The Influence of Fracture Strain Energy on the Burst Tendency of Coal Seams and Field Application

Coal is typically considered a special engineering rock mass because of its low strength, high internal fracture development, good permeability, and random distribution of microparticles and fractures. The results of cyclic loading and unloading tests indicate that the strain energy during the coal deformation process can be divided into three parts: plastic strain energy; fracture strain energy; and base-material strain energy. The energy composition ratio differs depending on coal strength. Lower proportions of fracture strain energy are associated with higher elastic energy indexes, and there is a negative correlation between fracture strain energy and other coal burst tendency indexes. The results were applied on the 4206 isolated island working face of coal mine A in Yan’an, Shanxi, China, yielding good benefits. The findings presented here provide a theoretical basis for understanding the principle of coal seam bursting and guidance for reducing burst risks.

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Energy Variation Law and Rockburst Characteristics of Coal under Cyclic Loading

Shock and Vibration ◽

10.1155/2021/5528555 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Hongjun Guo ◽

Ming Ji ◽

Dapeng Liu ◽

Mengxi Liu ◽

Gaofeng Li ◽

...

Keyword(s):

Cyclic Loading ◽

Strain Energy ◽

Base Material ◽

Elastic Strain Energy ◽

Economic Benefits ◽

Engineering Properties ◽

Adjustment Process ◽

Important Indicator ◽

Cyclic Loading And Unloading ◽

Coal Deformation

Coal mining involves numerous challenges and safety risks owing to the complex engineering properties of coal bodies, which include discontinuities, heterogeneity, and anisotropy. In this paper, the strain energy during the coal deformation process is redivided in combination with cyclic loading and unloading tests to determine the energy evolution law and discuss the rockburst tendency characteristics. The results show that the elastic strain energy, and particularly the base-material strain energy, consistently dominates during the energy adjustment process, which is an important indicator of rockburst tendency. The elastic energy index and rebound deformation index also show that moderate plastic deformation (e.g., crack expansion and local penetration) can reduce the rockburst tendency level and prevent rockburst accidents. On the basis of the obtained results, precracking and pressure relief measures of blasting are adopted on site in advance of the working face, and good safety and economic benefits are achieved. These findings, thus, provide an important engineering reference for mines under similar conditions.

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Safety Mining Technology of Coal Seams in Weathered Zone Based on Ground J-Type Pregrouting Reinforcement

Advances in Civil Engineering ◽

10.1155/2018/3210420 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10

Author(s):

Min Tu ◽

Jinlong Cai ◽

Hualei Zhang ◽

Chuanxin Rong

Keyword(s):

Industrial Test ◽

Coal Seams ◽

Strata Movement ◽

Research Results ◽

Weathered Zone ◽

Working Face ◽

Fracture Development ◽

Seam Mining ◽

Rock Strata ◽

Overlying Strata

A thin basement coal seam mining model under different overlying strata conditions was developed using the discrete element software UDEC. This approach is used to discuss the safety mining of the thin basement coal seams. Fracture development in overlying and rock strata movement law in the stope was discussed. The relationship between support and surrounding rocks under different overlying strata conditions was analyzed. Lastly, a field industrial test was conducted based on the research results. A few major conclusions could be drawn. Under load transmission in loose water-bearing strata, causing a large-scaled rock strata movement to advance into the working face is easy when only one bearing stratum exists in the overlying strata. Meanwhile, the support bears strong loads, which can easily be collapsed. When two bearing strata exist in the overlying one, the upper bearing stratum can form a voussoir beam structure. Loads on the support decreased substantially compared with those under single bearing stratum, whilst the probability of pressing frame was reduced accordingly. A weathered zone above the stope was reinforced by ground J-type drilling pregrouting, thereby improving the physical and mechanical properties and increasing the bearing capacity of the rock strata in the grouting range and safety mining of the working face in the lower coal seams. Research results provide important references for the safety mining of thin basement coal seams under similar conditions.

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Comprehensive technical support for safe mining in ultra-close coal seams: A case study

Energy Exploration & Exploitation ◽

10.1177/01445987211009390 ◽

2021 ◽

pp. 014459872110093

Author(s):

Wei Zhang ◽

Jiawei Guo ◽

Kaidi Xie ◽

Jinming Wang ◽

Liang Chen ◽

...

Keyword(s):

Coal Seam ◽

Technical Support ◽

Surrounding Rock ◽

Coal Seams ◽

Deformation Control ◽

Hard Roof ◽

Working Face ◽

Close Coal Seams ◽

Safe Mining

In order to mine the coal seam under super-thick hard roof, improve the utilization rate of resources and prolong the remaining service life of the mine, a case study of the Gaozhuang Coal Mine in the Zaozhuang Mining Area has been performed in this paper. Based on the specific mining geological conditions of ultra-close coal seams (#3up and #3low coal seams), their joint systematic analysis has been performed, with the focus made in the following three aspects: (i) prevention of rock burst under super-thick hard roof, (ii) deformation control of surrounding rock of roadways in the lower coal seam, and (iii) fire prevention in the goaf of working face. Given the strong bursting tendency observed in upper coal seam and lower coal seam, the technology of preventing rock burst under super-thick hard roof was proposed, which involved setting of narrow section coal pillars to protect roadways and interleaving layout of working faces. The specific supporting scheme of surrounding rock of roadways in the #3low1101 working face was determined, and the grouting reinforcement method of local fractured zones through Marithan was further proposed, to ensure the deformation control of surrounding rock of roadways in lower coal seams. The proposed fire prevention technology envisaged goaf grouting and spraying to plug leaks, which reduced the hazard of spontaneous combustion of residual coals in mined ultra-close coal seams. The technical and economic improvements with a direct economic benefit of 5.55 million yuan were achieved by the application of the proposed comprehensive technical support. The research results obtained provide a theoretical guidance and technical support of safe mining strategies of close coal seams in other mining areas.

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An analysis based on plastic strain energy for bilinearity in Coffin-Manson plots in an AlLi alloy

Scripta Metallurgica et Materialia ◽

10.1016/0956-716x(94)90297-6 ◽

1994 ◽

Vol 30 (12) ◽

pp. 1497-1502 ◽

Cited By ~ 14

Author(s):

N.Eswara Prasad ◽

A.G. Paradkar ◽

G. Malakondaiah ◽

V.V. Kutumbarao

Keyword(s):

Plastic Strain ◽

Strain Energy ◽

Plastic Strain Energy

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Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

Shock and Vibration ◽

10.1155/2021/5574563 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Wenyu Lv ◽

Kai Guo ◽

Jianhao Yu ◽

Xufeng Du ◽

Kun Feng

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Surrounding Rock ◽

Maximum Deflection ◽

Coal Seams ◽

Physical Similarity ◽

Working Face ◽

Rock Structure ◽

Backfill Mining ◽

The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

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Creep-fatigue life prediction of aged 13CrMo44 steel using the tensile plastic strain energy

European Structural Integrity Society - Temperature-fatigue Interaction, International Conference on Temperature-Fatigue Interaction, Ninth International Spring Meeting ◽

10.1016/s1566-1369(02)80063-2 ◽

2002 ◽

pp. 65-73

Author(s):

Geewook Song ◽

Jungseob Hyun ◽

Jeongsoo Ha

Keyword(s):

Fatigue Life ◽

Plastic Strain ◽

Strain Energy ◽

Life Prediction ◽

Fatigue Life Prediction ◽

Creep Fatigue ◽

Plastic Strain Energy

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Mine Pressure Behavior Characteristics and Control Methods of a Reused Entry that Was Formed by Roof Cutting: A Case Study

Shock and Vibration ◽

10.1155/2020/4276730 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Yajun Wang ◽

Haosen Wang ◽

Manchao He ◽

Qi Wang ◽

Yafei Qiao ◽

...

Keyword(s):

Deformation Zone ◽

Dynamic Pressure ◽

Field Application ◽

Surrounding Rock ◽

Mine Pressure ◽

Stress Increase ◽

Severe Deformation ◽

Working Face ◽

Roof Deformation

Noncoal pillar mining with automatic formation of a roadway is a new coal mining method that is tailored to improve the coal resource recovery rate and reduce the investment in roadway tunneling. Using this proposed method, a reuse entry is formed by roof cutting instead of tunneling. In this paper, the S1201-II working face of the Ningtiaota Coal Mine was used as a case study. The stress distribution of surrounding rock and the roof deformation characteristics of the reused entry during the mining process of the second working face were studied through FLAC3D numerical simulations combined with field measurements. The results indicate that the zone close to the reused entry led to higher stress in advance. If this stress is superimposed with the lateral pressure of the adjacent mined working face, it will be more difficult to maintain the reused entry. In the engineering case study described here, the reused entry created a stress increase zone and a severe deformation zone in the range of 0–80 m in front of the working face, and its range was approximately 37.5% larger than an ordinary entry. The stress peak in the stress increase zone increased by approximately 34.7% over that of an ordinary entry. The maximum amount of deformation within the severe deformation zone increased by 94.4% over that of an ordinary entry. To properly control the surrounding rock stress and deformation of the reused entry, a dynamic pressure bearing support in front of the working face with adaptability to the large roof deformation and high support strength is proposed here. Field application results showed that the final roof deformation with the dynamic pressure bearing support can be satisfactorily controlled within 110∼130 mm. These findings can provide a reference for researchers and field engineering technicians when engaging in the support work of reused entry.

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Ductile Tearing Simulation of Circumferential Cracked Pipe Under Cyclic Loading Using Damage Criteria Determined by Monotonic Pipe Test Data

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2018-84588 ◽

2018 ◽

Author(s):

Jin-Ha Hwang ◽

Gyo-Geun Youn ◽

Naoki Miura ◽

Yun-Jae Kim

Keyword(s):

Fracture Toughness ◽

Cyclic Loading ◽

Ductile Fracture ◽

Test Data ◽

Strain Energy ◽

Fracture Strain ◽

Damage Model ◽

Fracture Toughness Test ◽

Ductile Tearing ◽

Damage Criteria

To evaluate the structural integrity of nuclear power plant piping, it is important to predict ductile tearing of circumferential cracked pipe from the view point of Leak-Before-Break concept under seismic conditions. CRIEPI (Central Research Institute of Electric Power Industry) conducted fracture test on Japanese carbon steel (STS410) circumferential through-wall cracked pipes under monotonic or cyclic bending load in room temperature. Cyclic loading test conducted variable experimental conditions considering effect of stress ratio and amplitude. In the previous study, monotonic fracture pipe test was simulated by modified stress-strain ductile damage model determined by C(T) specimen fracture toughness test. And, ductile fracture of pipe under cyclic loading simulated using damage criteria based on fracture strain energy from C(T) specimen test data. In this study, monotonic pipe test result is applied to determination of damage model based on fracture strain energy, using finite element analysis, without C(T) specimen fracture toughness test. Ductile fracture of pipe under variable cyclic loading conditions simulates using determined fracture energy damage model from monotonic pipe test.

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