It is of great significance, for economic, environmental and security reasons, to investigate the strength characteristic of underground cemented paste backfill (CPB). Consequently, an ultrasonic test, uniaxial and triaxial compression experiment, and acoustic emission (AE) monitoring were carried out on CPB, for which the particles satisfied Talbot gradation. The homogeneity of CPB specimens was evaluated by ultrasonic pulse velocity (UPV). The stress–strain behavior and AE characteristic of CPB specimens under different Talbot indices and confining pressures were investigated. The effects of the particle size distribution and the confining pressure on the peak strength of CPB were analyzed. The strength parameter model of CPB under the coupled influence of the particle size distribution and the confining pressure was constructed based on the Mohr–Coulomb strength criterion. The results show that the peak strength of CPB is positively linear with confining pressure, however, the relationship between its strength parameters and the Talbot index can be characterized by a quadratic polynomial function. This suggests that there is an optimal gradation of particles reflected in the maximum strength of CPB.

The aim of this paper is to determine the influence of heating rate on the dynamic mechanical performance of coal measure rocks after heat treatment. Uniaxial compression tests were conducted using a split Hopkinson pressure bar system on coal measure rocks after heat treatment at 800°C at different heating rates. The results reveal that a high-temperature treatment changed the physical and mechanical properties of the sandstone. When the heating rate was increased, the natural and mechanical properties were reduced gradually. The failure mode of sandstone after heat treatment was tension destruction, and shear fracturing occurred locally only at high heating rates. Original cracks grew inside the sandstone after heat treatment, while the number of defects (including cracks and pores) increased gradually with an increased heating rate, which was the main reason for the change in the sandstone’s macromechanical properties. The energy dissipation during fracturing was correlated closely to the fracture characteristics and increased with increased heating rates. The results of this work can provide references for future engineering projects, such as underground coal gasification and coal-bed methane thermal exploitation.