The paper describes an investigation of the influence of rainfall infiltration on the negative pore-water pressures within residual soil slopes. Four research sites in Singapore were instrumented to measure rainfall, run-off and pore-water pressures/suctions. The results from one site are presented and show that when the initial pore-water pressures were already high (close to zero near the surface and positive at depth) that different rainfall events (86 mm and 13 mm in total) produced similar very small changes in the pore-water pressure. However, when the pore-water pressures were initially low then a very small rainfall event (1 mm in total) was able to produce much larger changes in pore-water pressure. Two other rainfall events (14 mm and 125 mm) during periods of low initial pore-water pressures produced similar large changes in the pore-water pressures. The pore-water pressure changes were not dependant only on the amount of rainfall but were significantly affected by the initial pore-water pressures. This shows the important role played by antecedent rainfall, as the rainfall that has fallen previously controls the initial pore-water pressures.
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