Abstract: Transition material is crucial to the deformation compatibility of high gravelly soil core rockfill dam. The gradation of transition material is required to be continuous, and the maximum particle size should be less than 300 mm according to specification. Blasting excavation is quite difficult because the average block size (d₅₀) is small (only 15 mm-55 mm), especially when the source material is granite or other hard rocks. By appropriately increasing the unit explosive consumption, arranging reasonable hole distance between gun holes, and adopting tinny difference sequence blasting network, the transition material of Changheba hydropower station could be directly obtained by blasting excavation method. According to the test results, a method is proposed to correct the uneveness index of Kuz-Ram model. To control the block size of the transition material blasting excavated from sound rock, the blasting area should be well chosen, and high power emulsion explosive, high-precision detonator and optimized blasting parameters could be adopted. This research provides reference for blasting excavation of rockfill dam material which is strictly required in particle size distribution.

Key words: transition material, blasting, Kuz-Ram model, unit explosive consumption, Changheba hydropower station