Novel theoretical considerations of the coefficient of earth pressure at rest

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.

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