A permeameter for unsaturated soil

A permeameter for unsaturated soil was developed by observing the way in which pore water recovers hydrostatic equilibrium. It works like an hour glass that is turned upside-down everytime the state of reference (or hydrostatic equilibrium) is reached. The hydraulic conductivity is deduced from the curves of evolution of pore-water pressure and from the distribution of partial density of water at hydrostatic equilibrium. Roman Letters a is defined by (10), kg m^–3 - A _n coefficients of the analytic solution, kgm^–3 - C ₁, C ₂, C ₃, C ₄ constants and constants of integration - D diffusivity, m² s^-1 - g gravity constant, m s^-2 - g gravity vector field - K hydraulic conductivity defined by (2), m⁵ s^-1 J^-1 - K _w hydraulic conductivity defined by (5), m ^-1 - k permeability - L length of soil sample, m - n integer in (22) - n porosity - p absolute pore water pressure, Pa - p ₀ absolute pore water pressure, Pa - p _a absolute air pressure, Pa - q volume flux or Darcy's velocity, m s^-1 - r exponent defined by (13) - S _w degree of saturation, % - t time variable, sec - u _n , v _n are defined by (22b), (22c) - x(x, y, z) space variable Greek Letters , are defined by (11), (13) - _w dynamic viscosity - water partial density, kg m^–3. It is the ratio of the mass of water to total volume of a representative elementary volume - ₀, _l water partial densities, kgm^–3 - _w density of water, kgm^–3 - _s density of solid particles, kgm^–3 - differences of partial density, kgm^–3 - p differences of water pressure, Pa - pi - , · gradient operator, divergence operator - Laplacian operator - volumetric water content, % - piezometric head, m