A Model of Frictional Creep Applicable in Geotechnique and Seismotectonic

Abstract

Viscosities of geomaterials are dealt with from the fluid phase (gases, water and bitumens) to the solid phase (soils and rocks). Within the plastic viscosity are included the frictional viscosity of particulate materials and the solid state viscosity of cristals and rock blocks.

Such viscosities are herein related to sizes from molecular to lithospheric ones.

A brief reference is made to laws and experimental evidences relating friction as well as to some models proposed to interpret them.

A model of frictional creep was proposed in which sliding of saliences in contact is expressed by the function deduced by Mindlin (1948) for elastoplastic sliding of elastic spheres in contact.

A description is made of a physical model, myriapod, for the experimental determination of that creep function, and some results are presented which point to a rate process.

Tha applicability of the model in Geotechnique is ilustrated by comparison with some experimental resultes on creep of soils and rockfills that are found in the literature.

The applicability in Seismotectonics is also exemplified for cases of inclined or horizontal lithosphere; in the latter case hydrostatic and non-hydrostatic states of stress were considered.

Based on some hypotheses, an attempt is made to calculate also the viscosity of the Atlantic lithosphere in Portuguese offshore.

Some conclusions are drawn and lines suggested for future research.