The thermal conductivity coefficient k is a material parameter depending on temperature, physical properties of the material, water content, and the pressure on the material . The coefficient k is measured in watts per meter Kelvin (or degree) (W/mK). In general, a material with a large k is a good heat conductor; one with a small k is known as a good thermal insulator. Therefore, this parameter has a marked effect both on working conditions in deep mines and on thermal energy storage capacity of underground openings. It relates also to geothermal energy production and radioactive waste disposal.
Thermal conductivity of rock is dependent on a number of factors such as temperature, axial stress, confining pressure, structure such as joints, density, P-wave velocity, and compressive strength, according to the experimental results from various types of rocks such as Basalt, marble, granite, and diorite.