Creep behavior of single coal particles based on uniaxial tests

The uniaxial creep test offers a robust approach for investigating the creep behavior of coal particles, while an empirical creep model based on the extended Langmuir equation accurately characterizes the creep curves. Prior to particle destruction, creep deformation progressively accumulates in three distinct stages with increasing load. Only when the diameter of particles exceeds a certain critical value, which is referred to as the matrix size, do both the crushing strength and effective elastic modulus exhibit size effects. The creep hardening effect results in a decrease in the matrix size of samples, leading to a significant increase in the effective elastic modulus of particles and an enhancement in the crushing strength of particles smaller than their original matrix size. The creep-induced damaging effect leads to creep failure in particles, resulting in a decrease in the crushing strength of particles with a diameter larger than the original matrix size. [Display omitted] •The matrix size indicates the dimension of coal with optimal mechanical properties.•Coal particles exhibit a similar creep behavior to that of standard coal samples.•A new empirical model for creep in coal particles is proposed.•The matrix size of particles is significantly reduced after creep.•Creep has conflicting mechanisms of hardening and damaging.