Importance of temperature control in surrounding environment during permeability test for measuring hydraulic constants of rock

Because rock masses serve as natural barriers for geological disposal of radioactive waste, information about rock permeability is essential. An understanding of the influence of the surrounding environment temperature on the results is necessary for highly accurate permeability measurements. Herein we describe how to perform precise permeability measurements. Then, to investigate the influence of the surrounding environment temperature, we show the results of permeability measurements under conditions with dramatic changes using the transient pulse method and a Toki granite sample obtained from Gifu Prefecture in central Japan. The measured permeability without a temperature change is used as a reference. A change in the surrounding environment temperature remarkably affects the pressure in the upstream and downstream reservoirs, their pressure difference, and the confining pressure. An increase in the experimental system temperature increases the pressure. This difference is directly related to the estimated permeability. To accurately measure the rock permeability, it is essential to minimize changes in the surrounding environment temperature because they significantly affect the pressure difference. (author)