Initial exploratory investigation of pore air pressure response during rainfall infiltration using 1d soil column modeling

In unsaturated soil mechanics, matric suction is often regarded as negative pore water pressure because the pore air pressure is regularly assumed to be atmospheric. Therefore, the component of pore air pressure is often being neglected although the actual response of pore air during infiltration is yet to be clearly understood. This study aimed at investigating the response of pore air pressure during rainfall infiltration to substantiate the mechanism of rainfall infiltration in affecting slope stability. Laboratory physical modelling using one dimensional (1D) soil column was utilized to initiate an exploratory study on pore air pressure response. Parametric study was performed by varying the rainfall intensities and initial water content on glass beads which is classified as uniformly graded sand. The outcomes of the physical modelling showed that soil subjected to higher rainfall intensity and initial water content will result in higher pore air pressure development compared to lower rainfall intensity and initial water content. Subsequently, this increase in pore air pressure may resist seepage flow thus affecting the overall mechanism of rainfall infiltration. Therefore, the effect of pore air pressure needs to be further explored before the hypothesis can be applied to real geotechnical applications particularly in slope stability.