Abstract: To address the engineering challenges such as the unclear carbon reduction mechanisms and missing micro-dynamic accounting boundaries for fully electrified integrated equipment systems in highway tunnels, the carbon emission reduction potential and its underlying physical evolution mechanism of fully electrified construction operations under complex geological conditions are quantified. Based on the complex geology featuring high insitu stress and great burial depth of the Qiaojia Tunnel in Yunnan, China, a micro-dynamic carbon emission accounting model converged to the “onsite construction machinery” unit is established using the life cycle assessment framework and high-frequency equipment operation log parameters. Through field measurements and cross-validation of multi-source data, a high-resolution quantitative comparison is conducted on the energy flow evolution and carbon emissions between the fully electrified integrated equipment system and the conventional dieselpneumatic hybrid machinery cluster under identical operational boundaries. The results show that: (1) Compared to traditional processes, the operational mode of the fully electrified integrated equipment system can achieve a leapfrog carbon reduction efficiency. Within the case study section, the new machinery cluster achieves an absolute greenhouse gas reduction of 2 564.5 tCO_2eq, with a relative reduction rate as high as 81.51%. (2) Sensitivity analysis indicates that this emission reduction exhibits strong engineering robustness against cross-regional grid carbon emission factor drift and short-term productivity fluctuations. (3) The significant synergistic carbon reduction benefits essentially stem from the reconstruction of the “energy flow topology” in deep confined spaces, pure electric direct drive not only bridges the thermal efficiency generation gap of traditional internal combustion engines, but also fundamentally eliminates multi-stage energy losses in long-distance pneumatic pipelines. Furthermore, its “zero exhaust” characteristic at the operation terminals effectively reduces the superimposed ventilation load other than the dilution of blasting fumes, thereby further lowering the auxiliary energy consumption of the system.

Key words: highway tunnel, fully electrified integrated equipment system, carbon emissions, emission reduction mechanism, micro-dynamic accounting, emission reduction benefit