Investigating the failure mechanism of tunnel sandstone under uniaxial loading and bedding structure

The sedimentary rocks exhibit distinct stratification features that can easily lead to instability and fracturing of surrounding rock masses. This research investigated the mechanical degradation behavior of sandstone under compressive loading, and analyzed the deterioration of mechanical parameters and acoustic emission (AE) responses. The results showed that the acoustic properties exhibit clear anisotropic patterns. The spectrogram transitions from a single-peak to a multiple-peak distribution, indicating that the acoustic behavior is influenced by the bedding angle. The bedding deterioration effect leads to notable compaction deformation, with plastic deformation being considerably reduced. The relationship between peak stress and peak strain follows a quadratic function relative to the bedding angle. The delay characteristics of the AE signal are positively correlated with the bedding deterioration effect. The macroscopic fractures exhibit significant anisotropic characteristics, and its fractal dimension of the macroscopic fractures is negatively correlated with the bedding deterioration effect. The pressure compaction factor was proposed to characterize the influence mechanism of bedding structure. The damage constitutive model of bedding sandstone is established and the method for determining the model parameters is given. The rationality of the theoretical model is verified by the test results of uniaxial compression of sandstone with different bedding structures. The research findings provide a theoretical basis for revealing the failure categories of bedded rock masses and evaluating their stability.