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2009, 28 (02): -0214 doi:
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RESEARCH ON BASIC THEORY OF MINING WITH WATER RESOURCES PROTECTION AND ITS APPLICATION TO ARID AND SEMI-ARID MINING AREAS

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2009, 28 (02): -0217 doi:
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The mining with water resources protection in arid and semi-arid mining areas is not only an important national development strategy，but also one of the key study contents in the basic and applied sciences. Combining with the specific geological and mining conditions in Shendong coal mine，some researches on basic theory of mining with water resources protection and their application to arid and semi-arid mining areas are performed systematically，including the analysis of hydrogeological structure，the development law of water flowing fractured zone in overburden rock，the stability of the water-resisting key strata，the water-preserved mining method with the aquifer above the water-resisting strata，the advance dewatering，transferring and storage of the water for the aquifer above the non-water-resisting strata，etc.. According to the analysis of hydrogeological conditions，the shallow water-bearing region is classified into four types of hydrogeological structure；and the water-resisting strata area is classified into five water-bearing structures，so five kinds of regionalizations in water-preserved mining are put forward. According to the field measurement，the numerical simulation and the theoretical analysis，the crack evolution law of mining strata and the seepage passage development law are revealed；and then the instability(destabilization) condition of the water-resisting key strata is given. Considering the various geological and mining conditions，aiming at the aquifer above the water-resisting strata，some water-preserved mining methods are proposed，such as the water-preserved mining by controlling the structural stability of the water- resisting key strata，the water-preserved mining by controlling the close of the mining water-conduct crack，and the water-preserved mining by filling in partial support area. Aiming at the aquifer above the non-water-resisting strata，the storage method of transferring water from the aquifer to goaf by advanced dewatering is put forward，which has a good application effect in practice.

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WATER INRUSH CHARACTERISTICS OF FANGEZHUANG COALMINE FIELD IN KAILUAN AND ITS GEOLOGICAL CONDITION ANALYSIS OF WATER INRUSH FROM COAL SEAM FLOOR

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2009, 28 (02): -0228 doi:
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Water inrush risk forecasting and evaluation of coal roof and floor are the basic issues of water inrush disasters prevention in coalmine field. Based on Fangezhuang coalmine field in Kailuan，water inrush characteristics and the sandstone fracture aquifer thickness of coal seams from No.12 to No.14，water inrush medium conditions(lithology，interlayer distance)，and water inrush structure conditions，are all analyzed from the two aspects of promotion and treatment of water inrush. Correlation and models between water inrush of coal seam floor and geological conditions are established. And also，the controlling mechanism is discussed. It is shown that water source that induces water inrush in this area takes the confined aquifer of sandstone fracture of coal seams from No.12 to No.14 as the main body. The thickness of sandstone fracture aquifer becomes thicker from the shallow to the depth of the mine field；and water abundance enhancement presents linear correlation. Water isolation of coal floor depends on the thickness of aquifuge and its shale percentage content. Limit thickness of floor mudstone has a positive correlation with water pressure；the abilities of mudstone layer¢s resisting water pressure enhance and water isolation becomes better with the increase of mudstone thickness of coal floor. Thus，the mudstone layer with intact structure floor has obviously larger ability of resisting water pressure than that of mudstone layer with fracture. Water inrush is closely related to the structures. Maximum water emission of water inrush point has positive correlation with fault density. Water inrush from fault is attributed to destructive effect of fault to coal and rock seams，resulting in the increase of its fracture，porosity and the considerable decrease of the mechanical strength around fault. Also，it is controlled by regional tectonic and modern tectonic stress environment. Those achievements provide theoretical basis for water inrush risk evaluation and forecast of floor of coalmine field No.12 and underground water inrush prevention.

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MONITORING AND SIMULATION RESEARCH ON DEVELOPMENT
OF WATER FLOWING FRACTURES FOR COAL MINING UNDER XIAOLANGDI RESERVOIR

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2009, 28 (02): -0238 doi:
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There are over 80 million tons coal under the water body of Xiaolangdi Reservoir in Xin¢an coal mine area，China¢s Henan Province. The coal thickness changes from 0.0 m to 18.8 m；therefore，it is difficult to calculate exactly the height of water flowing fractured zone that may cause water disaster by using the known methods. In order to determine the upper limit of water flowing fractured zone，ultrasonic imaging technology is used in 5 ground surface boreholes；and the parallel network electrical CT technology is used in 5 boreholes in the coal mine to observe the failure process and the maximum height of water flowing fractured zone. Furthermore，physical and numerical simulations are also used to observe the height in more different excavating cases. The detecting and simulation results demonstrate that the height of water flowing fractured zone is mainly determined by coal thickness excavated in a nonlinear relationship. A formula is given based on this research；and it is used to determine the safe area while mining under the water body of Xiaolangdi Reservoir with combination of other affecting factors of water inrush. The result is verified to be reliable by successful industrial mining experiments of three working faces in the safe area.

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RESEARCH ON WATER-RESERVED MINING WITH HIGH WATER PRESSURE UNDER LARGE-SCALE THRUST-FAULT IN ORDOVICIAN KARST

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2009, 28 (02): -0246 doi:
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The residual thicknesses of aquifuge and mining reactivations of the fault are the key factors to control the water inrush when mining is near the large-scale fault with karst aquifer under the floor. Taking the mining working face of deep coal seam under large-scale thrush-fault with high water pressure of Ordovician karst at Liuxin mine in Xuzhou mining area as a case，the numerical simulation，the mechanical analysis and the geological evolution process have been performed based on the viewpoint that aquifuges exist in Ordovician top and can be considered as key aquifuges，which can guarantee the safe mining of the working face. The research results show that in the experimental area，there are carbonatite aquifuge about 118 m in thickness，in which the karst cave is refilled and undeveloped. The fault in natural state is not water-conducting one；and the part of thrush-fault between coal seam in drop side and the Ordovician roof(about 60 m) in upthrust side is reactivated by mining，but the part of thrush-fault in top Ordovician aquifuge is not reactivated. If the Ordovician top is saturated with karst water，the water driven by high water pressure may infiltrate to the working face along the reactivation part of fault，which means the water inrush will occur. The aquifuge existing in Ordovician top is the primary reason for the mining safely around the fault.

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RESEARCH ON EXPERT SYSTEM FOR RISK ASSESSMENT OF WATER INRUSH FROM COAL FLOOR AND ITS APPLICATION

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2009, 28 (02): -0253 doi:
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Risk assessment of water inrush from coal floor is a complex problem of theory and technology，which is concerned with hydrogeology，engineering geology，mining conditions and rock mechanics. To aim at the above-mentioned problem，the expert system for risk assessment of water inrush from coal floor is combined with experts¢ experiences and theoretical achievements with artificial intelligence technology，adopting two inferred methods，which are the water inrush coefficient and the preferred water inrush plane. The inference strategy of weighted analogy analysis of typical water inrush cases is put forward. This system is basically capable of forecasting the development of limestone karst and potential fault structure below the coal floor. This system is composed of four knowledge bases，i.e. base of typical water inrush cases，base of expert experiences，base of theoretical achievements，and base of water control measures. The risk，location and type of water inrush can be forecast and assessed through this system. Simultaneously，this system also has a great consultant value for water inrush from coal floor. The answer of simulation analysis applying this system to the realistic water inrush cases is in good accordance with the truth condition. The expert system will be of some values for controlling and preventing water inrush from coal floor.

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RESEARCH ON TRANSIENT ELECTROMAGNETIC FIELD OF MINE WATER-BEARING STRUCTURE BY PHYSICAL MODEL EXPERIMENT

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2009, 28 (02): -0259 doi:
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[PDF 529 KB] (1282)

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By using the physical model experiment，the transient electromagnetic response character of mine water-bearing structure is studied，which provides an important basis for the improving interpretive method and advancing accuracy of detecting mine water-bearing structure. According to the similarity criterion of the physical model，the specific parameters of physical model and the corresponding correction factors are calculated. In addition，the mine water-bearing structure model and the transmitting and receiving devices are constructed；and the antenna parameters and detection abilities are comparatively analyzed. The results indicate that for the same transmitting antenna parameters，the more the turns of receiving antenna are，the stronger the received signal is；the larger the current in transmitting coil is，the stronger the received signal is. Under the same conditions，the inductive signal from the square antenna device is stronger than that of circular antenna. The physical model experiments are performed for interference characteristics of induction field from laneway space and metal body within laneway space. The results indicate when antenna lies near the side of the water-bearing structure，the received response value is the maximum. When the antenna lies away from the side of the water-bearing structure，the detecting ability is lower because of the influence of laneway space；the response values become strong for the metal(H-iron，metal netting and rail) in laneway space，but the response law of water-bearing structure is not affected.

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EXPERIMENTAL RESEARCH ON MINE FLOOR WATER HAZARD EARLY WARNING BASED ON RESPONSE OF GEOELECTRIC FIELD IN GROUNDWATER SEEPAGE

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2009, 28 (02): -0267 doi:
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[PDF 342 KB] (1320)

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Through the establishment of model of seepage-electric test，the temporal-spatial domain parameters of geoelectric field in the course of seepage are achieved by the network parallel electrical instrument(NPEI). For the first time，the geoelectric field transient response is obtained in space. Based on the characteristics of potential and current isochrones and apparent resistivity isochronous section，the experiments show that natural electric field represents rising trend in the temporal-spatial field in the course of seepage. The isochronal extreme point of natural potential indicates the position of seepage；and natural electric field possesses ahead of water surface. The fluid surface and the seepage velocity can be accurately ascertained through exciting voltage and exciting current of primary field；and it is suitable for revealing asymmetric seepage law of geologic body. The real-time apparent resistivity images have the ability to track and identify seepage zones and the quantity of water. With apparent resistivity stepping down，groundwater seepage tends to be saturated. Through the practical geoelectric field monitoring in the Wugou Mine，the water inrush of 1013 working face is successfully predicted ahead of two days. The isochronal extreme point of laneway natural potential indicates the position of water inrush. Apparent resistivity isochronal section indicates water-head horizon of water inrush. The spatial synchronization monitoring technology of geoelectric field is adopted in mine；and the real-time monitoring of the coal floor water disaster will be feasible. It possesses extensive application to mine water inrush prevention and controlling.

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RELATIVE STRATA IMPERMEABILITY IN ORDOVICIAN TOP AND RISK ASSESSMENT OF WATER INRUSH FROM COAL FLOOR IN XINYI COALFIELD

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2009, 28 (02): -0273 doi:
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[PDF 516 KB] (1444)

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In order to explore the safety mining of Carboniferous-Permian coal resources，especially a great deal of lower coal seams being threatened by Ordovician karst water，relative impermeability of Ordovician top is demonstrated through studying lithology，filling degree of the karst fissures as well as water leakage of drilling fluid and aquifer shown in well logging based on the viewpoint that water-resisting strata exist in Ordovician top and can be considered as water-resisting key strata. Furthermore，the main influencing factors on impermeability of coal seam floor are analyzed；and divisional risk assessment of floor water-inrush from Ordovician karst is performed. Overall，accuracy of risk assessment on floor water-inrush can be improved by considering the relative water-resisting strata in Ordovician top as part of the whole ones.

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INFLUENCES OF 3D INTERNAL CRACK DIP ANGLE ON TENSILE MECHANICAL PROPERTIES AND FRACTURE FEATURES OF ROCK-LIKE MATERIAL

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2009, 28 (02): -0281 doi:
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[PDF 387 KB] (1489)

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Uniaxial tensile experiments are conducted to study the influence of 3D internal crack dip angle on tensile mechanical properties and fracture features of rock-like material. Special mortar sample of which physical and mechanical parameters are closed to those of sandstone is prepared；and spatial location device for 3D crack is designed. Some improvements are performed for direct tensile experimental methods with rocks；and location equipment for rock-like material bonding tensile experiment is also presented. Experimental results indicate that the tensile loading and deforming process of mortar samples with preexisting crack can be divided into four stages：flaws opening stage，elastic deformation stage，elastoplastic deformation stage，and failure stage，among which elastic stage takes up the most proportion；and the abrupt failure stage is obviously different between tensile and compressive failure. Change of crack dip anglea has much influence on mortar mechanical properties. As a grows (0°＜a＜90° ，the peak strength，sP，of sample reduces gradually，and when a is around 45°，the sP change amplitude is the largest. Under uniaxial tensile stress，the wrapping wing crack and secondary crack initiate sequentially near the long axis front of internal crack；and the kink region also initiates near the short axis front of internal crack. Finally，the tensile propagation of cracks leads to sample fracture. The change of dip angle has great effects on crack propagation track and sample failure mode.

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NUMERICAL ANALYSIS OF PATHWAY FORMATION OF GROUNDWATER INRUSH FROM FAULTS IN COAL SEAM FLOOR

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2009, 28 (02): -0290 doi:
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APPLICATION OF FAULT TREE ANALYSIS TO RISK ASSESSMENT OF POTENTIAL WATER-INRUSH HAZARDS IN COAL MINING

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2009, 28 (02): -0298 doi:
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STUDY OF MECHANISM OF STOPE WATER INRUSH CAUSED BY WATER ACCUMULATION IN OVERBURDEN SEPARATION AREAS

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2009, 28 (02): -0306 doi:
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[PDF 324 KB] (1218)

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Through engineering geology investigation and theoretical analysis，the mechanism of abnormal water inrush in the roof of working face 745 under the condition of giant thick igneous rock cover in Haizi mine is researched. The results show that the water accumulation in the separation area under the giant thick igneous rock cover with 62 m away from the coal seam is the water source that causes the abnormal water inrush of working face 745. According to the traditional estimation method，the height of water flowing fracture zone is 25.3–36.5 m，which can not connect the accumulated water in the separation area under the giant thick igneous rock. However，the loading transfer effect of separation area water induces compound breakage of two inferior key strata in lower part，so height of water flowing fracture zone develops abnormally，and it connects separation area water，which is the reason of the 745 working face abnormal water inrush. The mechanism of separation area water inrush indicates that probing and discharging borehole drilled to the separation area can prevent this kind of water inrush.

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PREDICTION OF QUANTITY OF WATER INRUSH FROM COAL SEAM FLOOR AND ITS REINFORCEMENT TECHNIQUE BY GROUTING

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2009, 28 (02): -0312 doi:
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[PDF 353 KB] (1246)

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Based on the Chezy rule，which can describe crack water flow of bedrock，the mathematical model of confined aquifer is set up；and the formulae of water flow and water inrush according to Lagrangian method and Bernoulli energy equation are deduced. Calculating results indicate that the error of computed water inrush and actual in-situ water inrush is only 1.04%. Aiming at the situation of water from flooding to floor of coal seam at a majority of coal mines in Jiaozuo mining area，the method of reinforcement of floor aquifer by grouting to prevent water inrush disasters is put forward. The grouting holes are mainly arranged according to developing extent of fractures and its directions on the strike；and the spaces between grouting holes are determined by diffusing radius of grouting. Grouting parameters such as grouting pressure and grouting quantity are also analyzed；and high pressure water-stopping device is manufactured，which can solve the problem of water-stopping in advancing flow at grouting hole.

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DETECTION OF WATER-RESISTING LAYER IN UPPER ORDOVICIAN SYSTEM BASED ON SEISMIC INVERSION METHOD

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2009, 28 (02): -0319 doi:
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[PDF 547 KB] (1234)

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It is an important issue for coal seismic survey to detect lithologic distribution，to verify the existence and distribution characteristics of aquifuge in the upper portion of Ordovician system indirectly，and to solve water inrush problem on coal bottom for mining safety by utilizing 3D seismic results. Seismic inversion is one of important techniques in lithologic seismic survey. It combines both logging data with high vertical resolution and seismic data that are collected continually，improving both vertical and horizontal resolutions of 3D seismic data，and it can improve the study level of underground conditions. 3D seismic data in the test area are inversed by seismic inversion；and spacing distribution and thickness variation of both aquifer and aquifuge in the upper portion of Ordovician system are also determined. Researching results show that there is a aquifuge in the upper portion of Ordovician system，and the achieved results can lay a solid foundation for the water quantity forecasting model in mining water inrush.

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MMH SUPPORT VECTOR MACHINES MODEL FOR RECOGNIZING MULTI-HEADSTREAM OF WATER INRUSH IN MINE

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2009, 28 (02): -0324 doi:
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A novel hierarchy support vector machines(H-SVMs) model is presented to recognize the headstreams of water inrush in coal mine. Firstly，an analytical model is deduced to analyze the generalization power of H-SVMs. According to the results，a feasible approach is put forward to improve the performance of H-SVMs to guarantee the performances of each SVM node，whose position is located at a high level. Secondly，a novel method is presented to build H-SVMs，i.e. MMH-SVMs(maximal margin hierarchical SVMs)，taking the separating margins of each SVM node as indices for classification and clustering，using TopDown and BottomUp routes from top to bottom to classify the input samples at each SVM node by maximal separating margin and from bottom to top clustering the input samples by minimal separating margin. Experimental results show MMH-SVMs have a simple structure，and a good generalization performance. It can predict the headstreams of water inrush correctly；and its tree structure can also denote the hierarchy of headstreams. Moreover，the normal vector parameter W in each SVM decision function can describe the weights of discrimination indices of the headstreams of water inrush，in which a novel scientific method is introduced to predict the headstream of water inrush in coal mine.

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FISSURE-EVOLVING LAWS OF SURROUNDING ROCK MASS OF ROADWAY AND CONTROL OF SEEPAGE DISASTERS

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2009, 28 (02): -0330 doi:
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Water inrush in working face and support failure of the driven roadway caused by underground seepage occur from time to time. Based on experimental study on permeability behaviors of argillaceous rock during the complete stress-strain loading process，an analysis of the gradual development process of rock fissure under spatiotemporal changes in the roadway constructing area is carried out. Dynamic permeability evolving laws and three-directional(i.e. axial，radial，and circular) distributing characteristics of the surrounding rock have been explored. The laws are of great importance to determine key parameters of grouting depth，layout of grouting holes and optimum grouting opportunity. Further studies are presented to get perfect grouting opportunity and rational layout of grouting holes to prevent seepage disasters. A whole set of grouting control technology is put forward. A successful engineering case of a roadway crossing fault zone lying in sandstone bed aquifer is presented to provide valuable guidance for surrounding rock mass of roadway constructed under the threat of seepage. Thus，the slowing-down and even elimination of seepage disasters can be expected.

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EXPERIMENTAL RESEARCH ON FRACTURE EVOLUTION LAW OF WATER-RESISTING STRATA IN COAL SEAM FLOOR ABOVE AQUIFER

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2009, 28 (02): -0336 doi:
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[PDF 484 KB] (1562)

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The Ordovician karst water is one of the hazards in the safe mining in North China. Mining above aquifer is one of the effective methods，which is used to exploit the coal seam threatened by water-inrush from floor. In order to analyze the water inrush risk from coal seam floor above aquifer，a water pressure loading system of the confined aquifer on coal seam floor is self-developed to realize the physical simulation of the confined aquifer acting on the aquifuge in floor using pressure water bags. The deformation and failure characteristics of aquifuge in floor are analyzed to obtain the rules of the fractures of floor developing，extending and running through each other. And then，the water-inrush passageway will be formed. The research results can provide references to the mechanical mechanism of water-inrush from floor.

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MECHANISM AND TREATMENT METHOD FOR POTENTIAL WATER LEAKAGE OF AQUIFER THROUGH BOREHOLES IN ORDOVICIAN LIMESTONE

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2009, 28 (02): -0342 doi:
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Some of the water inrush accidents in mining are caused by unfavorable blocking of boreholes；and water inrush caused by unfavorable blocking of boreholes in aquifer of Ordovician limestone is the most harmful. Taking Xinglongzhuang coal mine for example，the potential water leakage of the boreholes in aquifer is introduced according to the hydrogeological data collected from the new water exits in coal crosscut of mining area I in Ordovician limestone. Water samples show that the water is located in Ordovician limestone and abnormal water level in X-down stratum of Ordovician limestone is found；and the potential leakage passage is determined，which may be caused by unfavorable cement blocking of boreholes. Because of the changes of the geological conditions of the boreholes¢ positions，the boreholes may penetrate into the water-enriched area of the Ordovician limestone；and then water drainages toward other aquifers with high pressure and high velocity will be formulated，which are the main factors induced by the unfavorable cement blocking of boreholes with the potential leakage passage. A chemical grouting method is presented；and it is found valuable references can be provided with the method for treating the water inrush hazards.

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RESEARCH ON ELECTRICAL PREDICTION FOR EVALUATING WATER CONDUCTING FRACTURE ZONES IN COAL SEAM FLOOR

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2009, 28 (02): -0348 doi:
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In the experiment，the variation in resistivity of different rock samples during the complete stress-strain process under the water-filling condition is studied；and the variation rule of conductivity of water conducting fractures formed in floor during the mining activity is obtained. In addition，the geoelectric model for dynamic evolution of mining induced water conducting fractures is constructed. From the numerical modeling with 3D electrical resistivity software，the response characteristics of apparent resistivity of water conducting fractures in coal seam floor are achieved，which can provide a theoretical basis for designing the data acquisition system and data processing. Based on the theory of full-space high-accurate 3D electrical resistivity method，the principles and technical requirements for designing the dynamic monitoring system of water conducting fractures are put forward，which have been successfully used in a certain coal mine in Anhui Province. The result shows that the application of 3D electrical resistivity in detecting the evolution of water conducting fractures in coal seam floor is effective；and it can present the failure mode of coal seam floor in mining process；so it is quite favorable for schemes of predicting and preventing water inrush from coal seam floor.

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EVOLUTION LAWS OF STEP OVERLYING STRATA UNDER LARGE MINING HEIGHT AND WATER INRUSH PREVENTION

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2009, 28 (02): -0357 doi:
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In condition of thick seam and large mining height，the step instability of rock covering is caused by height of the caving zone；and fractured zone is increased and activity degree of strata is enhanced in fractured zone. Therefore，it is the important factor that causes water inrush in mining. However，the step instability of stratum in fractured zone is related to lithologic structure and combination of lower strata. Based on the important influence of lithologic structure on step instability and the water inrush prevention under large and thick seam mining height，the law that different lithologic associations among coal seams with influences on integrity and continuity of upper coal seam are studied by numerical calculation and field test. The conclusions show，when lithologic association between coal seams is soft-hard，as the proportion of lower strata to spacing of layers is higher，the step generated in upper coal seam is lower，and soft strata structure is favorable for decreasing step of upper coal seam than hard strata structure. Components of lithologic structures are put forward to determine step values；and the step and distribution law of cracks are determined. The effective measures are presented to prevent the water inrush；and safety production of working face is guaranteed.

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ANALYSIS OF PROBABILITY OF WATER INRUSH FROM GROUT CURTAIN BASED ON BACKGROUND STRESS FIELD AND MICROSEISMICITY

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2009, 28 (02): -0366 doi:
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In order to understand the relation between background stress field of three-dimensional numerical simulation with microseismicity and water inrush probability，combining with an engineering case of grout curtain community for Zhangmatun iron mine，an operation microseismic monitoring system of ESG is used. Then，the accumulated three-dimensional geometry spaces of micro-rupture is delineated；and the possible dangerous water inrush regions of grout curtain community are divided. A three-dimensional mechanical model of curtain community is established by three-dimensional FEM，MSC.PATRAN，to simulate the background stress field distribution under high water pressure to obtain the stress field concentration region of curtain community. The comparative research results show that a large number of microseismic location events are accumulated at curtain southwest region and orebody bilateral mined-out area；the microseismicity information is very clear；original stress field greatly changes under high water pressure and mining disturbance in the above two region. There are the apparent stress concentrations here，which implies that micro-rupture will occur，develop and link under high stress. So microseismicity and background stress fields are almost consistent；and different scientific research methods illustrate the precursory characteristics of background stress field and microseismicity of grout curtain community. Then，the probability of water inrush is evaluated preliminarily. As a result，some reasonable exploitation methods and prevention measures can be adopted to provide safe measures for underground mining activities.

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SEEPAGE CHARACTERS OF ROOF AQUIFERS IN FAULTS AND SLIDING STRUCTURE AND RISK ANALYSIS OF WATER INRUSH

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2009, 28 (02): -0373 doi:
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Faults and folds are the key factors causing water inrush in mine. In order to study the seepage characteristics of direct water falling aquifer existing faults and sliding structure，roof aquifers of coal seam No.47 are simulated using finite difference software，MODFLOW，based on the analysis of hydrogeological conditions in Ningzhuang coalmine. Seepage fields of roofs of coal seam No.47 from 2003 to 2006 are simulated through spatial dispersing，stress field determining，wall treat of faults and input of sources and sink items. Then，aquifer model is established. Finally，seepage field laws after 5 and 10 years later are presented. It is shown that the water level of roof aquifer is higher，while in the place of sliding structure in mining，the water inrush risk is still high.

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EFFECTS OF PRIMARY KEY STRATUM LOCATION ON HEIGHT OF WATER FLOWING FRACTURE ZONE

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2009, 28 (02): -0380 doi:
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Theoretical analysis，simulation experiment and engineering exploration are adopted to study the impact of the location of primary key stratum(PKS) on the evolution range of water flowing fracture. The final result shows that，as the distance from PKS location to coal seam is shorter than a certain value，the fracture extends to the top of bedrock，while the height of water flowing fracture is obviously larger than its value calculated by the conventional estimation method based on “Regulations of buildings，water，railway and main well lane leaving coal pillar and press coal mining”(Regulations for short). The height of coal seam，the dispensability and compressibility of broken roof gangue，and the size of the broken block of PKS are the main evaluating factors of water-flowing fracture，which are concerned with the critical distance between PKS location and mining seam. The critical value can be generally concluded in the value 7–10 times as the height of coal seam. As the distance from PKS to coal seam is shorter than the critical value，the method based on the Regulations is unreasonable；as the distance from PKS to coal seam is larger than the critical value，the method based on Regulations is available. Therefore，the above research result is the certain explanation to the mechanism of irregular water inrush accident in some coal mines. The achieved results have been employed to conduct the water inrush protection in Bulianta coal mine，Shendong coal field；meanwhile，the significant benefits have been obtained.

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RESEARCH ON EFFECT OF FAULT DIP ON FAULT ACTIVATION AND WATER INRUSH OF COAL FLOOR

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2009, 28 (02): -0386 doi:
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According to the stress characteristics of coal floor with faults，corresponding simplified mechanical model is built to obtain the equations of shear stress and normal stress on the fault，as well as the influential rules of fault dip on shear stress，normal stress and fault activation. At the same time，under the circumstances of different normal fault dips，the fracture distributions and seepage distribution of coal floor as well as the variation characteristics of inflow quantity of coal floor in the mined area are simulated with mining carried out by using the RFPA2D-Flow software. The numerical simulation reveals the formation principle of water inrush channel in coal floor with fault structure as well as influential rule of fault dip on water inrush in coal floor. Overall，the results indicate that normal faults with low dip angles are more easily activated to induce water inrush in coal floor，which has an important value in the case of coal floor with faults when waterproof coal pillars are needed.

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RESEARCH ON SIMULTANEOUS EXPLOITATION OF COAL AND GROUNDWATER IN LU¢AN COALFIELD

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2009, 28 (02): -0395 doi:
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[PDF 385 KB] (1452)

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Based on the concept of green mining and dynamics of fluid in rock mass affected by mining，the viewpoint of simultaneous exploitation for coal and water to continuously utilize water resources as well as safely mining is put forward，which is different from the traditional mining methods，such as draining water before mining and combination of drainage and application for other purpose. At the same time，taking the Lu¢an coalfield as case study to analyze the characteristics of groundwater system，mining groundwater is successfully utilized and simultaneous exploitation of coal and groundwater by using the water-resisting capability of Ordovician top is implemented. The results indicate：(1) the simultaneous exploitation of coal and groundwater can not only properly exploit groundwater to maintain the dynamical balance state of spring group flow，but also make it possible to mining a great deal of coal resources in shallow part economically and safely，which is threaten by Ordovician water；(2) the discovery and utilization of aquifuges in Ordovician top are the precondition and guarantee to carry out simultaneous exploitation of coal and groundwater without reducing the water level of Ordovician groundwater under floor，which will release not only the coal seam No.3 but also the lower coal seams which account for one third of total reserve in the mine area；and (3) simultaneous exploitation and utility of coal and groundwater have played a major part in keeping the basic exploitation-recharge balance of groundwater in the mining area and even in the whole basin. Overall，the objective of the simultaneous exploitation of coal and groundwater is to exploit this two kinds of resources properly without destroying water and environment and decreasing safety.

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RESEARCH ON INFLUENCE OF OVERBURDEN PRIMARY KEY STRATUM MOVEMENT ON SURFACE SUBSIDENCE WITH IN-SITU DRILLING TEST

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2009, 28 (02): -0403 doi:
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Based on the contrastive analysis between the in-situ test on interior rock movement and surface subsidence observation at working face No.31401 of Bulianta coal mine in Shendong mining area，the influences of overburden primary key stratum on surface subsidence are researched. The results indicate that the movement and deformation of overburden strata and surface are controlled by the primary key stratum，which is siltstone with the thickness of 47.01 m；and the movement of overburden strata changes periodically with the breakage of primary key stratum. Controlled by the primary key stratum，the subsidence velocity curves of the measuring points are influenced markedly by the measuring interval. The shorter the measuring interval is，the more obvious the periodical jumping change phenomenon of corresponding subsidence velocity curve is. Otherwise，the subsidence velocity curve is more even. Therefore，the measuring interval should be shortened in order to reflect the dynamic process of surface subsidence exactly in shallow coal seam mining；and then the inherent relationship between interior rock movement and surface subsidence can be realized correctly，which can promote the development of surface subsidence prediction.

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TEST ANALYSIS OF DEFORMATION CHARACTERISTICS AND COMPRESSIVE STRENGTHS OF TWO TYPES OF COAL SPECIMENS CONTAINING GAS

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2009, 28 (02): -0410 doi:
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[PDF 432 KB] (1724)

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A manufacturing process of coal briquette specimen(CBS) and raw coal specimen(RCS) is introduced；and then the method and steps of triaxial test for coal specimens containing gas(CSCG) are designed. By means of triaxial compressive experimental apparatus composed of a self-developed triaxial creep gas-seepage device and a material testing machine，the tests of CSCG are performed on CBS and RCS and a large number of test data under different confining pressures and gas pressure conditions are obtained；and the deformation characteristics and compressive strength of the two kinds of CSCGs are mainly investigated in triaxial stress conditions based on the experimental results. The results show that the confining pressure and gas pressure have a certain extent effect on the deformation characteristics and compressive strength of CSCG. The CBS and RCS have a commonness to some extent in deformation characteristics and compressive strength，but there are distinct differences between the mechanical parameters of the two kinds of coal specimens. The elastic modulus and Poisson¢s ratio are not constant but variable during the distorting of CSCG；and the elastic moduli of the two types of CSCGs are very different and their Poisson¢s ratios are also not equal actually；the deformation of CBS is much larger than that of RCS under a same loading condition，and in addition，the shape change of CBS is also larger than that of RCS. The results have a reference valuable for further exploring the mechanical properties of coal containing gas in future.

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PREDICTION OF GROUND DEFORMATION INDUCED BY SHIELD TUNNELING CONSTRUCTION

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2009, 28 (02): -0418 doi:
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[PDF 279 KB] (2064)

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Theoretical analysis shows that ground movement patterns induced by shield tunneling construction for different kinds of soils will be different. Assuming soil is undrained，the Verriujt¢s formula is modified by N. Loganathan¢s method. Based on uniform ground movement pattern of shield tunnel，two-dimensional analytical solution of soil deformation induced by shield tunneling construction is deduced；and the method is applied to different construction phases. As shown in analytical calculation，the predicted ground displacements are in good agreement with the measured values；and this method is applicable for the clayey soil from flow-plastic state to stiffness state. While Loganathan¢s formula is only fitted for flow-plastic state clay，the predicted ground settlements for stiffness state clay are smaller than the measured values. The settlement of soil above tunnel by shield construction increases nonlinearly from ground surface down to deep；and it reaches the maximum value in the roof of tunnel；the closer the soil to tunnel is，the faster the settlement is. The horizontal displacement of the tunnel surrounding soil increases from ground surface down to deep；but it reaches the maximum value over the tunnel axial line and then gradually reduces to zero. The nearer the soil to tunnel is，the larger the horizontal displacement of soil is.

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METHOD FOR PARAMETERS DETERMINATION WITH UNIFIED RHEOLOGICAL MECHANICAL MODEL

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2009, 28 (02): -0425 doi:
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[PDF 217 KB] (1335)

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2009, 28 (02): -431 doi:
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[PDF 157 KB] (956)

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