Engineering facilities built in rocks, soil or under water are collectively referred to as underground projects, such as industrial construction projects (such as factories and power stations), civil construction projects (such as civil air defense works, underground shops and underground theatres), traffic engineering (such as subway, railway and highway tunnels), mine Engineering (such as mine), water conservancy project (such as water transmission channel), military engineering (such as command post and communication hub) And a variety of public service buildings. Underground engineering facilities can be constructed in the form of tunnel, or similar to the ground buildings. The layout of the underground engineering facilities adopts the chessboard and room layout to build a multi-storey and multi span frame structure. Its cross section can have various shapes. The most common ones are circular, rectangular, vault straight wall (including thick arch thin wall), vault curved wall (when the foundation is weak, add inverted arch at the bottom plate), floor arch, dome straight wall, etc. The characteristics of underground engineering facilities, on the one hand, it is bound to bear the pressure from surrounding rock and soil layer, which is called surrounding rock pressure or rock mass pressure; on the other hand, the rock and soil layer have good anti explosion, anti-seismic ability, good thermal stability and airtightness. Therefore, underground engineering facilities can be used as effective air defense and explosion-proof facilities to form an environment of constant temperature and humidity, earthquake and vibration prevention, and can save land for ground buildings. This is its advantage. However, the construction of underground engineering facilities requires higher geological conditions, construction is more difficult and investment is higher, which is also its disadvantage.