scholarly journals Water inrush and failure characteristics of coal seam floor over a confined aquifer

2021 ◽  
Author(s):  
Min Cao ◽  
Shangxian Yin ◽  
Bin Xu
Keyword(s):  
Coal Seam ◽  
Water Inrush ◽  
Confined Aquifer ◽  
Failure Characteristics

scholarly journals Numerical Analysis of Stress Fields and Crack Growths in the Floor Strata of Coal Seam for Longwall Mining

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Lingzhi Sun ◽  
Yunyue Xie ◽  
Hongtian Xiao
Keyword(s):  
Coal Seam ◽  
Crack Growth ◽  
Water Pressure ◽  
Water Inrush ◽  
Coal Extraction ◽  
Additional Stress ◽  
Mining Activities ◽  
Confined Aquifer ◽  
Working Face ◽  
Distribution Features

This paper predicts the possibility of water inrush from a confined aquifer under the action of mining activities and water pressure. The study uses numerical analyses to evaluate stress redistribution and crack growth which result from coal extraction operations. Two models are presented in this study. By simplifying the distribution of the disturbed vertical stress on the coal seam and floor around a working face, a model is established to analyze the additional stresses in the floor strata induced by mining activities. And some distribution features of all the additional stress components are described. By using the superposition principle in fracture mechanics, another model is developed to analyze the crack growth in the floor strata under the action of disturbed stresses and water pressure. And the stress intensity factors at the crack tip are presented and the process of crack growth is obtained in the advancement of a working face. Because of discretizing only loading areas and crack surfaces, the present methods can obtain the accurate numerical results. Finally, some suggestions are made for preventing the water inrush from a confined aquifer.

scholarly journals Failure Characteristics and Confined Permeability of an Inclined Coal Seam Floor in Fluid-Solid Coupling

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Jian Sun ◽  
Lianguo Wang ◽  
Guangming Zhao
Keyword(s):  
Stress Concentration ◽  
Coal Seam ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
Equivalent Stress ◽  
Confined Aquifer ◽  
Confined Water ◽  
Floor Water Inrush ◽  
Failure Depth

Secondary development of FLAC3D software was carried out based on FISH language, and a 3D fluid-solid coupling numerical calculation model was established for an inclined seam mining above a confined aquifer in Taoyuan Coal Mine. A simulation study was implemented on the mining failure depth of an inclined coal seam floor, conducting height of confined water, and the position of workface floor with easy water inrush during advancement of workface. Results indicated that, during the advancement of the inclined coal seam’s workface, obvious equivalent stress concentration areas existed in the floor strata, and the largest equivalent stress concentration area was located at the low region of workface floor. When the inclined coal seam workface advanced to about 80 m, the depth of floor plastic failure zone reached the maximum at approximately 15.0 m, and the maximum failure depth was located at the low region of the workface floor. Before the inclined workface mining, original confined water conducting existed on the top interface of the confined aquifer. The conducting height of the confined water reached the maximum at about 11.0 m when the workface was pushed forward from an open-off cut at about 80 m. Owing to the barrier effect of the “soft-hard-soft” compound water-resistant strata of the workface floor, pore water pressure and its seepage velocity in the floor strata were unchanged after the workface advanced to about 80 m. After the strata parameters at the workface floor were changed, pore water pressure of the confined water could pass through the lower region of the inclined workface floor strata and break through the barrier of the “soft-hard-soft” compound water-resistant strata of the workface floor and into the mining workface, resulting in the inclined coal seam floor water inrush. Results of this study can provide a basis for predicting, preventing, and governing the inclined coal seam floor water inrush above confined aquifer.

scholarly journals Investigation on Failure Characteristics of Coal Seam Floor in Paste Filling Working Face

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qingliang Chang ◽  
Xingjie Yao ◽  
Chongliang Yuan ◽  
Qiang Leng ◽  
Hao Wu
Keyword(s):  
Theoretical Model ◽  
Coal Seam ◽  
Water Inrush ◽  
Failure Behavior ◽  
Term Strength ◽  
Failure Characteristics ◽  
Working Face ◽  
Floor Failure ◽  
Failure Depth

Water inrush disasters are extremely prone to occur if the coal seam floor contains a confined aquifer. To find out the failure behavior of coal seam floor of paste filling working face, a beam-based theoretical model for the floor aquifuge was built, and then, the water inrush risk was evaluated based on the thickness of floor aquifuge. Next, the floor failure characteristics of the paste filling face was numerically studied and the effects of the filling interval and long-term strength of the filling body on the floor failure depth, stress and displacement distributions, and plastic zone were explored. The results showed that the theoretical model for evaluating the safety of the floor of the paste filling face based on the empty roof distance is proved to be consistent with that of the empirical formula judged based on the assumption that the paste filling working face was regarded as a cut hole with a certain width. The filling interval has a significant effect on the stress concentration of the surrounding rock, failure depth of floor, and roof-floor convergence. The smaller the filling interval is, the smaller their values are. When the filling rate is 98%, the long-term strength of the filling body is 5 MPa, and the floor failure depth is not more than 4 m. In contrast, the strength of the filling body has no obvious influence on the floor failure depth, but it has a certain impact on the roof-floor convergence. From the perspective of reducing floor failure depth, there is no need to increase the long-term strength of backfill, but it is necessary to increase the early strength of backfill so as to reduce the width of the equivalent roadway.

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.

Research on Automatic Detection Technology for Coal Seam Floor Failure Features

2011 ◽  
Vol 467-469 ◽  
pp. 1870-1875 ◽  
Author(s):  
Guang Ming Zhao ◽  
Xiang Rui Meng
Keyword(s):  
Coal Seam ◽  
Water Inrush ◽  
Damage Zone ◽  
Detection Technology ◽  
Floor Failure ◽  
Industry Practice ◽  
Iteration Model ◽  
Forward Calculation ◽  
Mining Coal ◽  
The Impact

By the impact of coal mining, coal floor will produce distortion and damage, and make the damage zone which may result in water inrush from the floor of coal seam. CT technology with DC electricity is used to analyze two-dimensional point source current field by employing the forward calculation, inverse iteration, model correction and other methods. On the basis, inverted resistivity image of the detecting zone is obtained, which can help to determine damage law and damage depth of coal seam floor. And then the possibility of water inrush from the coal floor is analyzed. Industry practice shows that the research results are credible and can play an important guiding role in the controlling of water inrush.

scholarly journals Exploration and application of directional long boreholes in coal measure strata

2021 ◽  
Vol 261 ◽  
pp. 03003
Author(s):  
Qin Ke ◽  
Peng Dong ◽  
Duan Huijun
Keyword(s):  
Coal Seam ◽  
Water Inrush ◽  
Critical Value ◽  
Coal Measure ◽  
Bottom Plate ◽  
Drain Water ◽  
Safe Water ◽  
Working Face ◽  
Water Hazard ◽  
Insulation Thickness

two roadways in adjacent working face of Baode Mine may have the risk of water inrush at the same time, so it is necessary to construct long borehole to cover the roadway excavation. On the basis of the hydrogeological conditions of the mine, the safe water insulation thickness and water inrush coefficient of coal seam No .8 are calculated. The results show that the water inrush coefficient is 0.035-0.037 MPa/m, which is less than the critical value 0.06 MPa/m and the bottom plate has no sudden water hazard. In the construction of No .10 coal seam, the directional long borehole is used to detect whether there is a hidden structure communicating with the floor limestone and to drain water. The test shows that there is no effluent phenomenon in the borehole, which proves that there is no hidden structure in No .10 coal seam.

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