Derivation for Coefficient of Consolidation from Settlement Observation

Based on the Terzaghi’s theory of consolidation, it is used to derive, directly from the time-compression curve of soil, the coefficient of consolidation which controls the rate of dissipation of the excess pore pressure. An assuumption is implied in this procedure that the degree of consolidation Uσ is equivalent to the degree of compression Uε In fact, owing to the non-linear stress-strain relation of soil, Uσ and Uε are not exactly the same in general. Two kinds of analytical relationship between Uσ and Uε are derived on basis of compression curve of hyperbolic and semi-logarithmic type respectively, and thence a method to predict the coefficient of consolidation for the in-situ soil from the settlement observation is proposed. It is shown by the calculation of a case record that the relation between Uσ and Uε obtained from the compression curve of hyperbolic type is preferred to that from semi-logarithmic type. This is mainly because that the shape of the compression curve of soil fits in better with the hyperbolic than with the semi-logarithmic equation.