金安桥水电站初次蓄水对导流洞稳定性影响的计算分析

金安桥水电站下闸蓄水后，陡升的库水位将对导流洞结构稳定造成不利影响。为保障堵头封堵前的导流洞结构稳定性，运用三维弹塑性损伤有限元，在模拟进水口边坡及导流洞开挖支护的基础上，计算汛前下闸水位时的岩体渗流场，对导流洞围岩和衬砌在岩体渗流作用下的结构稳定性进行复核分析。分析结果表明，导流洞的围岩稳定性在蓄水后仍有保障，衬砌结构受力较小，现有环向配筋满足结构内力要求，但在进水口变截面和导流洞变截面部位沿水流方向的拉应力较大，使得衬砌出现开裂。进一步分析表明，上述区域的开裂范围有限，对整体衬砌结构影响较小。

A Numerical Analysis of Stability of Diversion Tunnel at the Jin'anqiao Hydropower Plant under the Influence of Initial Impoundment

When the initial impoundment is conducted at Jin’anqiao hydropower plant, the zooming reservoir water level will have negative influence on the structural stability of diversion tunnels. It is necessary to recheck the structural stability of diversion tunnels before sealing the plug. The numerical analysis adopts 3D damage FEM approach. The excavation of intake slope and diversion tunnel is firstly simulated. The seepage filed of rock mass is then calculated considering flood water level with closed lock. Based on the above results, recheck analysis is done on surrounding rock and lining structures of diversion tunnel. The results indicate that when water is impounded, the surrounding rock stability of diversion tunnel can be still guaranteed. The internal force of lining structures is overall favorable. The current reinforced steel bars along ring direction are able to meet the requirements of internal force. However, the tensile stress at variable section area of intake and plug is considerable along water flow direction. This may cause lining crack. Further analysis indicates that the tensile stress area is restricted within small range and only has small influences on the whole lining structures.