早龄期喷射混凝土单轴静力学特性与宏细观损伤特征研究OA

To investigate the evolution law of early-age mechanical properties and damage characteristics of shotcrete in a deep-buried plateau railway tunnel,X-ray diffraction(XRD)tests,uniaxial compression tests,and computed tomography(CT)scanning tests were carried out on four types of specimens at different ages.The hydration product distribution,stress-strain curves,and CT slices of early-age shotcrete were obtained.Three constitutive models were used to fit the dimensionless stress-strain curves,and the fractal theory was combined to conduct quantitative analysis on the cracks in the slices.The results show that with the progress of hydration,the early-age performance of shotcrete improves gradually,and the compressive strength with the age of 5 d reaches more than 90%of the design value.Among the three constitutive models,the correlation co-efficients of the Guo Zhenhai model exceeds 94%,and the constitutive model of early-age shotcrete is obtained after modification.The average box dimensions of shotcrete with the age of 1,3,5,7 d are 1.764 8,1.776 2,1.759 2,1.761 7,respectively.By contrast,the box dimensions with the age of 1 and 3 d are larger,indicating that the cracks have a higher degree of irregularity,more complex geometric characteristics,and more severe overall damage.