Swelling potential characterization of clay-silt soil is an essential issue in stabilization, settlement, consolidation, and land suitability studies. This article attempts to explain the swelling characteristics of soils around the area of West Lampung, Lampung Province, Sumatra, Indonesia, in relation to environmental issues. An investigation in relation to the soil swelling potential was carried out using 15 disturbed soil samples collectd in the study area. The methods used were analyses of clay mineral geochemistry, physical characteristics, and the free swell ratio. These results showed that the soil in the study area was Quaternary tropical volcanic residual soil. These soils were formed in a proximal volcanic hydrothermal alteration environment. The soils of the study area have characteristics of high plasticity, a reddish-brown colour, and are clayey silt grained (MH) (USCS). The soils had loose physical characteristics in dry conditions; however, these soils tends to be plastic and sticky in wet conditions. Evidence of groove erosion was found at the soil surface. Based on XRD analysis, kaolinite, halloysite, and montmorillonite were types of clay minerals found in the soil. The soil had a clay content of 11.05–78.9%, a liquid limit value > 50%, a plasticity index value of 16.7–36.9%, a shrinkage value of 14.24–36.89%, a soil activity of 0.38–2.47; and an FSR value of 0.69–0.95. These characteristics have implications for swelling soil potential. The results showed that the soils in the study area had medium to very high swelling potential. These results suggest a risk of erosion in the area, which could cause soil degradation and a change in water quality. These soils are likely to affect land productivity and aquifer replenishment and will cause negative environmental and economic impacts. Thus, soil improvement techniques are needed. It is important to maintaining vegetative cover these soils and revegetation may be required.

Cilengkrang is a sub-village in the north of Ujung Berung and Cijambe sub-District Bandung Regency, Indonesia. It is located on the west of Cikeruh sub-watershed. This subwatershed is part of greater upstream Citarum watershed. This area has been developed rapidly by new settlement and villa. However, the available data of erosion potential in this area is less convenient. The erosion is a severe problem that has a strong relation to flood potential. This study starts with collected engineering geological data from 14 samples. These samples were taken from different soil types from its engineering characteristics. Based on the field and laboratory observation, this area is form by fine-grained soils as a result of residual soils from young volcanic rocks — the silt and very fine sand content range from 49 to 70 % of the total soil. The erodibility value (K) in this area is from 0.03 to 0.06. These values are indicating moderate soil erodibility class. The plasticity index (PI) also shows value from 9 to 48 %. This value is pointing low to high plasticity behavior of this soil. The regression linear shows strong correlation between PI and K with r = 0.7. This correlation is interpreted that the cohesion controls the soil characteristic in Cilengkrang area and affect the moderate erodibility value. This study hopefully giving new insight that soil mechanic data is can also support data on erosion potential.

Soil liquefaction is one of a major problem in infrastructure development. This disaster can occur on sandy soil and high seismicity region. Soil with liquefaction potential will affect as a liquid during earthquakes and has high potential to collapse after the earthquake. The purpose of this study is to identify liquefaction potential in Sanana, Sula Island, North Maluku where many infrastructure developments being carried out. The method used in this research is “simplified procedure” for evaluating liquefaction resistance of soils. This method considers geological and geotechnical characteristics based on Standard Penetration Test. The geological characteristics of Sanana region show that this region has liquefaction potential because it is composed of Holocene alluvium and located in high seismicity region. Furthermore, based on the geotechnical data from the SPT test, this region has liquefaction potential in the sand, silty sand and sandy silt with loose-medium density. The loose-medium properties affect a low seismic resistance to cyclic loads. This will lead to high liquefaction potential in this research area. Therefore, in order to prevent possible disaster caused by liquefaction, this problem needs to be considered in future infrastructure planning and development.

A regional development will decrease the open green space that will affect the less water infiltration during the rainy season and causing the high intensity of the erosion rate. Jatinangor is a well-known new satellite city that located in undulating volcanic hills as the part of the Southeast Mt Manglayang. This area has been degraded from agricultural land into the residential and educational area. This study aims to determine the erodibility factor potential as one of the important factors to an erosion prediction. The data were obtained by collecting several undisturbed samples and tested the grain size and hydrometer analysis, atteberg limit test to know the grain size distribution. This result showed that Jatinangor Area has a high potential value of erodibility that caused by the silt domination and Ilite clay mineral that potential to swelling. The high erodibility values are affected by volcanic material as the parent rock that consists of Tuff, Lapilli Tuff, Grain supported and matrix supported Breccia with Plagioclase and K-Feldspar percentage 15-35%. Whereas the low erodibility value in the higher clay soil percentage is affected by the less percentage of plagioclase and K-fledspar, and the Tuffaceous sand matrix that difficult to erodible. The conservations are needed to decrease the erodibility effect and minimize the erosion rate annual.

ANALYSIS OF GEOMORPHOLOGICAL ASPECTS OF SURADE SUB-DISTRICT, SUKABUMI DISTRICT, WEST JAVA