scholarly journals Dynamic Behavior of Coal Pillar under Different Load Percentage by Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Guo-Wei Dong ◽  
Hai-Yang Liu ◽  
Guang-an Zhu
Keyword(s):  
Numerical Simulation ◽  
Dynamic Behavior ◽  
Goodness Of Fit ◽  
Damage Model ◽  
Coal Pillar ◽  
Peak Stress ◽  
Transmitted Wave ◽  
Softening Function ◽  
Dynamic Disturbance ◽  
Disturbance Intensity

The stability and dynamic response of coal pillar is of great importance in underground coal mining. In this paper, a series of uniaxial compressive experiments were first carried out to investigate the mechanical properties of coal. Subsequently, a statistical constitutive damage model for coal was proposed and applied to the numerical simulation. The proposed strain damage softening function showed almost the same goodness-of-fit on the experimental curve. According to this investigation, a numerical model FLAC3Dwas created to investigate the dynamic behavior of the coal pillar under different load percentage (LP). Modelling suggests that the incident and transmitted wave stress evolution observes similar rule and its process can be divided into three stages, namely, static preload, dynamic disturbance, and stabilized stages. The effects of dynamic disturbance intensity are also studied at 10 MPa, 20 MPa, and 30 MPa of peak stress, respectively. The results indicate that under the same load percentage, the peak incident and transmitted wave stress increase with the increase of dynamic disturbance intensity. On the contrary, the attenuation decreases. It is also observed that the failure zone interior the coal can be predicted by the wave propagation.

scholarly journals Dynamic Behavior of Coal Pillar Under Different Load Percentage by Numerical Simulation

2020 ◽  
Author(s):  
Guo-wei Dong ◽  
Hai-yang Liu ◽  
Guang-an Zhu
Keyword(s):  
Numerical Simulation ◽  
Dynamic Behavior ◽  
Goodness Of Fit ◽  
Damage Model ◽  
Coal Pillar ◽  
Transmitted Wave ◽  
Softening Function ◽  
Dynamic Disturbance ◽  
Disturbance Intensity ◽  
The Stability

Abstract The stability and dynamic response of coal pillar is of great importance in underground coal mining. In this paper, a series of uniaxial compressiveexperimentswerefirst carried out to investigate the mechanical properties of coal. Subsequently, a statistical constitutive damage model for coal was proposed and applied to the numerical simulation. The proposed strain damage softening function showed almostthe same goodness-of-fit on the experimental curve. A numericalmodel FLAC3Dwas created to investigate the dynamic behavior of the coal pillar under different load percentage(LD). Modelling suggests that the incident and transmitted wave stress evolution observesa similar rule and its process can be divided into three stages, namely, static preload, dynamic disturbance and stabilized stages.Under the same load percentage, the peak incident and transmitted wave stress increase with the increase of dynamic disturbance intensity. On the contrary, the attenuation decrease. It is also observed that the failure zone interior the coal can be predicted by the wave propagation.

scholarly journals Dynamic Behavior of Fault Slip Induced by Stress Waves

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Guang-an Zhu ◽  
Lin-ming Dou ◽  
Yang Liu ◽  
Zhen-guo Su ◽  
Hui Li ◽  
...  
Keyword(s):  
Rock Burst ◽  
Dynamic Behavior ◽  
Stress Relief ◽  
Fault Slip ◽  
Stress Waves ◽  
Fault Rock ◽  
Dynamic Disturbance ◽  
Static And Dynamic Analysis ◽  
Disturbance Intensity ◽  
Mining Depth

Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB) occurrence.

scholarly journals Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
S. Talebi ◽  
R. Hedayati ◽  
M. Sadighi
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Energy Absorption ◽  
Peak Stress ◽  
Absorption Capacity ◽  
Unit Cell ◽  
Lattice Structures ◽  
Energy Absorption Capacity ◽  
Closed Cell ◽  
Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

Shock and Sine Response of Rigid Structures on Nonlinear Mounts

1991 ◽  
Author(s):  
R. Dufour ◽  
J. Der Hagopian ◽  
M. Pompei ◽  
C. Garnier
Keyword(s):  
Numerical Simulation ◽  
Power Spectrum ◽  
Dynamic Behavior ◽  
Dynamic Environment ◽  
Rigid Bodies ◽  
Nonlinear Parameters ◽  
Large Power ◽  
Passive Damper ◽  
Highly Nonlinear

Abstract The dynamic environment of embarqued structures such as radars or more generally electronic equipments consists of impacts, sine and large power spectrum excitations. Under these real conditions and amongst different kinds of isolation, the passive damper with nonlinear parameters can provide good performances. This paper is concerned with the dynamic behavior of rigid bodies on highly nonlinear mounts. The numerical simulation and the experiment carried out, show that the load-deflection behavior of the dampers have to be slightly ajusted with respect to impact vibrations to obtain a well designed behavior.

Various Types of Coexisting Attractors in a New 4D Autonomous Chaotic System

2017 ◽  
Vol 27 (09) ◽  
pp. 1750142 ◽  
Author(s):  
Qiang Lai ◽  
Akif Akgul ◽  
Xiao-Wen Zhao ◽  
Huiqin Pei
Keyword(s):  
Numerical Simulation ◽  
Dynamic Behavior ◽  
Chaotic System ◽  
Limit Cycles ◽  
Electronic Circuit ◽  
Strange Attractors ◽  
Bifurcation Diagrams ◽  
Coexisting Attractors ◽  
Signum Function ◽  
Multiple Coexisting Attractors

An unique 4D autonomous chaotic system with signum function term is proposed in this paper. The system has four unstable equilibria and various types of coexisting attractors appear. Four-wing and four-scroll strange attractors are observed in the system and they will be broken into two coexisting butterfly attractors and two coexisting double-scroll attractors with the variation of the parameters. Numerical simulation shows that the system has various types of multiple coexisting attractors including two butterfly attractors with four limit cycles, two double-scroll attractors with a limit cycle, four single-scroll strange attractors, four limit cycles with regard to different parameters and initial values. The coexistence of the attractors is determined by the bifurcation diagrams. The chaotic and hyperchaotic properties of the attractors are verified by the Lyapunov exponents. Moreover, we present an electronic circuit to experimentally realize the dynamic behavior of the system.

scholarly journals Study on Occurrence Mechanism of Coal Pillar in L-Shaped Zone during Fully Mechanized Mining Period and Prevention Technology

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zeng-qiang Yang ◽  
Hong-mei Wang ◽  
De-quan Sun ◽  
Xian-jian Ma ◽  
Ming-bao Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Rock Burst ◽  
Dynamic Load ◽  
Static Load ◽  
Coal Pillar ◽  
Simulation Software ◽  
In Situ Investigation ◽  
Simulation Results ◽  
Occurrence Mechanism

In order to study the occurrence mechanism of rock burst in L-shaped zone during a fully mechanized mining period, the No. 705 working face which is located in Baojishan Colliery is taken as a typical engineering background. By means of in situ investigation, theoretical analysis, numerical simulation, in situ tests, and relevant monitoring methods, the occurrence mechanism of rock burst and corresponding prevention technology are studied. The results show that a coal pillar with some confining pressure in the L-shaped zone is established by FLAC3D numerical simulation software, and the numerical simulation results indicate that the change in static load has a greater effect than dynamic load on coal pillar unstable failure; the static load plays a role in storing energy, and dynamic load plays a role in inducing rock burst; the bolt-mesh-cable support and high-pressure water jet unloading combined technology is put forward to prevent rock burst in roadways, and the numerical simulation results show that stress distribution of surrounding rock meets the model of strong-soft-strong (3S) structure, and the moment distribution is reasonable. In the follow-up mining, a limit value of coal fines is used to determine that this measure is a reasonable method to prevent rock burst. The study conclusions provide theoretical foundation and new guidance for preventing rock burst by synergistic effect technology in roadways.

scholarly journals Sizing of Refractory Castable Gas-Burner Using Thermomechanical Simulations

2010 ◽  
Vol 70 ◽  
pp. 173-178
Author(s):  
Fabien Nazaret ◽  
Thierry Cutard ◽  
Olivier Barrau
Keyword(s):  
Damage Model ◽  
Peak Stress ◽  
Internal Length ◽  
Damage Level ◽  
Refractory Castables ◽  
Before And After ◽  
Tension And Compression ◽  
Material Choice ◽  
Gas Burner ◽  
Refractory Structures

Damage is a crucial characteristic of refractory castables and has to be considered to simulate correctly the behaviour of refractory structures. But, damage modelling by finite element simulations remains difficult. Indeed, the use of a continuum damage model with softening leads to strain localization phenomena. Numerical results depend on the mesh. Several numerical methods allow solving this meshing dependence by introducing an internal length in the material constitutive laws. In this paper, a regularization method has been applied with the damage plasticity model, considering a scalar value for damage. This model enables to take into account permanent strains due to plasticity and damage before and after the peak stress in tension and compression. Thermomechanical simulations are performed with this model to predict damage in a gas-burner. The damage level is evaluated after a thermal simulation generating high temperature gradients. Interests to take into account damage in the refractory structures are discussed. Sensitivity of results to material properties is studied. This work gives an example of using thermomechanical simulations to improve the design of refractory castable structures and to help in the material choice.

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