Study on creep characteristics and damage evolution of surrounding rock and filling body (SR-FB) composite specimens

To study the structural parameter influence on the creep mechanical properties of sur-rounding rock and filling body (SR-FB) composite specimens, reveal their creep energy change laws and damage evolution characteristics, the composite specimens with different inner diameters (12 mm, 18 mm, 24 mm, or 30 mm) were prepared, conventional triaxial tests and triaxial creep tests were carried out. Besides, Computed tomography (CT) scanning was used to analyze the internal crack growth before loading and after creep failure. The results show that with the increase of inner diameters, the SR-FB creep deformation increased, peak strengths decreased from 87.42 MPa to 60.60 MPa, long-term strengths decreased from 69.10 MPa to 48.35 MPa, and the steady-state creep rate increased exponentially. The three-dimensional reconstruction shows that with the increase of inner diameters, the SR-FB failure modes were transformed from single slope shear failure to tension-conjugate shear failure, and the internal cracks significantly increased. Further-more, the creep energy and damage development of SR-FB were nonlinear related to the inner diameter and stress level. An improved creep damage constitutive model considering inner diameter and stress level was established, which can better characterize the whole creep process of SR-FB. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).