This study provides a theoretical foundation for optimizing tunnel boring machine (TBM) excavation parameters under diverse geological conditions, offering significant engineering value by enhancing construction efficiency and reducing costs. As the development of underground spaces advances, TBMs play a pivotal role in tunnel excavation. TBMs enhance safety in excavation by mechanically breaking rock, reducing the reliance on explosives, and the associated risks of blasts. The shield support minimizes surrounding rock collapse, advanced geological forecasting mitigates risks posed by complex geologies, and intelligent monitoring systems improve operational safety. To enhance TBM efficiency and safety, this study developed a 3D simulation model of rock breaking by disc cutters using the discrete element method. This study systematically examined the effects of excavation parameters, including disc-cutter diameter, cutter spacing, and penetration, on rock-breaking performance. The findings reveal, that as the disc-cutter diameter increases, the rolling force also increases, while the rock-breaking specific energy initially rises and then declines. The 19-inch disc cutter demonstrated a superior rock-breaking efficiency in conventional excavation operations. At a cutter spacing of 60 mm, the rock-breaking specific energy reached its lowest value, representing optimal efficiency. Furthermore, as the penetration increased, both the rolling force and rock fragmentation volume grew, whereas the specific energy decreased, further improving the rock-breaking efficiency.

In order to solve the problems of narrow roads, difficult construction, long construction period and high impact on the surrounding environment encountered during the construction of mountainous highways, railroads and other infrastructures, this paper proposes an assembled overhang composite roadbed structure. The mechanical analysis of the assembled overhang is carried out, and the three-dimensional finite element numerical model of the assembled roadbed structure is established, and the force characteristics of the overhang structure are analyzed. The results show that there is stress concentration between the two spans of the road panel, and the deformation of the road panel is mainly concentrated in the overhang side, and the deformation of the side span is larger than that of the middle span. The stress concentration phenomenon appeared on the outer side of the connection end of the middle overhanging and column, and the horizontal displacement of the middle column was larger, and the displacement was about twice that of the edge column. The research results can provide useful guidance for the design and optimization of assembled overhanging roadbeds.