Study on Vibration Characteristics of Roadheader Cutting Pre-cracked Hard Rock

In order to reduce the problems of severe vibration and low reliability of the tunnel boring machine in hard rock excavation, mechanical pre-splitting technology is used to improve the cutting characteristics of the tunnel boring machine. The discrete element method is used to establish a rock wall model, and the mechanical expansion and cracking method is used to realize that the three-dimensional rock wall model produces cracks under this action. Using DEM-MFBD two-way coupling technology, the vibration characteristics of roadheader before and after pre-splitting are analyzed. The study found that when using a boring machine to carry out rock wall pre-splitting operations, the average load of the cutting head was 8.2% lower than that when no pre-splitting operations were carried out, and the average load in the three directions of X, Y, and Z were reduced by 11.7%, 3.5% and 7.7% respectively. The load fluctuation coefficient decreased from 0.0242 to 0.0213; Frequency domain analysis revealed that the maximum acceleration amplitude in the 20–30 Hz primary vibration band for the cutting head, cutting arm, and rotary table decreased by 14.7%, 8.7%, and 3.6% respectively compared to the non-pre-cracking condition. The vibration suppression effect exhibited a pattern of ‘cutting head > cutting arm > rotary table’. Consequently, mechanical pre-cracking technology reduces excavator vibration during cutting operations by diminishing rock wall strength. This holds significant importance for enhancing excavator operational reliability and provides valuable reference for excavator cutting of hard rock formations.