Nonlinear softening of unconsolidated granular earth materials

Granular crystals: Nonlinear dynamics meets materials engineering

Theory of acoustic attenuation, dispersion, and pulse propagation in unconsolidated granular materials including marine sediments

A unified theory of sound propagation in saturated marine sediments is developed on the basis of a linear wave equation, which includes a new dissipation term representing internal losses arising from interparticle contacts. This loss mechanism, which shows a ‘‘memory’’ or hysteresis, is proposed as being responsible for the acoustic properties of sediments. To accommodate the memory, the loss ...

Non-cascade frequency-mixing processes for elastic waves in unconsolidated granular materials.

Due to disorder, contacts between beads in stressed granular assemblages are not equally loaded. There exists a distribution of contact static loads, containing weakly loaded contacts (the weak contacts) and strongly loaded contacts (the strong contacts involved in the so-called force chains). For an elastic periodic excitation with a given deformation amplitude, the weakest contacts are suppos...

Velocity of Shear Waves through Unconsolidated Materials

The elastic properties of the unconsolidated materials which cover most of the earth are, in general, unknown. In this paper, an attempt was made to measure, in the field, the shear and compressional wave velocities, with the emphasis on those for shear waves. For this purpose,'a simple source was devised which produced fairly pure shear waves. A portable refraction seismograph of standard desi...

Nonlinear Biot waves in porous media with application to unconsolidated granular media.

The nonlinear propagation through porous media is investigated in the framework of Biot theory. For illustration, and considering the current interest for the determination of the elastic properties of granular media, the case of nonlinear propagation in "model" granular media (disordered packings of noncohesive elastic beads of the same size embedded in a visco-thermal fluid) is considered. Th...