Analysis of Radial Consolidation Test Data Using a log-log Method

Vertical drains are extensively used to accelerate the consolidation of soft clay deposits. Barron’s theory is usually used to analyze this problem, in which the drainage occurs in the radial direction. The important input parameter in Barron’s theory is the coefficient of radial consolidation (c_r) and a rational assessment of c_r is necessary for the economic design of vertical drains. While several methods exist for the determination of the coefficient of consolidation (c_v) under vertical drainage, very few methods are available for the determination of c_r. In this paper, a log-log method is proposed for the determination of c_r from the experimental data obtained from consolidation tests under radial drainage, based on the characteristic feature observed from a log U_r versus log T_r plot for the equal strain condition. The validity of the method is evaluated by comparing the experimental data with the theory and comparing with the existing methods, such as the $t$ method and the inflection point method. In addition, the parameters obtained based on the proposed method are used to analyze a large-scale experiment with a prefabricated vertical drain.