Electrical Resistivity Tomography (ERT) technique has been widely used conventionally to monitor slope instability; however, a detailed study to validate ERT models with geotechnical properties for monitoring of slope instability is still rare. The objective of this work was to evaluate soil water conditions in gravelly sand soil that influences slope instability. The ERT investigation was conducted on a 60 m survey length with 1.5 m electrodes space to obtain subsurface geological structures and geotechnical laboratory tests, and experiments were carried out to obtain soil engineering properties for validation of the ERT model results. Our results revealed three geological zones namely: saturated, weathered granite, boulders and floaters, and resistivity values of 1–800 Ωm, 1,200–4,000 Ωm, and >4,000 Ωm, respectively. The saturated zones were characterized by subsidence during dry season and possible collapsed structures of boulders and floaters during prolonged heavy rainfall. The analyzed ERT models revealed that the slip surface of a potential landslide may occur at the boundary between the saturated and weathered granite zones within 3.0 m depth. The analyzed geotechnical properties also confirmed the ERT result because the potential landslide sliding surface was delineated within 3.0 m depth at the boundary between gravelly sand with a lowest angle of internal friction of 30° and a cohesion of 8 KPa, which was easier to destroy, and silty sand with a high angle of internal friction of 33.8° and a cohesion of 12.7 KPa, which was more difficult to destroy. These findings are very fundamental in shaping the earth's surface, especially in the formation of landscapes.

Strength and deformation parameters of compacted soil are known to be related to soil type and moisture. However, little attention has been directed towards understanding the influence of compaction energy on soil type and moisture. This study considers the effect of different compaction energy on certain geotechnical properties of Kaolin and Laterite soil. This paper describes a laboratory study conducted to evaluate the relationship between soil type, soil moisture content with different compaction energy and strength characteristic. Specimens were compacted with impact energy at levels of 596 kg/m³(Standard Proctor) and 2682 kJ/m³ (Modified Proctor) over a wide range of moisture contents to determine dry unit weight, and Unconfined Compression Strength Test (UCS). Result shows that compaction energy is an important factor in determining soil strength that should be considered during the planning phase of any earthwork construction operation.

This paper evaluated the influence of Standard Penetration Test (SPT) correction factors, namely the hammer energy efficiency, borehole diameter, drill rod length, and sampling method, on the correlations between SPT resistance (SPT-N) and undrained shear strength (Su). Comparisons were made between new equations (with and without SPT corrections), which were derived from soil data collected from Penang Island, Malaysia. The coefficient of determination, Absolute Average Relative Error, Standard Deviation, and Analysis of Variance (ANOVA) were employed as the basis for the assessments. Finally, a comprehensive analysis was carried out to evaluate the relationship between uncorrected ratio (Su/N) or corrected ratio (Su/N60) and Plasticity Index (PI)/Liquidity Index (LI). Based on the results, all correction factors recorded a significant impact on the estimated Su, as the ANOVA calculation suggested that the borehole diameter correction was the most statistically significant. Furthermore, the Su/N and Su/N60 exhibited increasing trends with increased PI and LI, which may be attributed to the soil’s state and behaviour. Additionally, cubic regression is the best-fit equation to correlate the parameters. In summary, this study provided new insights into the influence of correction factors, which can be used to improve the accuracy of the empirical correlations and engineering designs.

The groundwater contamination from petroleum by-products represented in Light Non-Aqueous Liquid (LNAPL) under groundwater table fluctuations has become a serious environmental problem. For this reason, developing a rapid response strategy incorporating experimental characterization of LNAPL distribution trajectories is crucial for assessing the threats of LNAPL contaminants in the subsurface environment. In this study, the influence of various LNAPL spills in a porous medium under dynamic groundwater conditions was investigated using the Simplified Image Analysis Method (SIAM). Single and intermittent LNAPL (diesel) spills of total volume (400 and 800 ml) were examined in a river sand ‎two-dimensional tank (70 cm × 70 cm × 3.5 cm) under the effect of groundwater table fluctuation. The results indicated that the contaminant was distributed above h=28 cm in the 400 ml LNAPL spill. However, it migrated below h=28 cm, and its saturation reached 36% when the LNAPL volume raised to 800 ml. The LNAPL saturation in the case of four LNAPL intermittent spills was more evenly distributed through the tank depth than in the cases of a single spill of 800 ml and two intermittent spills of 400 ml. Furthermore, LNAPL migrated to a larger depth in the system (h=18.5 cm) only in the case of four LNAPL intermittent spills and under groundwater table fluctuation, which poses a significant threat to the groundwater. This study highlights the importance of the effect of various LNAPL spills under dynamic groundwater conditions, which can offer valuable guidance for developing remediation schemes. Doi: 10.28991/CEJ-2025-011-01-017 Full Text: PDF