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.

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 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 An investigation on the effect of high energy storage anchor on surrounding rock conditions

2020 ◽  
Vol 7 (10) ◽  
pp. 201105
Author(s):  
Bowen Wu ◽  
Xiangyu Wang ◽  
Jianbiao Bai ◽  
Wenda Wu ◽  
Ningkang Meng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Energy Storage ◽  
Elastic Strain ◽  
Strain Energy ◽  
Hard Rock ◽  
Elastic Strain Energy ◽  
High Energy ◽  
Energy Evolution ◽  
Rock Bolts ◽  
High Energy Storage

High pre-tension bolt is an effective strata control technique and is the key to ensure the stability of anchorage and roadway. Based on the performances of high energy storage tension rock bolts in different rock properties, this study proposed a constitutive model to describe the energy balance of anchor under uniaxial compression. UDEC was used to simulate the behaviour of anchor in coal under uniaxial compression and the results were analysed to study the rock mechanical properties, degree of damage and energy evolution. Simulation results showed that tension rock bolts can improve the mechanical properties and energy storage capacities of the anchor. The energy evolution was divided into three stages: (i) the external work was stored in the form of elastic strain energy ( U e ) in the anchor prior to the yielding strength; (ii) the elastic strain energy reached its maximum near the peak strength; (iii) energy was dissipated from fracture friction ( W f) , plastic deformation ( W p ) and acoustic emission ( U r ) during post-peak stage. The installation of tension rock bolts was more suitable for medium hard rock (e.g. sandy mudstone), whereas it was not effective for hard rock (e.g. sandstone).

scholarly journals Experimental Investigation of Early-Warning Critical Energy for Strainbursts

2021 ◽  
Author(s):  
Wang Ling ◽  
Ruyu Yan ◽  
Zhang zhi ◽  
Xie Lei ◽  
Huang chuhui
Keyword(s):  
Acoustic Emission ◽  
Energy Dissipation ◽  
Early Warning ◽  
Elastic Strain ◽  
Strain Energy ◽  
Triaxial Compression ◽  
Elastic Strain Energy ◽  
Critical Energy ◽  
Input Energy ◽  
Energy Evolution

Abstract This research aimed to establish an early-warning critical energy for coal instability based on the energy theory and acoustic emission characteristics of coal under triaxial compression. To obtain an early-warning critical strain energy indicating the increase in the risk of coal instability, conventional triaxial compression and acoustic emission (AE) tests were carried out on coal specimens taken from a 980-m-deep mine with initial confining pressures of 10, 15, 20, 25, 30 and 35 MPa. Stress-strain relations, AE features, and energy evolution characteristics during triaxial compression were analyzed. It was found that the energy evolution and AE event count changes across different loading stages. With increasing axial stress, most of the input energy stored in the coal specimens was in the form of elastic strain energy and the AE event count was close to zero, indicating that the coal grains reach a state of balance. After the elastic deformation stage, a portion of the input energy was consumed by inelastic deformation. Once the stress level exceeded the volumetric compressibility–dilatancy transition stress, the AE event entered a period of relative quiet, and the rate of energy dissipation abruptly accelerated, indicating that the coal grains achieved another state of balance before THE instability or failure. The balance of the rock grains is broken again (AE event count and the rate of energy dissipation both increased dramatically), coal achieved the peak strength and instability soon. The point at which the dissipated energy ratio α increased rapidly or the starting point of a quiet period, indicates an increase in the risk of coal instability. The corresponding elastic strain energy accumulated within the coal can be regarded as a precursor to instability or strainburst. Accordingly, a fitting formula is presented to predict the early-warning critical energy for brittle coal subject to different minimum principal stress. The analysis results in this paper can be helpful in the assessment of coal instability risk.

Zur Formulierung der Hypothese von der elastischen Formänderungsenergiedichte mit einer Erweiterung auf den elastisch-plastischen Bereich / Formulation of the elastic strain energy theory with an enlargement to the elastic-plastic range

1973 ◽  
Vol 28 (1) ◽  
pp. 35-45 ◽  
Author(s):  
J. Betten
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Elastic Potential ◽  
Plastic Range ◽  
Elastic Case ◽  
Elastic Plastic ◽  
Energy Theory

Contrary to the MISES' theory, the effort of materials under load is discussed in this paper on the base of the elastic potential. This leads to the elastic strain energy theory due to BELTRAMI. This theory is only true for the elastic case. For υ = 1/2 we obtain the MISES' theory, and by changing υ to υep it is possible to enlarge the elastic strain energy theory to the elastic-plastic deformation. υep is the ratio between transverse and longitudinal elastic-plastic strain, and υ is the POISSON's ratio.

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 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.

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