Rock Mechanics and Rock Engineering

, Volume 45, Issue 5, pp 837–849 | Cite as

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

Original Paper

Abstract

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 

List of symbols

A

Contact area of indenter

Ac

Total crack areas

α

Internal crack angle

B

Brittleness

c

Constant coefficient

\( \tilde{D} \)

Average diameter of assemblage

δ

Arbitrary position angle

E

Young’s modulus

E

Young’s modulus for plane strain

Fc

Crack-related force

Ft

Peak load of indenter

GIC

Strain energy release rate for mode I

KIC

Fracture toughness for mode I

Kn

Normal stiffness

ks

Shear stiffness

μ

Friction coefficient

v

Poisson’s ratio

p

Penetration of disc cutter

θ

Contact angle between disc and rock sample

\( \dot{\theta } \)

Angular velocity

H

Material hardness

L

Unit length

Nc

Number of debonded particles

rc

Chipping radius

s

Spacing of disc cutter

σc

Compressive strength

σt

Tensile strength

t

Tip width of disc cutter

Tn

Normal bonding

Ts

Shear bonding

τ

Shear strength

Ut

Total energy

Us

Strain energy

Uf

Friction energy

va

Tangential velocity

vax

x Component of tangential velocity

vay

y Component of tangential velocity

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.PB Geotechnical and Tunneling, Parsons Brinckerhoff Inc.New YorkUSA

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