Soil Resistivity Assessment and Correlation on Geotechnical Properties of Backfill Soils for Substation Grounding
System in Thailand

This study investigates the relationship between soil resistivity and geotechnical
properties of backfill soils used in substation grounding systems in Thailand. The
study collected soil samples from four substations across different regions of Thailand
and conducted various fields and laboratory tests to measure parameters such as
water content, activity index, and soil resistivity. Regression analysis was performed
to examine the relationship between these parameters. The results showed an exponential
correlation between geotechnical properties, such as water content and activity
index, and soil resistivity. The coefficient of determination (R2) values for the
correlation between soil resistivity and water content were determined to be 0.8277
and 0.8926 for compaction levels of 85% and 95%, respectively. The R2 values of
0.9269 and 0.8815 demonstrate a strong relationship between soil resistivity and
activity index. Additionally, multiple relationships between resistivity, water content,
and soil activity index were investigated, demonstrating a strong correlation (R2
values are 0.9218 and 0.9345 for 85% and 95% compactions, respectively). Based
on these findings, a chart was proposed for estimating backfill soil characteristics
using resistivity measurements and activity values. This research provides valuable
insights for engineers involved in substation design by allowing them to assess substation
grounding systems accurately based on resistivity analysis.