Estimating radial attenuation of vacuum pressure for dredged clays

The radial attenuation of vacuum pressure in dredged clays limits the effectiveness of vacuum consolidation. In this study, a series of model tests were conducted on five dredged clays with varying initial water contents to investigate this radial attenuation. The significant radial attenuation can be divided into two stages: the increasing and stabilization stages. In the stabilization stage, exponential radial attenuation is observed. Lower initial void ratio (e₀) and higher void ratio at liquid limit (e_L) lead to a decrease in radial attenuation. Additionally, higher applied vacuum pressure (p_v) results in a greater reduction in the magnitude of the radial vacuum pressure. In the increasing stage, the radial vacuum pressure increases exponentially to a stable state after start-up. The radial attenuation is attributed to the differential start-up time (i.e., initial time-point at which the increase begins) and varying increase rates. Lower e₀, higher e_L, and higher p_v values reduce the start-up time and raise the increase rate. A changing pattern is proposed to describe the exponential radial attenuation using three parameters: radial attenuation coefficient (k₂), increasing coefficient (k₃), and time-delay coefficient (D_t). Furthermore, an empirical estimation for the radial attenuation is also suggested without relying on time-consuming tests.