The Experimental Study Of Beishan Granite Crack Propagation Mode Under Tbm Disc Cutter

Tunnel boring machine has been widely used in underground constructions in the world since the mid-1950 s, whice has advantages of friendly construction environment, high speed of construction, little disturbance of the surrounding rock and significant economic benefits of long tunnel.For high-level radioactive waste repository, the rock damage characteristics is an important factor in its long-term stability and operational safety impact, resulting in the evolution of rock damage and many factors related to mechanical excavation methods have dominated the TBM small disturbances surrounding rock, become the main excavation methods and high-level radioactive waste repository underground laboratory lot of high standard roadway projects selected. Therefore, The research on rock damage characteristics under TBM cutter and the effect of jointed rock breaking is to study the distribution repository infrastructure damage and subsequent radionuclide migration patterns is of great significance.In this paper, full-scale linear cutting tests are conducted and fluorescence was used to study effect on the influence of crack propagation characteristics of Beishan granite under different disc cutter spacing(70mm, 80 mm, 90 mm, 100mm). For the samples crushed characteristic, a classification of different zones and parametric statistics were conducted based on CorelDraw and Image J software, meanwhile the results and are compared with the ultrasonic tests of different crack zones. In this paper, full-scale linear cutting tests are conducted to study effect on the influence of crack propagation characteristics of Beishan granite under different joint spacings.The study indicates that the crack propagation length, depth, and crack zone area increases with the increase of the cutter space, and the ratio of each zone to the total damage zone is different. For Beishan intact granite, as the cutter spacing varies from 70 to 100 mm, the rock damage depth is less than 50 mm. Crack propagation mode has an important impact on the formation of rock breaking efficiency, the formation of rock chips and the damage zone size.During the tests, the three dimensional forces acting on the rolling cutter were recorded, and the rock chips collected after each cutting pass were weighed respectively. The impact of joint spacing on rock fragmentation process by TBM cutter was investigated by analyzing the obtained cutting force, crack propagation modes and rock chips. The results show that for the rock mass with joint spacing 100 mm, the normal force required to indent into the rock is less than that of intact rock. For the rock mass with joint spacing 400 mm the normal force required have a process of mutation, For the rock mass with joint spacing 100 mm, two fragmentation modes are found during TBM cutter cutting. While for the rock mass with joint spacing 400 mm, the fragmentation process can be divided into normal fragmentation and joint-affected fragmentation process, and the median crack can be promoted to propagate vertically to joint plane. The rock sample under joint plane is intact, joint plane can limit the crack propagating cross the joint plane.