Implementation Effects for Construction Ventilation in Extra-Long Tunnels under High-Cold and High-Altitude Conditions —A Case Study of Tianshan Shengli Tunnel

Abstract

To address the technical challenges of low air pressure, low temperature, long distance, and multiple working faces in the construction ventilation of extra-long tunnels in high-cold and high-altitude areas, this study takes the Tianshan Shengli Tunnel project as the engineering case and systematically investigates the comparison, optimization, and implementation effect of ventilation schemes by combining theoretical calculation, comparative analysis, and on-site systematic monitoring. Based on a construction organization arranged in two major stages and sixteen sub-stages, two ventilation modes are compared and analyzed: full-face simultaneous construction (Scheme I) and process-alternating construction (Scheme II). A required-air-volume calculation system is proposed with blast-fume exhaust as the controlling factor, yielding design values of 1980m³/min for the main tunnel by drilling and blasting method, 1500m³/min for the central pilot tunnel by TBM method, and 855m³/min for the shaft by drilling and blasting method. Combined with on-site conditions, Scheme II is further optimized to establish a combined ventilation mode of “forced ventilation in the main tunnel + drift ventilation in the central pilot tunnel + centralized smoke exhaust through the shaft,” supplemented by refined on-site management. Compared with Scheme I, the total power is reduced by approximately 60% on average, with a maximum reduction of 74.9% during peak periods and the cumulative cost savings over the entire construction cycle amount to approximately 128.10 million RMB On-site monitoring results show that the wind speed at all sections meets the requirement of ≥0.3 m/s and the CO concentration is controlled below the allowable limit. In addition, a significant blocking effect of the secondary lining trolley on pollutant transport is discovered, with a CO concentration difference reaching 3.96 times. The research findings can provide technical reference for the construction ventilation of extra-long tunnels in high-cold and high-altitude areas.