scholarly journals Critical Conditions and Energy Transfer Characteristics of the Failure Process of Coal-Rock Combination Systems in Deep Mines

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Haitao Sun ◽  
Linchao Dai ◽  
Yanbao Liu ◽  
Hongwei Jin
Keyword(s):  
Elastic Energy ◽  
Dynamic Instability ◽  
Coupling Effect ◽  
Limit Equilibrium ◽  
Failure Process ◽  
Elastic Strain Energy ◽  
Critical Conditions ◽  
Steady Increase ◽  
Rock System ◽  
Coal Rock

With the steady increase in the size, intensification, and modernization of coal production enterprises, the deep coal resources in large coal bases are gradually entering the mining stage. When the coal mining reaches the deep zone, the interactions between various underground dynamic hazards begin to occur. These interactions are affected by the engineering geological environment and can lead to the occurrence of severe compound hazards. When coal and gas outbursts occur and destabilize the mining area, the high geostress causes the multiphysical coupling effect of the laminated overburden system to become more pronounced. Therefore, we analyzed the development path of a coal-rock system under instability conditions from the perspective of coal–rock coupling, constructed a model of the coal-rock combination system’s structure, and proposed three directions (i.e., strain softening, limit equilibrium, and dynamic instability) for the development of coal-rock system instability. Then, we established a model for the critical conditions of the system’s failure process and elucidated that the release of the rock’s elastic energy promoted the instability of the coal. Furthermore, we verified the established critical conditions through laboratory tests on a coal-rock combination structure and obtained the patterns of the rock energy transferring into the coal seam during the instability failure process of the coal–rock combination structure. When the coal–rock combination structure failed, the rock strain reached its maximum value and the strain rebound phenomenon occurred. The stored elastic strain energy released by the rock into the combination system accounted for 26% to 53% of the accumulated energy in the rock itself, and the released elastic energy and the new surface area of the crushed coal sample followed a logarithmic relationship. The findings of this study provide theoretical support for the identification and quantitative analysis of instability due to the dynamic hazards of coal-rock gas in deep mines.

scholarly journals Investigation into the gas adsorption-loading coupling damage constitutive model of coal rock

2021 ◽  
Author(s):  
Zhongzhong Liu ◽  
Hanpeng Wang ◽  
Su Wang ◽  
Yang Xue ◽  
Chong Zhang
Keyword(s):  
Gas Adsorption ◽  
Coupling Effect ◽  
Influencing Factor ◽  
Failure Process ◽  
Damage Model ◽  
Strain Curve ◽  
In Situ Stress ◽  
Compression Tests ◽  
Damage And Failure ◽  
Coal Rock

Abstract Coal and gas outburst is the result of comprehensive action of in-situ stress, gas and mechanical properties of coal rock. The coupling effect of loading and gas adsorption eventually leads to the coal rock failure. Based on the principle of strain equivalence and considering the coupling effect of gas adsorption and stress loading, an adsorption-loading coupling damage model is established which breaks through the bottleneck of only considering single influencing factor. Taking briquette samples with controllable properties as the research object, uniaxial compression tests of coal rock at different gas adsorption pressures are carried out, and the model is verified based on the test results. The results of model calculation and tests show that the meso damage stage of coal body can well correspond to the macroscopic deterioration phenomenon and it is in good agreement with the stress-strain curve. It is proved that the model has good applicability and can accurately describe the damage and failure process of coal rock.

scholarly journals Experimental Investigations on the Progressive Failure Characteristics of a Sandwiched Coal-Rock System Under Uniaxial Compression

2019 ◽  
Vol 9 (6) ◽  
pp. 1195 ◽  
Author(s):  
Jinwen Bai ◽  
Guorui Feng ◽  
Zehua Wang ◽  
Shangyong Wang ◽  
Tingye Qi ◽  
...  
Keyword(s):  
Rock Specimen ◽  
Progressive Failure ◽  
Failure Process ◽  
Local Strain ◽  
Experimental Investigations ◽  
Rock System ◽  
Failure Characteristics ◽  
Coal Rock ◽  
Mining Design ◽  
Seam Mining

Overlapped residual coal pillars, together with the surrounding rock strata, play a combined bearing role in ultra-close multiple seam mining. Global stability of the whole bearing system is significant for the mining design, construction, and operation. Laboratory uniaxial compressive experiments for different kinds of sandwiched coal-rock specimens are carried out to investigate the progressive failure characteristics and mechanisms. Results show that: (1) The mechanical behavior of the sandwiched coal-rock specimen is mainly divided into four stages during the failure process. The response of the electrical resistivity and the evolution of acoustic emission (AE) energy are in good agreement with the mechanical behaviors at different stages, which are a reflection of the global failure characteristics of sandwiched specimens. (2) The distribution of AE events and the development of local strain can provide further insight into the local failure characteristics of coal elements or rock elements in sandwiched specimens. AE events are more likely to be generated in coal elements, which can propagate across coal-rock interfaces and induce damage to rock elements in a certain area. Similarly, the unbalanced deformation characteristics of coal elements and rock elements are apparently revealed in the progressive failure process. (3) Progressive failure of a sandwiched coal-rock specimen is closely associated with the interactions between the coal elements and rock elements. Initial failure usually appears in the coal elements. At this process, the recovery of elastic deformation and the output of strain energy are observed in the rock elements, which can accelerate the rupture of coal elements. In turn, the dynamic fracture energy generated in the rupture process of coal elements can propagate into rock elements and induce damage to rock elements a certain area. (4) The experimental results are helpful for maintaining the long-term stability of a sandwiched coal-rock system in ultra-close multiple seam mining.

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.

scholarly journals Numerical simulation for fracture network evolution in coal-bearing gas reservoir reconstruction based on damage theory

2021 ◽  
Vol 25 (6 Part B) ◽  
pp. 4423-4429
Author(s):  
Hai-Xiao Lin ◽  
Qiu-Yu Pan ◽  
Bang-Hua Yao ◽  
Wen-Long Shen ◽  
Feng Yang
Keyword(s):  
Numerical Simulation ◽  
Mechanical Response ◽  
Coupling Effect ◽  
Fracture Network ◽  
Network Evolution ◽  
Geological Strength Index ◽  
Forming Process ◽  
Brittle Damage ◽  
Coal Rock ◽  
Numerical Calculation Method

Based on the characteristics of mechanical response of coal rock under loading, an elastic-brittle damage constitutive relation of coal rock has been proposed, which has been extended to the 3-D stress state, based on the geological strength index. Besides, a numerical calculation method based on the elastic-brittle damage the?ory has been developed, by analyzing the seepage-stress coupling effect. Then, a computing program for fracture network transformation has been composed to perform numerical simulation of forming process of coal rock under different working conditions, by the APDL language in the ANSYS software platform. The mechanical mechanism of fracture network forming process of coal rock has been further analyzed.

Catastrophe Theory Analysis of Rock Mass Dynamic Destabilization

2012 ◽  
Vol 166-169 ◽  
pp. 2774-2781
Author(s):  
Yong Zhang ◽  
Da Jian Hu ◽  
Lu Xue
Keyword(s):  
Rock Mass ◽  
Elastic Energy ◽  
Quantitative Description ◽  
Scientific Basis ◽  
Rock System ◽  
Catastrophe Model ◽  
Rock Stability ◽  
Before And After ◽  
The Given ◽  
First Time

In step with body Ⅱ, analytic solution and illustration of elastic energy releasing amount of rock mass dynamic destabilization are given for the first time in the form of precise and approximate catastrophe model. It is upgraded from qualitative understand to quantitative description that study on rock stability at the stage before and after earthquake and rockburst. The halting point’s position of rock mass dynamic destabilization is ascertained strictly, and it offers scientific basis for the calculation on earthquake efficiency, the study on earthquake energy magnitude released, earthquake stress drop, fault offset after earthquake and amount of elastic strain recovery of surrounding rock. The system possesses the capability of applying work to surroundings when it destabilizes, and earthquake wave energy is the work that destabilizing rock system applies to surroundings by way of destructive. The given illustration of elastic energy releasing amount implicates wealth of information, it produces credible evidence for confirming that the mathematical abstract of rock dynamic destabilization is fold catastrophe model.

External work and potential for elastic storage at the limb joints of running dogs

1998 ◽  
Vol 201 (23) ◽  
pp. 3197-3210 ◽  
Author(s):  
C. S. Gregersen ◽  
N. A. Silverton ◽  
D. R. Carrier
Keyword(s):  
Elastic Energy ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
External Work ◽  
Negative Work ◽  
Extensor Muscles ◽  
Positive Work

The storage and recovery of elastic strain energy in muscles and tendons increases the economy of locomotion in running vertebrates. In this investigation, we compared the negative and positive external work produced at individual limb joints of running dogs to evaluate which muscle-tendon systems contribute to elastic storage and to determine the extent to which the external work of locomotion is produced by muscles that shorten actively rather than by muscles that function as springs. We found that the negative and positive external work of the extensor muscles is not allocated equally among the different joints and limbs. During both trotting and galloping, the vast majority of the negative work was produced by the two distal joints, the wrist and ankle. The forelimb produced most of the negative work in both the trot and the gallop. The hindlimb produced most of the positive work during galloping, but not during trotting. With regards to elastic storage, our results indicate that the forelimb of dogs displays a greater potential for storage and recovery of elastic energy than does the hindlimb. Elastic storage appears to be more important during trotting than during galloping, and elastic storage appears to be more pronounced in the extensor muscles of the distal joints than in the extensor muscles of the proximal joints. Furthermore, our analysis indicates that a significant portion of the external work of locomotion, 26% during trotting and 56 % during galloping, is produced by actively shortening muscles. We conclude that, although elastic storage of energy is extremely important to the economy of running gaits, actively shortening muscles do make an important contribution to the work of locomotion.

scholarly journals Dynamic Stability Discrimination Method for Concrete Dam under Complex Geological Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Liaojun Zhang ◽  
Tianxiao Ma ◽  
Hanyun Zhang ◽  
Dongsheng Chen
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Dynamic Instability ◽  
Limit Equilibrium ◽  
Element Model ◽  
Safety Factors ◽  
Stability Calculation ◽  
Dam Foundation ◽  
Geological Conditions ◽  
Dam Foundations

The instability of dams will bring immeasurable personal and property losses to the downstream, so it has always been a trendy topic worthy of investigation. Currently, the rigid body limit equilibrium method is the most commonly used method for the dynamic stability analysis of dams. However, under the action of earthquakes, the instability of the integral dam-foundation system threatens the safety of the dams and is of great concern. In this paper, a stability analysis method that can reflect the complex geological structural forms of dam foundations is proposed in this paper. The advantages are that this method deals with the difficulty in assuming sliding surfaces and the lack of quantitative criteria for the dynamic instability analysis of dams with complex geological structural forms of dam foundations. In addition, through the method, the sliding channels that may appear in the dam foundations can be automatically searched under random earthquake action, and the safety factors of the dynamic instability of dams be quantitatively obtained. Taking a high RCC gravity dam under construction in China as an example, the proposed method is applied to the three-dimensional finite element model of the dam-foundation system of this dam, and then the dynamic stability calculation is carried out. Through this method, the formation process of the dam foundation’s plastic zone and the failure of sliding channels with different strength reduction coefficients are studied on and analyzed detailedly, and the quantitative acquisition of the safety factors is realized. The results show that the method is reasonable and feasible, and helps provide a new idea and method for the dynamic stability analysis of dams.

MULTIFRACTAL OF ELECTROMAGNETIC WAVEFORM AND SPECTRUM ABOUT COAL ROCK SAMPLES SUBJECTED TO UNIAXIAL COMPRESSION

Fractals ◽  
2020 ◽  
Vol 28 (04) ◽  
pp. 2050061 ◽  
Author(s):  
LIMING QIU ◽  
DAZHAO SONG ◽  
XUEQIU HE ◽  
ENYUAN WANG ◽  
ZHENLEI LI ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Failure Process ◽  
Dominant Frequency ◽  
Rock Failure ◽  
Electromagnetic Signal ◽  
Failure Behavior ◽  
Electromagnetic Spectrum ◽  
Dimension Formula ◽  
Coal Rock ◽  
The Difference

During coal and rock loading, a significantly large number of electromagnetic signals are generated as a result of fracture appearance and crack expansion. The generation of electromagnetic signal is the comprehensive embodiment of the coal rock failure behavior. Therefore, the generated signals contain complex and rich messages that can reflect the damage process and degree of coal and rock. In this work, the multifractal theory is applied to analyze the nonlinear characteristics of the electromagnetic wave and its spectrum induced during coal rock, which present good correlation with failure process. The failure process of coal rock is non-uniform, non-continuous and nonlinear, during which, there is a good synchronization and correlation between the electromagnetic pulses and the stress drop, rather than the stress. Both waveform and its spectrum of electromagnetic signal have multifractal characteristics, the larger the fracture scale is, the more significant the multifractal characteristic of electromagnetic signal is, and the multifractal characteristic of electromagnetic signal from coal is higher than that from sandstone. The difference of fracture energy and size can be represented by the maximum of the multifractal dimension [Formula: see text] of the electromagnetic wave and its spectrum during coal rock failure. In the electromagnetic spectrum, small signals are always dominant, and the dominant frequency is only a few isolated points. What is more, with the increase of fracture size, the difference between the dominant frequency and the non-dominant frequency is gradually enhanced.

Sign in / Sign up

Export Citation Format

Share Document