Apparent-Depth Effects of the Dynamic Failure of Thick Hard Rock Strata on the Underlying Coal Mass During Underground Mining

Xu, Chao; Fu, Qiang; Cui, Xinyuan; Wang, Kai; Zhao, Yixin; Cai, Yongbo

doi:10.1007/s00603-018-1662-3

Cited by 82 publications

(38 citation statements)

References 29 publications

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“…As shown in Figure 9, the overlying strata of the working face present stepped plastic failure, the upper rock mass of the stepped failure line (white mark line in the figure) is complete, and there is no macroscopic failure such as mining fracture. e plastic failure area of the overlying strata presents a "hump shape," and the "hump shape" plastic failure pattern gradually transfers to the lower part with the increase of coal seam dip angle [35].…”

Section: Test Resultsmentioning

confidence: 99%

Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully‐Mechanized Workface of Steeply Dipping Coal Seams

Wei

Yang

Chi

et al. 2021

Shock and Vibration

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The fracture instability mechanism of the basic roof is the key to support selection and surrounding rock stability control, and it is also the guarantee of safe and efficient coal mining. By means of theoretical analysis and numerical calculation, the calculation model of basic roof of steeply dipping coal seams (SDCS) under linear load is established, the stress distribution expression of basic roof plate is deduced, the inclination effect of stress evolution of steeply dipping coal seams (SDCS) workface is analyzed, and the “sequential” weighting mechanism of workface is revealed. Based on the numerical simulation test, the evolution laws of vertical stress release and shear stress concentration of overlying strata in workface with different coal seam dip angles are obtained. The results show that there is shear stress arch in the overlying strata. With the increase of coal seam dip angle, the overlying strata are suddenly damaged under the action of shear stress. The roof is in the state of discontinuous movement due to its self-weight and overburden pressure. Support is affected by the discontinuous movement and moved along with the roof. The results of this study can be of theoretical reference to the control of SDCS.

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Section: Test Resultsmentioning

confidence: 99%

Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully‐Mechanized Workface of Steeply Dipping Coal Seams

Wei

Yang

Chi

et al. 2021

Shock and Vibration

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“…When the overburden contains hard roofs in ETCSM, breakages and instabilities in the multi-layer structures result in ground pressures of varying degrees. 1,2 In particular, breakages and instabilities in high-position hard roofs (HHRs) result in strong ground pressure behavior (SGPB) and support failures in the working face and entry owing to their large caving span and hanging area ( Figure 1). [3][4][5] These hazards represent a severe danger to safe production and pose a new challenge to achieving hard roof control in ETCSM.…”

Section: Introductionmentioning

confidence: 99%

“…[17][18][19] At present, the most commonly used technologies are coal pillar supports, gob-side entry retention, goaf filling, a spatiotemporal coupling fracturing method using a nonexplosive expansion material, water injection to weaken the roof, presplitting blasting, deep hole blasting, energy-cavity blasting, and hydraulic slitting. 2,14,15,[20][21][22][23][24][25][26][27][28] The main ideas can be summarized as follows: (a) maintain the stability of the hard roof and support the stope space; (b) weaken the hard roof and reduce its rock mass strength; and (iii) transfer the stress or release the strain energy to eliminate the source of SGP.…”

Section: Introductionmentioning

confidence: 99%

Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

Pan

Xia

et al. 2020

Energy Science & Engineering

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Traditional methods of controlling hard roofs have a limited scope of action and cannot effectively release the strong ground pressure behavior (SGPB) induced by high-position hard roofs (HHRs) in extra-thick coal seam mining (ETCSM). Thus, an innovative control technology of fracturing HHRs by vertical-well stratified fracturing (VWSF) has been proposed. However, the key parameters of VWSF, namely fracturing horizon and fracturing thickness of HHRs, which have a significant influence on stope stability, remain uncertain. In this study, a mechanical model of the "coal wall-hydraulic support-gangue" support system is established by considering the effective loading acting on HHRs, through which modified expressions for the periodic breaking span and impact kinetic energy of the stope are deduced. Based on the self-bearing of bulking rocks, the stability principle of the surrounding rock, and energy dissipation theories, the criteria for determining the fracturing horizon and thickness of the HHR are obtained. Next, a numerical model of ETCSM, which accounts for the supporting effect of gangue, is constructed in FLAC3D. The support load and energy released by stratum breakage are determined through modeling under various hard roof parameters, thus verifying the correctness of the determination criteria. The results show that the energy released by a hard roof, average support load, and critical support load are positively correlated with thickness, and first increase before declining with respect to an increase in the fracturing horizon.The key parameters for a real coal mine are obtained by theoretical calculations and numerical simulations. A field application demonstrates that the support load and advance roadway deformation can be decreased using the proposed parameterization. This provides theoretical support for determining the key parameters of HHRs for VWSF and facilitates the widespread application of VWSF technology in HHR control. K E Y W O R D Shigh-position hard roofs, microseismic monitoring, mine safety, strong ground pressure behavior, vertical-well stratified fracturing | 2217 PAN et Al.

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“…The water-conducted fracture zone (WCFZ) consists of the caved zone and fractured zone and can be considered plasticized [12]. Hence, its height is important for the safety of underground production and the surface ecological environment (Guo et al 2018; [13][14][15][16]). The height of WCFZ depends on the mining method, mining height, advancing speed, panel width, overburden strength, stratum structure, and geological structure [2,[17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Overburden Damage Degree-Based Optimization of High-Intensity Mining Parameters and Engineering Practices in China’s Western Mining Area

Chen

Han

2020

Geofluids

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China’s western mining area is an arid and semiarid area with a fragile ecological environment, and the high-intensity mining activities aggravate ecological damage. Reasonable choice of the mining parameters (i.e., mining height, panel width, and advancing speed) can not only improve the mining efficiency but also weaken the mining-induced deformation and failures of the overburden and surface. The statistical analysis of the relationship between the mining parameters and periodic weighting interval (PWI) proves that mining parameters have significant influence on overburden failure. In this study, the damage constitutive equation was derived, and the overburden damage degree was defined to quantitatively characterize mining-induced stratum damage in a three-dimensional space. FLAC3D numerical models embedded with a damage constitutive equation were built to compare the panel width effect and advancing speed effect between the overburden damage degree and the water-conducted fracture zone (WCFZ). The reasonable range for mining parameters of the panel 12401 was provided based on the fitting function of the overburden damage degree versus mining parameters. The field measurements were carried out on panel 12401 of the Shangwan coal mine, including the advancing speed, PWI, and ground crack development. The results show that, under constant engineering and geological conditions, the damage degree of overburden will be weakened by increasing the advancing speed, reducing the mining height, or shortening the panel width. The overburden damage degree is more accurate than the height of the water-conducted fractured zone. The reasonable mining parameters of the panel 12401 are 8.8 m in mining height, 300 m in panel width, and 13.47 to 20.58 m/d in advancing speed, respectively. The field measurement results of the PWI and ground cracks have verified the validity using the overburden damage degree to determine high-intensity mining parameters.

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Apparent-Depth Effects of the Dynamic Failure of Thick Hard Rock Strata on the Underlying Coal Mass During Underground Mining

Cited by 82 publications

References 29 publications

Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully‐Mechanized Workface of Steeply Dipping Coal Seams

Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully‐Mechanized Workface of Steeply Dipping Coal Seams

Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

Overburden Damage Degree-Based Optimization of High-Intensity Mining Parameters and Engineering Practices in China’s Western Mining Area

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