Research on the wind pressure coefficient in natural wind calculations for extra-long highway tunnels with shafts

Natural wind can be applied to the optimal design of extra-long highway tunnel ventilation systems for energy saving. The main objective of this paper is to study the values of the wind pressure coefficient to propose a more reasonable method for calculating natural wind. In this paper, the components of natural wind pressure in an extra-long tunnel are first analyzed, and a more reasonable calculation method for natural wind velocity in an extra-long highway tunnel with multiple shafts is proposed. Then, the values of the wind pressure coefficient under different working conditions are obtained through laboratory tests on a reduced scale model tunnel. Moreover, a field measurement of natural ventilation is carried out to validate the theoretical calculation above, and this method is used to analyze large amounts of meteorological monitoring data to obtain the design natural wind velocity inside the tunnel. The results show that the wind pressure coefficient is a critical parameter impacting the value of the wind wall pressure difference, ranging mainly from 0.6 to 0.85. The theoretical calculation results for the internal wind velocity are in good agreement with the field measurement data in the Liupanshan Tunnel, which validates the feasibility of the proposed calculation method.