The paper presents an experimental study on the creep behavior of a natural rock salt by means of digital image correlation (DIC) technique. To determine the creep rate and understand the creep mechanism of the rock salt, the time-dependent behavior of the material was studied at various scales (100 μm–1 cm) under different mechanical loading conditions. The results showed that the rock salt deformed at low constant stress. The strain rate at the macroscopic scale (cm) was about 10−9 s−1 at 11 MPa and it increased by an order of magnitude at 18 MPa. The strain rate at the mesoscopic scale (mm) depended on the microstructure, the boundary of subgrains deformed more rapidly than the subgrain, and the strain rate reached 10−7 s−1 at the interface of grains. The damage was identified by analyzing the full-field strain map and it was mainly caused by the open of cracks and it developed with the propagation of the cracks during creep tests.
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