Sedimentary Facies of the Cimanuk River Delta on the North Java Coastal Area and Its Geotechnical Properties

Abstract

Understanding the sedimentary facies and their engineering properties in the Cimanuk river delta is very important to support the regional infrastructure development and the environmental assessment of the north Java coastal area. This research is aimed to characterize the sedimentary facies association and its geotechnical properties of the Cimanuk delta, Indramayu, West Java. Methods included geotechnical boring and Cone Penetration Tests with pore water measurement (CPTu). The results show that the subsurface condition of the Cimanuk delta comprises several sedimentary facies development and boundaries, namely the delta plain, delta front, and prodelta. The delta plain consists of the fluvial channel sands and marsh-lagoon; the delta front consists of beach ridge, and the prodelta is of clay to silt thickening towards the northeast. The fluvial channel consists of fluvial sand and silt, dense and hard with SPT N value of 30 and cone resistance, qc of 2,000-10,000 kPa. The beach ridge comprises beach sand and sandy silt, loose to very dense, with qc value of 500-16,000 kPa and SPT N value of 30. The delta plain sandy silt has a variable consistency from very soft to hard with SPT N value of 1-37, and qc value of 300- 4,900 kPa. The prodelta clay and silt consist of very soft to medium consistency, with qc value of 200- 3,000 kPa and SPT N value of 1-8. The prodelta clay-silts engineering properties are very soft to a soft consistency. When development occurs in the marsh-lagoon and prodelta facies, particular caution must be taken. The vertical, lateral, and spatial sedimentary facies and their geotechnical properties can provide information for spatial planning in the coastal region.