TBM Cutting Edge Width Parameters for Excavation in Weakly Cemented Cretaceous Sandstone
The mechanical parameters of TBM cutter head hob are one of the main factors affecting the disturbing surrounding rock crack propagation.To reveal the internal structure of Cretaceous sandstone and explore the rock-breaking mechanism,the XRD test,SEM test and polarizing microscope test for a tunnel project in western China were carried out on the Cretaceous sandstone microstructure.PFC2D numerical simulation test was carried out by selecting the hobs with different edge widths.The crack characteristics,penetration force amplitude variation,cracks number,and specific energy consumption of cementation failure were compared and analyzed with Fish language to explore the crack formation mechanism and rock-breaking efficiency.The result indicates that the crack propagation channels of weakly cemented sandstone and feldspar minerals are characterized by the low roundness,poor sorting,little cement,loose cement,and many micro pores.Under the condition of same penetration degree,12 mm edge width offers numerous advantages.The horizontal crack is the closest to the free plane,making the rock-breaking process more efficient.The large rock block is the most prominent,indicating the significant rock-breaking effect.The middle crack is the least,reducing the unnecessary energy consumption,and the rock-breaking energy is the most effective.It is reasonable to select 12 mm edge width for excavation in Cretaceous weakly cemented sandstone.Because the rock-breaking mechanism changes when the edge width exceeds 12 mm,the rock-breaking force increases greatly,the specific energy consumption increases,and the rock-breaking efficiency decreases.The study result is consistent with the relevant theoretical model.It has been successfully verified in a tunnel project in western China.
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