Application of diffusion-advection equations to in-field monitoring of soil suction profiles

Structures built on expansive soils are susceptible to damage arising from the shrink-swell behaviour of soils. Due to this issue and the limitations of the existing methods that estimate displacement demand on structures, a new diffusion–advection equation that adequately models the variation of soil suction, responsible for shrink-swell movements has been proposed. A numerical scheme in MATLAB code has been presented in the paper. To validate the model, field monitored data of soil suction obtained over a one-year period has been compared with the proposed approach and the conventional approach. Results indeed show that the solutions based on the proposed diffusion–advection equation compare favourably with the field monitored data. The mean and the standard deviation of residuals are around 0.1 and 0.3 pF. In addition, the depth to equilibrium suction can easily be obtained using the numerical approach. Application of the simulations to estimate the surface movement of soils has been demonstrated using the discrete Australian Code approach and the continuum approach. The implication of these findings suggests that site-specific displacement demand on structures built on expansive soils can be realistically estimated for design purposes.