different width in the stage of excavation and mining was studied based on the theory analysis, numerical simulation, engineering practice, the similarities and differences of stress evolution of coal pillar and entity sidewall caused by different width of coal pillar was analyzed. The opinion was put forward that the infection of roadway driving and coal mining need considered simultaneously when determination the reasonable width for coal pillar. The results show that the proper width of coal pillar should large than six meters for the deformation is attenuation with the increased with of coal pillar. However, the increased width coal pillar such as eight meters not only have reduced contribution ratio to control the sidewall deformation in the stage of coal mining, but also caused top and floor deformation increased. Therefore, the reasonable width of coal pillar is eight meters.

Strata Behavior and Control Countermeasures for the Gob-Side Entry Retaining in the Condition of Large Mining Height

XUE Jun-Hua, HAN Chang-Liang

2012, 29(4):  466-473. 

Asbtract ( 5540 )   PDF (594KB) ( 4236 )  

Related Articles | Metrics

Combined with the production conditions of 24207 working face in Shaqu mine, distribution characteristics of roofs stress for gob-side entry retaining influenced by mining height was studied by the method of theoretical analysis and numerical simulation. Gob-side entry retaining is in the area of stress decreasing zone of bearing pressure area. The impact scope and range to the rock gets more widely with the increase of mining height of working face. Acute deformation will occur during the mining period for gob-side entry retaining, and the contraction of area will reach to 55.3% in the condition of large mining height. Effective supporting measures are required according to the deformation characteristics of each side in gob-side entry retaining. The optimal cross-height ratio and the high strength supporting system with the core of high pre-stress could be helpful to control the deformation of surrounding rock reasonably. The observation data shows that the violent mining influence extent to gob-side entry retaining is the ranges from working face to the rear of 200 m, which is similar to the length of working face in the industrial experiment. The deformation continues to grow and roof pressure continues to increase until the length extents 250 m the strata behaviors tends to stable.

Application of Support Technology With High Strength and High Pretension Stress for Weak-Broken Rocks

WANG Hong-Wei, JIANG Yao-Dong, ZHAO Yi-Xin

2012, 29(4):  474-480. 

Asbtract ( 4655 )   PDF (523KB) ( 3850 )  

Related Articles | Metrics

Due to high stress and low rock strength environment, the support of weak-broken rocks under the condition of deep mining should be solved through strengthening broken rock, reinforcing support resistance and decreasing the mine-induced stress. For the purpose of permanent support for the weak-broken rocks, this study has pointed out the support technology with high strength and high pre-tension stress which is based on the bolt-wire-shotcrete system combined with steel arched yielding support. This kind of support technology have combined the each support element and adequately taken advantage of load-caring capacity of surrounding rocks. Based on the monitoring data of Xiaokang coal mine and Muchengjian coal mine, the characters of weak-broken rocks and the features of the support technology with high strength and high pretension stress were analyzed. The results of field tests indicate that the support technology with high strength and high pretension stress has provided powerful support force to resist large deformation of weak-broken surrounding rocks for the various geological conditions. It is proved that the mine-induced stress can also be released by the support technology and the support technology with high strength and high pretension stress has economical significance.

Research on Deformation Failure Characteristics of the Deep High-stress Soft Rock Roadways

MENG Qing-Bin, HAN Li-Jun, QIAO Wei-Guo

2012, 29(4):  481-486. 

Asbtract ( 4845 )   PDF (561KB) ( 4270 )  

Related Articles | Metrics

Based on the engineering background of Tangkou Mine, affiliated to Jibei Mining Area, the basic geological characteristics of the deep high-stress soft roadway are illustrated on the basis of geological mechanical test. According to the visco-elastic analysis of the Burgers model on deep high-stress soft rock roadway, the expressions of surface displacement and displacement rate of surrounding rock in deep high-stress soft rock roadway are obtained, and the curves of surface displacement and displacement rate of surrounding rock in deep high-stress soft rock roadway under the different geo-stresses, elastic modules and viscosity coefficients are achieved. FLAC3D is used to simulate the rheological cha-racteristics, analyzing the deformation features of the roof, floor and two-sides of the surrounding rock under high-stress.

Large-size Test on Creep Characteristics of Filling Body beside Roadway for High Water Material

SUN Chun-Dong, ZHANG Dong-Sheng, WANG Xu-Feng

2012, 29(4):  487-491. 

Asbtract ( 4977 )   PDF (492KB) ( 3733 )  

Related Articles | Metrics

Aiming to the creep characteristics of the high-water material for filling body beside roadway, we conducted several experiments by means of a self-developed large-size test system (1500 mm×600 mm×900 mm) and numerical simulation software FLAC3D. The characteristics of the deformation and the stress of the filling body sample changing over the time were analyzed during the creep process which could be divided into three stages, instant, stable and accelerating, i.e., the limit loading of the filling body increases with the reduction of water-concrete ratio for the high-water material. Due to the great deformation speed during the accelerating creep stage, the filling body should stay at the instant creep stage for long-term stability. Generally, we believe that the appropriate loading on the filling body is not less than 70%~80% of its strength.

Experimental Study on the Sandy Mudstone Mechanical Properties of Shaft Sidewalls under the Frozen Conditions

YANG Geng-She, 吕Xiao-Tao

2012, 29(4):  492-496. 

Asbtract ( 4137 )   PDF (421KB) ( 3278 )  

Related Articles | Metrics

Freezing method is an effective construction method to pass through the thickest alluvium in coal mine shaft construction. It is more necessary to study the mechanical properties in order to provide reasonable design parameters for shaft frozen sidewalls. Taking the frozen shaft project of Hujia River coal mine in Shaanxi Bingchang coal mine area as the project background, sandy mudstone of passing through the key shaft were obtained from the engineering site, the uni-axial compression tests and tri-axial compression tests were conducted under different frozen temperatures. The strength and deformation characteristics of sandy mudstone were analyzed of the same temperatures under the condition of different confining pressures and the same confining pressure in the condition of different temperatures. The result shows that the uni-axial strength and tri-axial strength of sandy mudstone increases with the freezing temperatures dropping. The main reason is mainly due to the peak intensity of sandy mudstone greatly improved by mineral contraction, ice strength and frost heave force with temperature decreasing.

Experimental Research on the Failure Characteristics of Surrounding Rock Under high Ground Stress of λ<1 State

LUO Feng, YANG Ben-Sheng, SUN Li-Hui

2012, 29(4):  497-504. 

Asbtract ( 5976 )   PDF (1151KB) ( 4223 )  

Related Articles | Metrics

By using independent researched and developed CM60/10 plane strain test-bed, combining with the triaxial servo test machine which playing the servo regulator performance, utilizing similar material simulation and numerical simulation, the characteristics of deformation and failure process of roadways with no support under high stress of  <1 state was analyzed. The results show that: 1) The destruction develops first from the center line of both sidewalls of roadway, after the local failure, there gradually formed a pair of “wedge” failure zone. In the stress relief area, surrounding rocks are destroyed in the form of zonal disintegration. Deep slip-line takes place from the tip point of the “wedge” destruction zone, which conforms to the logarithmic spiral line roughly; 2) In the process of roadway destruction, it is followed successively by three partitions of “wedge-shaped destruction zone,” “second destruction zone,” “transfixion instability zone”. The related studys show that during the different deformation period in this kind of ground stress, the failure control should focus on the sidewalls, the skewback and the roof except the control of the initial deformation of roof and floor; 3) Through the numerical simulation of the rock mass failure in  <1 state, the following results can be found: the vertical stress of the sidewalls is the “wave-like” distribution; the plastic damage zone is “partition evolution”; the vertical displacement is “jaggies-like” distribution. All of these are consistent with the physical experiments.

Coupled Thermal-Hydrological-Mechanical Analysis of Exploiting Coal Methane by Heat Injection

ZHANG Feng-Jie, WU Yu, MAO Xian-Biao

2012, 29(4):  505-510. 

Asbtract ( 4908 )   PDF (457KB) ( 3832 )  

Related Articles | Metrics

Improving coal methane production  is an important subject in the current research for coal methane exploration.Some researches show that, coal methane exist mainly as adsorption state in coal seam pores.Improving coal seam temperature can make gas change into free forms from adsorption forms,and improve its seepage-diffusion ability. According to the thermoelasticity, nonlinear Darcy seepage theory and porous medium thermodynamics principle, this paper studied the mechanism of improving coal methane production by heat injection. The multiphysical coupling equations were been established, including coal deformation equation,gas percolation equation and heat transfer equation. By means of COMSOL numerical software ,the numerical solution of coupling model was been proceeded .The results demonstrated that rising injecting heat could promote desorption of coal methane, improve the permeability, achieve the purpose of improving coal methane production. The research results could provide corresponding theoretical basis for engineering practices of exploiting coal methane by heat injection.

Study on Correlation among Point Load Strength, Compression and Tensile Strength of Coal Samples

SU Cheng-Dong, TANG Xu, NI Xiao-Ming

2012, 29(4):  511-515. 

Asbtract ( 6555 )   PDF (479KB) ( 4521 )  

Related Articles | Metrics

A series of uniaxial compression test, Brazilian test, crushing compression test and point load test on coal samples from Zhangcun mine 3# coal seam were carried out. The results show that the dispersion degree increases by the following order: Brazilian test, uniaxial compression test, and point load test. After the irregular samples compared to the regular samples，the dispersion degree of point load test is obviously too large. Among all those regular samples, the point load strengths are roughly the same by parallel bedding and vertical bedding loading methods. There is a correlation among the Protodyakonov's coefficient, uniaxial compression strength, tensile strength and point load strength of the coal samples, which could obtains relevant parameters by their interconversion, and the conversion strength can be used as a reference of coal classification strength index.

Visualization of Micro-Seismic Data Based on Mining Maps

MIAO Hua-Xiang, JIANG Fu-Xing, SONG Xue-Juan

2012, 29(4):  516-521. 

Asbtract ( 3413 )   PDF (596KB) ( 2535 )  

Related Articles | Metrics

For the micro-seismic monitoring results and can present the dynamical process of strata fracturing, the method of synthesizing the micro-seismic monitoring results into mining maps was researched. The digitized mining maps , the micro-seismic monitoring results and accident data are respectively transformed into global, working face and fixed working face coordinate systems and are jointly processed. The processed results are visualized simultaneously by overlaying on each other in the time-spatial domains. All proposed techniques have been packed into a single software package for the optimized platform. This package enables us to visualize in real-time easily and efficiently and interpret monitoring results. The package has been deployed in several mining sites and highly evaluated. There-fore, it can be widely applied in coal mining.

Similar Simulation for Pressure Relief and Shock Absorption Mechanism in Rock-burst Danger Area

WU Xiang-Qian, DOU Lin-Ming, LU Cai-Ping

2012, 29(4):  522-526. 

Asbtract ( 2764 )   PDF (394KB) ( 2279 )  

Related Articles | Metrics

In order to improve the safety and efficiency while mining in coal seams with rock-burst tendency, the protective mining mechanism with pressure relief and shock absorption effect has been studied. Based on the analog simulation theory, the experiment on mining protective seam has been carried out according to the geological and mining conditions in No.12 Mining District of Jining No.3 Coal Mine. The results show that protective mining can weaken the stress concentration and energy accumulation of protected coal seam. The goaf of protective coal seam can form a kind of loosened-broken- weak structure, which can absorb seismic source energy of roof so that the down coal seam is protected. The collapsed coal seam will swell to the goaf of protective coal seam so that the protective area is formed. After the caving and compacting of protective coal seam, the deformation and break of protected coal seam is slowed down. The results of this study will provide theoretical basis and practical value for reasonable design and safety mining of coal seams with rock burst propensity.

Prediction Method for Rockburst Tendency Based on Rough Sets and Genetic Algorithm

LI Ya-Li

2012, 29(4):  527-533. 

Asbtract ( 2505 )   PDF (522KB) ( 2321 )  

Related Articles | Metrics

A new method based on rough sets and genetic algorithm was presented to predict the rockburst tendency in this paper. Taking the rockburst tendency of working face of the stope for example, the influencing factors of rockburst tendency were taken as the condition attributes, and the result of rockburst tendency of working face was taken as the decision attribute. The engineering data were chosen to make up the sample set. The sample set was randomly divided into two parts. One was the training sample set, and the other was the testing sample set. The attribute values of the two sets were quantified respectively, and then the decision tables of the training and testing samples were set up. Genetic algorithm was used to reduce the decision table of the training samples. Rough sets were used to extract the decision rules of rockburst tendency from the reduction results. Then the rockburst tendency of the testing samples were predicted by these decision rules. The results show that the predicted results agree well with the actual ones, which proves that the method is effective and available and can be applied to predict the rockburst tendency in actual engineering.

Application of Similar VCR Method in Caving Engineering of Metal Mine

CHEN Xian-Feng, ZHONG Yong-Xiao, WANG Ya-Ping

2012, 29(4):  534-537. 

Asbtract ( 3248 )   PDF (578KB) ( 2299 )  

Related Articles | Metrics

West mining area of Rongguan mining will switch to pillarless sublevel caving method in mine recovery under ▽1 158 level. In order to ensure the smooth progress of projects, the 6 gobs in ▽1 158 level should be eliminated and to form covers. According to typical gob, using ANSYS software to analysis the stability of gobs, combining with spot conditions we propose the similar VCR method. Drawing on experiences in handing previous goaf, detonate explosive depending on designed blasting parameters. The results show that similar VCR method is sensible and successful.

Roof Stability Analysis of Sublevel Open Stope and Caving Mining Method

ZHOU Zong-Hong, HOU Ke-Peng, REN Feng-Yu

2012, 29(4):  538-542. 

Asbtract ( 3811 )   PDF (449KB) ( 2684 )  

Related Articles | Metrics

The hanging wall and footwall of the ⅪV1 main ore body are unstable in Fengzishan lead-zinc deposit. The improved sublevel open stope and caving method was tested. Using three-dimensional finite element, the stability analysis of protective pillar and insulating pillar was presented. The distribution of stress, safety rate and plastic zone was analyzed, and the reasonable stope structural parameters were optimized in the four schemes. The results indicate that the thickness of protective layer has a significant influence on the roof stability, which improves with the increase of stope span during the room stoping. In addition, the roof stability decreases with the increase of stope span. It can effectively ensure the stope stability to select the suitable protective layer thickness and to control the stope span. The results can provide theoretical basis for the mining design and strata control.

Numerical Simulation for Determining the Safe Roof Thickness and Critical Goaf Span

ZHANG Min-Si, ZHU Wan-Cheng, HOU Zhao-Song

2012, 29(4):  543-548. 

Asbtract ( 8300 )   PDF (537KB) ( 5063 )  

Related Articles | Metrics

In order to determine the relationship between goaf roof thickness and critical span, an iron ore goaf is taken as an engineering instance. The rock mass mechanical parameters are obtained from the mechanical experiments of rock specimens sampled in situ. The relationship between the safe roof thickness and the critical goaf span is determinined according to K. B. Lu Peinie equation, ratio of thickness and span equation, structure mechanics of girder and plate beam equation. Meanwhile, the damage and failure process of goaf roof is simulated by RFPA numerical simulation program. The relationship between the safe roof thickness and the critical goaf span is determined, respectively, when the initial damage and instability of goaf roof are adopted as the criteria. The values predicted with K. B. Lu Peinie equation are most close to the numerical ones when the damage of roof begians. The ratio between them can be considered as a safety factor obtained from the numerical simulations. As it shows, it is kept a large safety factor by the critical roof thickness which is calculated by K. B. Lu Peinie equation. The numerical simulation with RFPA could obtain this safety factor, and it may have more extensive applicability.

Assessment of Water Environmental Status in Subsided Water Area of Coal Mine and Its Comprehensive Utilization

XU Liang-Ji, YAN Jia-Ping

2012, 29(4):  549-554. 

Asbtract ( 4705 )   PDF (416KB) ( 3366 )  

Related Articles | Metrics

In this paper, to accurate assess the water quality in subsided water area of coal mine, the methods of principal component analysis and fuzzy comprehensive assessment are adopted and mended to establish comprehensive evaluation model for water quality of subsided water area. 14 large-scale subsided water areas in Panji mining area of Huainan have been chosen to layout sampling sites and conduct sampling and monitoring for assessing the pollution status of water quality in subsided water area. The assessment results show that variance contribution rate of PC1 (first principal component) has been increased significantly after being improved, and enhanced to 98%. When the variance contribution rate of PC1 has exceed 85%, the whole indexes of PC1 are chosen as evaluation factors of fuzzy comprehensive assessment model to assess water quality, the assessment results show that all of subsided water areas have been polluted in various degree. Because the unified evaluation indexes have been chosen to assess water quality, the assessment results of the same type subsided water areas are comparable, and the results can be used as the foundation data for programming and utilizing subsided water resources and constructing “plain reservoir” in Huainan.

The Research of Integrated Geological Environment Eevaluation Based on Support Vector Machine (SVM)

DU Ping-Ping

2012, 29(4):  555-558. 

Asbtract ( 2827 )   PDF (415KB) ( 2099 )  

Related Articles | Metrics

The Yushenfu mining district, located in transition region between the hill ravine area of Loess Plateau in the north of Shaanxi province and Maowusu sand land, has many characteristics: the embedding depth of coal seam is shallow, the mining seam is thick and the thickness of overlying base rock is rather thin, in addition, the surface in this zone was covered by rather unconsolidated formation. Because of the drought and lack of rain all of the year and the sparse vegetation, it is a typically ecological vulnerability. Consequently, the large-scale coal mining easily result in some more serious problems of the geological environment. The research analyzes the geological mining factors and study the influence on geological environment exerted by coal mining. Adopting the theory and methods of the support vector machine (SVM), we built an assessment of integrated geological environmental quality and a nonlinear prediction model. By evaluating and forecasting the evolution result of nonlinear interaction of geological environment factors on coal mining, we got predicting results from five different comprehensive geological environment divisions and the mining change divisions. The method has a more scientific and more accurate effect, closer to the reality in evaluating the nonlinear interaction that comes from the factors of complex geological environment and predicting the evolution of comprehensive geological environment.

Study of the Formation and Propagation Characteristics of Shock Wave and Gas Flow of Outburst at Straight Roadway

WANG Kai, ZHOU Ai-Tao, WEI Gao-Ju

2012, 29(4):  559-563. 

Asbtract ( 3225 )   PDF (366KB) ( 2432 )  

Related Articles | Metrics

Shock waves and gas flow caused by outburst is destructive. Firstly, we analyzed the formation process of outburst shock waves and gas flow. Then movement process of shock waves and gas flow was simulated by establishing geometrical model of the straight roadway and setting the initial conditions, and the pressure, speed of shock waves and gas flow, the relative concentration of gas distribution at different times in the roadway were obtained. Simultaneously, average pressure and speed of shock waves and gas flow at different time in roadway were analyzed. From the simulation results, some qualitative and quantitative conclusions were obtained. Lastly, experimental system for outburst shock wave was constructed; shock wave propagation at straight roadway was studied by the experimental research. The results show gas flow and shock wave with higher speed can be formed induced by outburst; Compared with initial coal seam gas pressure, the pressure of gas flow and shock wave declines sharply. The intensity of gas flow and shock wave will attenuate at straight roadway, which decays more slowly earlierly, and attenuates faster in the late.

Study of Outburst Prevention Technology by Comprehensive Hydraulic Drilling Downward Through Coal-Seam

LIU Zhen, LI Zeng-Hua, YANG Yong-Liang

2012, 29(4):  564-569. 

Asbtract ( 2354 )   PDF (982KB) ( 2522 )  

Related Articles | Metrics

Aiming at the difficulty of regional outburst prevention in closed distance，low permeability and loose outburst coal seams, the outburst prevention technology by comprehensive hydraulic drilling downward through coal seam was proposed. We theoretically analyze the outburst prevention mechanism of this technology. The stress distribution of coal body around different diameters borehole before and after water infusion and wetting was simulated. The results show that released range of borehole increasing with the diameter of hydraulic flushing borehole growing. The released range increases after water infusion and softening under the same diameter condition. Pressure relief effect of increasing diameters is better than water-infusion softening. There is exponential function relationship between the released range and negative reciprocal borehole radius. This outburst prevention technology process was researched. The assessment index system of outburst prevention effect was established. The technology, which has been successfully applied in Qingdong mine, provides a new technical way for regional out-burst prevention in this condition.

Seepage Property of Coal Containing Gas Under Different Paths in Laboratory

ZHU Zhuo-Hui, FENG Tao, XIE Dong-Hai

2012, 29(4):  570-574. 

Asbtract ( 2545 )   PDF (422KB) ( 2986 )  

Related Articles | Metrics

According to experimental investigation on seepage property of coal containing gas, the change rule of permeability of coal containing gas is analyzed systematically under different stress paths.The quantitative and qualitative relations between the permeability of coal containing gas and axial pressure, confining pressure and gas pressure were established respectively. The controlling mechanism and changing law of permeability of coal containing gas under different stress paths are discussed. The results showed that stress path has an important impact on the permeability of coal containing gas, and the details are: 1) The permeability of coal containing gas decreases with increasing of axial pressure and confining pressure,and increases with increasing of gas pressure. 2) The relationship between permeability of coal containing gas and axial pressure, confining pressure and gas pressure obeys approximately an exponential law. 3) During the whole stress-strain process under the condition of triaxial compression, the change trend of permeability of coal containing gas versus strain curve displays nearly a shape of letter “V”. The permeability of coal sample decreases with strain first, then increases, and reaches its maximum finally. The rate of permeability at increasing stage is less mildly than that at decreasing stage.

Experimental Study on the Temperature Rising Characteristic of Spontaneous Combustion of Coal

XU Tao, WANG De-Ming, XIN Hai-Hui

2012, 29(4):  575-580. 

Asbtract ( 3011 )   PDF (516KB) ( 2505 )  

Related Articles | Metrics

To find out the reason for the sudden rise of the oxidation temperature in coal spontaneous combustion process, and provide theoretical basis for the prevention and control of spontaneous combustion in coal mines, the adiabatic testing method and programmed temperature rising method were used in this paper, to study the temperature rising, oxygen consumption, gas production (CO and CO2) characteristics of lignite in Baizao coal mine during the oxidation process. It is indicated that the oxidation of lignite has the subsection characteristic, and can be divided into two stages , that is, slow oxidation process during the low temperature and fast oxidation during the high temperature. The functional groups variation law during the whole oxidation process was tested by in-situ FTIR. The results show that the reaction of OH leads to the subsection characteristic of lignite during oxidation process, and the endothermic reaction of OH is the main reason why the heat is difficult to accumulate in the low temperature stage. Once OH is depleted, heat begins to accumulate and the temperature of coal rises immediately.

Study on Distribution of Gas Flow Fields in 1201-Face Under the Condition of Mining

DONG Gang-Feng, HU Qian-Ting, WANG Zhen

2012, 29(4):  581-585. 

Asbtract ( 5225 )   PDF (546KB) ( 3723 )  

Related Articles | Metrics

To master the distribution laws of gas flow fields is the premise of designing reasonable project for goaf gas extraction. Disallowed gas concentration occurred in return Air occurred at 1201-Face in WU Hu-shan mine. So studying the gas distribution was necessary. On the basis of gas emission analyzing, the distribution of gas flow fields in 1201-face under the condition of mining was researched by FLUENT numerical software. The difference of gas emission at the normal recovery and roof weighting periods was rationally explained. And theory basis was provided by the results to design reasonable project for goaf gas extraction. The research conclusion was verified scientificly and reliably by the field measured results.

Characteristics of the gas emission rate based on the monitoring data in the fully-mechanized working face

ZHANG Shi-He, CAI Qing-Xiang, CHEN Kai-Yan

2012, 29(4):  586-590. 

Asbtract ( 3094 )   PDF (428KB) ( 2384 )  

Related Articles | Metrics

The relation of gas emission, the two factors of the roof weighting and the advancing speed of working face are analyzed by the method of mathematical statistics according to the airflow and gas monitoring data for No.15158 longwall panel of Tucheng coal mine in Panjiang Coal Group. The result shows that the average of absolute gas emission rate of the working face closes to the cutting speed of the shearer. The overall average gas emission rate increases with the speed of the periodic progress per shift. The gas concentration presents three areas corresponding to the initial mining, normal mining and finishing work. Furthermore, there is a negative power function relation between the average of absolute gas emission rate and production per shift. The gas peak and uneven emission are mainly caused by the periodic roof weighting.

Adsorption-desorption characteristic on deformed coal under the conditions of high temperature and pressure and equilibrium Water

SONG Zhi-Min, LIU Gao-Feng, YANG Xiao-Na

2012, 29(4):  591-595. 

Asbtract ( 4935 )   PDF (382KB) ( 3930 )  

Related Articles | Metrics

Under the conditions of high temperature and pressure and equilibrium water, the adsorption-desorption experiments on CH4 were carried out with four destructive type of coal samples in No.12 Mine of Pingdingshan. The experiment results show that the equilibrium moisture of coal samples increase with the increasing extent of the coal damage in the conditions of 50℃. There are some new features on the adsorption-desorption of deformed coal，Langmuir volume of the VL (ash-free basis) first decreases and then increases, and decreases finally. Therefore, the characteristic of results of this adsorption-desorption experiments are due to the combined effects of the unique pore structure of deformed coal and water content. The adsorption-desorption isotherms of deformed coal are irreversible, and this irreversible degree increases with increasing extent of the damage of coal. The data selected by adsorption experiments should not be straightforward used in the desorption experiments on a coal, especially deformed coal.

Measurement of Effective Drainage Radius Based on Gas Flow and Pressure of Boreholes

YU Tao, LU Ping, SUN Jin-Hua

2012, 29(4):  596-600. 

Asbtract ( 5619 )   PDF (438KB) ( 4354 )  

Related Articles | Metrics

 In order to measure effective drainage radius exactly, we propose the method based on gas flow and pressure of boreholes. Under the index of remnant gas pressure less than 0.74 MPa and pre-drainage rate more than 30%, the computing formula is deduced based on the negative exponent attenuation law of gas flow, and the effective drainage radius is determined in combination with the variation of gas pressure. The method is applied in the arrangement of zonal pre-drainage boreholes. The effective drainage radius of different pre-drainage time and the utmost pre-drainage time are analyzed. Based on the premise that effective drainage radius reaches to 2.5 m in 90 pre-drainage days, the boreholes are designed to eliminate coal and gas outburst. The measurement method is demonstrated valid in outburst elimination by the examination of remnant gas pressure,pre-drainage rate and the zonal verification during the coal roadway driving.