Failure characteristics and constitutive model of coal rock at different strain rates

ZHENG Yu; SHI Haoran; LIU Xiaohui; ZHANG Wenju

doi:10.11883/bzycj-2020-0072

Volume 41 Issue 5

May 2021

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ZHENG Yu, SHI Haoran, LIU Xiaohui, ZHANG Wenju. Failure characteristics and constitutive model of coal rock at different strain rates[J]. Explosion And Shock Waves, 2021, 41(5): 053103. doi: 10.11883/bzycj-2020-0072

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ZHENG Yu, SHI Haoran, LIU Xiaohui, ZHANG Wenju. Failure characteristics and constitutive model of coal rock at different strain rates[J]. Explosion And Shock Waves, 2021, 41(5): 053103. doi: 10.11883/bzycj-2020-0072

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Failure characteristics and constitutive model of coal rock at different strain rates

doi: 10.11883/bzycj-2020-0072

ZHENG Yu^1
,,
SHI Haoran^{1, 2},
LIU Xiaohui^{1, 2
,
,},
ZHANG Wenju³

1.
School of Energy and Power Engineering, Xihua University, Chengdu 610039, Sichuan, China
2.
Key Laboratory of Fluid and Power Machinery, Ministry of Education, Xihua University, Chengdu 610039, Sichuan, China
3.
Southwest Municipal Engineering Design and Research Institute of China, Chengdu 610084, Sichuan, China

Received Date: 2020-03-19
Rev Recd Date: 2021-01-15

Available Online: 2021-04-08

Publish Date: 2021-05-05

Abstract

Abstract

With the increasing demand for coal resources, safe and efficient coal mining has attracted the attention of all sectors of society. In order to study the dynamic failure characteristics and constitutive relation of coal rock under different strain rates, uniaxial impact compression tests of coal rock were carried out over a strain rate range from 20 s⁻¹ to 100 s⁻¹ under nine air pressures by using a split Hopkinson pressure bar (SHPB) with a diameter of 50 mm, and a high-speed camera was used to monitor the whole process of coal rock failure. Based on the dynamic mechanical properties and fracture fractal dimension characteristics of coal rock under different strain rates, the dynamic failure characteristics of coal rock were deeply analyzed, and a dynamic strength statistical damage constitutive model was established based on Weibull statistical distribution and Drucker-Prager failure criterion. The results show that the dynamic stress-strain curves of coal rock under different strain rates exhibit obvious nonlinear characteristics, which can be roughly divided into linear elastic stage, plastic yield stage, peak stress stage and post-peak softening stage. As strain rate increases, dynamic uniaxial compressive strength and elastic modulus both show a significant linear growth. The failure mode of coal rock changes from axial cleaving failure at low strain rate to crushing failure at high strain rate. Coal rock fragments after dynamic failure are sieved and found to have obvious fractal characteristics. At the strain rates of 20−100 s⁻¹, average fragmentation of coal rock samples is concentrated in 30−40 mm, and fractal dimension ranges from 1.9 to 2.2. With the increase of strain rate, the degree of fragmentation increases and fractal dimension increases, indicating that the proportion of large-scale coal rock fragments to the total mass gradually decreases. Based on the relationship between the Weibull distribution parameters F₀, m and strain rate, the dynamic constitutive model of coal rock is modified. Comparing the model results with test results, it is found that the model can fully reflect the relationship between stress, strain and strain rate, and the rationality of this model is also verified.
- splitHopkinsonpressurebar(SHPB),
- dynamic strain rate,
- fragmentation,
- fractal dimension,
- dynamic constitutive model,
- coal rock

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References(29)

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