Abstract: In order to investigate the fracturing characteristics of jointed rock mass subjected to openended microwave and estimate the efficiency of microwaveassisted rock breakage by roadheader, tests are conducted on an artificial rock mass under openended microwave. The artificial rock mass (1.5 m×1.5 m×0.3 m) is erected by nine diorite blocks (0.5 m×0.5 m×0.3 m) to simulate a working face with a 0.5 m joint spacing. The rock mass is treated point by point at a spacing of 15 cm and 20 cm, respectively, using a 6 kW microwave source and an openended antenna. The influences of radiation spacing and the distance from radiation to joint on the fracturing of the artificial rock mass are analyzed. The equivalent rock quality designation (RQD) of the microwave treated rock mass is then calculated and the improvement in the rock breakage efficiency of a 200 kW roadheader is estimated based on the Bilgin empirical model. The Crechar abrasivity indexes (CAI) of diorite with and without microwave treatment are measured. The results show that the equivalent RQD is reduced from 100 to 62 and 50 at an radiation spacing of 15 cm and 20 cm, [HJ2.1mm]respectively, and the CAI is reduced from 4.0 to 3.4 at the radiation spacing of 20 cm. Microwave treatment can significantly enhance the rock breakage efficiency of the roadheader by 170%~280%, and reduce the tool wear by 11%.

Key words: open-ended microwave, rock mass, rock quality designation, rock breakage efficiency, tool wear