  One of the well-known and widely applied parameters in soil mechanics is the
so-called coefficient of earth pressure at rest (denoted by a K0). Field and
laboratory investigations show that this parameter is correlated with the
friction angle and the overconsolidation ratio of the soil deposit. For
normally consolidated clays, the expression developed by Jaky is considered to
hold good. The extension of Jaky's equation for overconsolidated soils is built
mainly on empirical observations; and there is lack of a theoretical framework
that satisfactorily explains the relationship. In this paper, these
relationships are investigated from the nature of energy dissipation of soil
aggregates. For the same, the cyclic stress-dilatancy relationship proposed by
the author is employed. Then, the stress ratio that maximizes entropy is
derived; and this stress ratio is shown to be reasonably close to the
coefficient earth pressure ratio proposed by Jaky. An exponential relationship
between K0 and OCR is derived; and for a special case, the exponent is shown to
be the sine of the critical state friction angle. Finally, some generalizations
are given and aspects which need further investigation are highlighted.
