Road damage often occurs in lowland areas, one of the reasons is unstable soil conditions. This study aims to determine the relationship between geotechnical characteristics of soil and road damage. Field observations were carried out in the Tanjung Api-Api lowland area to find out the type of road damage. Testing of soil physical and mechanical properties was carried out to determine the geotechnical characteristics of the soil at that location. Results from current study show that that generally the types of road damage lowland areas are cracking, grade depressions, potholes, and distortion. The soil properties test results obtained that the soil in the Tanjung Api-Api lowland area was classified by Unified Soil Classification System (USCS) as an inorganic silt (MH) and organic clay soil with moderate to high plasticity (OH). In general, soil of this type has a low bearing capacity so that it requires handling and selection of construction that is suitable with this type of soil. Based on the classification of American Association of State Highway and Transportation Officials (AASHTO), the soil in the Tanjung Api-Api area is A-7-5 and A-5, which are clay and silt land with moderate to poor criteria if used as subgrade so that this land usually require s special handling when used as subgrade because it has the potential to deformation.

It is well known that earthquake-induced liquefaction can cause remarkable damage to buildings. A recent disaster involving liquefaction in Palu damaged buildings and infrastructure and has become the focus of many researchers. Detailed study of liquefaction is necessary in order to have a good understanding and direct mitigation efforts for the future. In this study, the liquefaction potential of sands with various grain size distributions was analyzed. The research was experimental using a laboratory sieve shaker. The samples were taken from six areas near important facilities. From this, the relationship between grain distribution and liquefaction potential could be plotted and this information could become an important input for liquefaction mitigation efforts in sandy sediment areas.