Hyperbolic Method for Soft Soil Improved by Vertical Drain

摘要

The hyperbolic fitting method for vertical consolidation is discussed and extended to combined vertical and horizontal consolidation of soft soil treated with vertical drains. It is shown that the slope of the straight portion of the hyperbolic plot for vertical consolidation is constant within the range 60% ≤ U_v ≤ 90%, where, U_v is the average degree of consolidation. But the slope of the straight portion in the case of combined horizontal and vertical consolidation is dependent on three parameters; 1) drain ration 2) ratio of the length of vertical drainage path H to the drain diameter D_e and 3) ratio of horizontal to vertical coefficient of consolidations C_h/C_v. These three parameters determine the preferential direction for the dissipation of excess pore water pressure underneath the foundation of an embankment. Accordingly, a parametric study was conducted to determine the relationship between these parameters and an empirical formula has been proposed to represent the relationship. The proposed empirical formula was applied to carefully recorded field data of Zhanxu expressway in Guandong Province, P.R. China as well as to various case studies from literature and a satisfactory result was found. A comparison between results calculated using Asaoka's method and the proposed method show nearly the same results.