水电工程导流洞封堵体稳定性对于电站蓄水发电和安全运行至关重要。研究总结对比了国内外导流洞封堵体稳定性设计和计算方法；在此基础上，采用三维弹塑性数值分析方法对构皮滩水电站封堵体在设计水位下各种工况的应力、变形和稳定性进行了计算分析；进而引入超载方法，研究堵头及堵头与围岩接触面从局部到整体破坏的渐进失稳过程，对其稳定性进行分析和综合评价。研究结果表明：设计挡水水位条件下，各种工况堵头结构变形不大，最大变形在1.1～1.4 mm ；接触面剪切应变较小，接触面塑性区延伸范围和破坏比例不大；超载法计算表明，堵头结构可承受的安全荷载在3.5～5.5倍设计水头，大于规范要求的安全系数，堵头结构的设计长度和结构形式在安全稳定方面可以满足规范要求；采用超载安全系数法研究类似导流洞封堵体结构的极限承载能力更加合理有效。

The stability of diversion tunnel plug is very important for power generation and safe operation of hydropower station. Based on the summary and comparison of design and calculation methods for diversion tunnel plug at home and abroad, we carry out calculating analysis on the deformation, stress and stability of diversion tunnel plug under designed water level by 3-D numerical simulation analysis. Then, the progressive failure of plug from the parts to the whole is analyzed by over-loading safety factor method. The results show that the maximum displacement of plug is 1.1～1.4 mm and the shear strain on contact face is smaller with little extending range and failure under designed water level. According to the findings of over-loading safety factor method, the safety load factor that the plug can bear is 3.5～5.5 times of design water head, which can meet the standard requirements in safety and stability. And it is more reasonable and effective to adopt over-loading safety factor method to analyze the ultimate bearing capacity of diversion tunnel plug.