Influence of Matric Suction on Shear Strength and Road Stability: A Case Study of Lateritic Soil in Kanchanaburi

Abstract

Lateritic soil is a common material widely used in road construction in Thailand, especially in regions with significant moisture variations, which influence the shear strength and stability of roads. This study investigates the effects of suction on the shear strength and stability of roads constructed on lateritic soil from Phanom Thuan District, Kanchanaburi Province. Direct shear tests were conducted under suction values of 10, 30, and 50 kPa with 3 samples per case with suction controlled using the Axis Translation Technique. The experimental results indicate a significant increase in the shear strength of the soil with higher suction levels. The shear strength parameters obtained were utilized to analyze the stability of a 2-meter-high road embankment using the Extended Mohr-Coulomb equation to calculate the Factor of Safety (FOS). The analysis revealed that higher suction levels enhanced the FOS of the road, increasing from 6.8 at 10 kPa suction to 10.3 at 50 kPa suction. This highlights the positive impact of suction on road stability. The findings from this study can be applied to the stability assessment of roads in areas with significant moisture variations, providing practical insights for construction and maintenance.