Characterization of Subgrade Soil of Lowland Areas of Semarang City

Abstract

The northern part of Semarang city has been suffering a lot from settlement and inundation caused by rainfall and tidal flood. The settlement is predicted to emerge from the subgrade soil containing soft soil with low bearing capacity and high compressibility. This study aims to characterize subgrade soil of lowland areas of Semarang city. In order to define the depth of soft soil, site class, soil classification, and the settlement, soil data was taken from twelve locations distributed in five sub districts of Semarang lowland areas. The minimum depth of subgrade soil is 30 m below the ground surface. To predict the settlement, subgrade soil was loaded by a surcharge load of 80 kPa, and a safety factor of 2 was taken into account. The analysis was based on N-SPT, cone resistance, index properties, and engineering properties. The result shows that the subgrade soil of Semarang lowland areas is dominated by soft clay with a depth of 5 m to 20 m with the site class from SE to SD. Soil is classified as CL and CH. The predicted settlement is from 0.321 m (lasts one year) to 1.395 m (lasts 13 years).