Comparative analysis of deformation failure and energy properties of raw coal and sandstone under uniaxial compression

Abstract

This paper analyzes and compares the deformation, failure characteristics, and energy characteristics of coal and rock under uniaxial compression. It is considered that the change laws of the total stress–strain relationship curves of raw coal and sandstone samples are similar, and they all exhibit the primary fracture compaction and closure stage, elastic deformation stage, fracture expansion stage and stress drop stage. The failure mode of coal and rock is a predominantly columnar splitting, and the fractured coal and rock bite each other. The ultimate bearing capacity, elastic modulus and peak strain of coal samples are small for sandstone. Under uniaxial compression, the ultimate bearing capacity, elastic modulus, and peak strain of coal samples were 46.17%, 63.32%, and 69.54% of sandstone, respectively. In the compaction stage, the proportion of releasable elastic energy of the coal sample was higher than that of dissipated energy, while that of the sandstone sample is the opposite. The proportion of releasable elastic energy of coal samples in other stages was higher than that of dissipated energy, and more than 80% of the total energy absorbed by coal and rock specimens in the loading process was stored in the form of releasable elastic energy. Other total energy was dissipated by the internal defects of the samples during compaction, sliding and new micro-cracks in the yield stage.