A Study of Optimal Rock-Cutting Conditions for Hard Rock TBM Using the Discrete Element Method

J. Oh, T. Moon
Rock Mechanics and Rock Engineering
Brittleness, dem, LCM, Multi-indentation, s/p ratio, TBM

The efficiency of TBM performance affected by the specific s/p (s: spacing and p: penetration) ratio of the disc cutter is a research issue in demand. This article presents a multi-indentation simulation using discrete element method (DEM) analysis to study the optimal rock-cutting phenomena in terms of the interaction of the s/p ratio with intact rock properties. The multi-indentation simulation attempts to represent a linear cutting machine (LCM) test, which is a full-scale test for evaluating the optimal rock-cutting condition and measuring required reaction forces based on the intact rock condition in general practice.

A governing equation relating mechanical rock properties with geometric characteristics for the optimal rock-cutting condition is derived by the numerical simulation, and its performance is evaluated with the result of the laboratory LCM tests. The results of simulations and real LCM tests show that the effective rock-cutting condition corresponding to the minimum specific energy can be estimated by an optimized s/p ratio, which, in turn, is linearly proportional to the square of the material brittleness, B 2, and cutter tip width, t (i.e., s/p = cB 2 t, where c is coefficient). The limitation of the numerical simulation associated with the sample preparation is also discussed.

Keywords: LCM, DEM, Multi-indentation,  s/p ratio, TBM, Brittleness

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