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Numerical Analysis of Finite Deformation of Overbroken Rock Mass in Gob Area Based on Euler Model of Control Volume

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Journal of China University of Mining and Technology 2006年第3期16卷 245-248页

作者： LIU Wei-qun miao xie-xing School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields, formarion of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA＇2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area：（1） a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the beating pressure is nearly zero; （2） an overcompacted region, 10-20 m away from unbroken walls, where the beating pressure results in the maximum value of the gob area; （3） a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the beating pressures show basically no differences. Such a characteristic can exolain the easy-seeoaged “O”-ring phenomena around mining fields very well.

关键词： overbroken rock mass plastically finite deformation method of control volume bearing pressure

Bifurcation and catastrophe of seepage flow system in broken rock

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Mining Science and Technology 2009年第1期19卷 1-7页

作者： miao xie-xing LI Shun-cai CHEN Zhan-qing School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China School of Mechanical and Electrical Engineering Xuzhou Normal University Xuzhou Jiangsu 221116 China

The study of dynamical behavior of water or gas flows in broken rock is a basic research topic among a series of key projects about stability control of the surrounding rocks in mines and the prevention of some disasters such as water inrush or gas outburst and the protection of the groundwater resource. It is of great theoretical and engineering importance in respect of promo- tion of security in mine production and sustainable development of the coal industry. According to the non-Darcy property of seepage flow in broken rock dynamic equations of non-Darcy and non-steady flows in broken rock are established. By dimensionless transformation, the solution diagram of steady-states satisfying the given boundary conditions is obtained. By numerical analysis of low relaxation iteration, the dynamic responses corresponding to the different flow parameters have been obtained. The stability analysis of the steady-states indicate that a saddle-node bifurcaton exists in the seepage flow system of broken rock. Consequently, using catastrophe theory, the fold catastrophe model of seepage flow instability has been obtained. As a result, the bifurcation curves of the seepage flow systems with different control parameters are presented and the standard potential function is also given with respect to the generalized state variable for the fold catastrophe of a dynamic system of seepage flow in broken rock.

关键词： broken rock non-Darcy flow stability saddle-node bifurcation fold catastrophe

Waste-filling in fully-mechanized coal mining and its application

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Journal of China University of Mining and Technology 2008年第4期18卷 479-482页

作者： miao xie-xing ZHANG Ji-xiong FENG Mei-mei State Key Laboratory for Geomechanics ＆ Deep Underground Engineering China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China School of Mines China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

A fully-mechanized coal mining (FMCM) technology capable of filling up the goaf with wastes (including solid wastes) is described. Industrial tests have proved that by using this technology not only can waste be re-used but also coal resources can be exploited with a higher recovery rate without removing buildings located over the working faces. Two special devices, a hydraulic support and a scraper conveyor, run side-by-side on the same working face to simultaneously realize mining and filling. These are described in detail. The tests allow analysis of rock pressure and ground subsidence when backfilling techniques are employed. These values are compared to those from mining without using backfilling techniques, under the same geological conditions. The concept of equivalent mining height is proposed based on theoretical analysis of rock pressure and ground subsidence. The upper limits of the rock pressure and ground subsidence can be estimated in backfilling mining using this concept along with traditional engineering formulae.

关键词： fully-mechanized coal mining coal mining with gangue backfilling mining under buildings railways and water bodies rock pressure around coal face control of ground subsidence

Effect of ground stress on hydraulic fracturing of methane well

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Journal of China University of Mining and Technology 2008年第2期18卷 204-209页

作者： DU Chun-zhi MAO Xian-biao miao xie-xing WANG Peng School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the per- meability in the extraction of gas by ground drilling. The ground stress around the well was analyzed by using theory of elasticity. The pressure when the well fractured is formulated and the effect of ground stress on pressure is discussed. The effect of ground-stress-differences on hydraulic fracturing was analyzed by using the numerical software RFPA2D-Flow in reference to the tectonic stress in Jincheng coal area. The results show that: 1) the position where initial fracture appears is random and fracture branches emerge when the fractures expand if ground stresses in any two directions within a horizontal plane are equal; 2) other- wise, the fractures expand in general along the direction of maximum ground stress and the critical pressure decreases with in- creasing ground-stress-differences and 3) the preferred well-disposition pattern is diamond shaped. The preferred well spacing is 250 m×300 m. This study can provide a reference for the design of wells.

关键词： ground stress hydraulic fracturing breakdown pressure RFPA^2D-Flow design of wells

Experimental Study into Permeability of Broken Mudstone

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Journal of China University of Mining and Technology 2007年第2期17卷 147-151页

作者： MA Zhan-guo miao xie-xing ZHANG Fan LIYu-shou School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

Much attention should be paid to the permeability of broken rocks in goafs for the sake of water preservation in mining and to prevent disasters. Using a special device together with the MTS815.02 Rock Mechanics Test System,we tested the permeability of broken mudstone during its compacting process,and obtained the relations between axial stress and differential seepage pressure and between the pressure gradient and the seepage velocity. The effect of axial stress,grain size,and seepage velocities on the permeability coefficient is analyzed. The results show that 1) permability varies abruptly when the load reaches the compressive strength of rock samples,2) for a constant seepage velocity,the differential seepage pressure and the axial stress can be expressed by an exponential function,3) for a constant axial stress,the pressure gradient and the seepage velocity can be also expressed by an exponential function and 4) the permeability coefficient of broken mudstone of different sizes is closely related to its compaction state and will decrease with the increase of axial stress,expressed as a logarithmic function.

关键词： rock mechanics broken mudstone axial stress seepage properties test

Application of quantification theory in risk assessment of mine flooding

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Journal of China University of Mining and Technology 2008年第1期18卷 38-41页

作者： WANG Lian-guo miao xie-xing DONG Xu WU Yu School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

Hundreds of mine flooding accidents have occurred in China since the 1950s. These flooding accidents result in submerged working faces, even entire coal mines, leading to tremendous economic losses. It is reported that among 601 state-owned mines in China, 285 mines are exposed to water-inrush risks. The water pressure is becoming larger and larger with the increase of mining depth, leading to an increase of water-inrush hazards. Only when the risk of mine flooding is predicted in a reasonable manner, can we take timely and effective measures to prevent mine flooding from taking place. In our investigation quantification（H） theory is used to study the risk prediction problem about mine flooding. By investigating the main factors which affect mine flooding, eight risk assessment items have been identified. The extent of risk is classified into 4 grades. Given the data from different periods in the Feicheng mining area, a prediction model for the risk of mine flooding is established. The test analysis indicates a model correlation coefficient of 0.97 and the incidence of discrimination is as high as 97.37%, which implies that the effect of the model is quite satisfactory. With the help of computers, this method can be widely applied.

关键词： mine flooding quantification(II) theory prediction model assessment item

Structural motion of water-resisting key strata lying on overburden

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Journal of China University of Mining and Technology 2008年第3期18卷 353-357页

作者： PU Hai miao xie-xing YAO Bang-hua TIAN Mu-jun School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221116 China State Key Laboratory for Geomechanics ＆ Deep Underground Engineering China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

Water-preserved mining is one of the important parts of the ‘Green Mining’ technological system. The purpose of wa-ter-preserved mining is to prevent water from bursting out in coal mines and thus to protect water resources. The principle of wa-ter-resisting key strata (WKS) is proposed to establish a model capable of guiding and developing water-preserved mining technol-ogy. The experimental model of the WKS is constructed following requirements of the Data Image Correlative Method (DICM). Five experimental schemes are designed according to different combined patterns of the WKS. The water-resisting performance of the WKS is analyzed from observation of structural stability. All of them provide referential value for water-preserved mining.

关键词： water-preserved mining water-resisting key strata (WKS) digital image correlative method (DICM) water-inrush in coal mine

Movement characteristics of Karst water in a deep mining area

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Mining Science and Technology 2009年第1期19卷 14-18页

作者： CHAO Chen-ming BAI Hai-bo miao xie-xing YAO Bang-hua China Coal Research Institute Beijing 100013 China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China School of Sciences China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

In order to study the movement characteristics of groundwater in a deep mining area and solve the dispute of the distri- bution rule of hydro-chemical zoning which is contradicted by lixiviation water zoning in a horizontal direction, we directed our attention to the source of deep groundwater, its seepage and hydro-chemical characteristics in a typical mining area. We used a neotectonic water-control theory, chemical and isotope methods, as well as a method for analyzing dynamic groundwater conditions. The results indicate that 1) Karst water in the deep and medium parts of this mining area is recharged by vertical leakage through neotectonic fractures rather than seepage along strata from subcrop parts or surrounding flows; 2) from surface to deep leakage paths, the variation in the types of chemical groundwater agrees with the normal lixiviation water distribution rule and the age of mixed groundwater increases; 3) the water-rich zones along neotectonic fractures correspond with water-diluted zones in a hori-zontal direction; 4) the leakage coefficient and water capacity of aquifers increases during the flow process of Karst water along the antidip direction (from west to east) and 5) Karst water in shallow mining areas forms a strong runoff belt along strikes and quickly dilutes the water from deep and medium mining areas. Overall, chemical and dynamic water characteristics actually agree with in terms of the entire consideration for differences in vertical leakage and abnormalities in the zone of water chemical distribution, along a horizontal runoff direction.

关键词： deep mine area Karst water vertical leakage water chemicals dilution

Study of Slope Reinforcement Force Based on FLAC

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Journal of China University of Mining and Technology 2006年第2期16卷 123-127页

作者： HUANG Xian-wu MAO xian-biao miao xie-xing CHEN Zhan-qing School of Science China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China The Vocational College Guizhou University Guiyang Guizhou 550001 China

A slope will slide if the unbalanced force does not tend to zero when the stability of the slope is analyzed with the help of FLAC. Thus the ultimate reason of slope sliding is the unbalanced force determined by FLAC. The slope will remain stable if the unbalanced force is counterbalanced by a reinforcement force which is produced by a suitable reinforcement method. In this paper, the stability of the slope was analyzed by using FLAC, and the unbalanced force of the slope was obtained through the FISH function in FLAC. According to the equilibrium conditions, the relationship between the reinforcement force and unbalanced force was derived and accordingly the reinforcement force was determined. The reinforcement design was adopted by using pre-stressed anchor bars on the basis of the reinforcement force. An example is used to show that the effect of slope reinforcement based on the reinforcement force is safe and economical. The method doesn＇t need to suppose a sliding surface to obtain the reinforcement force, and it is also clear in physical meaning. So this method realized the organic unification of the stability analysis and the slope reinforcement.

关键词： slope reinforcement reinforcement force unbalanced force stability analysis pre-stressed anchor bar.