Abstract: The problems of slow construction speed and ventilation resistance increase caused by intermediate diaphragm wall made of concrete in parallel heading of extra-long highway tunnel should be solved. As a result, a new intermediate diaphragm wall in which the concrete is replaced by steel corrugated plate is proposed. And then the feasibility of the technology is analyzed by numerical simulation from the aspects of ventilation performance, mechanical performance, and fire-resistance performance. Finally, the properties of the wall such as durability and sealing are studied. The results show that: (1) The new intermediate diaphragm wall will cause the increase of cross-section area of ventilation parallel heading, which results in a slight decrease in the cross-section wind speed (about 4%), but it will not affect the ventilation effect. (2) The crown settlement of the parallel heading increases to 3. 783 mm, and the axial force of fixed column reaches 124. 576 kN, which indicates no influence on structural safety. (3) The smoke flow in the parallel heading does not return when fire occurs in the main tunnel, and the maximum temperature (168 ℃) does not exceed the normal range. (4) The durability and sealing performances of the steel corrugated plate also meet relevant requirements. (5) The new technology can meet the ventilation and disaster prevention requirements of extra-long highway tunnels and ensure the construction speed.

Key words: extra-long highway tunnel, ventilation parallel heading, intermediate diaphragm wall, steel corrugated plate