scholarly journals Study on Failure Modes and Energy Evolution of Coal-Rock Combination under Cyclic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Shilin Song ◽  
Xuesheng Liu ◽  
Yunliang Tan ◽  
Deyuan Fan ◽  
Qing Ma ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Loading Condition ◽  
Failure Modes ◽  
Failure Process ◽  
Strong Support ◽  
Dissipated Energy ◽  
Energy Evolution ◽  
Cycle Index ◽  
Cyclic Loading Condition ◽  
Coal Rock

The loading modes and roof lithology have a significant influence on the mechanical properties of coal seams. To reveal the failure modes and energy evolution law of underground coal during the mining process, conventional uniaxial and uniaxial cyclic loading tests were carried out on three types of samples: coal, rock, and coal-rock combinations. The results show that the samples mainly behave with three failure modes (shear slip, tensile splitting, and fracture), and all the coal sections in the coal-rock combinations fail, whereas most rock sections remain intact. The compressive strength of the coal-rock combination is higher than coal and much smaller than rock. Compared with the conventional uniaxial loading condition, both the maximum deformation before failure and Young’s modulus under the cyclic loading condition are greater, and the latter increases quadratically with the cycle index. The energy densities are also calculated, and their variations are analysed in detail. The results show that with increasing cycle index, both the elastic energy stored in the sample and the dissipated energy increase in a quadratic function, and the failure process becomes more intense. This research reveals the failure modes, deformation characteristics, and energy evolution of the coal-rock combination under different loading conditions, which can provide strong support for controlling underground surrounding rocks of the coal face and roadway in coalmines.

scholarly journals Experimental Study on Mechanical Properties, Failure Behavior and Energy Evolution of Different Coal-Rock Combined Specimens

2019 ◽  
Vol 9 (20) ◽  
pp. 4427 ◽  
Author(s):  
Shang Yang ◽  
Jun Wang ◽  
Jianguo Ning ◽  
Pengqi Qiu
Keyword(s):  
Kinetic Energy ◽  
Failure Modes ◽  
Rock Strength ◽  
Compressive Loading ◽  
Dissipated Energy ◽  
Failure Behavior ◽  
Peak Strain ◽  
Energy Evolution ◽  
Coal Rock ◽  
Axial Splitting

To investigate the effect of the pure coal/rock strength on the mechanical behavior, failure behavior, and energy evolution of coal-rock combined (CRC) specimens, an AG-X250 Shimadzu Precision Universal Test was used to conduct uniaxial compressive loading, uniaxial cyclic loading, and unloading compression experiments on pure coal, pure rock, and different CRC specimens. The results show that the uniaxial compressive strength, Young’s modulus, and peak strain of the CRC specimen mainly depend on the coal specimen instead of the rock strength. The major failure modes of CRC were the shearing fracture and axial splitting failure, and for the CRC specimen with the same hard rock, the CRC specimen severely failed due to axial splitting cracks. In addition, the released elastic energy Ue, dissipated energy Ud, and kinetic energy Ur increase with increasing rock mass/coal strength, and for CRC specimen with the same coal, the greater the difference in strength between the rock and coal is, the greater the kinetic energy is.

scholarly journals Research on Fracture and Energy Evolution of Rock Containing Natural Fractures under Cyclic Loading Condition

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xueliang Li ◽  
Yu Wang ◽  
Shuo Xu ◽  
Haonan Yang ◽  
Bo Li
Keyword(s):  
Rock Mass ◽  
Cyclic Loading ◽  
Natural Fracture ◽  
Dissipated Energy ◽  
Energy Evolution ◽  
Rock Engineering ◽  
Cyclic Loading Condition ◽  
Freeze Thaw ◽  
Fracture Evolution ◽  
Naturally Fractured

For rock engineering in cold regions, the naturally fractured rock is susceptible to repeated freeze-thaw (F-T) weathering, coupled fatigue conditions of freeze-thaw (F-T), and stress disturbance act on rock mass, which can lead to the instability of rock engineering and even occurrence of geological hazards. Knowledge of how natural fracture affects the overall fracture evolution of freeze-thawed rock is crucial to rock mass stability. Laboratory multilevel cyclic loading tests are conducted to reveal the fatigue behavior and energy evolution for naturally fractured marble, as well as the influence of natural fracture volume on fracture evolution. The test results show that the preexisting natural fracture impacts fatigue strength, lifetime, and energy dissipation. The dissipated energy is correlated to all kinds of natural fracture (i.e., opening-mode, closing-mode, and filling-mode), and it decreases with the increase of the total natural fracture volume. The dissipated energy presents a first slow and then faster pattern as the cycle number grows. Compared with newly formed cracks, the proportion of energy consumed by stimulating natural cracks is smaller.

Analysis the characteristic of energy and damage of coal-rock composite structure under cycle loading

2021 ◽  
Author(s):  
Tan Li ◽  
Guangbo Chen ◽  
Zhongcheng Qin ◽  
Qinghai Li
Keyword(s):  
Cyclic Loading ◽  
Elastic Energy ◽  
Composite Structure ◽  
Calculation Method ◽  
Composite Structures ◽  
Damage Variable ◽  
Dissipated Energy ◽  
Height Ratio ◽  
Coal Rock ◽  
The Stability

Abstract The stability of coal-rock composite structures is of great significance to coal mine safety production. To study the stability and deformation failure characteristics of the coal-rock composite structure, the uniaxial cyclic loading tests of the coal-rock composite structures with different coal-rock height ratios were carried out. Lithology and coal-rock height ratio play an important role in the energy dissipation of coal-rock composite structures. The higher the coal-rock height ratio, the greater the average elastic energy and dissipated energy produced per cycle of coal-rock composite structures, the smaller the total elastic energy and dissipated energy produced in the process of cyclic loading. Based on the difference of damage variables calculated by dissipative energy method and acoustic emission method, a more sensitive joint calculation method for calculating damage variable was proposed. The joint damage variable calculation method can more accurately and sensitively reflect the damage of coal-rock composite structure under cyclic loading. The macroscopic crack first appears in the coal specimen in the coal-rock composite structure, the degree of broken coal specimens in the composite structure is inversely proportional to the coal-rock height ratio. The strength and deformation characteristics of the coal-rock composite structure are mainly affected by coal sample in the composite structure.

Unresolved Issues With Regard to Creep and Creep Fatigue Life Prediction

2002 ◽  
Author(s):  
J. Oh ◽  
N. Katsube ◽  
F. W. Brust
Keyword(s):  
Cyclic Loading ◽  
Damage Evolution ◽  
Life Prediction ◽  
Loading Condition ◽  
Cyclic Strain ◽  
Rupture Process ◽  
Steady State Creep ◽  
Creep Failure ◽  
Cyclic Loading Condition ◽  
Creep Fatigue

This paper studies intergranular creep failure of high temperature service material under a stress-controlled unbalanced cyclic loading condition. The grain boundary rupture process was numerically analyzed using Tvergaard’s axisymetric model. The present numerical model incorporated the experimentally verified Murakami-Ohno cyclic strain hardening creep law and Norton’s creep law. The numerical results show that void growth accelerates under cyclic loading condition. Also, analysis shows that a steady state creep law is not sufficient to analyze damage evolution under cyclic loading conditions.

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