scholarly journals Law of coal caving behind the flexible shield support in pseudo-inclined working face

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261355
Author(s):  
Qinjian Zhan ◽  
Niaz Muhammad Shahani ◽  
Zhicheng Xue ◽  
Shengqiang Li
Keyword(s):  
Boundary Conditions ◽  
Force Field ◽  
Contact Force ◽  
Displacement Field ◽  
Bottom Plate ◽  
Steep Seam ◽  
Short Delay ◽  
Working Face ◽  
Time Space ◽  
Complex Boundary

Complex boundary conditions are the major influencing factors of coal caving law in the pseudo-inclined working face. The main purpose of this study is to analyze coal caving law of flexible shield support and then to establish the internal relations among coal caving parameters under complex boundary conditions. Firstly, the law of coal caving in different falling modes is simulated physically. Secondly, the coal caving shape, displacement field, and contact force field is simulated. Then, coal caving law and process parameters is analyzed theoretically. Finally, the test was performed in Bai-Ji Mine. The research shows that ellipsoidal ore drawing theory has universal applicability in coal drawing law analysis and parameter optimization. After the Isolated Extraction Zone and Isolated Movement Zone reach the roof, the expansion speed is marked by a short delay, and then, while expanding to the floor, two butted incomplete ellipsoids are formed. There is a time-space difference in coal caving after the support, and some coal will be mined in the next round of coal caving. There are obvious differences in the coal loosening range, displacement field, and contact force field on both sides of the long axis. When the support falls along with the bottom plate, it is more conducive to the release of coal. The test shows that the research is of great significance for optimizing the caving parameters of flexible shield support in the pseudo-inclined working face of the steep seam.

Using the Multi-Parameter Fracture Mechanics for more Accurate Description of Stress/Displacement Crack Tip Fields

2013 ◽  
Vol 586 ◽  
pp. 237-240 ◽  
Author(s):  
Lucie Šestáková
Keyword(s):  
Stress Distribution ◽  
Fracture Mechanics ◽  
Boundary Conditions ◽  
Displacement Field ◽  
Singular Term ◽  
Crack Tip ◽  
Higher Order ◽  
Precise Description ◽  
Accurate Knowledge ◽  
Higher Order Terms

Most of fracture analyses often require an accurate knowledge of the stress/displacement field over the investigated body. However, this can be sometimes problematic when only one (singular) term of the Williams expansion is considered. Therefore, also other terms should be taken into account. Such an approach, referred to as multi-parameter fracture mechanics is used and investigated in this paper. Its importance for short/long cracks and the influence of different boundary conditions are studied. It has been found out that higher-order terms of the Williams expansion can contribute to more precise description of the stress distribution near the crack tip especially for long cracks. Unfortunately, the dependences obtained from the analyses presented are not unambiguous and it cannot be strictly derived how many of the higher-order terms are sufficient.

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.

scholarly journals MFS fading regularization method for the identification of boundary conditions from partial elastic displacement field data

2018 ◽  
Author(s):  
L. Caillé ◽  
J L. Hanus ◽  
F. Delvare ◽  
N. Michaux-Leblonda
Keyword(s):  
Inverse Problem ◽  
Boundary Conditions ◽  
Displacement Field ◽  
Regularization Method ◽  
Synthetic Data ◽  
Fundamental Solutions ◽  
Image Correlation ◽  
Method Of Fundamental Solutions ◽  
Elastic Displacement ◽  
Isotropic Elasticity

A method is proposed to solve an inverse problem in twodimensional linear isotropic elasticity. The inverse problem consists of the determination of both the entire displacement field and the boundary conditions inaccessible to the measurement from the partial knowledge of the displacement field. The algorithm is based on a fading regularization method (FRM) and is numerically implemented using the method of fundamental solutions (MFS). The inverse technique is first validated with synthetic data and is then applied to the interpretation of experimental measurements obtained by digital image correlation (DIC).

Effects of complex boundary conditions on natural convection of a viscoplastic fluid

2019 ◽  
Vol 29 (8) ◽  
pp. 2792-2808 ◽  
Author(s):  
Behnam Rafiei ◽  
Hamed Masoumi ◽  
Mohammad Saeid Aghighi ◽  
Amine Ammar
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Natural Convection ◽  
Boundary Conditions ◽  
Yield Stress ◽  
Heated Wall ◽  
Uniform Heating ◽  
Content Type ◽  
Yield Stress Fluids ◽  
Complex Boundary

Purpose The purpose of this paper is to analyze the effects of complex boundary conditions on natural convection of a yield stress fluid in a square enclosure heated from below (uniformly and non-uniformly) and symmetrically cooled from the sides. Design/methodology/approach The governing equations are solved numerically subject to continuous and discontinuous Dirichlet boundary conditions by Galerkin’s weighted residuals scheme of finite element method and using a non-uniform unstructured triangular grid. Findings Results show that the overall heat transfer from the heated wall decreases in the case of non-uniform heating for both Newtonian and yield stress fluids. It is found that the effect of yield stress on heat transfer is almost similar in both uniform and non-uniform heating cases. The yield stress has a stabilizing effect, reducing the convection intensity in both cases. Above a certain value of yield number Y, heat transfer is only due to conduction. It is found that a transition of different modes of stability may occur as Rayleigh number changes; this fact gives rise to a discontinuity in the variation of critical yield number. Originality/value Besides the new numerical method based on the finite element and using a non-uniform unstructured grid for analyzing natural convection of viscoplastic materials with complex boundary conditions, the originality of the present work concerns the treatment of the yield stress fluids under the influence of complex boundary conditions.

Unsteady Flow Calculations by Numerical Methods

1972 ◽  
Vol 94 (2) ◽  
pp. 457-465 ◽  
Author(s):  
V. L. Streeter
Keyword(s):  
Numerical Methods ◽  
Boundary Conditions ◽  
Unsteady Flow ◽  
Various Boundary Conditions ◽  
Flow Problems ◽  
Velocity Flow ◽  
Compressed Gas ◽  
Order Of Magnitude ◽  
Metal Pipes ◽  
Complex Boundary

A review of methods of handling unsteady flow problems in metal pipes by numerical methods is undertaken. The characteristic method, typifying explicit methods, and the centered implicit method are developed, including the manner various boundary conditions are introduced into the solutions. High velocity flow is briefly reviewed, i.e., flow cases with the velocity of flow of the same order of magnitude as the pulse wave speed. Three complex boundary conditions are examined: turbomachinery, column separation, and the compressed gas accumulator.

Numerical Simulation of Levee Breach Flows Under Complex Boundary Conditions

2009 ◽  
Vol 21 (5) ◽  
pp. 633-639 ◽  
Author(s):  
Ming-hui Yu ◽  
Yin-ling Deng ◽  
Lian-chao Qin ◽  
Dang-wei Wang ◽  
Ya-ling Chen
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Levee Breach ◽  
Complex Boundary

scholarly journals Mixed insulating and conducting thermal boundary conditions in Rayleigh–Bénard convection

2017 ◽  
Vol 835 ◽  
pp. 491-511 ◽  
Author(s):  
Dennis Bakhuis ◽  
Rodolfo Ostilla-Mónico ◽  
Erwin P. van der Poel ◽  
Roberto Verzicco ◽  
Detlef Lohse
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Heat Transport ◽  
Bottom Plate ◽  
Bulk Temperature ◽  
Stripe Pattern ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

A series of direct numerical simulations of Rayleigh–Bénard convection, the flow in a fluid layer heated from below and cooled from above, were conducted to investigate the effect of mixed insulating and conducting boundary conditions on convective flows. Rayleigh numbers between $Ra=10^{7}$ and $Ra=10^{9}$ were considered, for Prandtl numbers $\mathit{Pr}=1$ and $\mathit{Pr}=10$. The bottom plate was divided into patterns of conducting and insulating stripes. The size ratio between these stripes was fixed to unity and the total number of stripes was varied. Global quantities, such as the heat transport and average bulk temperature, and local quantities, such as the temperature just below the insulating boundary wall, were investigated. For the case with the top boundary divided into two halves, one conducting and one insulating, the heat transfer was found to be approximately two-thirds of that for the fully conducting case. Increasing the pattern frequency increased the heat transfer, which asymptotically approached the fully conducting case, even if only half of the surface is conducting. Fourier analysis of the temperature field revealed that the imprinted pattern of the plates is diffused in the thermal boundary layers, and cannot be detected in the bulk. With conducting–insulating patterns on both plates, the trends previously described were similar; however, the half-and-half division led to a heat transfer of about a half of that for the fully conducting case instead of two-thirds. The effect of the ratio of conducting and insulating areas was also analysed, and it was found that, even for systems with a top plate with only 25 % conducting surface, heat transport of 60 % of the fully conducting case can be seen. Changing the one-dimensional stripe pattern to a two-dimensional chequerboard tessellation does not result in a significantly different response of the system.

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