Sand as a compressible fluid

The macroscopic volume changes of granular bodies during compression and sh earing are investigated in terms of compressible fluid. The proposed analog y between sand body and van der Waals fluid, and appropriate form of van de r Waals state equation, is demonstrated interpreting common soil mechanics tests in which the deviator stress is proportional to the mean pressure. Th e equation fits well the large range of applied pressures, and the proposed regular behavior is observed despite the severe grain crushing during load ing. The common position of sands in reduced coordinates is found. The simp le expression for pressure in sand in isothermal conditions is also propose d. (C) 2000 Elsevier Science B.V. All rights reserved.