Abstract: This study aims to investigate the energy and deformation characteristics of rock joints under multi-stage shear loading-creep-unloading conditions. The experiments were conducted on jointed marble specimens using a GCTS (RDS?200) servo-controlled testing machine. The results showed that the area of the hysteresis loop had linear or exponential relationships with cycling numbers, when the normal stress was lower than 6.5 MPa or higher than 7.8 MPa, respectively. The total deformation energy and the elastic deformation energy were positively related to the normal stress and exponentially related to the cyclic number, respectively. However, the plastic deformation energy was positively correlated with cycle number and normal load. At the ends of different levels of shear stress loading, the outer envelope of the shear displacement curve had the same trend as the direct shear displacement-shear stress curve. It could be divided into three stages: accelerated growth, linearly increasing segment and linearly decreasing segment. The accumulated plastic displacement increased with increasing loading cycles, but the increasing rates decreased gradually. Each shear loading or shear unloading curve can be divided into two stages according to the shear sliding point. Before the shear failure of rock joint, the normal displacement-shear curve became lower than the later ones under shear loading and unloading conditions. The accumulated normal displacement changed from increasing to decreasing at the ends of cyclic shear loading and creeping at each stress level.

Key words: rock joints, cycling loading and unloading, shear creep, energy evolution, deformation characteristic