|
Abstract On the basis of reasonably simplified practical tunneling conditions，from meso-level structure of rock mass，the 2D model of rock chipping process induced by tunnel boring machine(TBM) disc cutters was established using particle discrete element method. The dynamic response mechanism of rock fragmentation induced by two cutters was studied；and the relationships of cracks，penetration and cutting force of rock mass were obtained. The optimum cutter spacing under common cutting depths was simulated，from which the relationship between cutter spacing and specific energy consumption under different cutting depths was analyzed. Then，the corresponding experiments were carried out to verify the rock dynamic fragmentation characteristics and optimum cutter spacing. Finally，the field TBM performance was taken to corroborate the conclusion. The results show that：(1) The change of cutting force with penetration is in good consistence with the jump crashing of rock；and the failure of rock follows the Griffith theory. (2) The breakage of rock mass is shear failure under small cutting depth，while the breakage of rock is caused by tensile stress under large cutting depth. When the cutting depth equals to 10 mm，the specific energy has obvious inflection point at the cutter spacing of 100 mm. The specific energy is achieved minimum at the cutter spacing of 60 mm when the cutting depth equals to 6 mm. The crack can?t penetrate rock when the cutting depth is less than 2 mm.
|
|
Received: 07 May 2012
|
|
|
|
2012, Vol. 31 
