Birobuli is located in South Palu, which has highly vulnerable to earthquakes. One of the phenomena that usually occur after an earthquake is liquefaction which causes significant damage and loss of life. Furthermore, all the infrastructure is required to analyze the effect of external load and potential hazards. This research aims to investigate the liquefaction potential in Birobuli, South Palu. The method was divided into two categories: grain size distribution analysis and empirical formula based on CPT data. The result presented a similar trend in grain size analysis which consist of all the range in the potential to liquefaction, while the CPT result describes the same meaning. The CPT 1 result showed SF<1 between 0-5m and 9-11m, while CPT 2 had fluctuating data in ranges between 0.18-2.00 in 0-4m, SF under 2 in 6-8m and 9-11m. This study was expected to provide information for local government as disaster mitigation for Birobuli Area.

The method used in this study is to simulate slopes that occur crack and get the influence of water saturation. The simulation is made with a computer application program, which is a program for calculating slope stability. The results of the analysis in this study found that the occurrence of cracks on the slope surface, the slope safety number will decrease when the crack is entered by water. Water entering the soil crack will cause pore water pressure which will then provide additional impetus to the slope landslide field. The greater the pore water pressure, the greater the decrease in security numbers. Besides that, the crack position from the edge of the slope has an effect on decreasing slope safety factor. A far the position of the crack from the edge of the slope increases the safety factor. The biggest decrease occurred in the position of 3 m crack from the edge of the slope. Crack positions greater than 3 m are the same. This happens because the slope failure field occurs at about 3 m from the edge of the slope.

Untuk dapat melakukan analisa stabilitas lereng batuan diperlukan penentuan karakteristik dan klasifikasi batuan serta parameter fisis dan mekanis dari batuan. Tujuan dari penelitian ini adalah untuk mengetahui nilai parameter mekanik batuan dengan metode RMR dan GSI. Hasil dari penelitian ini adalah batuan kawasan pantai Melasti masuk ke dalam kelas batuan menengah (fair rock) dengan nilai GSI = 35 – 45. Parameter mekanik batuan kawasan pantai Melasti dari metode RMR adalah f = 25 – 35 dan c = 200 KPa – 300 KPa, sedangkan parameter mekanik dari batuan dengan menggunakan metode GSI adalah f = 24 – 29 dan c = 256 KPa – 330 KPa.

To evaluate soil resistance against liquefaction, a simplified procedure has been developed based on directly field soil testing. There are four recommended field tests, including CPT and SPT. Soil resistance to liquefaction is measured by the safety factor SF, which is the ratio between the capacity of the soil to resist liquefaction cyclic resistance ratio (CRR) and the soil stress occurs due to an earthquake cyclic stress ratio (CSR). If SF <1, liquefaction occurs. This research was carried out at Sanur area, Southeast Denpasar City, Bali, by conducting 6 pairs of CPT and SPT tests, each of 6-meter depth. The Ground Water Level (GWL) at this area is 1.5 meter below the soil surface. The soil type is silty sand to sandy silt, with the unit weight between 1.617 to 1.837 g/cm^3. The calculation results, both with CPT and SPT, show that the soil layer did not experience liquefaction with earthquake magnitude Mw = 4.0. At Mw = 5.0, liquefaction occurs in most soil layers, except the 1.5-meter upper soil layer. On Mw = 6.0, almost all soil layers experience liquefaction. Evaluation of soil resistance to liquefaction using CPT and SPT gives results that are not much different.