Oxygen-rich combustion refers to a high-efficiency combustion technology in the combustion process, the volume fraction of oxygen is greater than 21% oxygen content in the air as a combustion gas, when the combustion gas directly uses more than 99% of industrial pure oxygen, also known as pure oxygen combustion. Oxygen-enriched combustion technology can increase the combustion flame temperature, reduce the amount of primary air extraction, and save fuel consumption and reduce exhaust emissions.
Soil stabilization measures should be taken for shield tunneling. Currently, common soil stabilization technologies include SMW construction method, high-pressure rotary jet pile, deep mixing pile, grouting method, freezing method, etc. Many construction methods have their advantages and disadvantages, but none of them can be guaranteed. During shield tunneling, water and sand gush or even collapse will inevitably occur due to poor soil reinforcement, and the freezing temperature of liquid nitrogen is extremely low. The freezing speed is fast and the time is short, which is very suitable for the remedial and emergency construction in such accidents. At present, liquid nitrogen freezing shield technology is widely used in urban subway construction projects. Liquid nitrogen freezing is a low temperature liquefaction method. The advantages of using liquid nitrogen freezing for shield initiation are as follows: fast freezing speed and short time from freezing to forming effective carcass; The energy supply is fast and the freezing lift is easy to form, which is especially suitable for the implementation in the fluid water-rich sand layer with confined water. The freezing lifting strength is high, and the possibility of collapse is small when the tunnel door is broken.