ABSTRACT:

The objective of this paper is to explain field shrinkage-crack associations formed on an isotropic and homogeneous soil due to withdrawal of the interstitial water. The model is based on irreversible thermodynamics. Two functions are used to describe how the decrease in water content allows change of consistency accompanied by shrinkage and visible cracks.

  • The free energy lost from particles packing in a disrupted array of prismatic-angular modules, sometimes showing on a soil surface a net pattern of ring fissures superimposed on hexagonal symmetry, and

  • a conjugated function indicating the rate at which the length of each soil module is solidified.

Although a clay-silty soil is used as an example to explain the geomorphic features in soil surface layers, the model may be generalised to explain shrinkage-crack associations in other materials stressed with non-isotropic conditions.

INTRODUCTION

Shrinkage-crack associations developed in soil surface layers are a common problem in prevailing engineering practice. However, the analysis of desiccation and consistency change of soft soils remains empirical from Atterberg''s time. The shape of the shrinking curve, by plotting volume change of unconfined soil units against the gravimetric water content has been given by Haines (1923). Concepts of swelling and shrinkage of expensive soils are analysed by Low (1954), Quirk (1955), Philip (1969), Bronswijk (1990) and Karalis (1994,1995). The goal of this paper is to give a statement of this problem based on thermodynamic principles. The analysis is based on observable quantities and experimental data. Thermodynamic considerations concerning the partition of the recessed oncotic energy reflecting volume change and consistency differentiation, and also the topology of the array of prismatic-angular modules on the soil surface, are discussed and the rate of desiccation, shrinkage and solidification in each soil module is also considered.

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