(General session) Rock Engineering / Mining technologies

[1110-19-04] Effect of Bit Spacing on Cutting Efficiency in Sequential Edge Chipping Tests

○JIACHENG SONG^{1[Student presentation: Doctoral course]}, Kimihiro Hashiba¹, Katsunori Fukui¹ (1. The University of Tokyo)

司会：奈良禎太（京都大学）

Keywords:undercutting, edge chipping test, bit spacing, button bit, point attack pick

Undercutting technology has gained increasing attention in rock excavation due to its potential to reduce cutting force and improve energy efficiency. However, the interaction between adjacent tool paths—particularly the influence of bit spacing on rock fragmentation—remains insufficiently understood. This study explores the effect of bit spacing on edge chipping performance under undercutting-like conditions using two tool types: a point attack pick and a button bit. Tests were conducted at several cutting distances from the nearest edge of two representative rock blocks: Sanjome andesite and Tage tuff. Bit spacing was defined based on the length L of the rock chip formed by the preceding loading event, simulating varying degrees of interaction between adjacent tool-induced fracture zones. A single edge chipping test and then sequential edge chipping tests at several spacings with reference to L were performed to examine both single and interaction effects. The aim of these tests is to identify the optimal bit spacing that maximizes cutting efficiency for each tool and cutting condition, and to clarify how rock type and tool geometry influence this spacing. Key performance indicators, including force–penetration curves, peak force, penetration depth, chip volume, and energy consumption, were extracted for quantitative analysis. The results provide new insights into damage interaction mechanisms in sequential undercutting and offer guidance for optimizing cutter layout and tool path design in mechanical excavation.