Abstract:

The dynamic mechanical properties of rocks are one of the key factors in evaluating the stability of underground engineering. To further analyze the stability of deep rock engineering, taking sandstone from the north wing return air roadway in the eastern district of Guqiao coal mine as the research object, impact compression tests were conducted on sandstone specimens using the split Hopkinson pressure bar (SHPB) technique. Focusing on aspects such as stress-strain relationships, peak values, deformation modulus, and energy dissipation rate, the coupled effects of confining pressure and specimen length on the dynamic mechanical properties of sandstone during dynamic excavation were revealed. The results indicate that stress, strain, and deformation modulus exhibit a significant positive correlation with confining pressure and specimen length. Specifically, when the confining pressure reaches 20 MPa, the compressive strength of the 50 mm long specimen reaches a maximum value of 353.57 MPa; the results indicate that increasing both the confining pressure and the specimen length can significantly enhance the compressive strength of sandstone. In contrast, peak strain shows a negative correlation with confining pressure and specimen length, with the 50 mm long specimen under 20 MPa confining pressure exhibiting the smallest peak strain of only 0.008 45. The energy dissipation rate initially decreases and then increases with increasing confining pressure and specimen length, with the magnitude of decrease being much smaller than that of the increase. This indicates that an increase in confining pressure and specimen length can reduce the deformation capacity (ductility) of sandstone.

Key words: sandstone, confining pressure, deformation modulus, energy dissipation rate, dynamic mechanical property