Study On Acoustic Emission Characteristics Of Rock Fragmented By TBM Cutter

Tunnel boring machine(TBM)has been widely used in the construction of underground engineering due to its efficiency,security,environment-friendly construction and less disturbance to surrounding rock.The rock fragmentation of TBM is a result of cutter-rock interaction: crack generates and propagates under the action of rolling cutter,then large chips are formed between two adjacent cutters.Study on the characteristics of rock fragmentation contributes to well understanding of cutter-rock interaction and improvement of rock breaking efficiency.In order to study acoustic emission(AE)characteristics of rock fragmented by TBM cutter,the mechanical rock fragmentation experimental platform of Beijing University of Technology was used,and acoustic emission system was employed for real-time monitoring.After debugging of acoustic emission acquisition parameters,the diameter of the disc cutter with a constant cross section is 17 inches(432mm)and the size of test granite rock sample taken from Beishan,Gansu Province of China,is 680mm×680mm×450mm.A series of tests with different penetration were conducted and AE signals were collected during the process.AE energy and AE energy rate were analyzed,and AE location calculated with Geiger algorithm based on AIC Criterion were demonstrated after signal de-noising using wavelet transform.The results show that AE energy rate has the similar change trend with normal force during the cutting process.AE energy increases with the growth of penetration,and can be applied to representation of the energy consumed in rock fragmentation.An approximate description of damage zone which is obtained by AE location shows the whole process of crack accumulation and propagation during rock fragmentation.