Liquefaction Susceptibility Zonation in Lempuing Subdistrict, Bengkulu City, Indonesia

Abstract

Zonation of liquefaction potential is the important thing in understanding the liquefaction impact on an area. The liquefaction Severity Index (LSI) method can be applied to determine the liquefaction vulnerability level. This paper presents a study of liquefaction using LSI method to compose the liquefaction vulnerability map in a coastal area of Bengkulu City i.e., Lempuing Subdistrict. This study was conducted by analyzing CPT data in Lempuing Subdistrict to obtain the Factor of Safety and the probability of liquefaction. Peak Ground Acceleration (PGA) was assumed as 0.5g, which refers to SNI 03-1726-2012. Furthermore, the value of liquefaction probability and factor of safety obtained was analyzed to obtain LSI index and adjusted to the specific categories i.e., very low (0<LSI<15), low (15<LSI<35), moderate (35<LSI<65), high (65<LSI<85), and very high (85<LSI<100). Based on the analysis result, Lempuing Subdistrict was categorized as a very high to the very low susceptible area to liquefaction. The very high susceptible area was located on the eastern Lempuing Subdistrict bordering to the Gading Cempaka Subdistrict. The high susceptible area was located on the northern Lempuing Subdistrict bordering the Tanah Patah Subdistrict. Moderate to very low susceptible areas were located in the middle, west, and south of Lempuing Subdistrict.

Liquefaction potential analysis based on standard penetration test data at irrigation canals in Sibowi Area-Central Sulawesi Province

“…As a recap of the calculation of the LPI value at each depth that undergoes liquefaction and a description of the vulnerability level category, the SIB.02 point has an LPI index of 4.10 on a moderate scale because the thicker the layer that undergoes liquefaction, the higher the LPI index. The LPI scale is representative and is used to assess the level of potential liquefaction in an area because it can group the level of vulnerability into each category, facilitate data analysis, and clarify the information contained in the data [20]. Micro-zonation map of liquefaction vulnerability levels based on the calculation of the LPI values in the main irrigation canalss in the Sibowi area described in Figure 7.…”

“…This Equation gives a depth limit of up to 20 m because the given function gives an index value that tends to shrink close to zero at depths up to 20 m and a higher value closer to the surface. Calculation of the LPI index using Equation ( 16) with conditions and criteria in Equation ( 17) up to Equation (20).…”