Abstract
It is an important problem in soils physics to develop a technique making hard pans which have suitable permeability and sufficient bearing capacity for working machine in paddy fields. The fundamental properties ( deformation, strengeth and hardness) of soils concerning this technique are reviewed, partially including the author’s speculation.
1)On the basis of the considerations on the relation between incompressibility and poisson’s ratio, logarithmic strain is reasonable to express deformation of soils.
2) It is preferable to adopt deviatoric stress tensor rather than principal stress ratio or principal stress differences in order to express shear stress for soils.
3) A process of deformation to failure of soils can be expressed by the simplified model: generation of uniform strain, deformation of shear band and formation of a continuous shear failure band.
4) It is very difficult to physically define hardness of soils, so that it is practical to define it by the methods of measurement which are widely applied.
5) To develop the technique making hard pans so that their properties can be controlled, such investigations will be required on the relation between hardness and not only density of soils but also qualitative differences of bond force among soil particles, and on the physical relation between soil moisture and bond force among soil particles.
