Effect of specimen size on energy dissipation characteristics of red sandstone under high strain rate

Li, Ming; Mao, Xianbiao; Lu, Aihong; Tao, Jing; Zhang, Guanghui; Zhang, Lianying; Li, Chong

doi:10.1016/j.ijmst.2014.01.002

Cited by 34 publications

(11 citation statements)

References 7 publications

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“…Although the size effect on mechanical properties, especially for rock, is very complicated, it has been revealed that UCS reduces with an increase in specimen size, following the exponential decay laws on the basis of majority tests on coal specimens with increasing diameter [43][44][45][46][47]. The elastic modulus of coal specimens decreased with an increase of diameter by means of a negative power function, nearly independent of the confining pressure.…”

Section: Mechanical Property Measurementsmentioning

confidence: 99%

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

et al. 2018

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The mechanical properties and fracture propagation of Longmaxi shale loading under uniaxial compression were measured using eight cylindrical shale specimens (4 mm in diameter and 8 mm in height), with the bedding plane oriented at 0 • and 90 • to the axial loading direction, respectively, by micro computed tomography (micro-CT). Based on the reconstructed three-dimensional (3-D) CT images of cracks, different stages of the crack growth process in the 0 • and 90 • orientation specimen were revealed. The initial crack generally occurred at relatively smaller loading force in the 0 • bedding direction specimen, mainly in the form of tensile splitting along weak bedding planes. Shear sliding fractures were dominant in the specimens oriented at 90 • , with a small number of parallel cracks occurring on the bedding plane. The average thickness and volume of cracks in the 90 • specimen is higher than those for the specimen oriented at 0 • . The geometrical characterization of fractures segmented from CT scan binary images shows that a specific surface area correlates with tortuosity at the different load stages of each specimen. The 3-D box-counting dimension (BCD) calculations can accurately reflect crack evolution law in the shale. The results indicate that the cracks have a more complex pattern and rough surface at an orientation of 90 • , due to crossed secondary cracks and shear failure.Various experimental methods, e.g., electromagnetic radiation (EMR), acoustic emission (AE), micro-seismic (MS), infrared technique, high speed digital imaging, and computerized tomography (CT), have been used to analyze the mechanical behavior of rocks (including shale) during uniaxial or triaxial loading [15][16][17][18][19][20][21]. CT scanning has been widely applied in the investigation of damage propagation since 1997, due to the three-dimensional (3-D) visualization and high-resolution imaging [22][23][24][25][26][27][28]. Kawakata et al. used CT to study the initial mesoscopic damage characteristics of rock materials, and observed spatial fault development in granite undergoing compression [29,30]. In the experiment, only the damaged specimens, rather than the entire process from crack initiation to specimen destruction, were scanned, and then observed by 3-D reconstruction of X-ray CT images. To examine the entire process, Ge et al. investigated rock compression with a real-time CT test [23]. Through the use of the industrial CT images, the rock meso-damage propagation law was revealed. Rock failure started with micro-pore and micro-crack compression, growth, bifurcation, and development, followed by fracture. Sun et al. displayed real-time deformation in backfill body under loading using industrial CT in several slices, and provided insights into the process of faulting [31]. However, the relatively low spatial resolution and image quality of conventional industrial CT is not suitable for fine-grained rocks. Furthermore, the 3-D information was not fully captured or used, which limited the accuracy of further calculation ...

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Section: Mechanical Property Measurementsmentioning

confidence: 99%

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

et al. 2018

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“…The breakage energy dissipation (BED) shares a main proportion (about 90%) in the total energy dissipation [Zhang, Sun, Hao et al (2000)], thus the friction energy between the elastic bars and sample, the kinetic energy of fragment and others (such as thermal energy and sound energy) can be neglected [Li, Mao, Lu et al (2014)]. That is, BED is approximately equal to EA.…”

Section: Principle Of Shpb Testmentioning

confidence: 99%

Mechanical Response and Energy Dissipation Analysis of Heat-Treated Granite Under Repeated Impact Loading

Wang¹,

Tian²,

Wang³

et al. 2019

Computers, Materials &Amp; Continua

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The mechanical behaviors and energy dissipation characteristics of heat-treated granite were investigated under repeated impact loading. The granite samples were firstly heat-treated at the temperature of 20°C, 200°C, 400°C, and 600°C, respectively. The thermal damage characteristics of these samples were then observed and measured before impact tests. Dynamic impact compression tests finally were carried out using a modified split-Hopkinson pressure bar under three impact velocities of 12 m/s, 15 m/s, and 18 m/s. These test results show that the mineral composition and the main oxides of the granite do not change with these treatment temperatures. The number of microcracks and microvoids decreases in the sample after 200°C treatment. The mechanical properties of a sample after 600°C treatment were rapidly deteriorated under the same impact velocity. The average of peak stress is much smaller than those after 20°C, 200°C and 400°C treatments. The heat-treated samples have an energy threshold each. When the dissipated energy of a sample under a single impact is less than this threshold, the repeated impacts hardly lead to further damage accumulation even if its total breakage energy dissipation (BED) density is large. Under the same number of repeated impacts, the cumulative BED density of a sample after 600°C treatment is the largest and its damage evolves most quickly. The total BED density of the sample after 200°C treatment is the highest, which implies that this sample has better resistance to repeated impact, thus having less crack initiation and growth.

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“…5 Dynamic properties of interest include the following: density, wave velocity, porosity, strength, scale effect, bedding effect, the influence of moisture, and energy dissipation. 15,[33][34][35][36][37][38][39][40][41][42][43][44][45] Very high loading rate dynamic tests are usually conducted by using split Hopkinson pressure bar (SHPB) systems, 30,46 to determine dynamic properties of brittle materials including concretes, ceramics, rocks, and coals under wide range of impact loadings or strain rates of 10 1 -10 4 /s. [47][48][49][50][51][52][53] For determination of dynamic properties of different coals, the principal attributes are to recovery the dynamic magnitudes of Young's modulus and compressive/tensile strength based on the stress-strain curves at very high strain rates.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on dynamic strength and energy dissipation characteristics of gas outburst‐prone coal

Fan

Elsworth

et al. 2019

Energy Science & Engineering

113

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We report laboratory experiments to investigate the dynamic failure characteristics of outburst‐prone coal using a split Hopkinson pressure bar (SHPB). For comparison, two groups of experiments are completed on contrasting coals—the first outburst‐prone and the second outburst‐resistant. The dynamic mechanical properties, failure processes, and energy dissipation of both outburst‐prone and outburst‐resistant coals are comparatively analyzed according to the obtained dynamic compressive and tensile stress‐strain curves. Results show that the dynamic stress‐strain response of both outburst‐prone and outburst‐resistant coal specimens comprises stages of compression, linear elastic deformation, then microfracture evolution, followed by unstable fracture propagation culminating in rapid unloading. The mechanical properties of both outburst‐prone and outburst‐resistant coal specimens exhibit similar features: The uniaxial compressive strength and indirect tensile strength increase linearly with the applied strain rate, and the peak strain increases nonlinearly with the strain rate, whereas the elastic modulus does not exhibit any clear strain rate dependency. Differences in the dynamic failure characteristics between outburst‐prone and outburst‐resistant coals also exist. The hardening effect of strain rate on outburst‐prone coal is more apparent than on outburst‐resistant coal, which is reflected in the dynamic increase factor at the same strain rate. However, the dynamic strength of outburst‐prone coals is still lower than that of outburst‐resistant coals due to its low quasi‐static strength. The dissipated energy of outburst‐prone coal is smaller than that of outburst‐resistant coal. Therefore, the outburst‐prone coal, characterized by low strength, high deformability, and small energy dissipation when dynamically loaded to failure, is more favorably disposed to the triggering and propagation of gas outbursts.

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Effect of specimen size on energy dissipation characteristics of red sandstone under high strain rate

Cited by 34 publications

References 7 publications

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

Mechanical Property Measurements and Fracture Propagation Analysis of Longmaxi Shale by Micro-CT Uniaxial Compression

Mechanical Response and Energy Dissipation Analysis of Heat-Treated Granite Under Repeated Impact Loading

Experimental investigation on dynamic strength and energy dissipation characteristics of gas outburst‐prone coal

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