On the Mechanical Properties of Firm Soil

Rheological Structure of Soil (II)

Abstract

Terzaghi (1925) treated the elasticity of soil as pseudo high elasticity that was owed to the “honey-comb” structure. We, now, can put that Terzaghi's model is the first approximation which corresponds to the Hooke-body. From the rheological point of view the behaviour of soil is undoubtedly visco-elastic.
Soil can be treated as Burgers body in mechanical behaviourand “honey-comb structure made of gel”, which is composed of the Maxwell model and the Voigt model linked in series. In this treatment both initial set and strain hardening are however omitted from the behaviour of soil.
The unit system in soil is gel which is regarded as hydrophilic colloid. Gel behaves as the Voigt model and is entropy-elastic from the view point of thermodynamics. On the other hand, the Maxwell model corresponds to the porous structure of soil. The dashpot (η_M) of the Maxwell model linked in series to the Voigt model may be caused by pores in soil in the manner of the Hole Theory of liquid. And the spring (G_M) of the Maxwell model that represents instantantaneous elasticity depends on the honey-comb structure consisted of gel.
Initial set (ε_I) results from the compression by diagonal sum of stress tensor and the amount of initial set (ε_I) is one third of volume strain εV. Strain hardening occurs on all the model constants. Particularly it has much effect on η_M, because of the break-down of the pore structure,
The yiela value τ_f of the Burgers body can be determined by the pF value, and log (τ_f) is nearly equal to the pF value.