Consolidation charts for non-linearly time-increasing loads

Ground improvement techniques in the form of vertical drains combined with preloading are commonly employed to accelerate consolidation. In such situations, it is usually important to be able to consider the influence of the time needed for construction of the preloading on the time needed to achieve a certain degree of consolidation. Numerically computed charts for the design of vertical drains are presented in this paper, considering radial and vertical consolidation and non-linear schemes (i.e. parabolic, logarithmic) of the application of surcharge load increments against time. Examples are provided to illustrate how such charts can be employed to determine the required drain spacing in practical situations of preloading design. The influence of the type of preloading surcharge scheme is studied by means of a sensitivity analysis. Results indicate that the relative importance of radial consolidation with respect to vertical consolidation is the individual factor with the strongest influence on the results, and that drain spacing can be significantly increased when construction time is reduced. Results also indicate that the type of preloading scheme has a significant influence on the design of vertical drain spacing.