"Go in early and go out late" was first put forward by the commander of the railway corps at that time (later General Lu became the Minister of Railways), which meant that the tunnel should be long rather than short.

In tunnel construction, the surrounding rock at the entrance section is generally broken and the geological conditions are poor. The principle of minimum disturbance to the rock mass should be followed to improve the stability of the rock mass, edge and slope at the entrance section.

Matters needing attention in line selection in earthquake area:

(1) Trunk highways should avoid high-intensity earthquake areas as much as possible. If it is difficult to avoid, the route should pass at the narrowest place, and low embankment should be adopted.

(2) When the route must pass through a high-intensity earthquake zone, the favorable terrain should be used as much as possible to avoid steep cliffs, complex terrain and unfavorable geological sections, so as to reduce the possible damage caused by the earthquake.