Abstract: The accumulation of rock debris produced by mountain tunnel construction always causes resource waste and environmental damage. Therefore, the feasibility and practicality of partially replacing coarse aggregates in shotcrete by rock debris are examined based on a plateau tunnel project in the southwest China. Based on the determined benchmark experimental group of shotcrete mix proportions, indoor tests are conducted on the replacement rates of coarse aggregate by rock debris in shotcrete, 10%, 15%, 20%, 25%, 30%, and 35%, respectively, using the principle of unique variables. The tests include the slump, cohesion, water retention, compressive strength, flexural strength, etc. of shotcrete. Additionally, concrete spraying tests with different rock debris replacement rates and large plate tests of solid strength are conducted in the construction site. The indoor and onsite test results show that replacement rate of rock debris for coarse aggregates in shotcrete is better be controlled within 30%, which can guarantee the rebound rate of shotcrete in the tunnel arch and sidewalls. The large plate test further validates the recommended replacement rate.

Key words: rock debris, shotcrete, coarse aggregate, substitution rate