铁路隧道净空面积的确定，不仅应考虑隧道建筑限界和机车车辆限界，还要考虑列车通过隧道时诱发的空气动力学效应。基于一维、可压缩、非定常的流动假设，推导得到车内瞬变压力、洞口微气压波和空气阻力计算公式，并结合这3个指标对现有城际铁路、高速铁路隧道设计规范进行论证和优化。结果表明： 针对大于10 km的特长隧道，在一定长度范围内，且在提高列车密封水平、增加洞口微气压波缓冲结构的情况下，可对特长隧道净空断面进行优化。

Apart from the construction clearance and the rolling stock clearance, aerodynamic effects should also be considered in the determination of railway tunnel crosssection. In this paper, the formulas of transient pressure in train, micropressure wave and air resistance are obtained based on assumption of onedimensional, compressible and unsteady flow. According to the indices of transient pressure in train, micropressure wave and air resistance, the existing design codes of intercity and highspeed railways are demonstrated and optimized. The results show that the crosssection of an extralong tunnel(more than 10 km) can be improved under the conditions of a certain length, seal level improvement of train and microbarometric wave buffer structure at tunnel portal.