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Experimental Study on the Failure Characteristics and Damage Evolution of Sandstones from Typical Buried Depths in High In Situ Stress Area


 This study is aimed at exploring the mechanical properties and failure characteristics of the rocks surrounding a railway tunnel in Qinghai-Tibet Plateau at typical buried depths. Uniaxial compression and AE experiments were carried out on sandstones taken from the same borehole. The results show that the elastic modulus and peak strength of the 750 m depth sandstones are much higher than those of the 350 m depth sandstones. The crack evolution in the 750 m depth sandstones was more orderly, and its brittle failure characteristics were more obvious as compared with the 350 m depth sandstones. The fractal dimension of the samples from the typical depths reached the minimum value when the fracture volume state changed from compression to expansion. In addition, the damage variable based on the crack volumetric strain theory (DC) and cumulative ring counts of acoustic emission (DA) can, respectively, reflect the generation and penetration of cracks and the physical properties of rocks at the two typical depths. The combination of DC and DA can be used to analyze the evolution of the sandstone’s damage. The research results have basic theoretical significance for the excavation and geological disaster prevention of tunnels in sandstone sections at typical depths in the Qinghai-Tibet Plateau.