Rock drilling experiments with an Abrasive Suspension Swirling Jet (ASSJ) have been carried out under submergence. Results show that the ASSJ can improve rock drilling with 2.2 times increase in drilling-hole diameter and with 4-5 times increase in rock removal volume when compared with non-swirling jet drilling of rock under identical conditions. And with higher PAM concentration added to the fluid, the ASSJ can significantly increase drilling depth, especially when drilling at longer standoff distance. It is also shown that the mechanism of ASSJ drilling at medium pressure on hard rocks is the overall breakage of rock grains and the binding material, in which jetting abrasive particles play dominant roles. The bottom hole shape of rock drilling with the ASSJ under submergence looks like "V". The higher rock drilling efficiency of the ASSJ results from the swirling of the jet.
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