Development of a new creep testing equipment to obtain long-term deformation parameters of salt

Creep phenomenon in rock engineering plays a key role in the development of underground spaces as they must be stable enough for a long period of time. The study describes the main ideas of the design and manufacturing of a new creep testing machine that is set up at Shahrood University of Technology (SUT). The testing machine is capable of performing creep tests at low equivalent stresses on more than one cylindrical rock sample simultaneously at a very low cost. To evaluate the performance of the equipment, a series of creep tests were performed on salt rock samples and their axial and lateral deformations were measured by dial gauges. Measurements were taken under constant temperature, humidity and sustained loads. The results revealed that both axial and lateral creep behavior of specimens follow the same pattern with an idealized salt rock creep curve. The experiments also indicated that the steady state creep rate rises with increasing initial applied stress level.