A New Approach to Investigate Rock Salt Creep Behavior Under Triaxial Stress

Abstract Generally speaking, the rock formation with creep capability, where rocks undergo continuous deformation under constant stress, are commonly encountered especially in geomechanics, petroleum engineering, and mining science. This phenomenon significantly impacts the stability of underground engineering structures, such as petroleum/geothermal wellbores or the safety of coal mine tunnels. Therefore, investigating formation with viscous property, characterizing its creep behavior, and determining creep parameters are crucial for ensuring safe construction and production. Currently, the study of creep properties primarily relies on laboratory tests. However, rock samples obtained from underground may undergo changes in their physical and chemical properties during coring operation, transportation, and storage processes, potentially introducing discrepancies between the parameters acquired in lab and the actual value. Nowadays, apparatus capable of conducting creep or rock mechanic experiments are typically characterized by large overall dimensions, causing multiple challenges including disassembly, relocation, and poor environmental adaptability. As a result, they are typically restrained to usage in specialized laboratories. To address these limitations, this study employed a self-designed and fabricated true triaxial visualization rock mechanics test apparatus, characterized by rapid assembly, simple operation, compacting structure, etc. This apparatus allows for creep tests under true triaxial stress with only a single hydraulic power source. Moreover, even in unfavorable conditions, image acquisition can be accomplished using a phone camera, whose application has been verified through tests. Therefore, it is highly suitable for field applications in oilfields. Using this apparatus, a variety of creep experiments under different stress levels were conducted. The true triaxial visualization approach proved to be more direct in observing the influence of rock anisotropy/heterogeneity on rock creep. Through a single experiment, we were able to directly obtain creep patterns for different components, significantly enhancing experimental efficiency.