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

2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
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.

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

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Huai-Qian Liu ◽  
Lei Wang ◽  
Lian-Chang Han ◽  
Ping Liu ◽  
Peng Zou
Keyword(s):  
Energy Release ◽  
Elastic Strain ◽  
Strain Energy ◽  
Coal Pillar ◽  
Elastic Strain Energy ◽  
Surrounding Rock ◽  
Burial Depth ◽  
Moderate Pressure ◽  
Pillar Width ◽  
Energy Accumulation

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.

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

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.

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

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.

The function of the wishbone

1991 ◽  
Vol 69 (11) ◽  
pp. 2751-2758 ◽  
Author(s):  
Jason P. Bailey ◽  
M. Edwin Demont
Keyword(s):  
Kinetic Energy ◽  
Natural Frequency ◽  
Respiratory System ◽  
Elastic Strain ◽  
Strain Energy ◽  
Natural Frequencies ◽  
Bird Species ◽  
Elastic Strain Energy ◽  
Wingbeat Frequency ◽  
Respiratory Mechanism

The furcula of birds has traditionally been thought to have a static function. In recent studies it has been hypothesized that the furcula may be acting as a spring in a secondary respiratory mechanism that functions during flight. We tested this hypothesis by comparing the wingbeat frequency and the predicted natural frequency of this secondary respiratory system in 17 avian species, and found a correspondence of nearly 1:1 between these frequencies. Thus, the thoraco-abdominal complex in those birds that couple wingbeat with respiration in a 1:1 ratio may operate as a resonant oscillator during flight. Others have hypothesized that the furcula may function as a spring by assisting in the upstroke phase of the wingbeat cycle. We found that the furculas of 16 of the 17 bird species did not store a functionally important quantity of elastic strain energy compared with the kinetic energy of the wings. We further hypothesized that the furcula may be acting as a spring in a resonant panting system. However, the panting frequencies of three bird species were found to be different from the predicted natural frequencies of their thoraco-abdominal complex. Thus, the furcula does not appear to be functionally important in panting.

Do muscles function as adaptable locomotor springs?

2002 ◽  
Vol 205 (15) ◽  
pp. 2211-2216 ◽  
Author(s):  
Stan L. Lindstedt ◽  
Trude E. Reich ◽  
Paul Keim ◽  
Paul C. LaStayo
Keyword(s):  
Skeletal Muscle ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Normal Animal ◽  
Eccentric Contractions ◽  
Normal Muscle ◽  
Energetic Costs ◽  
Locomotor Muscles ◽  
Power Outputs

SUMMARYDuring normal animal movements, the forces produced by the locomotor muscles may be greater than, equal to or less than the forces acting on those muscles, the consequences of which significantly affect both the maximum force produced and the energy consumed by the muscles. Lengthening (eccentric)contractions result in the greatest muscle forces at the lowest relative energetic costs. Eccentric contractions play a key role in storing elastic strain energy which, when recovered in subsequent contractions, has been shown to result in enhanced force, work or power outputs. We present data that support the concept that this ability of muscle to store and recover elastic strain energy is an adaptable property of skeletal muscle. Further, we speculate that a crucial element in that muscle spring may be the protein titin. It too seems to adapt to muscle use, and its stiffness seems to be`tuned' to the frequency of normal muscle use.

The Elastostatic Axisymmetric Problem of a Cracked Sphere Embedded in a Dissimilar Matrix

1980 ◽  
Vol 47 (3) ◽  
pp. 545-550 ◽  
Author(s):  
R. Kant ◽  
D. B. Bogy
Keyword(s):  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Companion Paper ◽  
Infinite Medium ◽  
Applied Mechanics ◽  
Axisymmetric Solution ◽  
Material Parameters ◽  
The Difference ◽  
Elastostatic Problem

The axisymmetric elastostatic problem of a cracked sphere embedded in a dissimilar matrix is solved by using the solution for a spherical cavity in an infinite medium together with the axisymmetric solution for a cracked sphere given in the companion paper in this issue of the Journal of Applied Mechanics, Pages 538-544. Numerical results are presented for (a) interface stress for various composites (b) dependence of the stress-intensity factor on the material parameters and ratios of crack to sphere radii, (c) the difference in the elastic strain energy for a cracked and uncracked composite.

scholarly journals Effect of Joint Density on Rockburst Proneness of the Elastic-Brittle-Plastic Rock Mass

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jiliang Pan ◽  
Fenhua Ren ◽  
Meifeng Cai
Keyword(s):  
Rock Mass ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Joint Density ◽  
Dissipated Energy ◽  
Uniaxial Compression Test ◽  
Plastic Rock

The prediction of rockburst proneness is the basis of preventing and controlling rockburst disasters in rock engineering. Based on energy theory and damage mechanics, the quantitative functional relationship between joint density and energy density was derived. Then, the theoretical results were verified by numerical simulation and uniaxial compression test, and the effect of joint density on rockburst proneness of the elastic-brittle-plastic rock mass was discussed. The results show that the relationship between the joint density and the dissipated energy index of the jointed rock mass is a logarithmic function. With the same total input energy, the higher the joint density, the more the damage dissipation energy. Even in the case of high joint density, the rock mass still has limited resistance to external failure. Under the same joint density, the strength of parallel jointed rock mass is better than that of the cross-jointed rock mass, and the parallel jointed rock mass can accumulate more elastic strain energy and has higher rockburst proneness. The joint density is closely related to the ability of the rock mass to store high strain energy. The higher the joint density is, the weaker the ability to accumulate the elastic strain energy of rock mass is and the lower the rockburst proneness is. It is helpful to predict rockburst proneness by investigating and studying the properties of geological discontinuities. The research results have some theoretical and engineering guiding significance for the prediction of rockburst proneness of the jointed rock mass.

scholarly journals Dynamic Stability Critical State of Pin-Ended Arches under Sudden Central Concentrated Load

Mechanika ◽  
2020 ◽  
Vol 26 (5) ◽  
Author(s):  
Kai QIN ◽  
Jingyuan LI ◽  
Mengsha LIU ◽  
Jinsan JU
Keyword(s):  
Finite Element ◽  
Critical Load ◽  
Critical State ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
The State ◽  
Energy Principle ◽  
Concentrated Load ◽  
Elastic Plastic

The dynamic in-plane instability process of extreme point type for pin-ended arches when a central radial load applied suddenly with infinite duration is analyzed with finite element method in this study. The state of arch can be determined by the crown’s vertical displacement varied with time and the critical load can be obtained by repeating trial-calculation. When the arch structure reaches the dynamically stable critical state, the kinetic energy of the structure is very small or even zero. The dynamic critical load of elastic arch calculated with the theoretical analysis method which is based on energy principle is proved accuracy enough by comparing with the finite element calculation results and the percentage of the differences between them are no more than 4.5 %. The maximal elastic strain energy is certain for the elastic-plastic arch in certain geometry under both a sudden load and static load. The maximal elastic strain energy in static calculation can be used in determining the state of the elastic-plastic arch under dynamic sudden loads applied and this method is more accurate which errors won’t exceed 3.5 %. The accuracy of dynamic critical load calculation method for elastic arch is verified by numerical calculation in this study, and based on the characteristic of elastic strain energy in critical state, a method for determining the stability of elastic-plastic arch is presented.

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