scholarly journals Calculation Method of Overburden Damage Height Based on Fracture Mechanics Analysis of Soft and Hard Rock Layers

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Liang Chen ◽  
Shaowu Fan ◽  
Can Zhao ◽  
Lang Zhang ◽  
Zhiheng Cheng
Keyword(s):  
Fracture Mechanics ◽  
Coal Seam ◽  
Calculation Method ◽  
Hard Rock ◽  
Soft Rock ◽  
Mining Area ◽  
Overburden Rock ◽  
Rock Interaction ◽  
Mechanics Analysis ◽  
Seam Mining

Under the geological condition of soft and hard rock interaction stratum, the overburden damage height can provide a quantitative support for the design of the locations of gas drainage boreholes in the roof mining fracture zone and the determination of the hydraulic fracture zone in coal seam mining. The interbedded structure of overlying mud rock and sandstone in the Lu’an mining area in Shanxi is a typical soft and hard rock interaction stratum. In view of the lack of soft rock fracture mechanics analysis and the improper calculation of the damage height of overburden rock caused by constant rock residual bulking coefficient to be used regularly in the analysis, in this paper, we constructed a fracture model of soft and hard strata by giving a quantitative classification criterion of soft and hard rocks and introducing a fracture failure criterion of soft rock strata and the space constraint condition of broken-expansion rock formation. Aiming at improving the calculation precision of overburden damage height, we presented a calculation method based on fracture mechanics analysis of soft and hard strata, which could delineate the extent of intact rock in overlying strata from bottom to top to determine the damage height of overburden rock. This research took Yuwu coal mine in Lu’an mining area as an example. Results showed that (1) by the calculation method, the overburden damage height of the N1102 fully mechanized caving face in Yuwu coal mine was 51.44 m, which was less than the value obtained by an actual borehole TV method as well as the numerical simulation result of 53.46 m, with a calculation accuracy about 96.22%, which is quite high for both. The calculation accuracy of the proposed method was higher than that of the three conventional theoretical methods, and it effectively solved the limitation of the fracture analysis method without the inclusion of the soft rock layer in design and the distortion problem due to the residual bulking coefficient to be improperly used in simulation. (2) There was no noticeable fractures in the broken soft rock zone, and the whole fractures were mainly low-angle rupture; the fractures in hard rock layer had obvious ruptures and multiangle cracks, and the average fracture width of soft rock was 2.8 mm smaller than that of hard rock. The fracture modes of soft rock and hard rock were mainly tensile failure and tensile shear failure, which verified the correctness of the fracture mechanics model of soft and hard rock layers constructed in this paper. (3) It is noticed that the tensile strength of rock in this method needs to be obtained through rock mechanics experiment on overlying strata in the study area, and our proposed method was applicable to the mining conditions of near horizontal coal seam. The calculation accuracy of this method meets the engineering error requirements and can be applied to the prediction of overburden damage height in near horizontal coal seam mining.

scholarly journals Simulation Analysis of Influencing Factors of Subsidence Based on Mining under Huge Loose Strata: A Case Study of Heze Mining Area, China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Xianxiang Zhu ◽  
Wenquan Zhang ◽  
Zaiyong Wang ◽  
Chenghao Wang ◽  
Wei Li ◽  
...  
Keyword(s):  
Coal Seam ◽  
Simulation Analysis ◽  
Soil Layer ◽  
Soft Rock ◽  
Mining Area ◽  
Simulation Software ◽  
Surface Subsidence ◽  
Ground Movement ◽  
Hard Soil ◽  
Seam Mining

Based on the coal seam mining under the condition of thick soil layer, the mechanical mining subsidence process under the condition of thick soil layer was analyzed. Combined with the results of core drilling and laboratory test in the mining area, the mechanical analysis of the special transition strata of “hard soil-soft rock” at the bottom of the soil layer was carried out. Additionally, the characteristics of the shallow buried soil layer were compared and analyzed. Furthermore, the significance of this transitional font to the surface subsidence law was proposed. By using the numerical simulation software of FLAC3D and choosing the thickness of “hard soil-soft rock” transitional font as the influencing factor, a model was established and the surface subsidence characteristics of different stratum combinations were numerically simulated. The research results show that the transitional font is the special strata indicating that the hard soil is transiting to the soft rock, having a significant effect on the ground movement and deformation induced by coal mining. It cannot be designated into the loose strata. Also, it cannot be regarded as the bed rock to study the influence of it on the surface subsidence. The “hard soil-soft rock” transitional font has the support effect on the overlying strata during coal seam mining, which can restrict the surface subsidence. Furthermore, the larger the thickness of the transitional font is, the more obvious the restricting effect of it on the surface subsidence is. Meantime, this restricting effect will not be changed with the variation of the proportion between the loss bed and the bed rock thickness. Only the restricting extent is a little different.

Water inflow characteristics of coal seam mining aquifer in Yushen mining area, China

2021 ◽  
Vol 14 (4) ◽  
Author(s):  
Zhao Chunhu ◽  
Jin Dewu ◽  
Wang Qiangmin ◽  
Wang Hao ◽  
Li Zhixue ◽  
...  
Keyword(s):  
Coal Seam ◽  
Mining Area ◽  
Water Inflow ◽  
Seam Mining

scholarly journals A Mechanical Model of the Overlying Rock Masses in Undersea Coal Mining and a Stress-Seepage Coupling Numerical Simulation

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jie Fang ◽  
Lei Tian ◽  
Yanyan Cai ◽  
Zhiguo Cao ◽  
Jinhao Wen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Coal Mining ◽  
Water Inrush ◽  
Mining Area ◽  
Analysis Model ◽  
Fractured Zones ◽  
Working Face ◽  
Seam Mining ◽  
Overlying Strata

The water inrush of a working face is the main hidden danger to the safe mining of underwater coal seams. It is known that the development of water-flowing fractured zones in overlying strata is the basic path which causes water inrushes in working faces. In the engineering background of the underwater mining in the Longkou Mining Area, the analysis model and judgment method of crack propagation were created on the basis of the Mohr–Coulomb criterion. Fish language was used to couple the extension model into the FLAC3d software, in order to simulate the mining process of the underwater coal seam, as well as to analyze the initiation evolutionary characteristics and seepage laws of the fractured zones in the overlying strata during the advancing processes of the working face. The results showed that, during the coal seam mining process, the mining fractured zones which had been caused by the compression-shear and tension-shear were mainly concentrated in the overlying strata of the working face. Also, the open-off cut and mining working face were the key sections of the water inrush in the rock mass. The condition of the water disaster was the formation of a water inrush channel. The possible water inrush channels in underwater coal mining are mainly composed of water-flowing fractured zones which are formed during the excavation processes. The numerical simulation results were validated through the practical engineering of field observations on the height of water-flowing fractured zone, which displayed a favorable adaptability.

Study on Technology of Fully-Mechanized Sub-Level Caving Mining Technology in the Datong Permo Carboniferous Coal Seam

2012 ◽  
Vol 616-618 ◽  
pp. 565-568
Author(s):  
Bin Yu ◽  
Jun Zhao ◽  
Hong Chun Xia
Keyword(s):  
Coal Seam ◽  
Mining Area ◽  
Hard Coal ◽  
Control Technology ◽  
Mining Technology ◽  
Hard Roof ◽  
Sublevel Caving ◽  
Seam Mining ◽  
Longwall Top Coal Caving ◽  
And Control

This thesis briefly introduced roof control technology in fully-mechanized sublevel caving mining with hard roof and hard coal seam, Mining technology , gas prevention and comprehensive prevention and control technology in spontaneous combustion of coal, which in longwall top-coal caving face with hydraulic support in thickness seam in the Datong permo carboniferous coal seam . New development directions of fully-mechanized sublevel caving mining technology in the Datong mining area in the next few years.

Development of Probabilistic Fracture Mechanics Analysis Codes for Reactor Pressure Vessels Considering Recent Embrittlement Model and Calculation Method of SIF: Progress of the Work

2016 ◽  
Author(s):  
Jongmin Kim ◽  
Bongsang Lee ◽  
Taehyun Kim ◽  
Yoonsuk Chang
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Calculation Method ◽  
Reactor Pressure Vessel ◽  
Radiation Embrittlement ◽  
Calculation Methods ◽  
Probabilistic Fracture Mechanics ◽  
Mechanics Analysis ◽  
Reactor Pressure

It is widely recognized that the state of knowledge and data for the probabilistic calculations which had been proposed in the early 1980s made a conservative treatment of several key factors and models. Recently, applications of some new radiation embrittlement model, material database, calculation method of stress intensity factors and others which can improve fracture mechanics assessment of reactor pressure vessel (RPV) are introduced. This improvement on the accuracy and reliability of the probabilistic fracture mechanics (PFM) analysis necessitated changes in PFM analysis procedures and calculations. Modification and application of newly developed models and calculation methods are the main target of developing a probabilistic fracture mechanics analysis code based on the structure of existing R-PIE and VISA computer code to reflect the latest technical basis. Failure probabilities of reactor pressure vessel under pressurized thermal shock (PTS) conditions were calculated through finite difference method (FDM) and Monte Carlo simulation techniques with user friendly graphic interface. Moreover, various radiation embrittlement models and calculation methods of stress intensity factor at crack tip based on AFCEN code are applied and verified in the present work.

scholarly journals Influence of Valleys Terrain on Pressure of Fully Mechanized Working Faces in Shallow Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
YingJie Liu ◽  
Qingjie Qi ◽  
Anhu Wang
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Rock Fracture ◽  
Mine Pressure ◽  
Overburden Rock ◽  
Coal Seams ◽  
Valley Bottom ◽  
Key Stratum ◽  
Seam Mining ◽  
The Impact

The absence of a key stratum during overburden rock movement is crucial to the mining pressure of fully mechanized coal mining faces. Using physical and numerical simulations, the 21304 mechanized mining in Daliuta and Huojitu coal mining faces 1−2 appeared twice during a pressure frame accident analysis. The results indicate that a lack of key overlying strata is crucial to the mining of lower coal seams, particularly for the upper sections of a single key stratum of coal. When the key stratum of the upper coal seam is absent, a stable masonry structure is formed after mining. It is easy to form stable stacked strata at the bottom of a coal seam. When developing gullies in deep terrains, the formation of the key stratum will be an upper rock fracture affected by the impact, resulting in a partial absence of the key stratum. When the key stratum is absent, the mining of upslope working faces and the probability of dynamic strata pressure increase with the overburden on the working face and mining of downslope faces. The face mine pressure development laws on the upper and lower coal seam mining were similar, mainly manifesting as “slope section >valley bottom section >back slope section.”

Research on the Overlying Strata in Full-Mechanized Coal Mining of Datong Jurassic Coal Multi-Layer Goaf

2012 ◽  
Vol 616-618 ◽  
pp. 402-405 ◽  
Author(s):  
Hong Chun Xia ◽  
Guo Sheng Gao ◽  
Bin Yu
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Pillar ◽  
Mining Area ◽  
Mechanics Model ◽  
Roof Structure ◽  
Geological Conditions ◽  
Seam Mining ◽  
The Impact ◽  
Overlying Strata

According to the specific geological conditions in themulti-layer worked-out areas of Yongding coal seam, by the methods of integration of theoretic analysis, numerical value calculation and so on, we studied movement law of Overlaying Strata and influence of coal pillar in Coal seam mining, obtained the basic law of the overlying strata movement in multiplayer, provides a theoretical basis for the safe and efficient exploitation of the success of multiplayer. Many mining area in China is mining of closed distance coal seam group, By the impact of coal seam in the overlying, face and the tunnel roof structure will be different injury in sub-coal seam mining, Roof structure has changed greatly, even damage and easily take the roof leakage, When the the goaf communication with the overlying coal seams, caused by the induced secondary disasters such as face air leakage, Therefore, exploitation of the law of motion of the overlying strata in the multiplayer is a pressing problem. Exploitation multiplayer seam few theoretical and technical foundation at home and abroad, affecting the validity of the mining, rationality. although a lot of research on theory and technology of coal mining over the years[1~5], But it was not able to an overall comprehensive analysis of upper goaf adjacent goaf and overlying the coal pillar and present mining face, create a dynamic structural mechanics model, which is likely to cause the occurrence of disasters.

Quantitative analysis of parameters' influence on the stability of coal roadway clamped by upper and lower soft rock with extra thickness

2014 ◽  
Vol 05 (02) ◽  
pp. 1350023
Author(s):  
Zenghui Zhao ◽  
Weiming Wang ◽  
Jixing Yan
Keyword(s):  
Quantitative Analysis ◽  
Coal Seam ◽  
Significant Influence ◽  
Evaluation Method ◽  
Soft Rock ◽  
Mining Area ◽  
Remarkable Effect ◽  
Coal Roadway ◽  
The Stability ◽  
Rock Strata

In this paper, a physical model of coal roadway which is clamped by upper and lower soft rock with extra thickness was built according to the characteristics of soft rock strata in china's western mining area. Then, a series of orthogonal numerical experiments were carried out by selecting the strength and stiffness parameters of soft rock and coal seam as well as the in situ stress of soft rock strata as experimental factors and roadway displacements (convergence displacements of sides, displacement of roof to floor) as experimental indexes. By constructing the F statistics with different inspection levels, evaluation method for influence of the experimental factors on stability indexes were defined. Thus, influence degrees of specified parameters on the stability of roadway were divided into five classes as follows: highly significant influence, significant influence, relatively significant influence, little significant influence, and no influence respectively which realize the quantitative analysis of the influence degrees of experimental factors. The finite element calculation results showed that main failure mode of coal roadway that usually showed as tension failure of coal seam in roof and deformation factors of coal seam had the most remarkable effect on roadway displacements. The conclusions provide theoretical basis for further analysis of the mechanism of "roof burst" in roadway maintenance.

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