Strength, Deformation, and Acoustic Emission Characteristics of Raw Coal and Briquette Coal Samples under a Triaxial Compression Experiment.

Raw coal and briquette coal samples have similar deformation characteristics. Addition of binders added into briquette coal could change the coal property. To better capture the characteristics of briquette coal samples in comparison to raw coal samples, we performed triaxial compression tests on raw coal and briquette coal samples with 7% content of four different binders. The experiment results show that the MD group (7% rosin) briquette coal has strong similarities to raw coal samples in strength, deformation, and acoustic emission (AE) features. We find that although four different binders (water, cement, rosin, and coal tar) are added into the briquette coal samples, the failure characteristic has high consistence. Briquette coal samples always show plastic failure, but raw coal always shows brittle failure. The increase in raw and briquette coal samples' peak strength is associated with an increase in the confining pressure constant. However, as the confining pressure constant increases, the raw and briquette coal samples' residual strength gradually reaches close to the peak strength. After the peak strength is reached, briquette coal samples always show a stronger strain and the raw coal samples have a weaker strain characteristic. AE events have a peak value on compression and elastic stage of briquette coal samples. AE events do not show a positive correlation relationship with the material strength of the briquette coal samples. Our study highlights that briquette coal samples with 7% rosin have more similarity in strength, deformation, and AE characteristic with raw coal samples.