20 formwork trolleys. Secondary lining is a molded concrete or reinforced concrete lining applied to the inner side of primary support in tunnel construction, which forms a composite lining with primary support. According to relevant data, in order to ensure the progress of the project, the lining needs to be equipped with 20 formwork trolleys. Relatively speaking, the secondary lining and primary support refers to the lining constructed with concrete and other materials under the condition that the tunnel has been initially supported, so as to strengthen the support, optimize the waterproof and drainage system of the route, monitor and other facilities and meet the requirements of modern highway tunnel construction.