Table of Content

15 November 2012, Volume 29 Issue 6

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Control Principle and Its Application of Rock Burst in Roadway Driving Along Goaf with Outburst-Proneness Surrounding Rocks

LI Xue-Hua, LIANG Shun, YAO Qiang-Ling, QU Qun-Di

2012, 29(6):  751-756. 

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Aimed at controlling the stability of surrounding rocks of roadway driving along goaf in deep coal seam with outburst-proneness, intensity weakening mechanisms were proposed. Including stress controlling, support system designed and technical measured, which included rational design of narrow pillar’s width and roadway support system, were proposed by analyzing the failure characteristics and influencing factors of the roadway. Studies show that design reasonable narrow pillar’s width can help reducing stress of surrounding rocks. Creating soft interlayer with external measures can release stress and absorb impact energy, and high-performance bolting system can enhance the strength of surrounding rocks. The integrated approaches can make stability controlling of roadway driving along goaf in deep coal seam with outburst-proneness effectively.

Experimental Study on Gob Side Entry Retaining by Roadside Flexible Packing Under Hard Roof

CHENG Yun-Hai, JIANG Fu-Xing, LIN Ji-Kai, CHEN Qing-Hua, ZHANG Dong, ZHANG Feng

2012, 29(6):  757-761. 

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In order to achieve gob-side entry retaining with flexible filling body (filling gangue) under condition of hard and direct roof, uniaxial compression characteristics of sacked gangue body are gained by experiment, combined with the establishment of lateral overlying strata’s constructional model alongside gob side entry retaining, static load caused by overlying strata movement is quantitatively calculated. Dynamic effect of constructional model of roof is studied by means of dynamics, and dynamic load is quantitatively calculated. Thus, when filling width is designed as 2 meters, static load of filling body is 816 kN/m, and dynamic load is 257.3 kN/m with limestone’s fracture near the coal wall. Supporting demand of static load and dynamic load are satisfied by flexible filling body.

Study on the Rheology of Soft Rock with High Stress by Numerical Simulation

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

2012, 29(6):  762-769. 

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In connection with the characteristic of large deformation, high deformation rate, long duration and strong rheology in tunnel with soft rock under high pressure, the author has analyzed the regulation of their impact on the rheology of surrounding rock which is based on the software of FLAC3D numerical simulation through the model of Burgers, and four creep curves can be got to show the relationship between time and depth, lateral pressure coefficient, elastic modulus and viscosity coefficient respectively.

Mutation Instability Mechanism of the Room Mining Residual Pillars in the Shallow Depth Seam

WANG Fang-Tian, TU Shi-Hao, TU Hong-Sheng, LI Zhao-Xin, CHEN Fang

2012, 29(6):  770-775. 

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Shendong Mine Area is mining in the shallow depth seams and the room mining method results in a lot of residual pillars, which incline to be instability and caving suddenly induced by the nether seam mining, and cause shock type dynamic disasters, hence the stability of the residual pillars have significant implications for the nether seam mining safely. According to the geological and production conditions of Shigetai Mine, Wulan Group, we applied mutation theory to establish a cusp mutation model for studying the room mining residual pillars’ stability, and discussed the mutation instability rules of the room mining residual pillars in the shallow depth seam. The necessary condition for pillar mutation is that when the hemi-yield width in the scope of 0.33~0.43 of the overall width, the pillar will be mutation instability. Finally the calculation results have conformed to the observations.

Mechanical Monitoring and Analysis on Shotcrete Layer of Soft Rock Main Roadway Supported

FANG Shu-Lin, KANG Hong-Pu, LIN Jian, ZHANG Jian

2012, 29(6):  776-782. 

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Based on the soft rock，water-trickling and hard-maintain difficulty conditions of main air-return roadway in Tarangaole Colliery，high pretension stress and intensive bolt-shotcrete support program was designed. Mechanical property of shotcrete layer was specially monitored through utilizing concrete stress meter with a type of oscillating chord after the program was carried out in the roadway. It is indicated that the interior of shotcrete layer will emerge diverse stresses in axial，radial and tangential direction, and that its exterior will emerge contact pressures when the shotcrete layer gets in touch with surrounding rock and the earlier layer. With time prolonged，internal stresses in three directions whose average values were 0.517 MPa，0.043 MPa and -0.059 MPa respectively have been fluctuated and tended to stability. Nevertheless，two kinds of external contact pressures which were all compressive increased earlier and remained stable lately while contact pressures of layer-surrounding rock were up to 0.266 MPa and those of layer-layer were up to 0.648 MPa averagely. Spatially，along the section of roadway，all of internal stresses distributed symmetrically and increased gradually from the top of arch to the waist of wall，but stresses in the foot of wall reduced partly with bilateral symmetry. However，external contact pressures increased gradually from top to bottom and distributed unevenly along the surrounding of roadway. During the period of roadway excavating，the stress of shotcrete layer was less than its ultimate bearing capacity, and the deformation of shotcrete was limited. The two aspects show that high pretension stress and intensive bolt-shotcrete support technology meet the surrounding rock control requirement of main air-return roadway in Tarangaole Colliery.

The Stability of Key Block and Calculating the Width of Roadside Backfill in a Secondary Gob-Side Entry Retaining

LI Ying-Fu, HUA Xin-Zhu

2012, 29(6):  783-789. 

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In order to solve the problem of gas accumulation and gas transfinite in the upper corner of high gassy working face, the technology of the secondary gob-side entry retaining is proposed based on existing technology of the gob-side entry retaining. Firstly, according to the activity law of overlying rock of the secondary gob-side entry retaining, mechanical model of key block in the working face tail is established, the mechanism of action between key block and surrounding rock of the secondary gob-side entry retaining is analyzed, the stability coefficients K1, K2 of key block are introduced, the stability criterion of  the key block is determined, and calculating formula of roadside supporting resistance is derived. If K1>1, then extrusion instability will emerge; If K2>1, sliding instability will emerge. By taking haulage gateway of No. 512(5) working face at Xieyi coal mine in Huainan as project background, based on stability criterion of key block, determines reasonable width of roadside backfill, and the sensitivity of influencing factors on the stability of key block are analyzed. The example analysis shows that final strength of No.1 roadside backfill and its width, mining height have great influence on the stability of key block, it is critical to improve final strength of No.1 roadside backfill and design reasonable width of No.1 roadside backfill, applying the technique of the secondary gob-side entry retaining to working face with large mining height is of more difficulty.

Instability Mechanism and Reinforcement Technology of Brickwork Roadway

XU Ying, BAI Jian-Biao, WU Zeng-Rong, FENG Jin-Sheng

2012, 29(6):  790-796. 

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In order to extend the service life of the instable brickwork roadway, the instability mechanism and reinforcement technology were studied by analytical method and engineering practice. The results show that the vault wall back cavity or the spandrel wall back cavity are easily generated in the brickwork roadway because of the influence of over excavation, mining pressure, erosion of groundwater and so on. The interaction between brickwork structure and surrounding rock can make the bending compress stress in the local brickwork structure exceed the compress strength of the brickwork structure when the size of cavity reaches a level. This leads to instability of the brickwork roadway. In addition, the control effect of comprehensive reinforcement technology play an important role, which combined with wall back filling, grouting and bolt support based on amelioration of the brickwork support loading, improvement of surrounding rock strength and increment of the support resistance for the instable brickwork roadway.

Study on the Optimal Layout of Roadways of Contiguous Seams by Simultaneous Mining

LU Yan, GAO Jie, LIU Chang-You, MA Li-Qiang, WANG Ye-Chang

2012, 29(6):  797-801. 

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Based on the geological occurrence conditions in the Western 3 Mining Area of Liudong Mine, by the theoretical analysis, this paper firstly determined the contiguous seams were mined simultaneously by descending caving method, and the roadways of the working face by mining simultaneously were arranged outward staggered. The numerical simulation was adopted to optimize the distance between roadways of contiguous seams by mining simultaneously, we drew the conclusion that the reasonable distance between roadways was 15 m in the Western 3 Mining Area of Liu dong Mine. Finally，the results were applied to 37102 and 37202 working faces in the Liu dong Mine, and the application result showed that during the mining of 37102 working face, the convergence of side wall was 131 mm and the roof-to-floor convergence was 61 mm in the lower roadway of 37202 working face. The influence scope was limited in the range of 15 m in front of working face and 25 m behind working face. Layout of roadways in close contiguous seams by simultaneous mining is rational and the deformation of the surrounding rock of roadways is controlled effectively.

Study on Breaking Law and Control Mechanism of Lower Roof in Gob-Side Entry Retaining

GUO Jian-Wei, ZHAO Jia-Wei

2012, 29(6):  802-807. 

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The broken location of the lower roof determines the broken location of the upper roof and the stability of the surrounding rock in gob-side entry retaining. Generally, the broken location of the lower roof appears near the coal side or outside of entry-side support, which is controlled by the strength of entry-side and entry-in support. In the paper, mechanical models of the lower roof with different broken locations were established based on the limited analysis theory and the mechanical equilibrium theory. The relationships between the entry-side supporting resistance and the broken location of the lower roof were obtained, and the disturbance effects after the broken of the lower roof were analyzed. The results show that it benefits to the maintaining of the entry-side support and coal side if the lower roof breaks outside the entry-side support. And then, the implementation of the bolting support to the roof was analyzed from increasing the resisting bending capacity and tensile strength of the roof and improving the stress environment, which can make the lower roof break tending to the gob.

Research on the Reasonable Coal Caving Technological Parameters of Extra-Thick Coal Seam

ZHANG Yi-Dong, ZHANG Fu-Tao, JI Ming, GAO Lin-Sheng, JIN Zhi-Yuan, CHENG Liang, WU Lin-Ping

2012, 29(6):  808-814. 

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In order to increase top coal recovery ratio of extra-thick coal seam, we analyze the impact of drawing interval on top coal recovery ratio based on the complicated geological conditions of extra-thick coal seam with large dip angle on Danshuigou coal mine. It is found that top coal recovery ratio of “Two Wining and One Caving” technique is the highest and refuse rate the lowest in the three techniques. Top coal recovery ratios in different ways of top coal drawing of extra-thick coal seam with large dip angle are studied by numerical software PFC, we identify that the “Two Wining and One Caving”with top coal drawing ways of two-times order caving and drawing interval of 1.6 m is the reasonable coal caving technology. Industrial test indicates that optimized caving technology can significantly improve top coal recovery ratio which reaches to 87.62% and recovery ratio which reaches to 87.12%.

Research of Influences of External Environment to the Reasonable Coal Production Capacity in Mining Areas

MENG Xian-Rui, LI Hai-Feng, DONG Ming-Lei, WEN Xing-Xing, LI Bin

2012, 29(6):  815-820. 

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In order to determine the reasonable production capacity of mining areas, the concept of environmental restorative cost is introduced. The environment of coal mining areas has the ability to repair itself when it is damaged, and the environmental cost of mining coal per ton is certain within the flexible scope of its self-healing capacity. But once beyond the scope, environmental restorative costs will have a sharp increase, and the coal production corresponding to the sharply increasing point is the production which the environment can carry. This requires a series of production statistics and environmental quality assessments. An environmental quality assessment should give to the mining area each year, and if the evaluation is qualified, the coal production X and the environmental cost of coal per ton will be collected to analysis, then the ratios Y of the environmental cost of coal per ton and coal price per ton should be calculated based on years of dates which considering the impact of coal prices, then curves of Y and X should be draw, and the coal production corresponding to the sharply increasing point of the curves is the production which the environment can carry. Fenxi mining area is used as an instance for research, and the determined coal production capacity has a significant importance in the environment-friendly sustainable development.

Research on High Performance Grouting Material and Improving Surrounding Rock Mass Strength

LIU Yan-Wei, CHENG Yuan-Ping, LI Guo-Fu

2012, 29(6):  821-826. 

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In order to meet the project demands of controlling mine water flooding with high pressure and rein-forcement, a new high performance grouting material has been researched. Firstly, according to the factors affecting the strength of grouting material test results, a kind of optimized grouting material ratio is designed. Secondly, a series of indoor tests are developed by the improved consolidation apparatus, including grouting material expansion force, expansion ratio and unconfined condition stress strain relationship test, as well as the permeability test. Combined with the test results, the feasibility of the new grouting material to modify and reinforce roadway surrounding rock is analyzed. Finally, combined with the industrial experiment, the practicability and superiority of high performance grouting material in roadway surrounding rock reinforcing and modifying are further verified. Test results show that the new grouting material can well meet the requirements such as anti-seepage, water-proof, dynamic pressure and deformation, which could offer effective method to the enforcement of the strengthening technology of backfilling for soft rock tunnel and grouting for surrounding rock in condition that a mine is with a wet surrounding rock mass.

Study on the Rock Burst Risk Caused by the Irrational Layout of the Mining Exploitation

WANG Yi, CAO An-Ye, DOU Lin-Ming, GUO Xiao-Qiang, DU Bin-Bin, LIU Hui, ZHU Liang-Liang

2012, 29(6):  827-832. 

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In underground mining, the irrational layout of exploitation is often caused because of the complex geological conditions and production supersedure. Thus, it is easy to cause stress concentration around a variety of coal pillars, and may result in rock burst, which has been threat to the safety of the personnel and mining production. This paper takes the example of mining operation in Section 1, District 14, Layer 17 of the south in Level 4 of one coal mine to study. The study methods in this paper are as follows: 1) According to the timing analysis of microseismic monitoring data for nearly three months, we have summarized the relationship between the trends of time information entropy Qt ,Z and the rock burst events. 2) We carried out numerical simulation of the stress distribution in this region to identify the stress concentration pillar area around which the rock burst risk is high. 3) We analyzed the influencing factors of rock burst in the irrational layout region, including the pillar, stop line and unreasonable mining sequence in the coal seam group. In this paper, the analysis and monitoring data is actually collected, reliable and enough, and the method of the data processing and the use of the para-meters Qt and Z values to characterize the burst risk are reasonable. In addition, the model which is used in the numerical simulation is well related to the actual conditions. Thus, the conclusions in the paper are credible and correct, which can be used as a reference to improve the mining layout under the similar conditions.

Numerical Simulation for Burst Failure of Two-Body Rock Structure

DENG Xu-Biao, HU Hai-Juan, XU Gang, LI Xiao-Ting, CHEN Feng-Ying

2012, 29(6):  833-839. 

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It is known that two-body rock structure, formed by one hard rock and another soft one, is the most basic rock structures of rockburst and coal & gas outburst. It investigated entirely the deformation and failure behavior of two-body rock structure by model of strain hardening & softening (SS) from FLAC3D, which varied with mechanical properties and geometry parameters of the structure. Firstly, the elastic rebound and strain localization was reappeared first time by es_plastic contour from FLAC3D. It also indicated by the simulation that the strength difference is one of the necessary conditions of the burst failure while the modulus increase of hard part decreases the burst energy. Secondly, it distinguished failure pattern of one-body-two-property & two-body-two-property with modeling, which suggests that the strength increase of interface can decreases the burst energy. Finally, it implicated that the burst failure happened only if the ratio of height and radius of rock stay in a proper alteration (for soft part is 0.5, hard part is 0.05). With simulation of same height of soft part, the burst time of failure deduced with the height ratio of the hard and soft, which indicated a more sudden burst failure.

Study on Rock Burst Mechanism Based on Geo-stress and Energy Principle

LAN Tian-Wei, ZHANG Hong-Wei, HAN Jun, SONG Wei-Hua, WU Heng, CAI Zhong-Chao

2012, 29(6):  840-844. 

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In this paper, to study the mechanism of rock burst in hard rock roadway of deep mine, combined with the engineering practice of rock burst in basalt area of Datai Mine , the characteristics of regional tectonic stress field is analyzed, and the elastic energy distribution characteristics of coal-rock body in this area is studied. Meanwhile, in the view of the tectonic stress and energy, both the stress and energy conditions of roadway surrounding rock with burst tendency are further studied when rock burst happening. The results show that the happening of rock burst must be satisfied with the stress and energy conditions simul-taneously when excavating roadway in rock mass with burst tendency, and the rock burst location and intensity are related to the direction of maximum principal stress. The research results in this paper will offer theoretical basis to the rock burst prevention, horizon roadway layout in deep mining, and roadway supporting, et al, in Datai Mine.

Study on Cavability Classification based on Analysis of Rock mass Structure Characteristics

HE Chang-Sheng

2012, 29(6):  845-851. 

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In this paper, to evaluate the cavability of ore rock comprehensively for guiding the block caving design, according to geological conditions exposed by engineering geological survey, the factors influencing the cavability of ore rock are studied by using multifactor comprehensive evaluation method．The results show that the comprehensive consideration on distribution law of the rock mass structure characteristics indexes can reflect the cavability of ore rock better．Finally, we classify the ore body cavability of one mining area in this paper, and find that the cavability of this mining area is between the levels of middle to better, which can provide an important guidance for the future work in mine.

Experimental Research on Thermal Damage Properties of Mudstone at a High Temperature

ZHANG Lian-Ying, ZHANG Shu-Juan, MAO Xian-Biao, LI Tian-Zhen, LIU Rui-Xue, GUO Xiao-Qian

2012, 29(6):  852-858. 

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The deformation and strength characteristics of mudstone were studied by using MTS 810 Rock Mechanics Servo-Controlled Testing System and MTS 652.02 High Temperature Furnace under the action of temperatures ranging from room temperature to 800℃. Although the experimental results have some certain discreteness, they also have obvious overall regularity. The elastic modulus and peak of strength increase when the temperature is between room temperature and 400℃, while they decrease rapidly when the temperature is over 400℃. Based on rock damage mechanics and statistical strength theory, combining mechanical properties of mudstone at high temperature, the damage evolution equation and constitutive model of mudstone, considering effects of temperature and loading speed, are established. Furthermore, aimed at mechanical properties of tested mudstone, the corresponding detailed parameters of damage equation are given and constitutive model has a good agreement with the experiment results.

Study on Cracks Fractal Evolution Laws of Mining Rock Mass

WANG Guo-Yan, YU Guang-Ming, YU Yong-Jiang, LU Shi-Bao, KANG Yin

2012, 29(6):  859-863. 

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Crack propagation process in the overlying strata with initial crack was studied by using the numerical test of rock failure RFPA. Mining width and initial damage using of numerical test results were analyzed based on the fractal geometry fractal dimension characteristics of cracks distribution. Fractal laws of cracks evolution in the overlying strata were obtained. Results show that there is a clear correspondence between fractal dimension and initial damage rather than initial crack inclination. Different amount of initial damage is corresponded to the different fractal dimension of cracks distribution. Especially in the mining ending stage, fractal dimension of rock fracture induced by mining with initial damage is increased linearly. The greater initial damage is that the greater the fractal dimension of cracks distribution when mining ending. A new way is provided for studying on fractal dimension of cracks distribution induced by mining when random distribution of cracks.

Development Law of Surface Cracks Caused by Thick Seam Mining and Its Formation Mechanism and Hazard Analysis

HU Qing-Feng, CUI Xi-Min, YUAN De-Bao, DENG Xu-Biao

2012, 29(6):  864-869. 

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Combined with the measured data of the observation line above the 8104 face and its geological and mining conditions, the surface cracks development process mechanism were revealed. The reason that it did not cause obvious surface cracks above the lower gateway of the 8104 face was pointed out that the pillar between the 8104 and the 8103 face was crushed. The development cycle of the trend surface cracks and the cycle breaking distance of the immediate roof is basically the same. Surface cracks development were more obvious in the compression deformation zone near the tendency observation line above the upper gateway. The distinctive feature of the overlying rock of the 8104 face is characterized by bedrock thick and loose layer thin, which show that the thick hard rock could strongly weaken the mining-induced stress and strain transfer and effectively slow down the release of stress and strain, and then slow down the dramatic surface cracks occur. According to the geological and mining conditions in the mine for production and life of the mine people, the major hazards of surface cracks were analyzed, there are easy to derive geological disaster and pose a threat to mine safety in production and endanger mine ecological environment.

Mining Disturbance Analysis in Metal Mine Based on Micromine-FLAC3D Coupling Technology

FANG Zhi-Heng, WANG Li-Guan, XIONG Zhang-You

2012, 29(6):  870-875. 

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To analyze the mining disturbance influence scope in underground metal mine and its influence degree on ground structures more reasonably and quantitatively, combined with engineering practice in Hualinggou iron mine, we proposed that using Micromine to create true three-dimensional geological model in this paper, using hexahedral discrete technology to mesh the corresponding geological model, and using coupling technology and C language to reconstruct the numerical model in FLAC3D. On this basis, we analysed the influence scope of underground mining disturbance and its influence degree on ground tailings dam. The results show that, first, using coupling technology can create more complex three-dimensional geological model. Second, using numerical calculation method can delineate mining influence scope accurately. Finally, using this technology can analyze underground mining disturbance influence on ground structures in the quantitative view.

ANFIS Prediction of the Surface Subsidence of the Old Goaf of the Gypsum Mine in Hengshan

HE Gui-Cheng, DING De-Xin, LIU Yong, ZHANG Zhi-Jun

2012, 29(6):  876-881. 

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This paper firstly used FLAC3D for simulating the surface subsidence of the old goaf of the Hengshan gypsum mine where has been collapsed. Secondly, simulating the surface subsidence of the old goaf with different structural parameters has been used and analyzed the factors which is influencing the surface subsidence. Then, the simulating results were used for establishing the ANFIS (adaptive neuro-fuzzy inference system) model for predicting the surface subsidence of the old goaf and the fitting and predicting capabilities were analyzed. Finally, the ANFIS model was used for predicting the surface subsidence of the old goaf of a gypsum mine in Hengshan and the practical surface subsidence was measured. The results show that, the accuracies of the simulating results by FLAC3D amount to 97%, and with the mechanical parameters fixed, room span, interval pillar span and stope height are the key parameters influencing the surface subsidence of the old goaf. The accuracies of the fitting and predicting results by the established ANFIS model amount to 96% and 97%, respectively, and the predicted results of the surface subsidence of the old goaf of a gypsum mine by the established ANFIS model and the measured results are in good agreement. The interval pillar span and room span are suitable to 4 m and 10m for the mining stopes of the gypsum mine in Hengshan.

Stability Analysis of Open Pit Slope Influenced by Blasting Dynamics Based on Theory of Load-unload Response Ratio

HU Jun, LIU Xing-Zong, ZHONG Long

2012, 29(6):  882-887. 

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In this paper, based on the rock slope conditions of the final mining boundary in one open pit metal mine, the strength reserve safety factor of slope in natural condition is calculated by using the software of FLAC3D and the method of strength reduction. In order to analyze the dynamic stability of slope under different strength reduction factors, the explosive dynamic loading is applied on open pit bottom of -50 m level as the form of normal compressive stress by using the measured data. Meanwhile, the nonlinear theory of load-unload response ratio (LURR) is introduced to analyze the dynamic stability of slope, and the LURR model of slope under the explosive dynamic loading is then established. By considering the periodical variation of additional explosive loading at different feature points of slope as the load-unload amount, and the deformation of corresponding feature point as the response parameter, the LURR of slope feature point during the action process of explosive loading is then determined. The calculation results show that the LURR value of the feature point is near 1 when the slope system is stable, and it is gradually increased as the slope approaching instability. The LURR variation law men-tioned above presents that it is feasible to use LURR as the judgment basis of slope stability influenced by explosive loading. It also can extend the analysis function of strength reduction method, which is worth popularizing and has important theoretical significance.

Study on High and Steep Slope Stability in Condition of Underground Mining Disturbance

XU Shuai, LI Yuan-Hui, AN Long, YANG Yu-Jiang

2012, 29(6):  888-893. 

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According to the upward access filling mining scheme of the boundary ore body, the author accomplishes the numerical simulation of the impact from the underground mining methods on the high and steep slope stability. The numerical simulation of the large deformation of discrete element, the finite element static force and the slope stability under blasting dynamic load may be obtained. The calculating results demonstrate that the access and every-other-stope exploration method, with a vertical ore body layout of 4m height and 4m breadth and timely concrete filling, will acquire a safety factor of 1.50. Therefore, the stope production beside the nearest slope has not lead to connecting plastic zones or slip bands. Under the blasting dynamic load, the vibration velocity of the nearest slope toe will reach 3.2 cm per second, which is within the slope allowing limit. The discrete element calculating results show that after exploration the slope safety factor of boundary ore has reduced to 1.453, which still is the first-class slopes. The engineering practice has proved that the boundary ores had been explored and filled by the time of May, 2011. The slope project stability turns to be sound, and there is no sign of such disasters as landslide, collapse or subsidence until now.

Experimental Study on Regularity of Blasting Crack Spread in a Coal Contained Gas

CHU Huai-Bao, HOU Ai-Jun, YANG Xiao-Lin, YU Yong-Qiang, LIANG Wei-Min

2012, 29(6):  894-898. 

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In order to study the blasting mechanism of coal contained gas further, we have analyzed the mechanism of blasting crack formation and propagation theoretically, and designed the blasting crack propagation experiment. The blasting crack propagation velocity and the blasting strain waves have been measured. The theoretical and experimental results show that the blasting crack propagation has three stages. One is rapid decay stage under blasting stress wave, the other one is slow decay stage and the last one is approximate uniform propagation stage under detonation gas and coal mine gas. The coal mine gas plays a positive role in the blasting crack propagation, and it can increase the crack propagation velocity in a small range in the later stage.

Research on Gas Distribution under Stepwise Tectonic Control Mode in Kailuan Mining Area

WANG Meng, ZHU Yan-Ming, CHEN Shang-Bin, LI Wu

2012, 29(6):  899-904. 

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In this paper, based on the research on gas geological characteristics of 10 pairs of outburst mines, we analyzed the gas content, pressure and measured data of emission quantity, summarized the rules of gas geology in Kailuan Mining Area, and put forward the gas occurrence under stepwise tectoniccontrol mode. The results show that the axial part of syncline structure is beneficial to the gas occurrence, and the gas unusual district distribution is controlled by the distributions of reverse fault, groundwater runoff and magmatic rock. Meanwhile, the tectonic setting of gas occurrence is established by the regional structure, while the gas occurrence in Kailuan Mining Area is controlled by the strurctures in the mining area level. Moreover, the gas distribution is different in each syncline structure, and the gas occurrence in one mine is controlled by the structures in the mine area.