Development of large-span underground excavation engineering technology

According to research of large-span underground caverns in ancient China,summarize the design and construction technology of them.Furthermore,analyze the development of large-span underground engineering in nowadays.Lay emphasis on the design and construction technology of large-span harbor tunnel engineering,railway tunnel engineering,surge shaft engineering,liquefied petroleum gas engineering,underground engineering in unfavorable geological condition,underground hydroelectric power station engineering,the tunnel engineering through the Yellow River and underground engineering in soft soil.Finally,bring up the development tendency of it.These conclusions have some reference to propel more development of China's engineering technology.