Study on the Instability Mechanism and Control Measures of a Roadway in a Mine with Retained Coal Pillars and Close Coal Seams

The deformation and instability of roadway surrounding rock reflect the processes of energy accumulation and release. To reveal the instability of roadway surrounding rock, based on the engineering geological conditions of a certain mine, this paper established a nonuniform superimposed stress model of a coal pillar, starting from the energy accumulation and release of the surrounding rock of the floor roadway after coal pillar failure. The essence of the deformation of the lower roadway was revealed, and the following conclusions were drawn: (1) The elastic strain energy accumulated in the lower roadway roof and upper coal pillar is related to not only the physical properties of the coal seam but also the distance between the coal pillar and surrounding rock, the caving height and shape, the burial depth, and the retained pillar width. (2) The elastic strain energy accumulated in the lower roadway roof and the upper coal pillar induced large displacements of the roadway due to the energy release during excavation. (3) It is proposed that the “stress relief degree” and failure morphology are used to identify zones in the rock and coal, and the two zoning modes have a high consistency. (4) The stress distribution in a narrow coal pillar should be calculated in segments. (5) Based on the zoning and energy release characteristics, the following control factors are suggested regarding the coal pillar width and roadway layout: (a) for the coal pillar, avoid the overlap or intersection of the peak values in the limit equilibrium zone and ensure a sufficient elastic zone; (b) arrange the roadway in shear slip Zone B-2 or the moderate pressure relief Zone B-2 to reduce the accumulation of elastic strain energy in the surrounding rock.

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Experimental Study of Influence of Support Failures on Rockbursts under True-Triaxial Condition

Advances in Civil Engineering ◽

10.1155/2018/2105451 ◽

2018 ◽

Vol 2018 ◽

pp. 1-20 ◽

Cited By ~ 1

Author(s):

Guoshao Su ◽

Tianbin Li ◽

Jianqing Jiang ◽

Guoqing Chen ◽

Jinghai Mo

Keyword(s):

Kinetic Energy ◽

Elastic Strain ◽

Strain Energy ◽

Elastic Strain Energy ◽

Test System ◽

Surrounding Rock ◽

Underground Engineering ◽

True Triaxial ◽

Static Failure ◽

Rock Specimens

Supports can effectively reinforce the surrounding rock after excavation in underground engineering. However, a support failure may cause an extremely intense rockburst. Hence, the influences of support failures, including support forces, support failure timings, and support failure rates, on rockbursts were systematically investigated in the present study. Unloading tests on rock specimens, using a true-triaxial rockburst test system, were performed to simulate rockbursts induced by support failure. The experimental results indicate that increasing support forces increased the prepeak accumulated elastic strain energy, the kinetic energy of the ejection fragment, and the ratio between the kinetic energy and release strain energy, whereas the damage to the rock specimens declined. During the testing process, the longer it took to unload the minimum stresses was, which means that the later the support failed, the greater the prepeak accumulated elastic strain energy was, the kinetic energies of the ejection fragments were, and the ratio of the kinetic energy and release strain energy was. Furthermore, as the support failure rate incremented, the kinetic energies of the ejection fragments of the rockbursts linearly increased, the failure mode of the rock changed from static failure to dynamic rockbursts, and the intensities of the rockbursts increased.

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Achieving high uniformity of the elastic strain energy accumulation rate during the serrated plastic flows of bulk metallic glasses

Materials Science and Engineering A ◽

10.1016/j.msea.2018.09.003 ◽

2018 ◽

Vol 736 ◽

pp. 269-275 ◽

Cited By ~ 3

Author(s):

H.H. Tang ◽

Y.C. Cai ◽

Q. Zuo ◽

S.H. Chen ◽

R.P. Liu

Keyword(s):

Metallic Glasses ◽

Elastic Strain ◽

Strain Energy ◽

Accumulation Rate ◽

Bulk Metallic Glasses ◽

Elastic Strain Energy ◽

Energy Accumulation ◽

High Uniformity

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Incremental recrystallization/grain growth driven by elastic strain energy release in a thermomechanically fatigued lead-free solder joint

Acta Materialia ◽

10.1016/j.actamat.2006.11.023 ◽

2007 ◽

Vol 55 (7) ◽

pp. 2265-2277 ◽

Cited By ~ 87

Author(s):

A.U. Telang ◽

T.R. Bieler ◽

A. Zamiri ◽

F. Pourboghrat

Keyword(s):

Solder Joint ◽

Energy Release ◽

Grain Growth ◽

Elastic Strain ◽

Strain Energy ◽

Elastic Strain Energy ◽

Strain Energy Release ◽

Lead Free ◽

Lead Free Solder ◽

Free Solder

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Alaskan Earthquake, 27 March 1964: Vertical Extent of Faulting and Elastic Strain Energy Release

Science ◽

10.1126/science.147.3660.867 ◽

1965 ◽

Vol 147 (3660) ◽

pp. 867-868 ◽

Cited By ~ 17

Author(s):

F. Press ◽

D. Jackson

Keyword(s):

Energy Release ◽

Elastic Strain ◽

Strain Energy ◽

Elastic Strain Energy ◽

Strain Energy Release ◽

Vertical Extent

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A Study of the Anchorage Body Fracture Evolution and the Energy Dissipation Rule: Comparison between Tensioned Rock Bolts and Torqued Rock Bolts

Advances in Civil Engineering ◽

10.1155/2021/5542569 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Bowen Wu ◽

Xiangyu Wang ◽

Jianbiao Bai ◽

Shuaigang Liu ◽

Guanghui Wang ◽

...

Keyword(s):

Plastic Deformation ◽

Energy Dissipation ◽

Elastic Strain ◽

Strain Energy ◽

Elastic Strain Energy ◽

Surrounding Rock ◽

Rock Bolts ◽

External Work ◽

Fracture Evolution ◽

The Stability

Rock bolt support is an effective technique for controlling surrounding rock of deep roadway. The stability of the anchorage body composed of rock bolts and surrounding rock mass is the core in keeping the stability of roadways. In this paper, the UDEC Trigon model was used in simulating uniaxial compressive test on the anchorage body under different pretension loads. The energy equilibrium criterion of the anchorage body under the uniaxial compressive state was proposed. Furthermore, the fracture evolution and the energy dissipation during the failure process of the anchorage body were analyzed. Results showed that before the peak strength, the external work was stored in the anchorage body in the form of the elastic strain energy (Ue). After the peak, energy dissipated through three ways, including the fracture developing friction (Wf), plastic deformation (Wp), and acoustic emission (Ur). Based on the simulation results, the high pretensioned rock bolts can eliminate the continuous tensile fractures in the anchorage body, decreasing the damaging extent of the anchorage body and the energy that was consumed by the following two main approaches: fracture developing friction (Wf) and plastic deformation (Wp). Moreover, the surplus of the elastic strain energy (Ue) and the strength of the anchorage body can be improved. The pretension load had a positive relationship with elastic strain energy and a negative relationship with the anchorage body damage degree. Based on the above research, the transport roadway of the working face 6208 in the Wangzhuang Coal Mine selected tensile rock bolts to establish the high-performance anchorage body. The monitoring data showed that this reinforcement method effectively managed the serious deformation issue of the roadway surrounding the rock masses.

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Experimental Investigation on Deformation and Strength Behavior of Marble with the Complex Loading-Unloading Stress Path

Advances in Civil Engineering ◽

10.1155/2020/8853044 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Chen Chen ◽

Lipeng Liu ◽

Yu Cong

Keyword(s):

Elastic Strain ◽

Strain Energy ◽

High Stress ◽

Elastic Strain Energy ◽

Complex Loading ◽

Energy Criterion ◽

Confining Pressure ◽

Stress Path ◽

Surrounding Rock ◽

Strength Behavior

The excavation of deep tunnel in rock mass undergoes complex loading and unloading stress paths, resulting in rib spalling, flaking, and even severe rockburst disasters. Based on the variation law of the stress path of the surrounding rock, laboratory tests of rock mechanics are designed, and the deformation and strength behavior of marble with different initial confining pressure and unloading rates are systematically studied. By introducing strain increment, the characteristic stress, and the dilatancy index, the rock’s dilatancy and brittleness under different unloading conditions are quantitatively analyzed. During unloading, the energy transformation mechanism of rock is described, and the law of deformation and failure is discussed based on characteristic energy. The rock failure strength fitting formula is given by applying the Mogi–Coulomb criterion and elastic strain energy criterion. The advantages of the elastic strain energy criterion are theoretically explained. This study shows that comprehensive consideration of the complex stress paths, confining pressure levels, and the loading-unloading rates of surrounding rock is an effective way to accurately study unloading rock characteristics. The results can provide theoretical basis for stability analysis of high-stress underground engineering.

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A New Bursting Liability Evaluation Index for Coal –The Effective Elastic Strain Energy Release Rate

Energies ◽

10.3390/en12193734 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3734

Author(s):

Zhiguo LU ◽

Wenjun JU ◽

Fuqiang GAO ◽

Youliang FENG ◽

Zhuoyue SUN ◽

...

Keyword(s):

Energy Release Rate ◽

Energy Release ◽

Release Rate ◽

Elastic Strain ◽

Strain Energy ◽

Strain Energy Release Rate ◽

Elastic Strain Energy ◽

Strain Curve ◽

Strain Energy Release ◽

Stress Strain Curve

Because both faults and cleats exist in coal, sharp stress drops occur during loading when coal is deformed. These drops occur during the pre-peak stage and are accompanied by sudden energy releases. After a stress drop, the stress climbs slowly following a zigzag path and the energy accumulated during the pre-peak stage is unstable. A stress–strain curve is the basic tool used to evaluate the bursting liability of coal. Based on energy accumulation in an unsteady state, the pre-peak stress–strain curve is divided into three stages: pre-extreme, stress drop, and re-rising stage. The energy evolution of the specimen during each stage is analyzed. In this paper, an index called the effective elastic strain energy release rate (EESERR) index is proposed and used to evaluate the coal’s bursting liability. The paper shows that the propagation and coalescence of cracks is accompanied by energy release. The stress climb following a zigzag path prolongs the plastic deformation stage. This causes a significant difference between the work done by a hydraulic press during a laboratory uniaxial compression experiment and the elastic strain energy stored in the specimen during the experiment, so the evaluation result of the burst energy index would be too high. The determination of bursting liability is a comprehensive evaluation of the elastic strain energy accumulated in coal that is released when the specimen is damaged. The index proposed in this paper fully integrates the energy evolution of coal samples being damaged by loading, the amount of elastic strain energy released during the sample failure divided by the failure time is the energy release rate. The calculation method is simplified so that the uniaxial compressive strength and elastic modulus are included which makes the new index more universal and comprehensive. Theoretical analysis and physical compression experiments validate the reliability of the evaluation.

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