Creep behavior of sandstone containing impact-induced microcracks

Creep is a fundamental process responsible for the long-term crustal evolution and the stability of rock engineering. However, the influence of initial microcracks on the creep of rock has not been determined. Here, the influence of initial microcracks generated by repetitive impacts on the creep of sandstone is quantitatively investigated. Results show that the increase in the initial microcracks density reduces not only the compressive strength but also the stress of the crack damage threshold. Under the same creep stress, i.e. 24.6 MPa, the axial strain rate increases from 1.8×10−9 s−1 to 3×10−6 s−1 with the initial microcracks density increasing from 0.07 to 0.8. Both the axial strain and the cumulative acoustic emission (AE) energy at the onset of the tertiary creep phase increase with increasing initial microcracks density. The creep strain rate exhibits a quasi-linear relationship with the difference between the creep stress and the stress of the crack damage threshold. Based on the experimental results, a creep model considering the initial microcracks density is proposed. These results are helpful to better understand the long-term evolution of crust and stability of rock engineering with initial microcracks.