Abstract: Through the laboratory experiment, the compaction performance, water stability, CBR of the weathered mica gneiss have been studied. Because of the high elasticity and extremely smooth surface, mica sheets cause the low ability of inlay and anti-cuts. It is easy for the surface layer of the subgrade to peel, loose and to rebound. Then the water stability is bad, the intensity is somewhat low, and the CBR value cannot achieve the intensity standard of the roadbed in the highway. Increasing the work of tamping, the compaction performance of the material cannot be improved obviously. For the construction of the bed, the static pressure is suitable avoiding dynamic pressure. The compaction performance of the material may be obviously improved; and the intensity of the material may be enhanced after improving it with the clay, the weathered soil or the cement. The reasonable admixture dosage of the modified material can be proposed from the engineering economic aspects.

Key words: subgrade, mica gneiss, weathered material, CBR