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Mechanical analysis of effective pressure relief protection range of upper protective seam mining

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International Journal of Mining Science and Technology 2017年第3期27卷 537-543页

作者： Yin Wei Miao Xiexing zhang jixiong Zhong Sijian School of Mines Key Laboratory of Deep Coal Resource Ministry of Education China University of Mining & Technology Xuzhou 221116 China State Key Laboratory for Geomechanics & Deep Underground Engineering China University of Mining & Technology Xuzhou 221116 China

This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the development of a plastic zone. Also this study developed a stress change and fracture development model of the underlying coal-rock mass. In addition, the stress and depth of fracture of any point in the floor were deduced with the application of Maple Calculation Software. The specific engineering parameters of the Pingdingshan No. 12 colliery were applied to determine the relationship between the depth of fracture in the floor and the mining height. The pressure-relief principle of the underlying coal-rock mass was analyzed while varying the mining height of the upper protective seam. The findings indicate that as the depth of fracture in the floor increases, the underlying coal-rock mass experiences a limited amount of pressure relief, and the pressure relief protection range becomes ***, the stress distribution evolves from a ‘‘U" shape into a ‘‘V" shape. A 2.0 m mining height of protective seam situates the outburst-prone seam, Ji_(15), within the effective pressure relief protection range. The fracture development and stress-relief ratio rises to 88%, ensuring the pressure-relief effect as well as economic benefits. The measurement data show that: after mining the upper protective seam, the gas pressure of Ji_(15) dropped from 1.78 to 0.35 MPa, demonstrating agreement between the engineering application and the theoretical calculation.

关键词： Upper protective seam Principle of pressure relief Effective protection range Gas pressure

A state‑of‑the‑art review on rock seepage mechanism of water inrush disaster in coal mines

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International Journal of Coal Science & Technology 2022年第4期9卷 1-28页

作者： Dan Ma Hongyu Duan jixiong zhang Haibo Bai School of Mines China University of Mining and TechnologyXuzhou 221116JiangsuChina State Key Laboratory of Coal Resources and Safe Mining China University of Mining and TechnologyXuzhou 221116JiangsuChina MOE Key Laboratory of Deep Coal Resource Mining China University of Mining and TechnologyXuzhou 221116JiangsuChina Department of Sustainable Development Environmental Science and EngineeringRoyal Institute of Technology10044 StockholmSweden State Key Laboratory of Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116JiangsuChina

Water inrush is one of the most dangerous disasters in coal *** to the large-scale mining and complicated hydrogeological conditions,thousands of deaths and huge economic losses have been caused by water inrush disasters in *** are two main factors determining the occurrence of water inrush:water source and water-conducting *** on the formation mechanism of the water-conducting pathway is the main direction to prevent and control the water inrush,and the seepage mechanism of rock mass during the formation of the water-conducting pathway is the key for the research on the water inrush *** paper provides a state-of-the-art review of seepage mechanisms during water inrush from three aspects,i.e.,mechanisms of stress-seepage coupling,fow regime transformation and rock *** numerical methods and experimental analysis,the evolution law of stress and seepage felds in the process of water inrush is fully studied;the fuid movement characteristics under diferent fow regimes are clearly summarized;the law of particle initiation and migration in the process of water inrush is explored,and the efect of rock erosion on hydraulic and mechanical properties of the rock media is also ***,some limitations of current research are analyzed,and the suggestions for future research on water inrush are proposed in this review.

关键词： Rock seepage mechanism Water inrush Coal mine Stress-seepage coupling Flow regime transformation Rock erosion

Vertical transportation system of solid material for backfilling coal mining technology

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International Journal of Mining Science and Technology 2012年第1期22卷 41-45页

作者： Ju Feng zhang jixiong,zhang Qiang School of Mines China University of Mining&TechnologyXuzhou 221008China State Key Laboratory of Coal Resources&Mine Safety China University of Mining&TechnologyXuzhou 221008China

For transportation of solid backfill material such as waste and fly ash from the surface to the bottom of the shaft in a fully mechanized backfilling coal backfilling coal mining technology, we developed a new vertical transportation system to transport this type of solid backfill material. Given the demands imposed on safely in feeding this material, we also investigated the structure and basic parameter of this system. For a mine in the Xingtai mining area the results show that: (1) a vertical transportation system should include three main parts, i.e., a feeding borehole, a maintenance chamber and a storage silo; (2) we determined that 486 mm is a suitable diameter for bore holes, the diameter of the storage silo is 6 m and its height 30 m in this vertical transportation system; (3) a conical buffer was developed to absorb the impact during the feeding process. To ensure normal implementation of fully mechanized backfilling coal mining technology and the safety of underground personnel, we propose a series of security technologies for anti-blockage, storage silo cleaning, high pressure air release and aspiration. This vertical transporting system has been applied in one this particular mine, which has fed about 4 million tons solid material with a feeding depth of 350 m and safely exploited 3 million tons of coal.

关键词： Fully mechanized backfilling coal mining Feeding bore hole Conical buffer Security guarantee

Strata behavior in extra-thick coal seam mining with upward slicing backfilling technology

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International Journal of Mining Science and Technology 2016年第4期26卷 587-592页

作者： Deng Xuejie zhang jixiong Kang Tao Han Xiaole School of Mines China University of Mining and Technology Xuzhou 221116 China Key Laboratory of Deep Coal Resource Mining Xuzhou 221116 China

Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia,this paper describes the studies of the strata behavior and the stress distribution in the process of backfilling mining in extra-thick coal *** was achieved by setting up and analyzing the elastic foundation beam model using the ABAQUS *** results show that:(1) With the gradual mining of different slices,the roof appears to bend continuously but does not *** vertical stress in the roof decreases and the decreasing amplitude reduces,while the tensile stress in the roof grows with the mining slices and the maximum tensile stress will not exceed the allowable tensile stress.(2) The front vertical stress at the working face exceeds the rear vertical stress and both show a trend of decrease with decreasing amplitude of decrease.(3) The slices mined early have more influence on the surrounding rock than the later ***,the strata behavior experiences the same *** field measured data show that the roof does not break during the mining process,which is consistent with the conclusion.

关键词： Extra-thick coal seam Upward slicing backfilling mining Strata movement characteristics Strata behavior

Gateside packwall design in solid backfill mining-A case study

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International Journal of Mining Science and Technology 2016年第2期26卷 261-265页

作者： Jiang Haiqiang Miao Xiexing zhang jixiong Liu Shiwei School of Mines China University of Mining & Technology Key Laboratory of Deep Coal Resource Mining Ministry of Education of China

Based upon characteristic movement features of the overlying strata in solid backfill mining and in-situ observations,an associated model representing a roadway support system has been *** on the Winkler foundation and beam model,the current study presents a static analysis of the model,thus permitting acquisition of a theoretical formula pertaining to roof *** use of working face 6304-1(Jisan Colliery) as the research setting,the association between roof convergence magnitude and both packwall strength and width have been *** upon observed conditions at the working face,realistic packwall parameters have been formulated,with numerical simulation results and field application results indicating that design parameters garnered from the developed formula successfully adapted to local geological movement and ***,roadway deformation was shown to be within the permissible range,thus satisfying mine production *** proposed method in the current study may give a design basis for pack design in the context of SBM under similar conditions.

关键词： Packwall design Solid backfill mining Roof convergence Winkler foundation and beam model Numerical simulation

Backfilling technology and strata behaviors in fully mechanized coal mining working face

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International Journal of Mining Science and Technology 2012年第2期22卷 151-157页

作者： zhang Qiang zhang jixiong Huang Yanli Ju Feng School of Mines China University of Mining&TechnologyXuzhou 221116China State Key Laboratory of Coal Resources&Mine Safety Xuzhou 221008China

Based on the principle of fully mechanized backflling and coal mining technology and combined with the Xingtai Coal Mine conditions, we mainly optimized the coal mining equipment and adjusted the coal mining method in the Xingtai Coal Mine 7606 working face for implementation this technology. Firstly, we define the practical backfilling process as the ＂（from backfilling scraper conveyor＇s） head to tail back- filling, step by step swinging up of the tamping arm, gradual compacting, moving formed backfilling scra- per conveyor when the second tamping arm cannot pass and connecting the immediate roof by back material push front material movement＂. Meanwhile, the stress changes of backfill body in coal mined out area was monitored by stress sensors, and the roof caving law was analyzed by monitoring the dynamic subsidence of -210 west roadway of this face. The site tests results show that using this new backfilling and coal mining integrated technology, the production capacity in the 7606 working face can reach to 283,000 ton a year, and 282,000 ton of solid materials （waste and fly ash） is backfilled, which meets the needs of high production and efficiency. The goaf was compactly backfilled with solid material and the strata behavior was quite desirable, with an actual maximum vertical stress of the backfill body of 5.5 MPa. Backfill body control the movement of overburden within a certain range, and there is no col- lapses of major areas in the overlying strata upon backfilled gob. The maximum subsidence and speed were 231 mm and 15.75 mm/d respectively, which proved the practical significance of this integrated technology.

关键词： Fully mechanized backfilling and coalmining technologyHydraulic supportFormed backfilling scraper conveyorBackfilling technologyStrata behaviors

Overlying strata movement of recovering standing pillars with solid backfilling by physical simulation

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International Journal of Mining Science and Technology 2016年第2期26卷 301-307页

作者： An Baifu Miao Xiexing zhang jixiong Ju Feng Zhou Nan School of Mines China University of Mining & Technology State Key Laboratory of Geomechanics and Deep Underground Engineering China University of Mining & Technology

To analyze the overlying strata movement law of recovering room mining standing pillars with solid *** simulation experiments with sponge and wood as the backfilling simulation material were *** results show that:(i) The covering-rock mechanics of the overly strata comes from "two-arch structures + hinged girder + bend beam" to "backfilling material + hinged girder + bent beam" by increasing the fill ratio from 0%to 85%,the beginning of overlying strata movement appears later and the total duration of subsidence velocity increased from zero to the highest value *** trend of "single polarization" of the subsidence velocity curves becomes noticeable and the velocity variation trend becomes stable,(ii) The equiponderate aeolian sand was added to improve the anti-pressure ability of the loess,and the corresponding ground processing & transportation system was designed.

关键词： Room mining standing pillars Solid backfilling Physical simulation experiment Overlying strata movement

Random gravel model and particle flow based numerical biaxial test of solid backfill materials

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International Journal of Mining Science and Technology 2013年第4期23卷 463-467页

作者： Zhan Liu Nan Zhou jixiong zhang State Key Laboratory of Geomechanics & Deep Underground Engineering China University of Mining(&)Technology Xuzhou 221008 China School of Mines China University of Mining & Technology Xuzhou 221008 China

Fully mechanized coal mining with backflling(FMCMB)has become a major solution of‘‘green mining’’.The mechanical properties of backfll materials are key factors of ground control in FMCMB *** study the strength behaviors of the solid backfll materials,we developed a method of generating random gravel model by using computational geometry algorithms,then coded the generating method into a program with MATLAB software,and implemented several numerical biaxial tests under different confning stresses by using a generated random gravel model and the Particle Flow Code *** deviatoric stress,post-peak softening,initial contraction and dilation and the relations between them and confning stress can be *** the initial elastic modulus of the samples,Poisson’s ratio,frictional angle and cohesion can be derived from the numerical biaxial test *** results indicate a good feasibility study of mechanical properties of the solid backfll materials by random gravel model and particle flow based numerical biaxial test.

关键词： Backfill mining Backfill materials Biaxial test Numerical simulation PFC

Design and application of solid, dense backfill advanced mining technology with two pre-driving entries

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International Journal of Mining Science and Technology 2015年第1期25卷 127-132页

作者： zhang Qiang zhang jixiong Guo Shuai Gao Rui Li Weikang School of Mines China University of Mining & Technology Key Laboratory of Deep Coal Resource Mining Ministry of Education of China China University of Mining & Technology

New solid backfill mining technology provides unique technical advantages for ‘‘three-under'' coal mining which refers to coal resources trapped under buildings, railways, and water bodies. This technology has a much higher recovery rate and can effectively control the surface subsidence. However, successful application of this technology depends heavily on geological conditions. To avoid the disadvantages associated with downward mining and overhead backfilling with this new technology, a new advanced solid backfill mining design with two pre-driving entries is proposed here to ensure the backfill effect. Taking Huayuan coal mine as an example, this paper tests the double gob-side entries retaining with no pillar left scheme and optimizes an integrated technology setup for backfill mining and gob-side entry retaining. Field applications show that the recovery rate increased from 40% for strip mining to 85% for backfill mining. Moreover, the new backfill technology allowed for better control over the surrounding rock deformation caused by the gob-side entry retaining effect and better control of ground subsidence as compared to strip mining.

关键词： Two pre-driving entriesGob-side entry retainingSolid backfill miningStrip miningGround subsidence contro