Liquefaction potential analysis in Palu Bay area

Sulawesi Island has a Palu Koro Fault that actively moves with a high displacement magnitude but low seismicity. On 28 September 2018, at 18:02 local time, an earthquake occurred in Palu Koro Shear Fault. The field investigations along the Palu coast revealed new evidence regarding the extensive liquefaction in these areas, both inland and coastal land. The research command area was located in the Palu Bay coastal area, the Province of Central Sulawesi. The data used was in the form of the Standard Penetration Test of the area, and the potential liquefaction analysis was carried out using the simplified procedure method. Furthermore, to determine the level of liquefaction potential, Liquefaction Potential Index was applied. Geological observations showed that the soil condition in the Palu Bay area was dominated by non-cohesive soil (sand). Based on the liquefaction potential analysis, it was indicated that most of the eastern region of the Palu Bay area showed no liquefaction potential. On the contrary, the western and southern parts were indicated to have liquefaction potentials. The Liquefaction Potential Index analysis results showed that the western and southern areas were dominated with extremely high liquefaction potentials. Meanwhile, in the eastern area, it was extremely low.

Can geotechnical liquefaction indices serve as predictors of foundation settlement?

Geotechnical liquefaction indices, such as the liquefaction potential index, are commonly used as proxies for the risk of liquefaction-induced damage at site or regional scales. However, these indices were developed based on surficial manifestations of soil liquefaction in the free field, and, as such, they have been shown to correlate better with land damage than foundation damage. This study evaluates the ability of three geotechnical liquefaction indices to predict foundation settlement on liquefiable soils, as compared to both conventional ground motion intensity measures (IMs) and the term for site and ground motion effects in a probabilistic model specifically developed for foundation settlement. A new metric for the predictive ability of these measures, skill, is proposed to quantify the total uncertainty in settlement predictions using a given measure. The Ishihara-inspired liquefaction potential index is found to be the optimum index, and cumulative absolute velocity [Formula: see text] as predicted on outcropping rock is found to be the optimum IM. However, although both measures are regionally applicable, neither outperforms the site term from the probabilistic settlement model, which was developed using the same numerical database used in this study.

Mapping the liquefaction potential index (LPI) in Ratu Agung subdistrict, Bengkulu City, Indonesia using the shear wave velocity approach

On the 4th of June, 2000 and 12th of September, 2007, Ratu Agung Sub-district, Indonesia experienced significant damage due to liquefaction after the earthquakes. Therefore, this study aims to determine the Liquefaction Potential Index in the area. Data of shear wave velocity (Vs) was collected using the Multichannel Analysis of Surface Wave (MASW) method. The measurement location was set up on a grid of 32 observations points with field investigations. Furthermore, Simplified Procedure and LPI methods were used to measure the soil liquefaction potential and vulnerability level. The results showed that the value of shear wave velocity in the Ratu Agung Subdistrict ranged from 102 m/s to 442 m/s. Also, the liquefaction vulnerability levels varied from high to very high categories due to the maximum soil acceleration and conditions dominated by loose sand, as well as the influence of different geological formations in the zone. In conclusion, an empirical equation was successfully proposed to analyze the liquefaction vulnerability.

Liquefaction Analysis Based on Liquefaction Potential Index Method in Prambanan Temple Complex of Jogjakarta

Prambanan Temple is a cultural heritage located in Jogjakarta. Tectonically, the Special Region of Jogjakarta and its surroundings are an area with a fairly high level of seismic activity in Indonesia. Geotechnically, the soil in Jogjakarta is sandy with similar gradation. The thickness of the sand ranges from -50 m to -60 m. Whereas, the ground water level is located at a depth of -12 m during dry season and in rainy season, it rises from -6 m to -4 m. The impact of soil types and the high Ground Water Level (GWL) allow it for liquidation to occur during an earthquake. This study was conducted using liquefaction analysis, through Liquefaction Potential Index (LPI) method with ground water level variations. Before analyzing the liquefaction using LPI method, Peak Ground Acceleration (PGA) methods were used, and analysis could then be done through Cyclic Resistance Ratio (CRR) and Cyclic Stress Ratio (CSR) to obtain safety factors and the Liquefaction Potential Index analysis was then conducted. To analyze this liquefaction, earthquake data from 2004 to 2019 and the results of the SPT field test at the Prambanan Temple were needed. From the liquefaction potential analysis through Liquefaction Potential Index (LPI), the results showed that in CSR Seed & Idriss (1971) and CRR Tokimatsu & Yoshimi (1983), GWL 1 m at depths from 4.5 m and above, the potential of liquefaction occurrence was high. The largest PGA value was obtained based on the Matsuchka (1980) method on May 26, 2006 which was 0.102.

The Implementation of Ground Response Analysis to Quantify Liquefaction Potential Index (LPI) in Bengkulu City, Indonesia

Bengkulu City is one of the areas vulnerable to earthquakes in Indonesia and several studies have shown the city experienced a unique phenomenon called liquefaction during the Mw 8.6 Bengkulu-Mentawai Earthquake. This event has initiated a step by step intensive study on earthquake in the area but previous studies are generally limited by the use of site investigation data to empirically analyse liquefaction potential and those that used advance method such as the seismic wave propagation model are rare. This means the level of liquefaction damage in the study area is not totally understood, therefore, this research focused on implementing the ground response analysis to quantify the Liquefaction Potential Index (LPI) using several areas in Bengkulu City in order to determine their vulnerability. The process involved the collection of several site investigation data including boring log and shear wave velocity profile as well as a desk study to determine the geological condition of the observed sites. Moreover, a non-linear seismic ground response analysis was conducted to obtain maximum ground surface acceleration (amax) parameter which was further used to analyse the liquefaction potential in the study area. The results showed several sites have the potential to experience liquefaction during earthquakes. The method applied was considered successful and the results are expected to be implemented for city development. Furthermore, the framework is recommended for adoption in investigating the liquefaction in other areas.

Correlation of Soil Liquefaction Potential Index and Geotechnical Properties for Baghdad City, Iraq

This paper comprises the study and analysis of Baghdad soil for eight geotechnical properties, which extract from field experiments of 630 boreholes with depth taken to 30m and representing 200 sites. Soil investigation reports are composed from altered laboratory tests. The soil layers. Divided into each 2m, which means 15 studied’ layers and soil properties values were embraced and submitted. in tables and charts which have been analysis-using excel2013 and check the charts using curve expert program to get the relationships between the properties values and the factor of safety against liquefaction. The correlations between liquefaction potential represented by the safety factor and soil properties for the available data of 200 sites in Baghdad have been studied and statistically studied ‘to evaluate both of soil properties and liquefaction potential index. Eight factors affecting liquefaction have been correlated with factor of safety for all earthquake magnitudes (ML= 4to 6.5 with 0.5 interval). These factors are, groundwater table, fill layer depth, standard penetration test (SPT- N value), saturated unit’ weight (γ), Relative density (Dr %), soil fractions (clay, silt and sand %), and total settlement (Stot). For better correlations, the same factors have been correlated with safety factor but for each earthquake magnitude alone.