Validation of Numerical Modelling Techniques in Unsaturated Slope Behaviour

Knowledge in modelling unsaturated slope behaviour remains limited. Research findings have challenged the common assumption of fully saturated conditions for all soil problems thus widening the perspective of partially saturated states. The calibration of unsaturated soil parameters requires good understanding of the soil-water characteristic curve (SWCC) and the permeability functions. The modelling of unsaturated slope behaviour involves the setting out of the model geometry, boundary conditions and flux boundaries when it comes to rainfall. It is a norm where certain unobtainable data had to be assumed and the results are consequently under or over-estimated. Hence, this paper aims to validate the numerical techniques in modelling the groundwater flow and safety analyses for a slope model under the effect of typical rainfall in Hubei, China. The model is developed using Finite Element package; Plaxis and the results are compared to the field results and literature findings. The important parameters of hydrological and mechanical properties were gathered from the literature along with the boundary conditions. The flux boundaries are presented by simulated rainfall for a period of one month and the calculation is conducted in transient flow analysis. The results in terms of pore-water pressure are well validated with minor differences which can be explained by the unavailability of data for example the void ratio used and exact location of measurement taken in the field and literature findings. The analysis is also extended to calculate the factor of safety which contributes to familiarising the techniques in modelling by means of utilising the phi-c reduction method. In summary, the results demonstrated that the numerical modelling of unsaturated slope behaviour can be undertaken provided that all major information such as soil parameters, slope geometry and boundary conditions used are available and reliable.