The objective of this study is to investigate the correlation between Standard Penetration Test (SPT) results and the output of LiqIT software in evaluating soil liquefaction potential. The methodology is structured into three main phases: data collection, analysis, and correlation assessment.
1. Data Collection
The first phase of the study involves the collection of SPT data from various sites with known liquefaction potential. The SPT data includes the N-values (blow counts) at different depths for each site. The selection of sites is based on their susceptibility to liquefaction as reported in previous geotechnical studies and seismic hazard assessments (Seed et al., 1983; Boulanger & Idriss, 2004).
The SPTs are conducted following the standardized procedures outlined by Skempton (1986) to ensure consistency and reliability of the results. Specifically, the tests are performed using a standard split-spoon sampler and a 63.5 kg hammer with a free fall of 760 mm, in accordance with ASTM D1586-11. The number of blows required to drive the sampler through three successive 150 mm intervals is recorded, with the N-value being the sum of blows for the last two intervals.
2. Liquefaction Potential Analysis Using LiqIT
In the second phase, the collected SPT data is input into the LiqIT software for liquefaction potential analysis. LiqIT uses empirical correlations, such as those developed by Seed et al. (1983) and Idriss & Boulanger (2006), to calculate the factor of safety against liquefaction for each layer of soil at the test sites.
The analysis in LiqIT is performed by first defining the soil profile for each site, including parameters such as soil type, unit weight, and groundwater table depth. The software then simulates seismic loading scenarios based on historical earthquake data and site-specific ground motion records. The calculated factor of safety is compared across different soil layers to assess the overall liquefaction risk (Idriss & Boulanger, 2006; Sao-Jeng et al., 2018).
3. Correlation Assessment
The final phase involves a statistical analysis to assess the correlation between the SPT N-values and the corresponding factor of safety against liquefaction computed by LiqIT. The primary objective is to determine the strength and nature of the relationship between these two variables.
The correlation is analyzed using regression analysis, with the SPT N-values as the independent variable and the LiqIT factor of safety as the dependent variable. Various statistical metrics, such as the coefficient of determination (R²) and p-value, are used to evaluate the significance and accuracy of the correlation (Alamdari et al., 2022).
Additionally, the study investigates any deviations or anomalies in the correlation, particularly in cases where LiqIT predictions do not align with empirical expectations based on SPT data. Such anomalies are further examined to identify potential influencing factors, such as soil heterogeneity or differences in seismic loading conditions (Devi et al., 2018).
4. Validation and Sensitivity Analysis
To validate the findings, a sensitivity analysis is conducted by varying key input parameters in both the SPT and LiqIT analyses. This includes adjusting the assumed ground motion parameters and soil properties to assess their impact on the correlation results. The validation process ensures that the correlation established is robust and applicable across different geotechnical conditions (Seed & Idriss, 1971).