Relationship between Mechanical Properties of Saturated Fissured Sandstone and Fissure Angle after Freeze-Thaw Cycles

Abstract

The change of mechanical properties of the surrounding rock of underground engineering in cold regions decreases engineering safety. In order to explore the influence of fissure angle on the mechanical properties of surrounding rocks, uniaxial compression and acoustic emission tests were carried out on the fissured sandstone in a saturated state. The results showed that the stress-strain curves of the fissured sandstone had “stress drop” phenomena, the acoustic emission ringing count rate and the cumulative ringing count versus time curve could describe the various stages of fissured sandstone failure, and the increase in the fissure angle made the acoustic emission activity more active. Fissures degraded the mechanical properties of sandstone. The peak strength and elastic modulus of the fissured sandstone increased with the increase of the fissure angle due to the large fissure width of the saturated sample and the freezing-thawing effect, and the peak strain and Poisson’s ratio had no obvious regularity. As the fissure angle increased, the dominant cracks in the failure mode changed from tensile cracks to shear cracks and then to tensile cracks, and the failure mode changed from splitting failure to shearing failure and then to splitting failure. This study can provide guidance and suggestions for the design of underground engineering in cold regions.