Study and Application of Gneiss in Preparation of Graded Gravel Base Material

Because a lot of abandoned tunnel slag is produced in road engineering construction and the using rate is low, based on the Shijiazhuang section of the Xifu section of the Taihang mountain highway, the lithology of abandoned tunnel slag is analyzed. Its physical and mechanical properties are evaluated by laboratory tests, and its feasibility as an aggregate of graded gravel base is demonstrated. The gradation of the crushed stone mixture is composed of fine aggregate limestone mixed with abandoned tunnel gneiss, and the related characteristics are studied. The results show that the strength of the mixture could be significantly improved by replacing the fine aggregate with limestone, and the California load ratio (CBR) value of the crushed stone mixture with 0 similar to 3 mm and 3 similar to 5 mm limestone could reach 377.2%, and the unconfined compressive strength could reach 1.2 MPa.