scholarly journals Coal Pillars Safe Mining

2018 ◽  
Vol 41 ◽  
pp. 01026
Author(s):  
Natalya Pirieva ◽  
Inna Ermakova
Keyword(s):  
Underground Mining ◽  
Economic Effect ◽  
Coal Pillar ◽  
Strain Analysis ◽  
Fracture Zones ◽  
Stress Strain ◽  
Mining System ◽  
Actual Structure ◽  
Coal Pillars ◽  
Experimental Values

Safety pillars are the necessary objects for underground mining of coal seams. The having been mines; safety pillars, which include the development workings, lose their purpose. The coal reserves in these pillars are significant and can be mined. However, the pillars have fracture zones in the edges. The size of the fracture zones in the marginal parts of the pillars should be taken into account when choosing a mining system and its parameters. Coal pillar stress-strain analysis was carried out by the finite element method. The developed technique for coal pillar stress-strain analysis takes into account the post-critical strain of the coal seam edge. The reliability of the technique was verified by the experimental method. The calculated and experimental values differ insignificantly. The geomechanical condition of the nine safety pillars in A.D. Ruban mine of OJSC “SUEK-Kuzbass” was studied. The enterprise mines three low dip seams at a depth of up to 290 m. The amount of losses in fracture zones is defined for the pillars, which include slopes and entries. Fracture zones in the pillars were sized taking into account the actual structure of the seam roofs: the depth of bedding, their thickness and strength characteristics. The economic effect of mining of the safety pillars is pre-computed.

scholarly journals Improvement of the Loading Capacity of Narrow Coal Pillars and Control Roadway Deformation in the Longwall Mining System. A Case Study at Khe Cham Coal Mine (Vietnam)

2020 ◽  
Vol 1 (2) ◽  
Author(s):  
Le QUANG PHUC ◽  
V. P. ZUBOV ◽  
Phung MANH DAC
Keyword(s):  
Longwall Mining ◽  
Coal Pillar ◽  
Rock Bolt ◽  
Mining System ◽  
Pillar Stability ◽  
Roadway Support ◽  
Coal Pillars ◽  
The Stability ◽  
Safe Condition ◽  
Cable Bolt

Currently, the application of coal pillars to protect an adjacent roadway is a common method in Vietnam when exploiting according to the longwall system. Therefore, the width of a coal pillar is an important issue for the stability of a roadway. In order to reduce coal loss in these coal pillars, they tend to be designed in a narrow coal pillar style but still have to ensure that the adjacent roadway can meet safe coal production conditions. The stability of roadways and coal pillars is related to many factors such as technical mechanical characteristics, physical and mechanical properties of coal, stress environment and support methods. The bearing structure of the coal pillar and the around rock a roadway is analyzed and it has been shown that enhancing roadway support and improving the carrying capacity of coal pillars can control the deformation of the surrounding rock. A study related to the stability and safety of roadways and small coal pillars in the longwall mining system has been carried out. Stabilization factors have been considered, especially the state of stress in the coal pillars and the deformation of the roadway. By applying the numerical simulation method, the stress of the coal pillar and the deformation of the adjacent roadway under different supporting solutions were analyzed and evaluated. By using this method, the rock bolt roadway support solution combined with the long cable bolt in the roadway roof and the coal pillar was selected in the safe condition of the mining process. Because cable bolt can improve the flexibility of the coal pillar such as: reducing the size of the plastic area on both sides of the pillar; enhancing coal pillar stability in the core area by providing great drag and tensile for coal pillars; contributing to improving the anchor point fixation of rock bolt. The conclusions obtained may provide a certain reference parameters to improve mining efficiency and labor safety in underground coal mines.

scholarly journals Design a Reasonable Width of Coal Pillar Using a Numerical Model. A case study of Khe Cham basin, Vietnam

2020 ◽  
Vol 174 ◽  
pp. 01043
Author(s):  
Phuc Le Quang ◽  
Vladimir Zubov ◽  
Thang Pham Duc
Keyword(s):  
Numerical Simulation ◽  
Coal Pillar ◽  
Linear Increase ◽  
Underground Mines ◽  
Support Pressure ◽  
Efficient Production ◽  
Mining System ◽  
Geological Conditions ◽  
Coal Pillars ◽  
Roadway Deformation

Problems in surrounding rock displacement, roadway deformation and complex support are the hallmarks of the long wall mining system. Such problems seriously affect the safety and efficient production of coal mines. To control the deformation of the rocks around the roadway next to the goaf, to reduce the support pressure, in Vietnamese underground mines often leave supporting coal pillars. Identification of a reasonable design for roadway supporting pillars by a numerical simulation study was conducted under the geological and technical foundation of I-10- 2 working faces at the Khe Cham coal mine, Vietnam . The characteristics of stress and pressure distribution of roof layers on coal pillars are modeled under different pillar widths. The results show a great linear increase of the vertical stress on the narrow coal pillar and as the width of the coal pillar increases, the area of the elastic core area also increases and the level of stress increase tends to be stable without any apparent uptrend. Coal pillar deformation decreases with increasing coal pillar width, but it leads to large coal loss and waste of resources. Therefore, with the current supporting solutions to increase the stability of the coal pillar, the size range of a coal pillar is determined to be 6-8 m through numerical simulation. The conclusions obtained may provide a certain reference number to choose the logical location of the furnace lines under similar geological conditions.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Stress-Strain Analysis and Simulation for Estimation of Cutting Forces on the Skin

2015 ◽  
Vol 9 (6) ◽  
pp. 583
Author(s):  
Dario German Buitrago ◽  
Luis Carlos Ruíz ◽  
Olga Lucia Ramos
Keyword(s):  
Cutting Forces ◽  
Strain Analysis ◽  
Stress Strain

Stress-Strain Relations and Vibrations of a Granular Medium

1957 ◽  
Vol 24 (4) ◽  
pp. 585-593
Author(s):  
J. Duffy ◽  
R. D. Mindlin
Keyword(s):  
Energy Dissipation ◽  
Contact Forces ◽  
Face Centered Cubic ◽  
Stress Strain ◽  
Differential Stress ◽  
Elastic Bodies ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Face Centered ◽  
Experimental Values

Abstract A differential stress-strain relation is derived for a medium composed of a face-centered cubic array of elastic spheres in contact. The stress-strain relation is based on the theory of elastic bodies in contact, and includes the effects of both normal and tangential components of contact forces. A description is given of an experiment performed as a test of the contact theories and the differential stress-strain relation derived from them. The experiment consists of a determination of wave velocities and the accompanying rates of energy dissipation in granular bars composed of face-centered cubic arrays of spheres. Experimental results indicate a close agreement between the theoretical and experimental values of wave velocity. However, as in previous experiments with single contacts, the rate of energy dissipation is found to be proportional to the square of the maximum tangential contact force rather than to the cube, as predicted by the theory for small amplitudes.

Modeling of the stress-state longwall face during coal mining with the technology of roof management complete drop and stowing

2020 ◽  
pp. 99-106
Author(s):  
I. E. Mazina ◽  
A. A. Stel’makhov ◽  
L. F. Mullagalieva
Keyword(s):  
Coal Mining ◽  
Strain State ◽  
Underground Mining ◽  
Negative Impact ◽  
Hydrological Regime ◽  
Coal Bed ◽  
Stress Strain ◽  
Environmental Friendliness ◽  
Modeling And Analysis ◽  
Stress Strain State

Underground mining of coal deposits has a negative impact on all components of the environment. When developing a coal deposit, it is coal mining technology that determines the scale and consequences of the negative impact. Changes in the stress-strain state of the geo-environment can lead to a violation of the hydrological regime, increased gas emission from the host rocks, the initiation of gas-dynamic processes. Choice of roofing management technology - as a geotechnological method of natural and technical system management determines the environmental friendliness of coal mining and creates safety conditions. The article deals with the technology of roofing control during coal production. For this purpose mathematical modeling and analysis of stress-strain state of the bottomhole part of the coal bed for the conditions of S.M. Kirov is performed. As a result of modeling, two technologies of roof control were analyzed - complete caving and stowing. For the worked out clearing leaves filled with either caving rocks or stowing material, there are characteristic unloading zones in the massif to be worked and overworked, as well as pressure reference zones, which fall on the parts of the pillars associated with the lava. It was found out that the application of the stowing technology creates conditions for minimization of gravitational stresses in the geoenvironment, as well as significantly reduces the potential energy of form change.

Stress Analysis of Pipeline Subjected to Differential Frost Heave

2013 ◽  
Author(s):  
Yan Di ◽  
Jian Shuai ◽  
Lingzhen Kong ◽  
Xiayi Zhou
Keyword(s):  
Strain Analysis ◽  
Element Model ◽  
Frozen Soil ◽  
Computational Method ◽  
Frost Heave ◽  
Safe Operation ◽  
Stress Strain ◽  
Segregation Potential ◽  
Differential Frost Heave ◽  
Design Construction

Frost heave must be considered in cases where pipelines are laid in permafrost in order to protect the pipelines from overstress and to maintain the safe operation. In this paper, a finite element model for stress/strain analysis in a pipeline subjected to differential frost heave was presented, in which the amount of frost heave is calculated using a segregation potential model and considering creep effects of the frozen soil. In addition, a computational method for the temperature field around a pipeline was proposed so that the frozen depth and temperature variation gradient could be obtained. Using the procedure proposed in this paper, stress/strain can be calculated according to the temperature on the surface of soil and in a pipeline. The result shows the characteristics of deformation and loading of a pipeline subjected to differential frost heave. In general, the methods and results in this paper can provide a reference for the design, construction and operation of pipelines in permafrost areas.

Numerical Modeling and Analytical Investigation of Autofrettage Process on the Fluid End Module of Fracture Pumps

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Mahdi Kiani ◽  
Roger Walker ◽  
Saman Babaeidarabad
Keyword(s):  
Residual Stresses ◽  
Kinematic Hardening ◽  
Analytical Formula ◽  
Strain Analysis ◽  
Material Model ◽  
Analytical Investigation ◽  
Stress Strain ◽  
Element Analysis ◽  
Hardening Material ◽  
Strain Evolution

One of the most important components in the hydraulic fracturing is a type of positive-displacement-reciprocating-pumps known as a fracture pump. The fluid end module of the pump is prone to failure due to unconventional drilling impacts of the fracking. The basis of the fluid end module can be attributed to cross bores. Stress concentration locations appear at the bores intersections and as a result of cyclic pressures failures occur. Autofrettage is one of the common technologies to enhance the fatigue resistance of the fluid end module through imposing the compressive residual stresses. However, evaluating the stress–strain evolution during the autofrettage and approximating the residual stresses are vital factors. Fluid end module geometry is complex and there is no straightforward analytical solution for prediction of the residual stresses induced by autofrettage. Finite element analysis (FEA) can be applied to simulate the autofrettage and investigate the stress–strain evolution and residual stress fields. Therefore, a nonlinear kinematic hardening material model was developed and calibrated to simulate the autofrettage process on a typical commercial triplex fluid end module. Moreover, the results were compared to a linear kinematic hardening model and a 6–12% difference between two models was observed for compressive residual hoop stress at different cross bore corners. However, implementing nonlinear FEA for solving the complicated problems is computationally expensive and time-consuming. Thus, the comparison between nonlinear FEA and a proposed analytical formula based on the notch strain analysis for a cross bore was performed and the accuracy of the analytical model was evaluated.

Stress – Strain Analysis on ZnO Nanostructures Synthesized via Wet Chemistry Method

2015 ◽  
Vol 1112 ◽  
pp. 57-61 ◽  
Author(s):  
Amalia Sholehah ◽  
Akhmad Herman Yuwono
Keyword(s):  
Crystallite Size ◽  
Strain Analysis ◽  
Xrd Analysis ◽  
Heating Process ◽  
Zno Nanostructures ◽  
Stress Strain ◽  
Wet Chemistry ◽  
Chemistry Method ◽  
Hall Method ◽  
Scherrer Equation

In the present work, ZnO nanostructures were synthesized via wet chemistry method. The seeding solution was prepared from zinc nitrate tetrahydrate and hexamethylenetetramine. Prior to the heating process, the seeding solution was immersed in cold bath (0°C). XRD analysis had shown sharp peaks in diffractogram, indicating the high crystallinity of ZnO nanostructures. The crystallite size was determined using Scherrer equation and Williamson-Hall method. Other relevant parameters including stress, strain, and energy density were calculated using Williamson-Hall assuming UDM, UDSM, and UDEDM. The results had revealed that crystallite size calculated with Williamson-Hall method is more accurate than Scherrer equation.

Sign in / Sign up

Export Citation Format

Share Document