Analysis of failure mechanical behavior and structural stability of rock under dynamic load

Rock serves as a crucial source of building materials. Understanding the dynamic strength of rock under varying prestressed conditions is essential for evaluating structural stability and engineering design. This research investigates the strength and failure characteristics of sandstone under different impact velocities (v = 1m/s-5.5 m/s) and intermediate principal stresses (sigma(2) = 3/6/9/12 MPa) using a true triaxial Hopkinson pressure bar. The results show that as both impact velocity v and intermediate principal stress sigma(2) increase, the peak stress and peak strain of rock samples rise correspondingly. The strain rate of rock samples ranges from 40s(-1) to 120s(-1) under uniaxial impact and from 40s(-1) to 100s(-1) under triaxial impact, indicating more severe deformation without confining pressure. The degree of rock breakage is greater under uniaxial impact compared to triaxial impact, as evidenced by macroscopic damage patterns. Microscopic analysis shows that the internal crystal structure of the rock sample is mainly transgranular fracturing post-impact. Wave velocity tests pre- and post-impact show that increasing v exacerbates rock damage, while increasing sigma(2) mitigates it. A mechanical constitutive model for rock under triaxial conditions, considering dynamic load, prestress, and strain rate, has been developed and validated, with a fitting degree R-2 exceeding 0.9. This study offers significant insights into the mechanical behavior of rock under different prestresses, diverging from conventional rock mechanics (prestress sigma(1)not equal sigma(2) = sigma(3) >= 0) by discussing the macroscopic and destructive behaviors of rock samples under different prestresses (sigma(1)not equal sigma(2)not equal sigma(3) >= 0) and providing a referential mechanical model for similar material studies.