Buckling and Post-Buckling Behavior for Roof Strata in Longwall Mining

2012 ◽  
Vol 170-173 ◽  
pp. 751-754
Author(s):  
Qun Song ◽  
Zhi Lin Yang
Keyword(s):  
Longwall Mining ◽  
Main Roof ◽  
Equilibrium Path ◽  
Fracture Characteristics ◽  
Key Stratum ◽  
Buckling Behavior ◽  
Roof Stratum ◽  
Post Buckling ◽  
The Stability ◽  
Roof Strata

In accordance with the occurrence behavior of roof strata and the fracture characteristics of key stratum in shallow seam longwall mining, this paper studied the post-buckling behaviors of key roof stratum in the process of mining by using initial post-buckling theory, which derived a critical load and a breaking span of the main roof during the first weighting, determined the final subsidence for broken key stratum, and presented an application with the example of Daliuta 1203 face. The results indicate that the rock blocks a in are state of non-equilibrium after main roof breaking, the equilibrium path of main roof is unstable from breaking to final subsidence; thick unconsolidated layers above roof have effect on post-buckling behaviors of key stratum; the stability for bifurcation point equilibrium configuration and post-buckling equilibrium path of roof strata could be revealed and an effective method for determining displacement field of imperfection structure could be provided by using initial post -buckling theory.

Post-Buckling Analysis of Heavy Columns with Application to Marine Risers

1985 ◽  
Vol 29 (03) ◽  
pp. 162-169
Author(s):  
Theodore Kokkinis ◽  
Michael M. Bernitsas
Keyword(s):  
Boundary Conditions ◽  
Small Strain ◽  
Equilibrium Path ◽  
Drilling Mud ◽  
Tubular Columns ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Combined Action ◽  
Raphson Iteration ◽  
Good Agreement

The post-buckling behavior of heavy tubular columns following static instability under the combined action of weight, tension/compression at the top, and fluid static pressure forces in the gravity field is studied. A two-dimensional nonlinear small-strain large-deflection model of the column is derived, consisting of an integrodifferential equilibrium equation and two end rotation conditions. The equation of equilibrium is discretized using a finite-element method. An approximate solution valid in the neighborhood of the bifurcation point and an incremental solution are used to determine the secondary equilibrium path. The results of both methods are corrected by Newton-Raphson iteration. Conditions for unstable initial post-buckling behavior and existence of limit points on the secondary equilibrium path are presented. The numerical solution is applied to the problem of the elastica and is found to be in good agreement with the analytical solution. The secondary equilibrium path for a 500-m-long (1640 ft) marine drilling riser is calculated for two sets of boundary conditions and various values of the drilling mud density. The effect of the drilling mud density and the boundary conditions on the riser's post-buckling behavior is discussed.

Numerical and Experimental Buckling and Post - Buckling Analysis of Composite Cylindrical Panel with Delamination

2013 ◽  
Vol 477-478 ◽  
pp. 39-42
Author(s):  
Marek Barski ◽  
Aleksander Muc ◽  
Przemysław Pastuszak ◽  
Agnieszka Bondyra
Keyword(s):  
Numerical Analysis ◽  
Experimental Verification ◽  
Experimental Analysis ◽  
Cylindrical Panel ◽  
Composite Panel ◽  
Fem Method ◽  
Buckling Behavior ◽  
Post Buckling ◽  
The Stability ◽  
Composite Cylindrical Panel

The present work is devoted to the analysis of a buckling behavior of a cylindrical composite panel. The considered structure is subjected to the uniform axial compression. The wall of the panel consists of the 8 layers. In addition, in the geometrical center of the structure there is a square delamination located between the fourth and the fifth layer. The main goal is to determine the buckling and post - buckling behavior as well as the influence of the delamination on the stability of the structure. The nonlinear numerical analysis is carried out with aid of the FEM method. The experimental verification is also performed. The results obtained from numerical and experimental analysis show very similar behavior of the structure.

scholarly journals Analytical Solution for the Deformation and Support Parameters of Coal Roadway in Layered Roof Strata

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Kai Wang ◽  
Bao-gui Yang ◽  
Zhong-kui Wang ◽  
Xiao-long Wang
Keyword(s):  
High Efficiency ◽  
Design Method ◽  
Beam Theory ◽  
High Strength ◽  
Failure Criteria ◽  
Key Stratum ◽  
Coal Roadway ◽  
The Stability ◽  
Roof Strata

In order to meet the security and high-efficiency production needs, high-strength bolt (cable) reinforcement technology is usually used to maintain the stability of roadways. However, due to the great variability of lithology and mechanical properties, the failure form and stability of the layered roof in coal roadways are significant differences. The traditional supporting design method of the layered roof support in coal roadways is the engineering analogy method, which depends on experiences rather than theoretical analysis. Based on the theory of the elastic foundation beam and key stratum, this paper establishes a simplified analytical model of layered roof strata in coal roadways. Based on the Mohr-Coulomb theory, this paper gives the failure criteria of the layered roof strata, and the failure range of the layered roof strata is obtained. The length and pretightening force of bolt (cables) of the layered roof strata can be calculated based on the suspension theory and composite beam theory, which providing a quantitative theoretical basis for the determination of supporting parameters. Finally, as a case, the layered roof strata failure range and supporting parameters of the S1301 auxiliary transportation roadway in Gucheng coal mine are calculated.

scholarly journals Practical Use of Measuring the Deflection of Roof Layers in the Assessment of the Stability of Mining Excavations in the Polish Copper Ore Mine “Polkowice-Sieroszowice”

Mining ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 13-31
Author(s):  
Lech Stolecki ◽  
Krzysztof Szczerbiński
Keyword(s):  
Longwall Mining ◽  
Underground Mine ◽  
Copper Ore ◽  
Copper Mine ◽  
Highly Sensitive ◽  
Continuous Registration ◽  
The Stability ◽  
Roof Strata ◽  
Made In

The paper presents the results of long-term continuous measurements of the deflection of the roof layers in the underground copper mine Polkowice-Sieroszowice, Poland belonging to KGHM Polska Miedź S.A. The measurements were performed with the use of the inclinometric method consisting of continuous registration of changes in the angle of inclination of the roof strata. The measurements were carried out using an inclinometer sensor fixed to the end of a rockbolt in the roof. Measurements presented in the article were made in various regions of the underground mine. The monitoring covered: The exploitation front, machinery chamber and the region of the experimental longwall mining of copper ore. The obtained results proved the usefulness of the developed method in the process of the evaluation of the stability of mining excavations. The sensors were highly sensitive and performed the measurements in a simple way; highly accurate and reliable results were obtained.

Research on the Simulation of the Roof Fracture about the Gob-Side Entry Retaining

2013 ◽  
Vol 734-737 ◽  
pp. 624-627 ◽  
Author(s):  
Jian Jun Shi ◽  
Run Hua Wu ◽  
Tao Yong ◽  
Jing Zhong Guo
Keyword(s):  
Main Roof ◽  
Rock Stratum ◽  
Effective Measure ◽  
Energy Group ◽  
Key Stratum ◽  
Working Face ◽  
Geological Conditions ◽  
Research Findings ◽  
The Stability ◽  
Basic Features

The geological conditions of haulage roadway of the working face 1528 in GeQuan Coal Mine, which belongs to the JiZhong Energy Group CO., Ltd., and the research findings of Key Stratum Theory was taken into consideration, based on which established a mechanical model could reflect the basic features of rock stratum and made a profound investigation on the form and conditions of the fractures on main roofs. A systematic study on the stress, deformation, and damage characters of fractures on main roofs beyond a retained entry has been made by the laboratory test. The experiment shows that the deeper the fracture is in the rib, the greater the differences between dimension of compression and deformation will likely be, and the greater the influences on the stability of surrounding rock will it has. At the same time, smaller is the overhanging beam in mined-out area, more beneficial to roadway maintenance. On a certain deformation of main roof, it creates subsidence that is great difference in different position of a roadway. The subsidence near those mined-out areas is much more than those near the ribs. The application of a strong and effective measure could help cut the roof out and assure its stability.

scholarly journals Fracture Characteristics and Zoning Model of Overburden during Longwall Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhengyi Ti ◽  
Jiazhen Li ◽  
Meng Wang ◽  
Xiaoyan Li ◽  
Zhupeng Jin ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Longwall Mining ◽  
Shear Fracture ◽  
Coal Pillar ◽  
Tensile Fracture ◽  
Fracture Mechanisms ◽  
Winkler Foundation ◽  
Fracture Characteristics ◽  
Fracture Evolution ◽  
Key Stratum

The fracture characteristics and zoning model of overburden during longwall mining are the basis of coal mine disaster prevention. However, the existing theoretical model is inconsistent with the field measurement. In order to further research into the strata’s fracture characteristics and optimize the overburden’s zoning model, we used the elasticity and Winkler foundation theory to establish first fracture and periodic fracture mechanics models of clamped boundary supported by an elastic foundation with a key stratum as the research object. We analyzed the stress distribution characteristics and fracture evolution pattern of the mining-induced key stratum. We analyzed the zoning characteristics of mining-induced overburden and established the zoning model according to different fracture mechanisms. The results show that the key stratum formed a double “O-X” shaped interconnected fracture zone after the first fracture. The key stratum formed a double “C-K” shaped interconnected fracture zone after the periodic fracture. We divided the mining-induced overburden into three zones along the horizontal direction: the original rock zone, the inverted triangular compression-shear fracture zone, and the trapezoidal tensile fracture zone. The study revealed the mechanism of inverted step fracture in the separation zone, explained the fracture mechanism of the coal pillar support zone, and has significant theoretical value for the prevention and control of water disasters, gas outbursts, and strata movement.

Buckling Behavior of Tire Breaker Structure

1983 ◽  
Vol 11 (1) ◽  
pp. 3-19
Author(s):  
T. Akasaka ◽  
S. Yamazaki ◽  
K. Asano
Keyword(s):  
Elastic Foundation ◽  
Elastic Moduli ◽  
Wave Length ◽  
Bending Moment ◽  
Experimental Results ◽  
Automobile Tire ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Steel Cord ◽  
Interlaminar Shear

Abstract The buckled wave length and the critical in-plane bending moment of laminated long composite strips of cord-reinforced rubber sheets on an elastic foundation is analyzed by Galerkin's method, with consideration of interlaminar shear deformation. An approximate formula for the wave length is given in terms of cord angle, elastic moduli of the constituent rubber and steel cord, and several structural dimensions. The calculated wave length for a 165SR13 automobile tire with steel breakers (belts) was very close to experimental results. An additional study was then conducted on the post-buckling behavior of a laminated biased composite beam on an elastic foundation. This beam is subjected to axial compression. The calculated relationship between the buckled wave rise and the compressive membrane force also agreed well with experimental results.

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