Fracture Mechanism of Sandstone Under Triaxial Extension at Different Loading Rates

• Published in: Rock mechanics and rock engineering 2023-05, Vol.56 (5), p.3429-3450
• Main Authors: Ma, Chunde, Tan, Guanshuang, Lv, Zhihai, Yang, Wenyuan, Zhang, Junjie
• Format: Article
• Language: English
• Subjects: Asperity; Civil Engineering; Confining; Cracks; Dimensions; Direction; Dredging; Earth and Environmental Science; Earth Sciences; Electron microscopy; Excavation; Fractal geometry; Fractals; Fracture mechanics; Fracture surfaces; Geophysics/Geodesy; Height; Load distribution; Loading rate; Mechanical properties; Microcracks; Modulus of elasticity; Optical scanners; Original Paper; Oxidation; Physical characteristics; Pressure; Sandstone; Scanning electron microscopy; Sedimentary rocks; Shear
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-023-03246-x

After excavation, the rock mass often fails in the state of triaxial extension. To explore the fracture mechanism of sandstone under triaxial extension at different loading rates, the triaxial extension tests under confining pressure of 10 MPa and 30 MPa with different loading rates (range from 1 × 10 –4  to 1 mm/s) were carried out on sandstone. Scanning electron microscopy and 3D optical scanning were used to obtain fracture characteristics. The results show that failure strength and elastic modulus increase with the increasing loading rate. Based on the analysis of asperity height, slope angle, aspect direction, fractal dimension, and fracture pattern, the fracture mechanism of sandstone at different loading rates was obtained: at a lower loading rate, microcracks propagate along weak structures. Microcracks grow into tensile cracks under lower confining pressure; grow into shear cracks under higher confining pressure. At a higher loading rate, more grains are damaged. Microcracks grow into tensile cracks under lower confining pressure; microcracks grow into tensile–shear cracks under higher confining pressure. Highlights Triaxial extension tests at different loading rates were carried out on sandstone under confining pressure of 10 MPa and 30 MPa. The fracture patterns at different loading rates were determined. The 3D morphological characteristics of fracture surfaces were obtained by using 3D optical scanner, and asperity height, slope angle, aspect direction, and fractal dimension were calculated. The influence of confining pressure and loading rate on fracture behavior was determined.