Full-Scale Linear Cutting Experiment to Study the Rock Breaking Characteristics of the SBM Inclined-Mounted Cutter
摘要
The downward excavation of a shaft boring machine (SBM) is realized by dozens of disc cutters mounted on the conical cutterhead to break the rock. The cutterhead drives the inclined-mounted cutter to penetrate the inclined rock surface in the direction of excavation, with the cutter symmetry axis forming an acute angle relative to the thrust direction. It leads to significant differences in the rock-breaking method between the inclined-mounted cutter on the conical cutterhead and the normal-mounted cutter on the planar cutterhead. To study the rock breaking characteristics of inclined-mounted cutters on SBM conical cutterheads, a series of full-scale rock cutting experiments using an inclined-mounted cutter with an installation angle of 25 degrees and a cutter spacing of 80 mm were conducted. Three different rock types were used in the tests to represent the changing geological conditions during downward excavation. The cutting force, particle distribution of rock muck, and specific energy under varying geological conditions and cutting parameters were analyzed. The results indicate that the relationship between vertical force and penetration depth can be fitted by a power function, while the rolling force and side force exhibit a linear function relationship with penetration depth. The vertical force is linearly positively correlated with rock compressive strength. The maximum coarseness index values obtained during the cutting of sandstone, marble, and granite are 746.11%, 653.29%, and 440.51%, showing that the proportion of large-sized rock debris and rock breaking efficiency decrease. As the rock compressive strength increases, reducing the penetration depth of SBM can achieve higher excavation efficiency. The lowest specific energy occurs at penetration depths of 8 mm, 6 mm, and 5 mm for sandstone, marble, and granite, respectively. Furthermore, compared to the normal-mounted cutter, as the cutter installation angle increases, the specific energy of rock breaking using an inclined-mounted cutter increases, indicating that reducing the cone angle of the cutterhead can enhance the rock breaking efficiency. The results can offer valuable insights and guidance for SBM conical cutterhead design and construction operations.
Highlights The full-scale inclined-mounted cutter breaking rock test with adjustable inclination angle was built. The rock-breaking characteristics of an inclined-mounted cutter under different rock types were investigated. The differences in rock breaking characteristics between normal-mounted and inclined-mounted cutters were studied.