Determination of Coefficient of Radial Consolidation Using Steepest Tangent Fitting Method

Barron (Trans ASCE 113:718–724, 1948) theoretical relationship between degree of consolidation (U _r ) and time factor (T _r ) is generally used to determine the coefficient of radial consolidation c _r . Several researchers have proposed different laboratory techniques for obtaining the value of c _r . However, the usual approach is to compare some salient features of the theoretical U _r –T _r relationship with the compression, δ and time, t based on the laboratory data. In this paper, rapid consolidation test procedure originally proposed by Su (J Soil Mech Found Div Am Soc Civ Eng No. 95: Proc. Pap. 1729 (1–9), 1958) to determine the coefficient of vertical consolidation (c _v ) is extended to evaluate Barron’s coefficient of radial consolidation c _r for the case of equal strain. The characteristic feature of the proposed method is the identification of the steepest tangent from the δ–log t plot. The slope of steepest tangent is independent of the drain spacing ratio (n) with a value of 0.847. This approach is rapid, and it predicts more reliable values of c _r as it is less influenced by the secondary compression. In addition, this method is more versatile and can be applied for consolidation trends which do not always exhibit the typical S-shape.