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Uniaxial compression test and numerical simulation of rock-like specimen with T-Shaped cracks

Liangxiao Xiong, Chen Haijun, Xu Zhongyuan, Hu Deye

Archives of Civil Engineering

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2023

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Vol. 69, nr 2

227--244

EN

In this study, the uniaxial compression test and PFC2D numerical simulation were carried out on the artificial rock specimen with T-shaped prefabricated fractures. The effects of the lengths l1, l2 of the main fractures, the length l3 of the secondary fracture, and the angle β between the secondary fracture and the loading direction on the uniaxial compressive strength and crack evolution law of specimen were studied. The research results show that the change of l1, l2 and β has obvious effect on the compressive strength and crack growth of the specimen, but the change of l3 has little effect on the compressive strength of the specimen. When l3 = 40 mm and l1 ≠ l2, the angle β influences on the crack propagation and failure mode of the specimen.

2

Experimental study on biaxial dynamical compressive test and PFC2D numerical simulation of artificial rock sample with single joint

Liangxiao Xiong, Chen Haijun, Gao Xinghong, Xu Zhongyuan, Hu Deye

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

213--229

EN

Dynamic biaxial compression tests and Particle Flow Code numerical simulations of the cement mortar specimens with a single joint were carried out to study the mechanical properties and crack evolution of artiﬁcial rock samples with a single joint. The effects of lateral stress σ2, loading rate V, the dip angle β (between the vertical loading direction and the joint) on the biaxial compressive strength σb, and the evolution law of crack were investigated. Test results showed that; (1) when both the dip angle β and the loading rate V remained unchanged, the biaxial compressive strength σb increased with the increase in the lateral stress σ2, while σ2 had no obvious effect on the crack evolution law; (2) when both the dip angle β and the lateral stress σ2 were kept unchanged, the loading rate V had an insignificant effect on the biaxial compressive strength σb and the crack evolution law; (3) when both the lateral stress σ2 and the loading rate V were constant, the biaxial compressive strength σb decreased first and then increased with the increase in the dip angle β; however, the dip angle β did not significantly affect the crack evolution law. The conclusions obtained in this paper are presented for the first time.

3

Analysis of uniaxial compression of rock mass with parallel cracks based on experimental study and PFC2D numerical simulation

Yang Jie, Chen Haijun, Liangxiao Xiong, Xu Zhongyuan, Zhou Tao, Yang Changheng

Archives of Civil Engineering

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2022

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Vol. 68, nr 1

111--128

EN

In this study, the uniaxial compression test and the numerical simulation of the two-dimensional particle flow code (PFC2D) were used to study the mechanical properties and failure laws of rock masses with parallel cracks. The experiment considers the influences of crack length (l), crack angle (β1L β2), and numerical changes in the rock bridge length (ℎ) and bridge angle (α) on failures of rock-like specimens. The results indicate that the uniaxial compressive strength (UCS) of the rock-like specimens with parallel cracks decreases with increasing l under different α values. The smaller angle between the preset crack and the loadinging direction (β) resulting in higher UCS. In addition, a larger ℎ results in higher UCS in the specimen. When β1 or β2 is fixed, the UCS and elastic modulus of the specimen show an ‘M’ shape with an increase in α. Moreover, the crack growth or failure mode of samples with different l values is similar. When β1 or β2 is small, the failure of the specimen is affected by the development and expansion of wing cracks. If one of β1 and β2 is large, the failure of the specimen is dominated by the expansion and development of the secondary cracks which is generated at the tip of the prefabricated crack. Furthermore, when the angle between the prefabricated crack and the loading direction is β1 = 0º, the rock bridge is less likely to reach penetration failure as ℎ increases. Secondary crack connections between the prefabricated cracks occur only when α is small.