Simplified Method to Calculate Groundwater Level inside a Hillside Slope during Rainfall

In order to estimate the stability of slope during heavy rainfall, rainfall infiltration forming groundwater flow should be known. This groundwater flow is desired to be known from on-going rainfall records so that the necessity of warning can be evaluated rapidly. However, there is no simple and practical method to estimate the groundwater flow using on-going rainfall records, though studies on this kind groundwater flow are being conducted in academic area. This paper describes a newly developed simplified method to evaluate the groundwater flow for a two dimensional slope using on-going rainfall records based on an actual behavior of groundwater formation monitored at site. Comparison between the calculated groundwater levels and the monitored level at site shows that this simplified method can well estimate a groundwater rise up. Furthermore, this simplified method is applied to slopes where actual failure was caused during the heavy rain on 29June, 1999 heavy rain