为探索深覆土超大跨明挖隧道的合理断面形式及优化思路，以覆土厚5 m、单孔跨度31 m的广州新白云国际机场第二高速北段工程为依托，开展结构力学行为、技术经济、施工工艺等多方面分析。借助有限元法建模计算，明确直墙折板式断面总体最优，适用于高速公路深覆大跨隧道断面； 且通过探讨不同直墙折板尺寸对隧道结构内力的影响，得到折板最优尺寸(2 m×1.25 m)方案。同时设置不同断面高度与增设横隔梁等方式，提出在隧道顶覆土大于5 m区段断面抬高1.5 m的措施，并对超大跨的断面分析可知，难以通过加大隧道结构顶板厚度来满足深覆土承载要求，为此制定了在隧道顶设置空心板的结构设计方案。

The rational crosssection form and optimization idea of the super largespan opencut tunnel with large overburden should be carefully studied. Hence, the north section of the second highway of Guangzhou New Baiyun International Airport with the covered soil thickness of 5 m and singlehole span of 31 m is taken for an example to carry out analysis on the structural mechanical behavior, technical economy, construction technology, etc. It is concluded that the crosssection form of the folded plate of straight wall is the optimum for the largespan tunnel with large overburden according to the finite element modeling and calculation. In addition, the optimal folded plate size (2 m×1.25 m) scheme is obtained by discussing the influence of different sizes of folded plate of straight wall on the internal force of tunnel structure. At the same time, by setting different crosssection heights and adding diaphragm beam, the measure of 1.5 m raising of the crosssection with the tunnel roof covering soil more than 5 m is put forward. Based on the analysis of the crosssection of the super largespan tunnel, it is difficult to increase the thickness of the roof of the tunnel structure to satisfy the bearing requirements of the deep cover soil. As a result, the structural design scheme of hollow slab at the roof of the tunnel is formulated.