Table of Content

15 March 2013, Volume 30 Issue 2

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Rational width of the support body of gob-side entries in fully mechanized backfill mining

ZHANG Ji-Xiong, JIANG Hai-Qiang, MIAO Xie-Xing, ZHOU Nan, ZAN Dong-Feng

2013, 30(2):  159-164. 

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In this paper，we analyzed the surrounding rock deformation features of retained entry and the action mechanism of gob-side support body based on the strata movement characteristics in solid backfill mining. The main factor influencing the deformation and instability of the support body is the lateral force caused by tamping operation．A mechanical model of support body stability influenced by lateral force was established，and the width calculation formula of the support body was deduced．The deformation of the support bodies of different widths was analyzed using numerical simulation method with relevant parameters of Huayuan mine．The result shows that the deformation of the support body can be effectively controlled when its width is more than 2.5 m and it is supported by bolts together with bands and net．The field test proves that the technology is successful and effective；the mechanical model of support body stability as well as the width calculation formula is rational．

The deformation failure mechanism and control techniques of soft rock in deep roadways in Zhaolou mine

MENG Qing-Bin, HAN Li-Jun, QIAO Wei-Guo, LIN Deng-Ge, FAN Jia-Dong

2013, 30(2):  165-172. 

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Based on the means of geological mechanic test, such as the investigation on the mineral composition of surrounding rock, the rock mechanics experiments in laboratory, the stress measurement in roadways and the tests of surrounding rock loose zone, the deformation failure mechanism in deep roadways is deeply revealed. Aimed at the supporting problem of low rock strength and the high stress in deep roadways in Zhaolou mine, we put forward the combined support system of “three anchors” which are known as anchor chain, anchor injection and anchor joint with the inside grouting bolt at the core. In order to reveal the deformation laws of surrounding rock and the loading conditions of supporting structure, the displacement of surrounding rock and axial force of rock bolt are monitored in real time. The monitoring result shows that the large displacement of surrounding rock and the heaving floor can be effectively controlled by the combined support system of “three anchors”, ensuring the long-term stability and safety of roadways.

Research and application of pressure relief anchor box beam support system in deep coal roadway

WANG Qi, LI Shu-Cai, LI Wei-Teng, RUAN Guo-Qiang, LI Hai-Yan, WANG De-Chao, JIANG Bei, ZHANG Hong-Jun

2013, 30(2):  173-180. 

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The current situation of coal roadway support, especially pressure relief support theory and technology, was summarized. The necessity and engineering significance of the support idea, which is controlling at first, pressure yielding behind and then resistance, was researched. Guided by the support idea, and considering the demand of deep high stress coal roadway support, high strength pressure relief anchor box beam support system was developed, and the high strength pressure relief performance of the system was analyzed, and the function and mechanical property of box supporting beam, yielding link and other combined members were researched. The contrastive analysis with channel steel and I-beam indicated that box supporting beam had the advantage of high strength and stiffness, high-level economical efficiency, good surface protection effect and load-transmitting performance. The result of uniaxial compression test showed that the yielding link had unique second order determinant pressure relief performance, high pressure relief point, long pressure relief distance and good pressure relief stability. The supporting system has the advantage of multiple compound mode, wide area of application and easy application. Based on geological condition of 3302 headentry in Zhaolou coal mine, high strength pressure relief anchor box beam support scheme was designed and simulated. Result shows that the new scheme is better than the original, achieving good support effect in the test section of headentry.

Research on failure characteristics and control measures of roadways affected by multiple overhead mining in Huaibei mining area

LI Gui-Chen, MA Zhen-Qian, ZHANG Nong, WANG Peng-Peng, MA Rui

2013, 30(2):  181-187. 

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Although high-frequent maintenance work has been performed on roadways affected by multiple overhead mining in Huaibei mining area, these roadways still cannot meet the requirement of normal coal production．Taking II82 gallery in Luling coal mine as an example，we summarized four common failure characteristics, namely the breakthrough of mental net joint，floor heaving，ingression of support leg，and asymmetric deformation of U-steel support based on the comprehensive analysis of engineering geological conditions．The deformation mechanism of roadways affected by multiple overhead mining was studied by theoretical analysis and numerical simulation，enhanced control technology including new hollow grouted anchor cable，high-effective bolt and grouting reinforcement technique was put forward．Field practice shows that the deformation affected by multiple overhead mining can be effectively controlled by using the supporting technology of hollow grouted anchor cable combined with high-effective bolt. Roof-to-floor relative displacement ranged from 126 to 393 mm after mining，which can meet normal production demand with routine maintenance．

The mechanical characteristics analysis of fully anchored pre-stressed bolts in coal mines

LI Chong, XU Jin-Hai, LI Ming

2013, 30(2):  188-193. 

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Theoretical analysis, field measurements, and other methods were used to analyze the relationship between axial stress, shear stress, and pre-load on the bolts and the distribution of the axial and shear stresses. The results show that the axial stress increases as the pre-stress increases. The axial stress shows a curve changing with the pre-stress upon moving from the bolt tail to its head, that is, the axial stress first increases and then decreases along the bolt and at the neutral point the axial stress reaches a maximum value. The maximum value of the axial stress, moves toward the bolt tail end as the pre-stress increases. The shear stress decreases between the roadway surface and the neutral point and then increases between that point and bolt end. The shear stress equals zero at the neutral point. The proper pre-load for the fully anchored bolt is not "the bigger the better". There is a reasonable range for the pre-load that should match the bolt support system strength.

Roof mechanics analysis and backfill technology for abandoned roadway

ZHANG Zi-Zheng, BAI Jian-Biao, HAN Zhi-Ting, WANG Xiang-Yu, XU Ying, WANG Meng

2013, 30(2):  194-198. 

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Taking No. 4217 fully mechanized caving face crossing abandoned roadway of Guojiashan Coal Mine (uphill pillar recovery) in Liulin as a case study, a mechanical model of abandoned roadway roof subjected to advance mining influence was established, and support resistance was derived based on interaction relations between roof stability and backfill body in abandoned roadway. The support re-sistance of backfill body in the abandoned roadway is more than 3.58 MPa. The technology of backfilling abandoned roadways with high moisture quick-setting material is put forward：1) High moisture quick-setting backfill material grout can cement both the broken coal/rock and cracks around the aban-doned roadway together into an integral structure, improving the load-bearing capacity of surrounding rock；2) The strength of backfill material (Water cement ratio is 2.5:1) not only meets strength re-quirement of supporting the abandoned roadway roof, but also avoids main roof slide and rotation de-formation. Field test shows that the application of high moisture quick-setting backfill material in abandoned roadway can keep the roof and ribs stability. It provides an effective approach to make the working face pass through an abandoned roadway quickly and safely.

Experimental study on deformation and failure characteristics of anchored body in roadway surrounding rock

WEI Si-Jiang, GOU Pan-Feng

2013, 30(2):  199-204. 

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In this paper, to find out the failure characteristics and fracture evolution law of anchored body in roadway surrounding rock, the deformation and failure progress of anchored bodies and working resistance varation of bolts under the combined loadings were simulated. The results show that the horizontal stratifications which are perpendicular to bolts will appear when the lateral pressure coefficient λ meets the condition of 1≤λ≤1.4. When λ satisfies 1.4＜λ≤1.6, fine fractures will appear in anchored rock mass, bolts plates are entrapped in stratum, rock bodies between bolts fall off in pieces, loosening damages appear in the rock mass on the bottom of anchored body, and the anchored body is stable, but the inclined fractures will appear outside of anchored body, which are 30°~40° relative to the strata planes. When λ is equal to 2.0, separations between bolted area and no-bolted area increase, block size and depth of strata on the bottom of anchored body are increased, the bolt plates are disabled, and the integral instability of anchored body appears. Meanwhile, there exists obvious positive correlation between λ and fractal dimension of anchored body, D. With the increase of λ, the working resistances have little differences between bolts, which show a wavy decreasing tendency, and the bearing capacity of anchored body in the wall of roadway changes little, while the bearing capacity in the roadway roof decreases gradually. Moreover, the horizontal loadings have more obvious influence on the stability ofanchored body in roadway roof, while the separations increase with the increase of λ, and inhomogeneous subsidence appears within anchored body.

Numerical simulation of overlying hard strata rupture in a coal face

CAO Sheng-Gen, JIANG Hai-Jun, WANG Fu-Hai, CHENG Zheng-Gang, WU Zhong-Jin

2013, 30(2):  205-210. 

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Large area hanging arch formed by strong roof seam mining can usually cause serious damage to stope even the whole mine. Movement law of overlying strata under different conditions of support resistance and distance between hard rock bed and coal seam has been analysed by theoretical calculation and numerical simulation. The results show that when the overlying strata of coal seam directly is hard rock bed (distance between hard rock bed and coal seam is 0 m), the concentrated parameter of abutment pressure and the released energy from this system reaches the maximum, the rapture of hard rock bed easy to cause fully mechanized supports crushing accidents or impulsion pressure which constituted a great threat to safety production. Good effect has been gotten in the field application by using forced roof caving technology to process this roof type.

Analysis on the rock failure and strata behavior characteristics under the condition of hard and thick roof

YANG Jing-Xuan

2013, 30(2):  211-217. 

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Theoretical analysis and field measurement were adopted to analyze the hard and thick roof breaking characteristics under the different support boundary conditions in Shigetai coal mine. Steps of determining the roof broken location and size include: 1) the rock stress expressions was solved according to the different roof support boundary; 2) determining the broken and dangerous size according to the characteristics of the stress distribution between the general long and deep beam structure; 3) adjusting the broken and dangerous size and obtaining the distribution of the maximum principal stress and shear stress in the hard and thick roof strata; 4) selecting and determining the safe limit size of the hard roof when the maximum tensile stress or shear stress values close to the limited strength. Results show that the hard roof mainly presented shearing characteristics in Shigetai coal mine, and the first and periodic weighting length equals 35.0 m and 9.8 m respectively.

Key technology for safe effective mining under complex geological conditions

HE Fu-Lian, YANG Lu-Gang, XIE Sheng-Rong, ZHANG Shou-Bao, XIAO Dian-Cai, TIAN Chun-Yang

2013, 30(2):  218-222. 

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Series of scientific problems such as gas overrunning, roof flaking, roadway collapsing and so on occurred in a colliery with complex geological conditions of high gas in coal seams group with short distance, low permeability and weak surrounding rock. By using theory and practice research, the new technology of gas management and support-surrounding rocks control in fully mechanized coal face, the active support technology of surrounding rock of coal entry were put forward and studied further. The key support parameters were determined, and the field industrial test was carried out. Results showed that this set of technology has solved the key problem restricting the mine development and ensured the safe effective mining. Meanwhile, it has provided a technique support for the application and dissemination in the same complex geological conditions.

Mechanism and case studying of secondary strip mining in a deep coal seam under the building structures

FANG Xin-Qiu, ZOU Yong-Ming, CHENG Yuan-Wei, YANG Hai-Xin

2013, 30(2):  223-230. 

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In order to solve the problem of recovering coal resources under ground buildings at Linxi coal mine，combined with its geological conditions of large embedded depth and hard roof，smaller mining width and larger retaining width were adopted when strip mining，the secondary strip mining was carried out in the reserved coal pillar，after a period of time when the surface deformation stabilized．Based on the key strata theory，the strip mining and the secondary strip mining were studied by using the methods of the oretical analysis，numerical simulation and field measurement；the inferior key strata 1 was put forward as mining design basis；then the strip mining scheme can be determined，the mining width and retaining width were respectively 60 m and 120 m；the roadway driving along next goaf with narrow coal pillar was adopted when secondary strip mining，the mining width was 60 m and the retaining width was 55 m．The results show that the surface subsidence deformation is controlled by the inferior key strata 1；the destruction of surface deformation caused by strip mining and secondary strip mining to buildings is in damage grade I．The industrial test has been conducted at Nine-East area，then good results have been achieved．

Determination of height of “Three Zone” in the stope with stagger position and internal misaligned roadway layout

WANG Zhi-Qiang, ZHAO Jing-Li, LI Ze-Quan

2013, 30(2):  231-236. 

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Based on the importance of reasonable division of the“Three-Zone”to the security and economic of working face in stagger arrangement roadway layout conditions，we proposed a new division method which considered influencing factors such as working face area and fracture angle based on the key stratum theory．The geometric relationships between upper and low key strata，or between key stratum and working face are studied in the experiment；the movement characteristics of heights of caving zone and fracture zone，and the movement characteristics of overburden along the working face direction in stagger arrangement roadway layout conditions determined．The geometric model is established combining with the spatial relationship between the hanging size of key stratum and working area．The results show that working face area，fracture angle，mechanic properties and thickness of rock etc．are the influencing factors of division of the“Three-Zone”．In addition，the influence factor of working area should be considered with the total number of working faces in division of the“Three-Zone”in stagger arrangement roadway layout conditions．

Acoustic emission characteristics in quasi-quiet stage of damage and fracture of sandstone

SUN Qiang, ZHANG Wei-Qiang, XUE Lei, QIAN Hai-Tao, ZHU Shu-Yun

2013, 30(2):  237-242. 

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Accroding to uniaxial rigid loading tests of sandstone, the acoustic emmission (AE) signals present sharp increase characteristics in the yield point, and the strain value corresponding to the yield point is about 74.6% of that in the peaking state. Meanwhile, the time consuming in the unsteady loading stage is relatively long, while the AE signals exit the quasi-quiet stage before the brittle failure of rock samples, and the avearege value of the duration ratio between the durations associated to quiet stage and peaking state respectively is about 8%. In addition, the damage values during the loading process are calculated based on AE information. The results show that there is a rapid growth in the yield point, and the damage value in the inflection point of stress-stain curve in the post-peak is more than 0.9. Moreover, the shape of damage-time curve before the peaking state is concave, while the curve in the post-peak shows the convex type, and the peak value locates in the inflection point of the curve.

Stability analysis of rockmass based on acoustic emission monitoring in deep stope

LIU Jian-Po, LI Yuan-Hui, ZHANG Feng-Peng, XU Shi-Da, SHI Chang-Yan, HE Rong-Xing

2013, 30(2):  243-250. 

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Aimed at the serious condition of ground pressure disasters, such as rock burst and roof caving, appeared in Hongtoushan Copper Mine, acoustic emission (AE) monitoring technique was used to assess the rockmass stability during mining process in the deep stope, and the duration time of rock mass retraced to the stable state after blasting and the spatial distribution characteristics of AE signals were emphatically studied. The results show that AE activities suddenly jump to a higher level after the blasting, and decrease gradually with time going on. Additionally, a linear relationship is found between the duration time of rockmass retraced to stable state and the distance of monitoring area from blasting position. In the zone over 35 m from the blasting position, AE activity can be recoverd to stable state within 90 minutes after blasting, while in the zone within 20 m from the blasting area, the duration time of AE back to the initial background activity needs more than 2 hours. Moreover, AE events are mainly concentrated in the roof and side walls, and the spalling is more serious in the slope ramp.

Study on the effect of floor burst induced by dynamic disturbance at different lateral pressure coefficients

XIE Long, DOU Lin-Ming, LV Chang-Guo , YU Gui-Liang, WANG Yi

2013, 30(2):  251-255. 

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In order to reveal the influence of lateral pressure coefficients on floor burst induced by dynamic disturbance, dynamic response rules and burst process of floor in extra-thick coal seam induced by dynamic disturbance at different lateral pressure coefficients were studied by using the rock mechanics and FLAC2D finite difference numerical software. The results show that the ultimate stress equilibrium in floor can be disturbed by dynamic loads so that floor burst is induced. With the increase of the lateral pressure coefficients, critical horizontal stress and maximum stress difference of floor will increase linearly, maximum vertical displacement of floor will increase nonlinearly if  and then decrease slightly as  under dynamic loads. These indicate that instability difficult degree is not positively correlated with burst strength for floor completely. The floor burst process is: 1) horizontal stresses reaches critical value instantly, 2) plastic area extends, 3) elastic energy releases rapidly, 4) vertical displacement of floor increase suddenly, 5) the floor burst occurs. The conclusions will provide reference for the study on mechanism of floor burst and its prevention in the same conditions.

Catastrophe progression method on comprehensive evaluation of rock burst

JIN Pei-Jian, WANG En-Yuan, LIU Xiao-Fei, HUANG Ning, WANG Si-Heng

2013, 30(2):  256-261. 

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In this paper, based on the catastrophe progression method which combining the catastrophe theory and the fuzzy mathematics, a new catastrophe progression index to evaluate rock burst was proposed. Meanwhile, by comprehensive considering of the influence factors of rock burst risk, a new evaluation model of rock burst was built. In addition, after the nondimensionalization and normalization processing of the influencing factors, the sample learning on the model was conducted according to the field data in coal mine, the catastrophe progressions of different burst risk grades were ascertained, and the model was verified by using the existing data. Finally, the evaluation model was applied to engineering practice, and was compared with other evaluation methods. The results show that this method has accuracy evaluation results, high precision and good practical value.

Supporting technique with advanced pipe-shed grouting in extremely complicated faulting zone

ZHAO Yi-Xin, JIANG Yao-Dong, MENG Lei, WANG Tao, LIU Hua-Bo

2013, 30(2):  262-266. 

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Based on the application cases of roadways successfully passing through the complicated fault zones by using supporting technique with advanced pipe-shed grouting, the technical problems of roadway support in passing through the extremely complicated fault zone were analyzed firstly in this paper. Meanwhile, the design parameters of advanced pipe-shed grouting were calculated, and the stress and deformation of surrounding rock in the fault zone under various supporting conditions were also analyzed by numerical simulation. Moreover, the in-situ deformation of roadway supported by advanced pipe-shed grouting was measured, and the successful application experiences of the pipe-shed grouting technique were summarized. The practice results show that the supporting technique with pipe-shed grouting can not only improve the integrity of surrounding rock and the supporting capacity, but also form a strong pre-support system. It can be well used as one of effective roadway support techniques in the complicated geological zones. However, some other measures, such as geophysical prospecting, effective in-situ monitoring, et al, are needed to improve the grouting quality and ensure the safety of passing through the complicated fault zones. The experiences in this paer can provide reference to the design and construction of similar projects in complicated geological zones.

Research on properties of coaly shale compression deformation and its damage identification

WANG Jing-Huan, LU Yi-Yu, LU Zhao-Hui, ZUO Wei-Qin, TANG Ji-Ren, SHEN Xiao-Yun

2013, 30(2):  267-272. 

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In order to explore properties of coaly shale compression deformation and its damage identification, by using the mechanical testing & a simulation system, the uniaxial and triaxial compression curves of coaly shale were obtained and their difference of damage softening properties was analyzed. Based on these, the mechanism of external work，energy dissipation，energy release were studied. Meanwhile, a damage formulation based on energy principle was deducted according to shale mechanics characteristic and rock strength and failure theory．① The resultant constitutive model based on energy principle can be used to simulate the damage of shale under uniaxial compression．② Under the condition of triaxial compression, the constitutive model of shale can be simulated by linear equation (or constitutive equation based on energy principle) when the axial stress is less (or more) than confining pressure. The comparison between the model and the experiment results shows that the mechanical parameters of model are simple and its physical parameters clear. It can also reflect deformation characteristics of softening under uniaxial compression and hardening under triaxial compression.

Influencing factors on time-varying characteristics of displacement coalbed methane by gas injection

YANG Hong-Min, XIA Hui-Hui, WANG Zhao-Feng

2013, 30(2):  273-277. 

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In this paper, to analyze the influencing factors on time-varying characteristics of displacement coalbed methane by gas injection, the mathematical model of displacement coalbed methane technology by N2 injection was established, and the effects of the influencing factors, such as gas injection pressure, drainage negative pressure, gas injection time, et al, on the time-varying characteristics of displacement coalbed methane by gas injection have been simulated by using COMSOL multiphysics software, then the variation laws of the methane content and outburst elimination cycle under different conditions were studied. The results show that the greater the gas injection pressure is, the faster the methane content decreases, and the shorter the outburst elimination cycle is, while the reasonable gas injection pressure is 0.5 MPa. In addition, the influence of drainage negative pressure on the time-varying characteristics is not obvious, and the reasonable drainage negative pressure is 5-13 KPa. Moreover, the methane content decreases gradually with the increase of injection time, while the position near the gas injection borehole is the weak area in the displacement coalbed methane technology by gas injection. Furthermore, the field tests were carried out in Shigang Company. By comparing with the numerical results, the measured methane contents are always slightly smaller than that in simu-lation results under the same conditions. The reasons for this difference were also analyzed.

Safety roof cutting thickness in mining gently inclined and extremely thick ore body

XIE Cheng-Yu, LUO Zhou-Quan, JIA Nan, YANG Biao, CHENG Gui-Hai

2013, 30(2):  278-284. 

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In this paper, in view of the safety problems of the roof cutting chamber above goaf during ore extraction process step by step, by using high-level, large-diameter and deep boreholes in the stope of gently inclined and extremely thick ore body in one tin mine, the safety thickness of roof cutting in stope mining was studied based on elastic mechanics theory and numerical analysis method. According to elasticity mechanics, the length and span of drilling chamber in slope were confirmed as 26 m and 12 m, and the safety thickness of roof cutting was determined as 6 m. On this basis, the roof cutting thickness was analyzed and verified by numerical analysis, and the field monitoring including the surface displacement and surrounding rock stress of roof cutting chamber was also conducted. The results show that the maximum tensile stress value obtained from numerical analysis is 0.96 MPa, which is less than the tensile strength and the safety rate is 2.98, while the maximum displacement monitoring value is 7.58 mm, which is close to the numerical analysis value of 8 mm. Thus, the roof cutting in stope with 6 m in thickness is reasonable, which can ensure operation safety during roof cutting proces in the stope. The study results have been put into mining practices, and have effectively solved the safety problems of roof cutting chamber in the slope, when mining the gently inclined and extremely thick ore body in the tin mine by using ore extraction of large-diameter and deep boreholes.

Match mode of combined system with dragline oriented system

ZHOU Wei, CAI Qing-Xiang, SHANG Tao

2013, 30(2):  285-288. 

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With the development of mining industry，the mining area and depth have been increased in a single open pit．At the same time，deposit occurrence of ore and rock in mining limits become complex and changeable，which makes combined mining system has wider application．This paper put forward to analyzing the concept of combined mining system，and brings up spatial match mode of each single system in the combined one，facade and planar match．Apart from that，the concepts of strict limited system and nonstrict limited system have been established．Basic features of strict and nonstrict limited systems are analyzed based on a case study of combined mining system dominated by dragline stripping system．Stability model of combined mining system including strict limited system has been established．Dynamic adjustment strategy of mining parameters in combined system has been proposed on the basis of strictly limited system service area．

Optimal layout of surface borehole network for gas drainage from abandoned gob

QIN Wei, XU Jia-Lin, PENG Xiao-Ya, HU Guo-Zhong

2013, 30(2):  289-295. 

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In this paper, to optimize the surface borehole network for gas drainage above the abandoned gob, considering the geometric boundary intersection of the gas leading fracture zones as the criterion for the connection of adjacent abandoned gobs, the method and procedures to judge the connection of adjacent abandoned gobs both in longitudinally and horizontally were given, and the region division method of gobs based on the connectivity of abandoned gobs was put forward. Meanwhile, according to the gas sources in abandoned gob, the calculation model of gas reserves in abandoned gob was built by using separate source method. In addition, the pipe network optimal layout problem of the surface borehole for gas drainage from abandoned gob was transferred equally to a graph theory problem solving in the minimum spanning tree of weighted connected graph, and Kruskal method was clearly illustrated to solve the formation of the minimum spanning tree. Finally, the method and procedures were further explained to optimize the surface borehole network arrangement for gas drainage from abandoned gob.

Experimental study on the inhibition of injection water to the gas desorption of coal

CHEN Xiang-Jun, CHENG Yuan-Ping, WANG Lin

2013, 30(2):  296-301. 

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In order to study the inhibition of injection water to the gas desorption, the desorption process of the coal injected water was determined using the home-made instrument. The result shows that the injected water has a restrain effect on the gas desorption. When the moisture increases from 0.05% to 8.39%, the maximum gas desorption amount decreases from 12.525 mL/g to 4.284 mL/g, reduces by 65.80%, and the initial gas desorption velocity decreases from 2.07 mL/(g.min) to 0.33 mL /(g.min), reduces by 84.06%. The maximum inhibition rate of the injection water to the gas desorption is 42.48%. The gas desorption index reduces in a logarithm relationship as the water increased. By increasing the moisture of coal seam, the gas desorption index of coal can be effectively reduced. According to the condition of this research, the gas desorption index of drilling cuttings would be less than 0.5 mL /(g.min1/2), the critical value of coal and gas outburst risk, when the moisture of coal sample is greater than 5.19%. The study shows that it is feasible to eliminate coal seam gas outburst danger by water injection.

Experimental test of methane solubility in surfactant aqueous solution

YANG Yong-Liang, LI Zeng-Hua, HOU Shi-Song, SUN Liu-Tao, LIU Zhen, TANG Yi-Bo

2013, 30(2):  302-306. 

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During the process of coal seam water infusion or roadway spray, if the aqueous solution is modified so that it can absorb mathane gas well, the gas content of coal seam will be effectively reduced, and the outburst danger of coal seam may be eliminated. In this paper, the experimental device for methane dissolution was developed and processed, and the methane dissolution experiments under different temperatures, concentrations and pressures were conducted by selecting different surfactants with stong solubilization capacities. The results show that the methane solubility increases mainly in logarithmic way with the growth of gas concentration and gas pressure, and decreases exponentially with the increase of temperature. In addition, the solubility data of polypropylene glycol (PG) is largest among the four kinds of surfactants. The data can reach to 24.66 mL/100 mL in 10% PGM solution at normal temperature and pressure, which is 7.45 times to the pure water. In conclusion, the order of solubilization capacities among the four types of surfactants is: PG> Polyvinyl> THF> F-500. According to the experimental results, the calculation equation of methane solubility under different conditions was established, and the estimated values agree well with the experimental values. The results can provide reference to improve the effects of gas control by using hydrodynamic hydraulic measures in coal mines.

Effect of gas pressure on infiltration characteristics of coal gas

LI Jian-Lou, YAN Jia-Ping, HU Shui-Gen

2013, 30(2):  307-310. 

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In order to study the characteristics of gas infiltration in coal body surrounded by rigid rock under conditions of different gas pressure, a self-developed coal-gas sorption/desorption simulation device is used to establish a physical coal-gas infiltration model. In the infiltration experiments of coal body, we use two types of gases (N2 & CO2) respectively to monitor gas pressure, total stress and infiltration velocity. The results show that the infiltration velocity of N2 is higher than that of CO2 under the conditions of same temperature and same pressure. The results also show that the relationship between gas infiltration velocity in gas-contained coal and gas pressure is fitted by second-order polynomial. This experimental study has important reference value for the prevention of coal-gas dynamic hazard and the theory and technology of CBM exploration in coal mine.

Prevention and control technique of complex disaster caused by gas and spontaneous combustion for fully-mechanized sublevel caving face in close-distance seams

QIN Bo-Tao, LU Yi, YIN Shao-Ju, CAO Kai, WANG Mei-Guang

2013, 30(2):  311-316. 

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In this paper, to solve the great hidden danger caused by complex disasters of gas and  spontaneous combustion which may exist in the production process of high gas and easily spontaneous combustion coal seam, based on the study of gas occurrence regularity and coal spontaneous combustion characteristics in anomaly gas zones of Fucun Coal Mine, the stereo gas drainage system in condition of “W- type” ventilation mode was established, which containing the staggered high-level gas drainage, bypass tendency high-level gas drainage, and gas drainage near goaf areas, etc. Meanwhile, the “inject-plug” packaged key technology of fire prevention and extinguishing was put forward , in which three-phase foam was used to cover float coal in goaf, noncombustible high multiples curing bubble was used to plug the air leakage location rapidly, nitrogen was injected to make easily spontaneous combustion area inerting, and plastic sodium silicate was injected into the back of hydralic support to stop loopholes and lower temperature, etc. In addition, according to the phenomenon that coal combustion may easily be induced in the gas drainage process, the “drainage-inject” integration method was presented to control the gas and spontaneous combustion in the goaf simultaneously, in which bypass high-level drilling holes were used for gas drainage, and large flow three-phase foam was injected through the gas drainage holes, etc. The key techniques mentioned above were used successfully during the prevention and control of gas and spontaneous combustion in the fully-mechanized sublevel caving face of the lower No.3 coal seam in Fucun Coal Mine, and have achieved remarkable application effects, which effectively solved the gas problems in the coal face and greatly reduced the coal combustion risk in goaf, and can have widely application prospect.