The creep behaviour of evaporites is generally determined by loading core samples uniaxially under a fixed stress at the ambient mine temperature and observing the deformation of the specimen. This process is usually carried out in sequence of stages of increasing stress with the final one leading to steady state or accelerating creep.
In some cases, it is desirable to determine the creep behaviour in samples which are also subject to confining stress. This is particularly the case where the evaporite is being used for waste storage and the changing permeability of the mass is of importance, such as in hazardous waste storage. Under these circumstances, it is important to be able to determine whether the creep is associated with dilation and a development of permeability.