Study on Water Sinking Sand Method for Sand Backfilling

Abstract

Based on the partial culvert backfilling project of the JI-HEI Expressway construction in Heilongjiang Province, China, this study investigates the impact of the physical and mechanical characteristics of backfill sand on the compaction degree of sand backfilled using the water sinking sand method. The research includes on-site sampling of the backfill sand, indoor geotechnical testing, water sinking sand method backfilling, and compaction degree testing of the backfilled material. The study explores the particle size distribution, moisture content, density, compaction characteristics, California Bearing Ratio (CBR), rebound modulus, and other physical and mechanical attributes of the sand. It also delves into the water sinking sand method backfilling process and the compaction degree of the soil layer after backfilling. The findings indicate that the backfill sand in this project is a loose, medium to coarse sand with a low moisture content. Its maximum dry density is approximately 1.92 g/cm³, and the optimal moisture content is around 8%. When the sand reaches maximum dry density, both CBR value and rebound modulus reach their highest levels. The reduction in rebound modulus of the sand is not significant, suggesting good water stability. The actual compaction degree of the soil layer achieved through water sinking sand method backfilling ranges from 96% to 99%, meeting the compaction requirements of conventional engineering practices. The application of the water sinking sand method for sand backfilling is characterized by its simplicity, high construction efficiency, and quality assurance, making it suitable for widespread adoption in future engineering projects.