Damage analysis of rocks with different properties under cyclic splitting action

Abstract

In underground construction operations, there are different types of rocks in repeated loading and unloading environments. For this reason, in this paper, two rock samples—slate and metamorphic sandstone, which contain different properties, were subjected to cyclic splitting experiments and were analyzed for damage using scanning electron microscopy, acoustic emission (AE) and stress–strain. It can be seen that the internal grains of the slate are angular and distributed in a directional arrangement, and the metamorphic sandstone has a large difference in size and shape between the grains, and it is a small-sized nodular step-like; Slate is dominated by damage forms of single shear and conjugate shear composite damage forms, with sudden changes in cumulative energy occurring just prior to the peak stress in each cyclic phase, and in metamorphic sandstone at the location of the peak stress in each cyclic phase, and the total energy of the loading phase accounts for more than 90 per cent of the entire cycle phase; Dissipation energy $u_n^d$ obtained damage value D in the cyclic loading process, there is an obvious turning point when a large damage, and the later stages of loading damage will be more serious when the slope of slate is significantly larger than the metamorphic sandstone, the trend of change in the value of damage D is more obvious, the difference in slope between the two is nearly double, and it is more representative of the pattern of changes in the rock damage process.