6.2　Shield Fault and Detection Technology

Shield is the most advanced super-large special equipment for tunneling in the world.Today，with increasing emphasis on the development and utilization of underground space，shield construction has a very broad market prospect.In order to ensure the smooth progress of shield construction，it is necessary to continuously inspect and monitor the equipment status of the shield during the shield construction，master the status of the equipment，and provide guidance or prediction for the maintenance of the shield.It will avoid the sudden damage of the shield due to the lack of prior preparation，which will lead to the long-term shutdown of the shield to be repaired，affect the smooth progress of the construction and bring safety hazards.At the same time，due to the complex structure of the shield，it involves many specialties such as machinery，electricity and fluid.Once a fault occurs，how to analyze and judge the cause of the fault as soon as possible and eliminate the equipment fault as soon as possible is also an urgent problem to be solved in shield construction.

Due to the large number of shield equipment and strong correlation，the failure of any single set of equipment will affect the tunneling progress of the shield to varying degrees.The damage of key parts will lead to the stagnation or even paralysis of the whole shield，which will affect the progress of the whole project and greatly increase the engineering cost.Therefore，it is necessary to develop a set of shield maintenance procedures，carry out the research on the technology and method of condition monitoring and fault diagnosis，and quickly determine the fault location，so as to effectively shorten the maintenance time and improve the utilization rate of equipment.This section summarizes the common faults and maintenance methods of shield，and introduces the shield fault detection technology based on virtual instrument technology and oil analysis technology combined with Nanjing Yangtze River tunnel project.