Dynamic damage and fracture mechanism of curved ripper cutting reinforced concrete composites: Numerical simulation combined with engineering practice

Abstract

Shield tunnels inevitably cross existing structures like reinforced concrete pile foundations and concrete walls due to the spatial interlocking of underground structures in the construction process. The objective of minimizing cutter damage during the cutting of reinforced concrete pile foundations is widely pursued in engineering. In this study, a numerical model of curved ripper cutting reinforced concrete composites was established, with the engineering background of Nanjing Metro Line 10 shield tunnel crossing the pile foundation of Youth River Bridge. The dynamic damage and fracture of reinforced concrete composites under the cutting of single, double, and multiple rippers were comprehensively investigated. The effects of the operating parameters and geometric parameters on the cutting performance were discussed. Finally, a statistical analysis was carried out to evaluate the damage of 148 rippers and the fracture of rebar in an actual engineering project. The simulation results reveal that coordinated cutting of five rippers has optimized the fracture mechanism of the rebar, weakening the compression effect between the ripper and the rebar, and highlighting the tensile fracture of the rebar. It is appropriate to set the alloy blade angle at 90° and the blade width at 10 mm for practical engineering applications. The penetration has a significantly greater influence compared to cutting speed. In practical engineering, adopting a low penetration and high rotation speed grinding mode is advantageous for reducing blade fractures. The central fishtail cutter and the rippers in the outer area of the cutterhead are more prone to damage during the pile cutting process and warrant additional reinforcement measures. The findings provide comprehensive and innovative insights into shield cutting reinforced concrete pile foundations.