Study on Broken Floor Rock Mass by Mining Underground Pressure

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Ming Sun ◽  
Chen Guo ◽  
Wenxiang Zheng ◽  
Huiqiang Duan
Keyword(s):  
Rock Mass ◽  
Water Inrush ◽  
Theoretical Formula ◽  
Practical Situation ◽  
Floor Rock ◽  
Limit Value ◽  
Stress Contour ◽  
Mining Disturbance ◽  
Mining Face ◽  
Chinese Coal

As the dangerous level of floor water inrush in Chinese coal field is becoming more and more serious annually, the widely used formulas of broken floor rock mass are belonged to nonlinear type or empirical type. However, they are not well conformed to the practical situation and including mining underground pressure. The biggest depth of broken floor rock mass and the length of gob-floor or mining-floor until the maximum broken floor location are expressed by theoretical formulas on integrity theory. Taking a mining face in Chinese Anhui Province as the object, the relationship between broken floor rock mass and mining underground pressure is studied by numerical simulation, the theoretical analysis, and the DC exploration. The peak and scope of broken floor rock mass will enlarge until reaching limit value with the increasingly advanced distance. The mining gob stress contour is saddle-shaped, and its growing speed is becoming slower, so the 180 m coal mining face has reached the sufficient mining stage. Wave velocity of broken floor rock mass from 0 m to 16 m is greatly decreased by the mining disturbance, and it is basically conformed to theoretical formula and practical situation. The results can be relatively better used in the pressure mining of the Ordovician limestone, because it can provide some safe guarantee for mining deep coal seam.

Study on Floor Pressure Relief Law of Simultaneous Mining Working Faces in close Distance Seam Group of Dongsheng Coalfield

2014 ◽  
Vol 941-944 ◽  
pp. 2525-2532
Author(s):  
De Ming Chen ◽  
Chun Lei Zhang
Keyword(s):  
Rock Mass ◽  
Pressure Change ◽  
Theoretical Formula ◽  
Coal Pitch ◽  
Mine Pressure ◽  
Pressure Relief ◽  
Floor Rock ◽  
Working Face ◽  
Damage Depth ◽  
The Impact

In order to research floor pressure relief law of shallowly buried descending coal-mining working face covered with thin soft bedrock in Dongsheng coalfield , taking Lijiahao coal mine for example, firstly, to calculate the impact depth was 18.86m by the theoretical formula, then analyzing coal and rock mass stress and displacement variation of the upper work surface to its floor during mining based on numerical simulation. Obtaining coal and rock pressure relief depth of the floor was 70m, with the working face advancing, the pressure relief depth and range became larger, to achieve stable at a certain number;affected by the mining of 2-2 coal, coal and rock mass strength of its floor was weak, the largest damage depth was about 18m,this result would provide a basis to the roadway of the 3-1 coal in different coal pitch; affected by the mining, the goaf overburden and floor of 2-2 coal working face appeared "O" shape fracture zone, the floor rock fissure of 2-2 coal got through to the roof of 3-1 coal,cracks formed transfixion,which made the pressure change of 3-1 coal working face, Mine pressure appearance tended to be ease, it would be easily control if the roadway of 3-1 coal was arranged in the area of pressure relief. The theoretical results would be useful to actual production.

Microseismic Monitoring and Numerical Simulation Research of Floor Failure Depth in Extra-Thick Coal Seam

2014 ◽  
Vol 881-883 ◽  
pp. 1799-1804 ◽  
Author(s):  
Ai Ping Cheng ◽  
Yong Tao Gao ◽  
Chao Liu ◽  
Jin Fei Chai
Keyword(s):  
Numerical Analysis ◽  
Coal Mining ◽  
Microseismic Monitoring ◽  
Floor Rock ◽  
Thick Coal Seam ◽  
Floor Failure ◽  
Mining Disturbance ◽  
Microseismic Events ◽  
Mining Face ◽  
Failure Depth

Based on the condition of fully mechanized caving face in one mine, two methods of microseismic monitoring and numerical analysis were combined to study the evolution characteristics and development law of floor failure depth in extra-thick coal seam. Microseismic monitoring results show that the number of microseismic events partly reflects the influence of mining disturbance in the roof and floor rock mass. The distribution of microseismic events are intensive near the coal mining face, which show the floor rock mass is seriously damaged during the coal mining. The greatest floor failure depth estimated from mine microseismic monitoring is 31 meters. Numerical analysis indicate that the rock stress around the mine stope is redistributed during the coal mining, due to the effect of mining disturbance. The abutment pressure increases in front of the coal mining face and the stress reduces in the mined areas. The concentration and release of the stress makes contribution to the destroy of the floor rock. The maximum floor failure depth is up to 28 meters calculated from numerical simulation. The consistency of microseismic monitoring results and numerical analysis improve that it is effective and reliable to obtain floor failure depth and considerably possible to predict the water inrush using microseismic monitoring technology with its inherent ability to remotely monitor the progressive failure caused by mining. The research results have great popularization and application values for the similar mine.

scholarly journals Evolution Law of Floor Fracture Zone above a Confined Aquifer Using Backfill Replacement Mining Technology

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Shan Ning ◽  
Weibing Zhu ◽  
Xiaoyong Yi ◽  
Laolao Wang
Keyword(s):  
Water Inrush ◽  
Measurement Techniques ◽  
Force Model ◽  
Strip Mining ◽  
Confined Aquifer ◽  
Floor Rock ◽  
Study Results ◽  
Mining Face ◽  
Coal Pillars ◽  
Failure Depth

Disturbances owing to coal mining result in the movement and failure of floor strata. Mining-induced fractures within the floor may propagate to the confined aquifer, thereby causing water inrush disasters. In this study, we propose using strip mining and backfill replacement mining above the confined aquifer to investigate the failure depth of the floor. The problem is simplified as a distributed force model on a half-plane body. First, the stress disturbance of the floor during strip mining is calculated and the results are combined with the von Mises yield criterion. Then, the destruction of the floor after replacing the remaining coal pillars is explored. The results show that the widths of the strip mining face and coal pillars play an important role in affecting the failure depth of the floor: the greater the width, the larger the failure depth. Based on the parametric study results, the mining face and retention coal pillar width of 20 m is sufficient to prevent the occurrence of water inrush accidents. After the replacement of the remaining coal pillars, the failure area of the floor rock mass increases, but the maximum failure depth remains unchanged. Finally, we employed field measurement techniques at the Bucun coal mine to monitor the shear and vertical strains of the floor. The data collected was compared with the predicted results obtained from the proposed theoretical model. Good agreement was found between the monitoring and calculation results, which demonstrate the effectiveness of the proposed method.

scholarly journals Fracture Propagation and Hydraulic Properties of a Coal Floor Subjected to Thick-Seam Longwalling above a Highly Confined Aquifer

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Shaodong Li ◽  
Gangwei Fan ◽  
Dongsheng Zhang ◽  
Shizhong Zhang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Coal Seam ◽  
Longwall Mining ◽  
Water Pressure ◽  
Water Inrush ◽  
Volumetric Strain ◽  
Longitudinal Direction ◽  
Confined Aquifer ◽  
Floor Rock ◽  
Fracture Development ◽  
Mining Disturbance

The high-pressure and water-rich confined aquifer occurring in the Ordovician limestone sequence poses great threats to the routine production of underground longwall mining. Considering the intense cooperation of mining disturbance and water pressure, water-conducting fractures within a coal seam floor can connect the lower aquifer and upper goaf, and this hydraulic behavior is considered the root of water inrush hazard and water loss or contamination. In this paper, the panel 4301 of the Longquan coal mine serves as the case where the panel works closely above the floor with high water pressure. By the combination of physical and numerical modelling approaches, the variation characteristics of fracture development and volumetric strain of floor rocks subjected to mining disturbance are analyzed. A numerical computation model is constructed based on the volumetric strain-permeability equation obtained by curve fitting, and on such basis, the impacts of different mining parameters on floor rock permeability are studied. The results show that the floor rocks experience fracture generation, extension, and convergence procedures as the workface advances along the longitudinal direction, and fractures appearing in front of the workface are more developed. In the whole process of coal seam extraction, the volumetric strain profile exhibits “Λ” shape and an inverted saddle shape before and after overburden strata collapse. By controlling a single variable, the paper reveals that panel height is of greater impact on floor permeability changes than panel length and panel width.

scholarly journals Analysis of Mining Crack Evolution in Deep Floor Rock Mass with Fault

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Juntao Chen ◽  
Yi Zhang ◽  
Kai Ma ◽  
Daozeng Tang ◽  
Hao Li ◽  
...  
Keyword(s):  
Rock Mass ◽  
Water Inrush ◽  
Coal Pillar ◽  
Simulation Software ◽  
Shear Cracks ◽  
Crack Evolution ◽  
Floor Rock ◽  
Fault Activation ◽  
Initiation And Propagation ◽  
Tension Cracks

To further explore the crack evolution of floor rock mass, the mechanism of fault activation, and water inrush, this paper analyzes the crack initiation and propagation mechanism of floor rock mass and obtains the initiation criteria of shear cracks, layered cracks, and vertical tension cracks. With the help of simulation software, the process of fault activation and crack evolution under different fault drop and dip angles was studied. The results show that the sequence of crack presented in the mining rock mass is vertical tension cracks, shear cracks, and layered cracks. The initiation and propagation of the shear cracks at the coal wall promote the fault activation, which tends to be easily caused at a specific inclination angle between 45° and 75°. The fault drop has no obvious impact on the evolution of floor rock cracks and will not induce fault activation. However, the increase of the drop will cause the roof to collapse, reducing the possibility of water inrush disaster. Research shows that measures such as adopting improved mining technology, reducing mining disturbance, increasing coal pillar size, and grouting before mining as reinforcement and artificial forced roof can effectively prevent water inrush disasters caused by deep mining due to fault activation.

scholarly journals Research on Stress Distribution and Failure Depth of Mining Floor During the First Weighting of Main Roof

2015 ◽  
Vol 9 (1) ◽  
pp. 763-767
Author(s):  
Bingchao Zhao ◽  
Zhangrong Liu ◽  
Chao Tong
Keyword(s):  
Stress Distribution ◽  
Main Roof ◽  
Failure Criteria ◽  
Elastic Model ◽  
Floor Rock ◽  
Stress Contour ◽  
Coulomb Failure ◽  
Mining Face ◽  
Failure Depth ◽  
Safe Mining

In order to research stress distribution and failure depth of mining floor during the first weighting of main roof, based on the analysis of abutment pressure distribution in this case, an elastic model was established to calculate the stress of any point on the floor. The expressions for this model were deduced, and a failure criterion of floor rock was put forward according to the Mohr-Coulomb failure criteria. Taking the parameters of 3612 mining face of Zhu Zhuang coal mine as an example, and through solving stress distribution of mining floor during its first weighting of main roof, stress contour and failure district of floor were determined . The result showed that, the failure depth of 3612 mining floor is 12.4m, which is rather close to the measured value 13m, thus, the utility and reliability of this study method were effeciently verified. The result provided theoretical basis for bottom grouting strengthening before the first weighting of main roof, and established theoretical foundation for further research on safe mining of confined waters.

scholarly journals Evolution Pattern and Matching Mode of Precursor Information about Water Inrush in a Karst Tunnel

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1579
Author(s):  
Jie Song ◽  
Diyang Chen ◽  
Jing Wang ◽  
Yufeng Bi ◽  
Shang Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Displacement Field ◽  
Water Inrush ◽  
Seepage Field ◽  
Karst Tunnel ◽  
Rock Mass Structure ◽  
Evolution Pattern ◽  
Water Blocking ◽  
Precursor Information

The water inrush of the Shangjiawan karst tunnel is used to study the evolution pattern of precursor water inrush information in water-filled caves and to further reveal the matching mode of the information. The three-dimensional numerical method FLAC3D was used to simulate the evolution process of water inrush after damage to a water-blocking rock mass structure in a water-filled cave and to obtain the evolution pattern of precursor water-inrush information caused by the damage. The results show that the multifield response to the characteristic precursor information of the water-inrush pattern after the fracture of the water-blocking rock mass follows the order of stress-field displacement-field seepage-field. Further, the matching pattern of the information shows that the stress field increased first and then decreased, the displacement field always increased, and the seepage field increased first and then decreased.

scholarly journals The impact of drilling and slitting construction on damage field: evolution characteristics in low-permeability coal seam

2021 ◽  
Vol 37 ◽  
pp. 205-215
Author(s):  
Heng Chen ◽  
Hongmei Cheng ◽  
Aibin Xu ◽  
Yi Xue ◽  
Weihong Peng
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Damage Mechanics ◽  
Effective Strain ◽  
Secondary Development ◽  
Distribution Area ◽  
Finite Element Program ◽  
Element Program ◽  
Mining Face ◽  
The Impact

ABSTRACT The fracture field of coal and rock mass is the main channel for gas migration and accumulation. Exploring the evolution law of fracture field of coal and rock mass under the condition of drilling and slitting construction has important theoretical significance for guiding efficient gas drainage. The generation and evolution process of coal and rock fissures is also the development and accumulation process of its damage. Therefore, based on damage mechanics and finite element theory, the mathematical model is established. The damage variable of coal mass is defined by effective strain, the elastoplastic damage constitutive equation is established and the secondary development of finite element program is completed by FORTRAN language. Using this program, the numerical simulation of drilling and slitting construction of the 15-14120 mining face of Pingdingshan No. 8 Mine is carried out, and the effects of different single borehole diameters, different kerf widths and different kerf heights on the distribution area of surrounding coal fracture field and the degree of damage are studied quantitatively. These provide a theoretical basis for the reasonable determination of the slitting and drilling arrangement parameters at the engineering site.

scholarly journals Numerical Analysis of the Mud Inflow Model of Fractured Rock Mass Based on Particle Flow

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yongjian Pan ◽  
Huajun Wang ◽  
Yanlin Zhao ◽  
Qiang Liu ◽  
Shilin Luo
Keyword(s):  
Rock Mass ◽  
Pressure Gradient ◽  
Flow Direction ◽  
Fractured Rock ◽  
Water Pressure ◽  
Water Inrush ◽  
Quadratic Function ◽  
Particle Flow ◽  
Fractured Rock Mass ◽  
Particle Flows

Water inrush and mud outburst are one of the crucial engineering disasters commonly encountered during the construction of many railways and tunnels in karst areas. In this paper, based on fluid dynamics theory and discrete element method, we established a fractured rock mass mud inflow model using particle flow PFC3D numerical software, simulated the whole process of fractured rock mass mud inflow, and discussed the effect of particle size and flow velocity on the change of pressure gradient. The numerical simulation results show that the movement of particles at the corner of the wall when the water pressure is first applied occurs similar to the vortex phenomenon, with the running time increases, the flow direction of particles changes, the vortex phenomenon disappears, and the flow direction of particles at the corner points to the fracture; in the initial stage, the slope of the particle flows rate curves increases in time, and the quadratic function is used for fitting. After the percolation velocity of particles reaches stability, the slope of the curve remains constant, and the primary function is used for fitting; the particle flow rate and pressure gradient are influenced by a variety of factors, and they approximately satisfy the exponential function of an “S” curve.

Sign in / Sign up

Export Citation Format

Share Document