Effects of Moisture Content, Compaction Energy, Particle Gradation, and Rainfall-Induced Wetting on the Compaction and Settlement Behavior of Coarse-Grained Soils in High Embankments: A Malaysian Case Study

Abstract

High embankments constructed from coarse-grained soils play an important role in transportation and infrastructure development, particularly in projects requiring substantial elevation changes. The deformation behavior of such embankments is governed by the combined effects of particle gradation, moisture condition, compaction level, embankment height, and stress-dependent soil compressibility. These factors are of particular significance in tropical regions, where seasonal rainfall and repeated wetting–drying cycles can modify the hydraulic and mechanical characteristics of compacted fill materials. This study presents an integrated evaluation of the compaction and settlement behavior of coarse-grained soil used in high embankments under Malaysian climatic and engineering conditions. The analysis incorporates particle-size characterization, heavy compaction testing at nominal moisture contents of 2%, 4%, 6%, 8%, and 10%, compression-modulus measurements under vertical stresses ranging from 100 to 400 kPa, and finite-element simulations conducted for different compaction levels and embankment heights. The investigated material consists predominantly of coarse particles, with more than 80% of the particles falling within the 2–20 mm size range and a maximum particle size below 40 mm. The compaction analysis indicates an optimum moisture content of 6.2% and a maximum dry density of 2.13 g/cm³. A strong relationship is identified between compression modulus and degree of compaction, expressed as E_s = 1727.9x² − 2958x + 1308.8, with R² = 0.96, where x denotes the degree of compaction. Finite-element results demonstrate close agreement with the corresponding settlement calculations, with differences of approximately 2% for embankment-fill compression and 5% for foundation settlement. Parametric simulations for compaction degrees ranging from 85% to 100% and embankment heights between 5 and 40 m show that settlement increases nonlinearly with embankment height, while the influence of compaction quality becomes progressively more pronounced as embankment height increases. Moisture condition is also identified as an important state variable in assessing the potential effects of rainfall-induced wetting under tropical conditions. Since rainfall intensity and duration are not independently quantified within the analysis, their effects are considered through the climatic and moisture-state interpretation rather than through direct rainfall calibration. The findings provide an integrated engineering basis for assessing the performance of high coarse-grained embankments in Malaysia and support the coordinated consideration of compaction control, moisture management, particle gradation, drainage conditions, and settlement prediction in tropical earthwork design.