Page - 715 - in Book of Full Papers - Symposium Hydro Engineering

2.1. PRINCIPLE Emergency monitoring should be rapid and efficient. The hereinafter should be followed. (1) A detailed inspection and monitoring plan should be made in advance based on the dam danger type, dam danger consequences and risk degrees. The inspection and monitoring should be combined, and the related monitoring items should be monitored synchronously. (2) Portable monitoring equipments should be the first selection for emergency monitoring, and the layout of monitoring equipments should be accessible and convenient. The technical performance of monitoring equipments can meet the requirements in extreme conditions. The installation of the instruments should minimize the impact on the safety of the project and avoid aggravating the occurrence of emergencies. (3) The emergency monitoring methods should be fast, simple, practical, accurate and reliable. The automatic observation should be adopted to improve the efficiency and frequency of the monitoring if it is possible. (4) The emergency monitoring frequency should be determined by the development speed and degree of the emergency, and the variation of observation values should be monitored. When the degree of emergency became more serious, the monitoring frequency should be increased. (5) Information of the record should be normative and integrated, including emergency types, emergency degrees, weather conditions, monitoring items, monitoring methods, monitoring frequency, monitoring date, monitoring value, etc. Monitoring data analysis should focus on comparison of historical data and data after the occurrence of events. 2.2. DAM UNEXPECTED EVENT GRADING Four grades of dam unexpected events are classified according to emergency degree and hazard consequence. The classification standard in China is show in Table 1. When the dam unexpected events grades determined by different standards are inconsistent, whichever is the highest. Table 1 The classification standard of dam unexpected events Grade Ⅰ Grade Ⅱ Grade Ⅲ Grade Ⅳ Reservoir water level surpass maximum flood level Reservoir water level surpass design flood level Reservoir water level surpass top of level of flood control Reservoir water level surpass level of flood control Fatal incidents uncontrolled, probably failure Fatal incidents but can be controlled Serious incidents convenient-controlled Ordinary incidents convenient-controll ed 715