Grusbackfill

Grusbackfill is a backfill material consisting primarily of coarse-grained gravel or crushed rock (grus) used to fill excavations in civil engineering and construction. The material is selected for its high permeability, dimensional stability, and ability to transmit loads while allowing drainage and reducing pore pressure around structures. The term is used in Scandinavian engineering contexts, with “grus” meaning gravel.

Typically composed of well-graded gravel or crushed rock with limited fines, grusbackfill is placed in layers and compacted with appropriate equipment to achieve a specified density. The exact specification varies by project and jurisdiction, but installers aim for sufficient compaction to minimize settlement and piping while avoiding excessive necking or segregation of larger particles. In frost-susceptible soils, the material is often used with a protective filter or geotextile to prevent fine migration.

Drainage is a key feature of grusbackfill; its permeability allows water to flow away from the structure, reducing hydrostatic pressure. Because of this, grusbackfill is frequently used in combination with drainage layers and backwater protection around basements, under roadbeds, or behind retaining structures.

Health, safety, and environmental considerations include using natural rock sources free from deleterious materials and ensuring compliance with local standards for grain size distribution and compaction. Grusbackfill offers a balance of load-bearing capacity and drainage, but improper grading or inadequate filtration can lead to settlement or piping problems.

See also: backfill, drainage gravel, gravel backfill.