Abstract: The headrace tunnel of Changdian hydropower station has been in operation with low water level or shut-down condition for a long time after completion. Due to the large buried depth, poor geological conditions and high external water pressure on the middle section of the tunnel, the huge difference between actual operation state and the design condition is harmful to the tunnel safety. The operational safety of the section with maximum buried depth is calculated and analyzed by 3D finite element method. The results show that the operational safety of surrounding rock with long-term low water level can be guaranteed by existing supporting measures, but the safety margin is not much large. Therefore, it is suggested to evaluate the safety status of the surrounding rock regularly in the future, in combination with site conditions.

Key words: Changdian hydropower station, headrace tunnel, running with low water level, deep-buried, external water pressure, finite element method

摘要： 长甸水电站投运后长期处于低水位状态运行或停机状态，而引水隧洞中部洞段埋深大、地质条件差、外水压力高，实际运行状态与设计工况的巨大差别对隧洞运行安全不利。通过三维有限元法对引水隧洞最大埋深洞段的运行安全性进行计算分析。分析表明，在现有支护措施下，最大埋深洞段围岩在长期低水位状态下运行的安全性基本能够得到保证，但安全裕度不大，建议今后结合现场情况定期评估其安全状况。

关键词: 长甸水电站, 引水隧洞, 低水位运行, 深埋, 外水压力, 有限元