Geological and geotechnical review of gas and mudflow area as mitigation efforts in the risk of failure on Toll Road Project, Banten

Abstract

Abstract The toll project in Banten shows that there is an area of gas burst at one of the locations. The embankment road passes through the gas burst. The geoelectric results that there is a silt/sandy soil layer and rock on the surface (10-20m), the second layer is soft silt to silt (20-40m), and then a rock layer. The second layer has gaps towards the first layer from the bottom layer, which is identified carrying gas and water, which is passed through the gaps to the surface. The seismic refraction also results that there are basins with gaps through the top and bottom of soil layers. The layer which indicates the gas and water carrier line is volcanic, sandy, forming a layer that has undergone deformation and partly a water-bearing layer (sand). The result of LEMIGAS explained that the gas bursts are also not methane that comes from the humus decomposition. The gas bursts are originated from depth and related to petroleum activity. The CO2 content is up to 97.87%, which is poisonous. However, the burst area is open, and the morphology is flat and does not form a cup, this gas spreads out so that the impact is not too pronounced.