Loading Rate Effect of Rock Material with the Direct Tensile and Three Brazilian Disc Tests

Gong, Fengqiang; Le, Zhang; Wang, Shanyong

doi:10.1155/2019/6260351

Cited by 17 publications

(8 citation statements)

References 20 publications

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“…It can be found that there is an obvious loading rate effect with the peak tensile stress of red sandstone and the logarithmic function can be used to fit this loading effect trend. is rate effect of peak stress has been confirmed in many literature studies [4,6,7] and can be considered as one of the dynamic tensile properties of rock.…”

Section: Mechanical Propertiesmentioning

confidence: 79%

“…Many rock engineering failures are often caused by local or global tension stress. Currently, the Brazilian disc test is a commonly used indirect tensile test method recommended by many experimental procedures [1][2][3][4][5]. On the other hand, rock materials are often subjected to dynamic loads, such as impact, blasting, and vibration, and the Split Hopkinson pressure bar (SHPB) has become a common device used for studying the dynamic failure of rocks under high loading rates or strain rate.…”

Section: Introductionmentioning

confidence: 99%

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Energy Dissipation Characteristic of Red Sandstone in the Dynamic Brazilian Disc Test with SHPB Setup

Gong

2020

Advances in Civil Engineering

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In order to quantitatively investigate the energy dissipation characteristic during the dynamic tension failure of rock materials, the dynamic Brazilian disc tests on red sandstone were conducted using the split Hopkinson pressure bar (SHPB) setup. The states of the specimens after different incident energies can be divided into three forms (i.e., the unruptured state, the ruptured state, and the broken state), and the failure processes of the specimens were recorded by using a high-speed camera. The results show that the ruptured state of the specimen corresponds to the critical failure strain. Taking the critical incident energy as a turning point, two positive linear fitting relations between the dissipated energy and incident energy before and after the point are obtained, and the dynamic linear dissipation law is found. When the incident energy is less than the critical energy, specimens were unruptured after impact. When the incident energy is greater than the critical energy, specimens will be broken after impact. According to the obtained linear energy dissipation law, the dynamic tensile energy dissipation coefficient (DTEDC) was introduced for quantitatively describing the dynamic energy dissipation capacity of rock materials in the dynamic Brazilian disc test. When the specimen is in the unruptured state, the ideal DTEDC is a constant value. When the specimen is in a broken state, the DTEDC increases with the increase of incident energy.

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Section: Mechanical Propertiesmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Energy Dissipation Characteristic of Red Sandstone in the Dynamic Brazilian Disc Test with SHPB Setup

Gong

2020

Advances in Civil Engineering

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“…ASTM specifications specify that a Brazilian tensile strength measurement must be conducted within the stressing rate of 3 to 21 MPa/min, achieving failure within 1–10 min, though the ISRM guidelines propose a loading rate of 0.2 kN/s, which comes to approximately 9.5 MPa/min for the sample geometry used here, and specify a failure time of 15–30 s (ASTM, ; ISRM, ; Newman & Bennett, ). Given this dichotomy in failure time and that previous studies have found an influence of deformation on loading rate (Gong et al, ; Newman & Bennett, ), here we conduct tests at variable displacement rates of 0.04, 0.004, and 0.0004 mm/s and measured sample temperatures ( T s ) of 25 °C, 752.4 ± 11.3 °C, and 800.8 ± 12 °C (note that, for the sake of brevity, we refer to these as three sets of tests at sample temperatures of 25, 750, and 800 °C hereafter) to examine the effect of rate on the ductile‐brittle response of a suite of variably porous rocks. Failure time and loading rate for room temperature tests conducted at 0.004 mm/s meet the standards to be termed a Brazilian tensile test.…”

Section: Experimental Setup and Data Collectionmentioning

confidence: 99%

Brittle‐Ductile Deformation and Tensile Rupture of Dome Lava During Inflation at Santiaguito, Guatemala

et al. 2019

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Gas-and-ash explosions at the Santiaguito dome complex, Guatemala, commonly occur through arcuate fractures, following a 5-to 6-min period of inflation observed in long-period seismic signals. Observation of active faults across the dome suggests a strong shear component, but as fault propagation generally proceeds through the coalescence of tensile fractures, we surmise that explosive eruptions require tensile rupture. Here, we assess the effects of temperature and strain rate on fracture propagation and the tensile strength of Santiaguito dome lavas. Indirect tensile tests were conducted on samples with a porosity range of 3-30% and over diametral displacement rates of 0.04, 0.004, and 0.0004 mm/ s. At room temperature, the tensile strength of dome rock is rate independent (within the range tested) and inversely proportional to the porosity of the material. At eruptive temperatures we observe an increasingly ductile response at either higher temperature or lower displacement rate, where ductile deformation is manifest by a reduction in loading rate during constant deformation rate tests, resulting in slow tearing, viscous flow, and pervasive damage. We propose a method to conduct indirect tensile tests under volcanic conditions using a modification of the Brazilian disc testing protocol and use brittleness indices to classify deformation modes across the brittle-ductile transition. We show that a degree of ductile damage is inevitable in the lava core during explosions at the Santiaguito dome complex and discuss how strain leading to rupture controls fracture geometry, which would impact gas pressure release or buildup and regulate explosive activity.Plain Language Summary Using instruments we installed at Santiaguito, an active lava dome complex in Guatemala, we detected repeating cycles of inflation and deflation. The inflation took less time leading up to explosions compared to weak gas puffing, which led us to suspect that lava breaking and flowing might be responsible. To investigate this, we made laboratory tests where we put lava samples under tension, which is the most common way they break. We ran tests where we squeezed lavas at faster and slower rates in a press, and we also heated the lavas to their eruption temperatures-about 800°C-for some tests. Since the lavas contain volcanic glass, in some high temperature tests the glass partially flowed. In other tests the lavas were completely brittle, which means they stored up stress and then broke without flowing. The lava's behavior depends on the temperature and how fast they are squeezed. Finally, we considered how fast dome lavas at Santiaguito would have to be deformed to either break or stay intact during inflation of the dome. This study gives us a better idea of how dome lavas deform and how that affects hazardous activity during eruptions.

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“…Split Hopkinson pressure bar (SHPB) equipment has become the most effective device to test the dynamic tensile strength and deformation properties of rock at high strain rates [13][14][15][16]. In recent years, researchers have shown an increased interest in dynamic tensile tests on rock, which have acquired plenty of achievements [17][18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

“…e main representative study results were as follows: Gong and Luo [17,18] used four test methods to compare the tensile strength of sandstone under different loading rates (10 − 2 MPa/s to 10 0 MPa/s), and the test results indicate that the tensile strength of sandstone specimen increases with increase in the logarithm of loading rate. Ai et al [19] analyzed the dynamic fracture properties, crack propagation law of rock with different impact loading rates using experiments, and numerical simulation approach.…”

Section: Introductionmentioning

confidence: 99%

Coupled Static-Dynamic Tensile Mechanical Properties and Energy Dissipation Characteristic of Limestone Specimen in SHPB Tests

Ping

Fang

et al. 2020

Advances in Civil Engineering

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To investigate the dynamic splitting tensile mechanical property of limestone under coupled static and dynamic state, the dynamic split tensile tests of limestone under one-dimensional coupled static and dynamic load with different strain rates were performed with the help of modified split Hopkinson pressure bar (SHPB) equipment. The dynamic splitting tensile mechanical property and energy dissipation characteristic under two stress states were also compared in this research. Test results indicated that the dynamic tensile strength of the limestone specimen increased with the increase of average strain rate, exhibiting an obvious strain rate effect. In addition, dynamic tensile strength under uniaxial state was higher than that under one-dimensional coupled static and dynamic load state under the same test condition. Moreover, the deformation modulus increased with increasing average strain rate under uniaxial state, while it decreased with increasing average strain rate under coupled static and dynamic state. Both the reflected energy and absorbed energy linearly increased with increasing incident energy. The preload in the radial direction could increase the reflected energy and decrease the absorbed energy. Moreover, the transmitted energy with preload state was slightly lower than that under uniaxial state. Finally, the dynamic tensile strength of limestone specimen increased as a power function with increasing absorbed energy.

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Loading Rate Effect of Rock Material with the Direct Tensile and Three Brazilian Disc Tests

Cited by 17 publications

References 20 publications

Energy Dissipation Characteristic of Red Sandstone in the Dynamic Brazilian Disc Test with SHPB Setup

Energy Dissipation Characteristic of Red Sandstone in the Dynamic Brazilian Disc Test with SHPB Setup

Brittle‐Ductile Deformation and Tensile Rupture of Dome Lava During Inflation at Santiaguito, Guatemala

Coupled Static-Dynamic Tensile Mechanical Properties and Energy Dissipation Characteristic of Limestone Specimen in SHPB Tests

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