Experimental Study of a Novel Composite Rock–Drilling Process and Energy Consumption Characteristics for Cutting and Reaming Damaged Surrounding Rock

In response to the limitations of the existing drilling processes in mining operations, a novel composite rock drilling process is proposed. This process involves drilling a center hole into a rock, followed by cutting and reaming the surrounding rock using a custom-made experimental impact drilling and roller-cone reaming bench. In this study, the cutting characteristics and energy consumption of the composite rock drilling process were analyzed based on drilling and reaming test data. The experimental results indicated that during the cutting and reaming processes on the damaged rock surrounding the center hole drilled with impact loads, both the cutting force and cutting torque decreased with increasing impact loads. The energy consumption of composite rock drilling decreased with an increase in the impact power, and this reduction was closely related to the impact power and diameter ratio (impact drilling hole diameter/roller-cone cutting and reaming hole diameter). Compared with roller-cone drilling without a center hole, the composite rock drilling process significantly reduced the comprehensive energy consumption of drilling. For composite rock drilling under low and medium-impact loads, the diameter ratio was between 1.2 and 1.3, and the comprehensive energy consumption was lower. Under high-impact loads, the diameter ratio was between 1.3 and 1.4, resulting in lower comprehensive energy consumption. These experimental results can aid in determining a reasonable reaming range for the composite rock drilling process and provide a basis for the structural design of composite rock drilling tools.