Abstract:

Based on the simplified model of the unit of particles, the basic principles and characteristics of the unit of particles were analyzed; and considering the deformation and strength of sand with the effect of intermediate stress, the interaction properties of the units of particles were discussed in detail. The effects of intermediate principal stress on the strength of sand were analyzed from the results of previous triaxial texts. Some macro features of the effect of intermediate stress on strength of sand were interpreted in view of meso-scale study through the analyses of the basic states and properties of the unit of particles, the features of macro-pore and unit pore, the interaction properties of the units of particles and relative physical mechanism. The macro features include that the strength of loose sand is improved gradually if the intermediate principal stress increases from the minor principal stress ?3 to the maximum principal stress ?1; but the strength of dense sand is improved at the beginning and reduced if the intermediate principal stress approach the maximum principal stress ?1; the segment of constant strength increases with the increase of sand density; the rate of strength improvement is effected by the initial ratio of sand if the intermediate principal stress is close to the minor principal stress ?3.

Key words: sand, intermediate principal stress, strength, unit of particles, mesomechanics