Waves in porous media

Wave propagation in fully saturated elastic porous media has been studied by Biot (1956a-b) with a macroscopic approach: the medium is modeled as a binary continuum arising from the superposition of a fluid and a solid phase occupying simultaneously the same regions of space. The porosity is the link between the two. For in situ testing, the relevant formulation is the one in the low frequency range, in which there is no relative motion between solid skeleton and pore fluid (undrained behaviour). Biot theory reports the existence of three different body wave: one shear wave and two compressional waves. The first (fastest) compressional wave is of interest for site characterization, whereas the second (Biot wave) is of little interest because it is difficult to detect in experimental data. Introducing the further hypothesis of grain incompressibility, soil porosity n can be expressed as a function of the velocity of propagation of the first compressional wave Vp and of shear wave Vs:

considering that specific density of the grains and of the fluid, as well as bulk modulus of the fluid KF assume rather standard values, the above formula may be used to estimate soil porosity from measured values of seismic velocities if an assumption is made on the value of the Poisson ratio of the (evacuated) solid skeleton (usually in the range 0.2-0.35).

Validation and examples are reported in the papers below.



  1. Evaluation of porosity and degree of saturation from seismic and electrical data

    Cosentini, RENATO MARIA; Foti, Sebastiano
    Thomas Telford
    Vol.64 pp.9 (pp.278-286) ISSN:0016-8505 DOI:10.1680/geot.13.P.075

  1. Soil porosity from seismic velocities

    Foti, Sebastiano; Lancellotta, Renato
    Vol.54 (8) (pp.551-554) ISSN:0016-8505

  1. Porosity of Fluid-Saturated Porous Media from Measured Seismic Wave Velocities

    Foti, Sebastiano; Lai, C. G.; Lancellotta, Renato
    Vol.52 (pp.359-373) ISSN:0016-8505

Total: 3