Development and Evaluation of a Portable In Situ Direct Shear Testing Device for Field Applications

Soil sample disturbances leading to a decline in sample quality have long been a concern in geotechnical investigations. This research addresses these issues by developing and evaluating a portable in situ direct shear testing apparatus for field assessments of soil shear strength. The study was conducted in a landslide-prone area in Margawati village, Garut district, West Java, Indonesia, and was motivated by the limitations of conventional laboratory methods, particularly their susceptibility to sample disturbance. Multiple in situ tests were carried out to assess the reproducibility of shear strength measurements under varying normal stress conditions. The apparatus was tested with both in situ and reconstituted samples, allowing for a comparative analysis with conventional laboratory direct shear tests. The results indicated that in situ tests consistently yielded slightly higher peak shear strength values than laboratory tests, likely due to the minimal disturbance of natural soil samples. This research highlights the importance of considering sample disturbances in geotechnical testing and suggests that in situ testing offers a valuable complement to laboratory methods, providing more reliable data for geotechnical analysis and design. The findings have significant practical implications for field engineers, particularly in slope stability analysis, foundation design, and landslide risk assessment. The portable nature of this device makes it especially valuable for challenging terrain where conventional testing equipment cannot be deployed, and it can be adapted for various soil conditions, including sandy soils, clayey soils, and areas with fluctuating water tables. The findings emphasize the potential of the in situ direct shear apparatus to significantly enhance the accuracy of soil shear strength evaluations, particularly in field settings where sample integrity is critical.