Experimental Study on the Effect of Brittleness on the Dynamic Mechanical Behaviors of the Coal Measures Sandstone

Xu, Junce; Pu, Hai; Sha, Ziheng

doi:10.1155/2021/6679333

Cited by 5 publications

(7 citation statements)

References 28 publications

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“…Moreover, the uniformity of the stress at both ends of the samples must be verified before performing the dynamic tests. As shown in Figure 6, the superposition of incident and reflected waves largely coincides with the transmitted waves, which means that the stresses at both ends of the sample are in equilibrium during loading [24]. εi(t), εr(t), and εt(t) refer to the incident, reflected, and transmitted strain, respectively.…”

Section: Dynamical Testing Schemementioning

confidence: 82%

“…The primary mineral composition of the rock was determined by X-ray diffraction (XRD) (Figure 2), revealing that the sandstone is composed mainly of quartz (47.3%), feldspar (31.5%), and illite (9%), with minor amounts of calcite and chlorite. As shown in Figure 3, fresh red sandstone block was processed into standard samples with a diameter of 50 mm and a length-to-diameter ratio of 1 [24]. To reduce the influence of rock structure, all samples were taken from the same block and in the same direction.…”

Section: Materials and Samples Preparationmentioning

confidence: 99%

“…In addition, five samples with a length and diameter of 50 × 100 mm were selected for physical and mechanical tests, with the results listed in Table 1. As shown in Figure 3, fresh red sandstone block was processed into standard samples with a diameter of 50 mm and a length-to-diameter ratio of 1 [24]. To reduce the influence of rock structure, all samples were taken from the same block and in the same direction.…”

Section: Materials and Samples Preparationmentioning

confidence: 99%

“…Brittleness is an important parameter to describe the deformation and failure process of the rock [35]. Various external factors such as water content and temperature inevitably change the brittle state and failure pattern of rock [24]. Therefore, a brittleness index (BI) is used to characterize the effect of saturation on the pre-peak deformation characteristics of the frozen sample, as follows:…”

Section: Dynamic Brittleness Indexmentioning

confidence: 99%

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Dynamic Mechanical Behavior of the Frozen Red Sandstone under Coupling of Saturation and Impact Loading

Sha

2022

Applied Sciences

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Saturation is one of the critical factors causing frost damage to rock masses in alpine regions, and dynamic stress perturbations further complicate the damage process. Therefore, the effects of water content and loadings should be considered in the construction and maintenance of rock structures during winter in cold regions. In this study, the effects of saturation and impact loading on the dynamic mechanical behavior of frozen red sandstone were investigated using a low-temperature split Hopkinson pressure bar system (LT-SHPB). By combining low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM), the dynamic evolution of the microstructure of the frozen sandstone due to changes in saturation was investigated. The results indicated that the increase of saturation reshapes the pore structure of the frozen sandstone and promotes the expansion of pores of different sizes during freezing, while at complete saturation the frozen samples are mainly developed with meso- and macropores. The dynamic strength, elastic modulus, and brittleness index of the frozen sandstone under impact loading, which are limited by the critical saturation Src, tend to increase and then decrease with saturation. For the four impact loads, the dynamic strength of the samples increased by 21.2%, 27.1%, 32.5%, and 34.3% when the saturation was increased from 0 to 50%, corresponding to 1.38, 1.43, 1.51, and 1.56 times the dynamic strength of the fully saturated samples, respectively. In contrast, the ultimate deformation capacity of the frozen sandstone showed an opposite trend with saturation. As the impact load increases, the dynamic strength, elastic modulus, and peak strain of the frozen sandstone show a significant strengthening effect due to the increase in strain rate, while its brittleness index gradually decreases, dropping by 11.2% at full saturation. In addition, the energy dissipation capacity of the frozen sample first increases and then decreases with increasing saturation, with the enhancement effect of saturation on energy dissipation smaller than the weakening effect.

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Section: Dynamical Testing Schemementioning

confidence: 82%

Section: Materials and Samples Preparationmentioning

confidence: 99%

Section: Materials and Samples Preparationmentioning

confidence: 99%

Section: Dynamic Brittleness Indexmentioning

confidence: 99%

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Dynamic Mechanical Behavior of the Frozen Red Sandstone under Coupling of Saturation and Impact Loading

Sha

2022

Applied Sciences

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“…Brittleness is a crucial parameter describing the behavior of rock and soil material failure [1][2][3], and is closely influenced by mineral composition [4], loading condition [5], micro-fracture [6], physical properties [7,8] and mechanical characteristics [9][10][11]. In underground engineering field, the brittleness index provides a convenient and effective method to assess the mechanical properties and failure mode of surrounding rock.…”

Section: Introductionmentioning

confidence: 99%

Rock Brittleness Evaluation Index Based on Ultimate Elastic Strain Energy

Zhang

Shaikh

et al. 2022

Processes

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Brittleness is an essential parameter to determine the deformation and failure behavior of rocks, and it is useful to quantify the brittleness of rocks in numerus engineering practices. A novel energy-based brittleness evaluation index is proposed in this study, which redefines the dissipated proportion of ultimate elastic strain energy relative to post-peak failure energy and residual elastic strain energy. A series of conventional triaxial compression (CTC) tests were performed on shale rock to verify the reliability and accuracy of the brittleness index. The results show that the proposed index can precisely reflect the deformation and failure characteristic of rocks under different confining pressures. Based on the testing data from six types of rocks in previous studies, the universality of the novel index was verified. According to comparison with existing brittleness indices, the new brittleness index can more precisely characterize the brittleness of rock.

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Effect of Freeze-Thaw Damage on the Physical, Mechanical, and Acoustic Behavior of Sandstone in Urumqi

Sha

2022

Applied Sciences

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The Urumqi area in China is a seasonally cold region, and the rock structures in the region are susceptible to freeze-thaw (F-T) weathering. Therefore, this study investigated the effect of F-T on the physical, mechanical, and fracture behavior of sandstone from Urumqi. The acoustic emission method (AE) was used to determine the stress thresholds for the initiation and development of cracks in the samples under cyclic F-T action. The results suggested that parameters such as P-wave velocity, elastic modulus, and peak stress presented a significant negative correlation with F-T damage, while porosity exhibited a close positive correlation. The elastic modulus of the sample was more sensitive to the F-T action with the smallest half-life (27 cycles) and the largest decay factor (0.0254). In addition, the stress threshold for micro-cracks development and macro-cracks initiation in the samples decreased with increasing F-T damage. After 30 F-T cycles, the stress threshold for micro-cracks propagation in the samples decreased from 20.73 MPa to 5.02 MPa by approximately 76%. The normalized stress threshold for the macro-cracks initiation was also decreased from 0.93 to 0.71. Moreover, the macro-cracks damage zone of the samples showed an increasing trend with F-T damage, from 7% under natural conditions to 29% after 30 cycles. It is concluded that F-T action lowers the stress thresholds for cracks development in sandstone in the Urumqi area, posing serious safety concerns for mass rock engineering in this area.

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Experimental Study on the Effect of Brittleness on the Dynamic Mechanical Behaviors of the Coal Measures Sandstone

Cited by 5 publications

References 28 publications

Dynamic Mechanical Behavior of the Frozen Red Sandstone under Coupling of Saturation and Impact Loading

Dynamic Mechanical Behavior of the Frozen Red Sandstone under Coupling of Saturation and Impact Loading

Rock Brittleness Evaluation Index Based on Ultimate Elastic Strain Energy

Effect of Freeze-Thaw Damage on the Physical, Mechanical, and Acoustic Behavior of Sandstone in Urumqi

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