Characteristics of Excess Pore Pressure Isochrones in Heterogeneous Soil Layers based on Finite Element Method Andrian Putra Arifin, Aswin Lim
This study investigates the consolidation behavior of soft clay with interbedded thin and permeable sand layers using excess pore pressure isochrones and time-settlement curves. Based on the model proposed by Nogami & Li (2002), a two-dimensional finite element analysis was conducted using PLAXIS 2D. The research includes variations in model geometry, inclusion and exclusion of initial overburden stress generation, horizontal-to-vertical permeability ratio (kx/ky), the permeability ratio (λ-) between the sand layer and clay soil, and a model without sand layers to serve as a preliminary benchmark model. It has been proposed that a λ- value of 20 is sufficient for drainage and the isochrones will be similar in magnitude above as well as below the sand layers. However, this study shows that the initial overburden stress significantly affects pore pressure behavior. When included, it results in non-uniform isochrones and faster dissipation in deeper layers. Without it, the distribution of the isochrones is uniform but results in unrealistically large settlements and slow dissipation rate. A λ- value of 20 was also found insufficient for effective drainage- higher values are necessary to achieve meaningful pore pressure reduction.
