Correlation of CPT, SPT, and ERT data for a better understanding of soils condition: A case study in SPG Merbau, South Sumatra

Abstract Soil investigation at a project site is crucial for understanding soil properties and layers, which is essential for designing a robust foundation and preventing future construction failures. This study evaluates the relationship between Cone Penetration Test (CPT), Standard Penetration Test (SPT), and Electrical Resistivity Tomography (ERT) methods at the Merbau Gas Gathering Station (SPG) in South Sumatra, Indonesia. The methods used include CPT for determining geotechnical parameters and soil characteristics, SPT for measuring soil consistency through blow counts, and ERT for assessing soil resistivity, which correlates with soil type and moisture content. CPT and SPT results exhibit a very strong correlation (R 2 = 0.9962 at Location 01 and 0.9839 at Location 02), indicating that CPT’s qc values are reliable predictors of SPT blow counts. In contrast, the correlation between ERT resistivity and CPT is moderate, with R 2 values of 0.5564 and 0.6465 at the two locations, suggesting a moderate negative relationship where higher resistivity corresponds to lower qc values. The correlation between ERT resistivity and SPT is weaker at Location 01 (R 2 = 0.0882) but stronger at Location 02 (R 2 = 0.7114), indicating that resistivity has a more significant influence on SPT results at Location 02. In conclusion, while CPT and SPT show strong correlation and consistency in soil characterization, ERT provides supplementary data whose influence varies by location. This analysis underscores the complexity of integrating different geotechnical testing methods and the importance of considering site-specific conditions when interpreting subsurface data.