Distinct element modeling of rock fragmentation by TBM cutter

Abstract

There are many tunneling engineering practices all over the world, in which the tunnel boring machine (TBM) is a main construction way due to its serial advantages such as safety, high efficiency and environment-friendly. TBM cutters are the crucial parts, whose interaction is one of main factors to affect the efficiency of TBM. In this article, a two-dimensional (2D) distinct element method (DEM) code, PFC2D, incorporating an improved microscopic bond contact model proposed for rock, is used to investigate the macro- and micro-mechanical responses during the invasion process of cutter. The influences of the cutter’s geometrical parameters, that is, cutter width and cutter angle, and confining pressure, are investigated in study. The DEM results show that: (1) the whole cutter invasion process can be described into three stages: loading stage, unloading stage and residual leaping broken stage; (2) cutter width has more influence on the capability and efficiency of TBM than cutter angle, and both the capability and efficiency of TBM are the best when confining pressure ratio equals to 0.1; (3) consistent with microscopic information, the analyses on specimen failure modes show that cutter with large width and small angle is helpful to rock fragmentation.