Study on dynamic characteristics of sandstone-damaged by loading and unloading

• Published in: Engineering failure analysis Vol. 157; p. 107911
• Main Authors: Hu, Shang, Zuo, Yujun, Chen, Qinggang, Pan, Chao, Chen, Bin, Rong, Peng, Sun, Wenjibin, Lin, Jianyun, Du, Shuyan, Tang, Xiaocheng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2024
• Subjects: Energy evolution; Fractal dimension; Loading-unloading damage; Rock dynamics; SHPB; SHPB; Energy evolution; Rock dynamics; Loading-unloading damage; Fractal dimension
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2023.107911

•The elastic modulus which is more consistent with the stress–strain relationship is defined.•There are stress thresholds for dividing different stages of ultimate strain and dynamic strength.•The linear variation law of strain rate and fractal dimension is obtained.•The law of energy evolution shows that the threshold is the best position. To investigate the impact of unloading on the dynamic mechanical properties of surrounding rock in roadway excavation, sandstone specimens were subjected to loading and unloading at six levels ranging from 0% to 80% of the uniaxial compressive strength (UCS). Subsequently, an improved SHPB was employed to perform dynamic compression tests, aiming to analyze the mechanical characteristics of the sandstone at various degrees of loading and unloading damage, investigate fractal attributes, and examine the dynamic failure process. The study uncovered that the stress–strain curve exhibits three distinct stages. Correspondingly, a more suitable set of dynamic elastic modulus denoted as Ed1, Ed2, and Ed3, were defined. Using 45% of the UCS as the threshold for unloading stress (75 MPa), both the dynamic elastic modulus and dynamic strength displayed an initial upward trend, succeeded by a subsequent decline. In contrast, the defined damage peak strain ratio ηεp and damage ultimate strain ratio ηεm demonstrated the opposite trend, amounting to 45.64% and 51.03% at the threshold. In addition, increasing unloading damage stress (UDS) decreases the sandstone strain rate(ε̇max and ε̇ave) gradually. Simultaneously, the fractal dimension of the cracks exhibited a linear increase, ranging from 1.159 to 1.481. Similarly, the rock exhibited the lowest proportion of reflected energy and absorbed energy at the threshold. This holds noteworthy implications for examining the dynamic load response behavior of surrounding rock in roadway unloading, ensuring the dependability of blasting unloading techniques.