Effects of bedding plane dip angle and lithology on the mechanical and micro-failure behavior of stratified rock under uniaxial compression test

Abstract

To investigate the mechanical and micro-failure behavior of stratified rock, a series of uniaxial compression and CT scanning tests of stratified limestone and sandstone at different bedding plane dip angles (α) were conducted. The experimental results showed that with the increasing α, uniaxial compressive strength (UCS), peak strain (ε_1p), Poisson’s ratio (μ) of stratified limestone and sandstone all first decreased and then increased, elastic modulus (E) of stratified limestone continuously increased, E of stratified sandstone first decreased and then increased. At different α, UCS and E of stratified limestone were larger than that of stratified sandstone, ε_1p and μ of stratified limestone were smaller than that of stratified sandstone. For stratified limestone, anisotropy coefficient of μ was the largest and anisotropy coefficient of E was the smallest. For stratified sandstone, anisotropy coefficient of ε_1p was the largest and anisotropy coefficient of E was the smallest. Anisotropy degree of stratified limestone and sandstone was approaching for UCS. Anisotropy degree of stratified limestone was larger than stratified sandstone for ε_1p and μ. Anisotropy degree of stratified limestone was smaller than stratified sandstone for E. The failure category of stratified limestone and sandstone at different α was quite different. Due to differences in failure mode, the morphology and distribution characteristics of micro-cracks along the sample height showed a significant difference. With the increasing α, volume fraction (VF) and the maximum area fraction (AF) first decreased and then increased for stratified limestone, and showed no obvious change trend for stratified sandstone. At α = 0º, 30º, 90º, VF and the maximum AF of stratified limestone were significantly larger than that of stratified sandstone. At α = 60º, VF and the maximum AF of stratified sandstone were larger than that of stratified limestone.