Dynamic characteristics and constitutive model of coal samples with different length diameter ratio

Abstract

In order to study the dynamic performance of coal samples with different length diameter ratio under impact load, this paper used an improved Hopkinson compression bar experimental device (ϕ75 mm), and carried out the impact compression experiments under 6 impact grades (4.18~8.03 m/s)and 4 aspect ratios(0.33~1.33).It analyzed the correlation between the dynamic parameters and the aspect ratio in combination with the gray correlation theory, and this study then established a 4-parameter uniaxial strength type statistical damage model of coal and rock based on the mechanical mechanism, Weibull distribution and D-P failure criterion.Results show that: ① The length diameter ratio of coal samples has a quadratic function relationship with the strain rate and dynamic compressive strength; The relationship between the dissipation energy and the aspect ratio is a quadratic function, and the dissipation energy decreases with the increase of the aspect ratio; The relationship between the electromagnetic energy and the aspect ratio is a linear function and keeps a positive correlation. ② According to the grey correlation theory, this study obtained the influence order of length diameter ratio of coal sample on dynamic parameters: electromagnetic energy(0.88)>dynamic compressive strength(0.84)>dissipation energy(0.81)>strain rate(0.78).③ The initial constitutive model is constructed based on Weibull distribution and D-P criterion, and the dynamic compressive strength σmax and strain rate、the relationship between length to diameter ratio n was corrected, and then the experimental stress-strain curves were compared to verify the reliability of the model(R2>0.91).

Keywords

• aspect ratio
• strain rate
• shpb
• grey correlation
• damage constitutive model