The effects of apparatus size and surface area of charge on the impact strength of rock

Abstract Fundamental work into the effects of apparatus size on the impact strength of rock is reported. A series of tests using three sizes of a ‘Protodyakonov’ type drop hammer are carried out and the resulting values of impact hardness are compared. The effects of size of charge on the impact hardness of rock are investigated using crushed rock fragments. An empirical equation, containing impact hardness, Shore Hardness and operating pressure, is suggested for predicting the performance of percussive drills.