Pressure and density of air in mines

Abstract

Mines are the deepest cavities in the Earth’s crust, where man has set foot and worked. The observed temperature gradients within the mines range from 10 to 50 K/km. In this paper, the pressure and density of air inside mines are calculated by integrating the governing equation for the number density obtained from the hydrostatic equation and the perfect gas laws. The variation of the acceleration of gravity with depth is seen to have only minimal effects on the pressure and air density. The higher temperature gradients inside the mines are found to depress both the pressure and density of air there. Whereas the pressure must necessarily increase with depth due to the hydrostatic equation, the density of air can increase, remain constant, or actually decrease with depth, for temperature gradients of less than, equal to, or greater than 34 K/km, respectively. Air conditions in the deepest mine in the world are discussed.