Impact of various multishaft combined ventilation modes on the removal of harmful gases released from mussel decay in a long-distance water conveyance tunnel

[Display omitted] •A mussel decay experiment for release rule of harmful gases is conducted.•A numerical model considering the influence of harmful gases is implemented.•The numerical model is validated based on the data of a ventilation model test.•Rational multishaft combined ventilation mode for long-distance tunnel is clarified. The harmful gases released from the decay of biologically invasive mussels are a major threat to the maintenance safety of long-distance water transfer projects in hot and humid climate areas. Setting up multiple working shafts along the long-distance underground water conveyance tunnel for maintenance ventilation can eliminate harmful gases and improve ventilation efficiency. The rational multishaft combined ventilation mode is an important guarantee for effective decontamination and maintenance safety in long-distance water conveyance tunnels. However, research on the release rule of harmful gases produced by rotten mussels and the multishaft combined ventilation modes of long-distance water conveyance tunnels has rarely been performed. In this study, a ventilation mathematical model considering the influence of harmful gases released by rotten mussels was implemented. The release rule of harmful gases was obtained by a mussel decay experiment, and the mathematical model was validated based on the data of a ventilation model test. Furthermore, the ventilation performance of multishaft combined ventilation modes was compared using a series of numerical simulations. The obtained results show that NH3 is the main component in harmful gases released by rotten mussels. The cumulative concentration of NH3 increases with the decay time of the mussel, reaching a peak value of 309.26 mg/m3. The maximum release rate of NH3 is 185.51 mg/(m3·d). In addition, the ventilation mode of alternately delivered and discharged airflow between adjacent working shafts is confirmed to be the best for long-distance tunnels with multiple working shafts according to the comparison of the airflow distribution and the removal effect of harmful gases under different modes of multishaft combined ventilation. This study provides useful guidance for the design and optimization of maintenance ventilation schemes in long-distance water transfer projects.