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In China,many mining areas with extremely thick and hard rock strata has strong mine earthquake and strong rock burst caused by the movement of extremely thick and hard rock strata which have serious consequences,is difficult to be controlled and has become the main obstacle to mine safe production.Based on the analysis of the occurrence law of rock burst under extremely thick and hard rock strata, the paper puts forward three common characteristics of rock burst in such mines: "the effect of key working face", "the effect of vibration-induced rock burst"and "the effect of rock burst and vibration. ""Key working face "means that the mining of this working face will lead to the fracture and strong movement of extremely thick and hard rock strata and the occurrence of strong earthquake or rock burst. "The effect of key working face"refers to the strong dynamic disasters occurring in the mining process of "key working face". "The effect of vibration-induced rock burst"refers to the rock-burst hazards caused by the dynamic stress which generated by the fracture and vibration of extremely thick and hard rock strata propagating to the coal body in the high stress state. Its feature is that "the location of the source is different from that of rock burst. ""The effect of rock burst and vibration"means that when the key working face is mined, the transmission pressure of extremely thick and hard rock strata will increase sharply.When part of the coal reaches the condition of rock burst, the rock burst will occur and cause vibrations with great energy. The characteristic of this kind of rock burst is that" the location of the source is the same as that of rock burst. "Using the theory of overlying strata spatial structure, surface subsidence observation and monitoring data of microseism and stress, a method for identifying the key working face is proposed. This paper describes the concrete methods of preventing rock burst and ensuring safety in three different types of mines with extremely thick and hard strata and the possibility of rock-burst disasters in Shandong Energy Group. These methods include protection layer mining, negative coal pillar design,determination and parameter design of key working face, mining design to avoid the boundary of vibration damage, small coal pillar design and parameter optimization design of sequential mining face. [ABSTRACT FROM AUTHOR]

Groundwater reservoir technology is a vital way to achieve both efficient mining and water conservation in western coalfields in China. The stability of coal pillar dam is an emphasis of reservoir design, which plays an important role in the stability of groundwater reservoirs. Coal pillar dam should ensure the safety of coal mining, as well as the safe operation of groundwater reservoirs. The stability of coal pillar dam is closely related to water weakening and engineering geological conditions, such as buried depth, mining stress, geological structure and so on. In order to study the strength weakening law of coal pillar dam of groundwater reservoirs under water, this paper took Madiliang mine No.5 in western mining area as the research object, carried out a non-destructive water immersion test on coal sample and a uniaxial compression test on coal sample under various water content and repeated soaking. The results show that the water content of coal samples with various water content increased rapidly within 0-20 h; after 20 h, the grew rate slowed down; and in 20-70 h, the water content grew slowly; in 70-140 h, the growth of water content of coal sample was nearly stable. In conclusion, the water content of coal sample increases with the soaking time, but the increase rate gradually decreases, and finally tends to be flat. With the increase of water content( the number of times of soaking), the uniaxial compressive strength of coal sample decreases gradually, but the peak strain increases gradually, and the elastic modulus decreases gradually. Compared with the dry coal sample, the uniaxial compressive strength of the first water-saturation coal sample and the coal sample with the third soaking decreased by 27.1% and 50.0% respectively, and the elastic modulus decreased by 34.6% and 58.5% respectively. Combined with the above results and the elasticplastic mechanics theory, this paper discussed the damage zone and plastic zone width of coal pillar dam under various water content, carried out the research of coal pillar dam width considering overburden rock pressure, water pressure and water weakening, and designed the width of the groundwater reservoir combining with the engineering geological conditions of Madiliang mine. At the same time, the paper further analyzed the influencing factors of the width of coal pillar dam, concluding that the width of coal pillar dam is closely affected by water content, buried depth, and mining thickness. [ABSTRACT FROM AUTHOR]

Currently more coal resource is buried in deep and more high-quality resource is located in the west of China. It makes a deep mining and a mining in the west become the new normal of coal resources exploitation. Thus a green mine construction, green mining development and green mining propulsion are imperative. This paper puts forward a"mining-dressing-backfilling+X"technical conception of green mining of coal resources. That is an underground integrated production system, which is integrated coal mining, coal-waste separation, and gangue backfilling with "active control of strata movement, gob-side entry retaining, gas extraction, disaster prevention, water-preserved-mining". The system forms a coal mining-dressing-backfilling+X(control, retain, extraction, prevention and preserved) collaborative production mode. The paper defines the"mining-dressing-backfilling+X"technical connotation and framework of greenmining, expounds "mining-dressing-backfilling+X"evolution of four generations, analyzes the specific technical advantages of its practice of green mining and gives the scientific engineering design method. The paper elaborates five aspects of typical "mining-dressing-backfilling + X"technology corresponding technical principle, engineering requirements, design process and methods, key technology and process equipment. Engineering practice of the Tangshan Coal mine, Zhaizhen Coal mine and 12 th Coal mine of Pingdingshan Group has respectively proved that "mining-dressingbackfilling+ control", "mining-dressing-backfilling + retain", "mining-dressing-backfilling + extraction " technologies have a remarkable technical superiority and the engineering demonstration effect. "Mining-dressing-backfilling + X "green mining extension in the future combines "mining-dressing-backfilling+processing", "mining-dressing-backfilling+intelligent", "mining-dressing-backfilling+adjustment"and "mining-dressing-backfilling +coordination". The overall formation of the "mining-dressing-backfilling+X"technology system can provide a strong technical support for the realization of green mining of coal and associated resources. [ABSTRACT FROM AUTHOR]

The exploitation of underground coal resources can easily lead to the loss of precious shallow water resources, which leads to the death of surface vegetation and the imbalance of ecosystem. To protect the shallow water resources( river, lake and diving of quaternary sand aquifer), which maintains the ecological environment of the western mining area, especially to protect the underground diving( ecological) water level, the concept of water conservation mining in short-distance coal seams was put forward based on the previous theoretical achievements of water conservation mining in shallow single coal seam and the experience of rock control engineering. The concept integrated the protection of ecological water level, and the prevention and control of water inrush. In order to achieve an efficient water conservation mining under the mining conditions of short-distance coal seams and extremely short-distance shallow water resources, this paper studied the technical problems, such as the collaborative control of strata water-conducting fractures in the disturbed area of repeated mining, the low-damage control of ultra-thin barrier layers and the monitoring and warning of water inrush( outburst) on mining surface. The study presented the long wall water conservation mining method, the water conservation mining under continuous mining and filling with wall system and the infrared monitoring and warning methods for water inrush in working face to realize the safe and efficient mining. More specifically, the methods included the strata control of short-distance coal seams, the calculation of the height of water-conduct fractures, the deformation calculation of aquicludes, the infrared radiation theories of loaded coal and rock, the control of water diversion fractures in the disturbed area of repeated mining, the filling body actively connected to the roof and the rapid operation technology among mining, supporting and transportation. Meanwhile, the weak areas of water conservation mining were determined. Based on water resource protection, the optimized working face layout of shallow buried and short-distance coal seams, mining method allocation and water resource movement monitoring, an efficient mining theory was formed. The achievements have been achieved in the practice of water conservation mining in north Shaanxi and north China, which provides supports for green mining in China. [ABSTRACT FROM AUTHOR]

Shenfu mining area is a China’s important coal production base and a typical high intensity mining field, and also a typical fragile ecological environment of arid and semi-arid areas, in which the burnt rock aquifer is one of the main groundwater resources. In order to study the influence and the protection of the burnt rock aquifer, taking the 5-2 coal mining in the first mining area of Zhangjiamao Mine field as an example, by studying the hydrogeological structure system and the water flowing fractured zone of 5-2 coal roof, this paper investigates the types and characteristics of water resources, establishes the water-preserved mining target of 5-2 coal seam, divides the water-preserved coal mining partition of 5-2 coal seam, and puts forward a new water-preserved coal mining technology which is burnt rock grouting curtain interception method. The results show that there are six main types of water resources in the study area, where only the burnt rock aquifer of 4-2 coal seam has the significance of water-preserved mining and the 5-2 coal mining area is divided into anhydrous mining area and water-preserved limited mining area of the 4-2 coal burnt rock aquifer. In the water-preserved limited mining area of 5-2 coal seam, the designed curtain wall spatial morphology, the position and quantity of curtain line and the row spacing and structure of grouting drilling are reasonable. In addition, the procedure and processes of drilling and grouting planed are scientific, and the implemented key technologies of grouting curtain, such as dual-site bidirectional water diversion grouting, zoning grouting of burnt rock full section, immediate test of anti-seepage and interception effect, are feasible. The pre-drainage of the 4-2 coal burnt rock aquifer of the working face before mining, and the measurement of the working face water inflow after mining in the water-preserved limited mining area of 5-2 coal seam show that the static reserve and the dynamic recharge of the 4-2 coal burnt rock aquifer water quantity are about 20 000 m3 and less than 5 m3 per hour respectively. It means the grouting curtain closure realizes the effective isolation of the 4-2 coal burnt rock water inside and outside the curtain, and greatly reduces the water discharge of the 4-2 coal-burnt rock water and the Changjiagou reservoir water with which it has direct hydraulic connection, and the protective mining effect of water resources is remarkable. [ABSTRACT FROM AUTHOR]

Coal mining with water protection is an inevitable choice for the sustainable development of ecologically fragile mining areas. The study and application of coal mining with water protection is an urgent problem to be solved in coal development planning, construction and production in northwest China. Taking Yushen mining area in northern Shaanxi Province as an example, this paper studies the types of water-preserved coal mining coalmines in combination with the quantity distribution of shallow water resources( water-preserved coal mining target seam) and the impact of coal mining on shallow water resources. Firstly, the spatial occurrence structure characteristics of eco-water-coal measures strata in the study area are analyzed. Also, the eco-geological environment types for the purpose of water-preserved coal mining are proposed, which are divided into oasis type with phreatic water and bottomland in desert, oasis type with surface water and valley river, loess gully type with surface runoff, and regional deep groundwater enrichment type. Secondly, the distribution of total storage per unit area of shallow water resources is calculated and determined. Then, based on the influence degree of coal mining on ecological layer and shallow water, four types of environmental engineering geological patterns( basically unaffected model, gradually restored model after destruction, gradually deteriorated model and disaster model) are proposed. Based on the analysis of the key indicators affecting the division of environmental engineering geological patterns, including the height of the water-flowing fractured zone and the mining water-resisting of residual aquiclude, etc., the zoning threshold and determination method for environmental engineering geological patterns is established. Finally, based on the distribution characteristics of shallow water resources and environmental engineering geological patterns, the grade types of water-preserved coal mining coalmines are put forward for the first time, which is divided into normal mining mine, water-preserved coal mining first-class mine, water-preserved coal mining second-class mine and water-preserved coal mining third-class mine. [ABSTRACT FROM AUTHOR]

Coal bump often occurs in the mining process between two adjacent mines under the control of large geological bodies. In order to study the coal bump mechanism between adjacent working faces of two adjacent coal mines under the condition of large fault and huge thick overburden conglomerate, this paper investigates the 23070 working face at Yuejin coal mine and the 21220 working face at Changcun coal mine in China. The analyses of monitoring data are carried out on the characteristics of coal bump behavior, microseismic spatio-temporal evolution and microseismic energy. Furthermore, the theoretical analysis and numerical simulation of stress distribution of overburden structure during the mining process of two working faces are conducted. The results show that the activation of F16 thrust fault and overall control of massive conglomerates in Yima mining area provide the stress conditions for coal bump. During the mining process of two mines’ adjacent working faces, the "asymmetric T-shaped"structure is formed between the rock beamabove the goaf and coal-rock pillar between two mines. The coal bump around the 21220 working face leads to the stress transfer onto the two mines’ pillar and the 23070 working face, which induces the coal bump around the 23070 working face. Mining disturbance between two mines leads to stress transfer and induces rock burst, which is closely related to the initial bump intensity and mining length of later working face. Finally, based on theory and engineering monitoring, a coal bump controlling technique with chain-weakening and consumption-increasing between two coal mines is put forward, which regards the weakening of the structural chain of high stress transfer as core. The results provide a theoretical basis for the study on the mechanism and control of coal bump between two adjacent working faces in two adjacent mines. [ABSTRACT FROM AUTHOR]