Factor Safety of Pasak Jolasid Dam, when Water Level is Higher than Normal Water Level (NWL) for A Long Time

Abstract

Pasak Jolasid dam inspection performed by Royal Irrigation Department (RID), some longitudinal cracks were still found on the road of dam crest. In 2014, Geotechnical Engineering Research and Development Center (GERD), The cause of longitudinal cracks was caused by the evaluation of swelling soil potential of Pasak Jolasid dam (earth-zone dam) by Consolidation-Method B (ASTM D 4659-96), The laboratory testing shows clay of high plasticity (CH) that the soil mineral are montmorillonites and the degree of swelling soils of dam is moderate to high. Each year, From the statistics of water storage of the dam, the reservoir water level is higher than Normal Water Level (NWL) is +42 m.MSL for a period of 3-5 months, show unusually high record from piezometer and observation Well (OW) during the flooding downstream in 2010. Numerical model software GeoStudio was used to predict the behavior of the dam in specific scenario, for instance the case of the high water level within the embankment. This behavior of the dam will use to the analysis of seepage and slope stability, applied properties of swelling soil from wetting-drying cycles test, to result the factor safety of Pasak Jolasid dam.