The interaction between the TBM cutters and the rock mass is the main factor in TBM tunneling.The rock damage characteristics under the cutters are directly associated with the cutting efficiency and rock fragmentatio...The interaction between the TBM cutters and the rock mass is the main factor in TBM tunneling.The rock damage characteristics under the cutters are directly associated with the cutting efficiency and rock fragmentation mechanism.Four sets of linear cutting tests were performed in this paper with various cutter spacing to obtain the cutter force and muck.Then,fluorescence experiments were conducted to evaluate the rock damage characteristics by sawing the rock samples after the tests.The findings reveal that the effect of cutter spacing on mean normal force increases gradually as penetration depth increases,but only affects mean rolling force for penetration depths exceeding 2.0 mm.The optimal cutting efficiency is achieved at an S/P of 20-60.The area ratio of the crushed zone and the crack dense zone decreases as cutter spacing increases while that of the crack sparse zone increases.Moreover,increasing the cutter force or cutting spacing at the same penetration depth expands the crack sparse zone,increasing the cutting efficiency.This study could provide ideas and data support for designing the TBM cutterhead and optimizing the TBM operation.展开更多
It is inevitable to cut reinforced concrete(RC)appeared in cross passage of city metro by cutting tools when constructing in densely populated area.The previous cutters employed to cut RC are insufficient and easily d...It is inevitable to cut reinforced concrete(RC)appeared in cross passage of city metro by cutting tools when constructing in densely populated area.The previous cutters employed to cut RC are insufficient and easily damaged,so a new polycrystalline diamond compact(PDC)cutter is used to solve this question.Based on the theoretical analysis of cutting mechanism,both circular and tapered PDC cutters with cutting edge angle of 90and negative front rack angle of 10are used to cut RC.The peeling and breaking patterns of cutting concrete are proposed,the nodular and grainy chips are the preferred modes in cutting steel bars.The LS-DYNA is employed to investigate the cutting performance in advance.The simulation results show that the average and peak cutting forces increase with the growth of penetration depth,cutting speed,and roundness,and subsequently the recommended penetration depth less than 1.2 mm is obtained to cut RC due to the existence of steel bars.Moreover,the linear cutting platform is adopted to investigate the force ability and damage state of PDC cutters.It is concluded that the cutting force increases abruptly and fluctuates heavily when cutting the coarse aggregates.The patterns occurred in both numerical and experimental results are generally similar.Notably,the steel bar is pulled out and the PDC cutter is damaged at the penetration depth of 0.8 mm,while a good cut occurs at the penetration depth of 0.3 mm.The tapered PDC cutter with a relatively low cutting force is prone to be broken compared with circular PDC cutter.It is suggested that the circular PDC cutter at the penetration depth of 0.3 mm should be used to cut RC in practical engineering.展开更多
基金supported by the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202400720)。
文摘The interaction between the TBM cutters and the rock mass is the main factor in TBM tunneling.The rock damage characteristics under the cutters are directly associated with the cutting efficiency and rock fragmentation mechanism.Four sets of linear cutting tests were performed in this paper with various cutter spacing to obtain the cutter force and muck.Then,fluorescence experiments were conducted to evaluate the rock damage characteristics by sawing the rock samples after the tests.The findings reveal that the effect of cutter spacing on mean normal force increases gradually as penetration depth increases,but only affects mean rolling force for penetration depths exceeding 2.0 mm.The optimal cutting efficiency is achieved at an S/P of 20-60.The area ratio of the crushed zone and the crack dense zone decreases as cutter spacing increases while that of the crack sparse zone increases.Moreover,increasing the cutter force or cutting spacing at the same penetration depth expands the crack sparse zone,increasing the cutting efficiency.This study could provide ideas and data support for designing the TBM cutterhead and optimizing the TBM operation.
基金supported by the Shanghai Science and Technology Development Funds(Grant No.20QB1401800)Xuzhou Science and Technology Plan Social Development Key Special Project(Grant No.SHFZZDZX20210017)Yunlong Lake Laboratory of Deep Underground Science and Engineering Project(Grant No.104023006).
文摘It is inevitable to cut reinforced concrete(RC)appeared in cross passage of city metro by cutting tools when constructing in densely populated area.The previous cutters employed to cut RC are insufficient and easily damaged,so a new polycrystalline diamond compact(PDC)cutter is used to solve this question.Based on the theoretical analysis of cutting mechanism,both circular and tapered PDC cutters with cutting edge angle of 90and negative front rack angle of 10are used to cut RC.The peeling and breaking patterns of cutting concrete are proposed,the nodular and grainy chips are the preferred modes in cutting steel bars.The LS-DYNA is employed to investigate the cutting performance in advance.The simulation results show that the average and peak cutting forces increase with the growth of penetration depth,cutting speed,and roundness,and subsequently the recommended penetration depth less than 1.2 mm is obtained to cut RC due to the existence of steel bars.Moreover,the linear cutting platform is adopted to investigate the force ability and damage state of PDC cutters.It is concluded that the cutting force increases abruptly and fluctuates heavily when cutting the coarse aggregates.The patterns occurred in both numerical and experimental results are generally similar.Notably,the steel bar is pulled out and the PDC cutter is damaged at the penetration depth of 0.8 mm,while a good cut occurs at the penetration depth of 0.3 mm.The tapered PDC cutter with a relatively low cutting force is prone to be broken compared with circular PDC cutter.It is suggested that the circular PDC cutter at the penetration depth of 0.3 mm should be used to cut RC in practical engineering.
