Abstract: The influence of middle partition wall structure and  crosssection type of the parallel pilot tunnel on the ventilation effect  is investigated by using the FLUENT numerical simulation software to comparatively analyze the ventilation effects of the semicircular arch, threecentered circular, and straightwall crosssections on the ventilation effect under concrete, uncorrugated steel plate, and corrugated plate middle partition walls, respectively. The results show that, (1) under the same crosssection type, the new types of uncorrugated steel plate and corrugated plate middle wall effectively reduce the ventilation resistance coefficient by 10%~17% compared with the traditional concrete middle partition wall. The uncorrugated steel plate middle wall illustrates an excellent reduction effect of the ventilation resistance along the path, followed by the corrugated plate middle wall. (2) Under the same middle partition wall, the tunnel crosssection with a large equivalent diameter effectively reduces the ventilation resistance coefficient and the friction resistance because the parallel pilot tunnel crosssection area and the absolute rough height are the same. (3) The threecentered circular crosssection depicts the best performance.

Key words: tunnel ventilation, parallel pilot tunnel, corrugated steel plate, ventilation resistance coefficient, numerical simulation