Abstract: For the challenges associated with silty-soil subgrade—including difficulty in achieving adequate compaction and deviations in compaction-degree test results—this study examines a construction project involving a silty-soil embankment. Through particle-size analysis, light compaction tests, and related laboratory experiments, key parameters such as grain-size distribution, Atterberg limits, and maximum dry density were obtained. The sand-cone method was adopted as the in-situ testing technique for evaluating subgrade compaction. A systematic analysis was conducted on the application of the sand-cone method, covering its working principle, sand-cone apparatus, selection of calibration sand, and operational procedures. The method’s applicability and the actual compaction performance of the subgrade were verified using field test results. The findings indicate that the maximum particle size of the silty soil in the test section is less than 13.2 mm; therefore, a 10 cm diameter sand cone is appropriate for compaction testing. Calibration sand with a particle size of 0.15~0.3 mm yields the smallest dispersion in calibration results. As the number of roller passes increases, the degree of compaction also increases, though the incremental gain per pass gradually decreases. After sufficient rolling, the achieved compaction meets the requirements for subgrade performance.

Key words: Silty Sand Embankments, Sand Fill Method, Sand Filling Cylinder, Degree of Compaction