Embankment Stability on the Effect of Rainwater Infiltration on Clay Shale Laminated Soil

Construction safety is one of the main issues that need to be considered in nowadays construction industries, for instance, is in Toll Road Construction. Balikpapan - Samarinda Toll Road Construction that planned to constructed through 99.02 km. At the embankment on Sta. 06+300 the slope goes through failure. In terms of structural geology, one of the main cause of slope failure is because the construction site categorized as the kampungbaru formation. The kampungbaru formation is formed from clay shale which immensely vulnerable to climate change and weather so it can reduce the shear strength of the soil. The purpose of this research is to analyze the influence of water content on clay shale's shear strength and analyze the effect of rainfall infiltration on slope stability and recommend suitable slope improvement for the site. In this study, laboratory tests were conducted to determine the properties of clay shale, analyze safety of factor (SF) using SLOPE / W for embankment without rainwater infiltration, and analyze safety of factor (SF) using SEEP / W and SLOPE / W for embankment with the influence of rainwater infiltration. The results of the laboratory tests show that the research location is on the clay shale soil layer due to laboratory results that proved the percentage of water content is in contrary with the shear angle and soil cohesion. The results show that rainwater infiltration affects the SF value. SF value without rainwater infiltration is 1.337 whereas SF value with rainwater infiltration is 0.907. The rainwater infiltration effect could decrease soil strength causing slope to become unstable. One of the suitable recommendations of soil improvements that can be chosen is chemical stabilization by adding lime additives. From the previous studies, the optimum percentage to add lime additives is 12%.