Abstract:Along the highway from Yichang to Enshi city,section of the national main line from Shanghai to Chengdu,a new structural style of tunnel named forked tunnel,is put forward and successfully applied to the construction of Baziling,Miaoya and Qishucao tunnels. The emphasis is put on the influence of exhaust air on the two-lane highway tunnel¢s ventilation considering different spaces and air speeds of the two tunnels;the relation formula among intake air speed,discharge air speed and tunnel space is deduced based on a great number of numerical simulation and multivariant nonlinear regression analysis. The corresponding physical model test and field monitoring are also conducted. The technical measures,such as constructing midboard and staggering the tunnel entrance,are suggested and applied to the forked tunnel¢s design and construction in practice.