Analysis of liquefaction potential at public facilities in Petobo area based on CPT and SWS test results

The liquefaction event that occurred in Petobo Village, Palu City, Central Sulawesi was causedby an earthquake on September 28, 2018 with a magnitude of 7.4 and a depth of 10 km. This study aims to determine the potential for liquefaction and the bearing capacity of the soil at SDN Inpres Petobo based on the Swedish Weight Sounding (SWS) and Cone Penetration Test (CPT) tests. The test was conducted at SDN Inpres Petobo, Petobo Village, Palu City, Central Sulawesi. Determination of liquefaction potential and soil bearing capacity using SWS as primary data and CPT as secondary data and also supported by laboratory tests of sieve analysis, Atterberg limits, and direct shear. The sieve analysis test obtained SP classification of soil types at all points. The Atterberg limits test obtained PI values < 7, so that it entered the criteria for silty soil, low plasticity, and partially cohesive, and LL values < 35% which is a type of soil that has the potential for liquefaction. In direct shear testing, the cohesion value at point T1 is 0.225 kg/cm² with a shear angle of 13.534° and at point T2 the cohesion value is 0.19 kg/cm² with a shear angle value of 35.829°. Based on the results ofthe SWS test, at point T1 at a depth of 0 m to 5.5 m, liquefaction has the potential to occur as indicated by the FS value less than 1. From the results of the CPT calculation, it was found that the soil at point T1 with a depth of 0.20 m to 4.40 has the potential for liquefaction to occur. However, the liquefaction did not occur because of its location in the upper side of the Gumbasa irrigation canal and the groundwater table was deep. The calculation of bearing capacity for shallow foundations with SWS data, shear strength data and CPT data, obtain that at a depth of 1 m with dimensions of 1 m x 1 m foundation size is sufficient to support simple construction loads.