水工隧洞衬砌底板缺陷诱因及其对结构安全的影响分析

Analysis on the Inducement of Defects in the Lining Bottom Plate of Hydraulic Tunnel and Its Influence on the Structural Safety

水工隧洞长年运行会出现裂缝、磨损、掉块、冲坑等缺陷,极大影响工程安全。针对水工隧洞衬砌底板冲坑产生的原因及其对结构安全的影响问题,开展隧洞断面水力特征参数的数值模拟,从水力学角度分析衬砌底板冲坑产生的原因,并开展运行和检修工况下不同冲坑深度对衬砌结构受力的影响分析,结合监测数据与模拟成果对冲坑所在位置截面承载能力进行验算,结果表明:隧洞底板流速与紊动能均较大,在运行过程中受高速水流冲蚀作用最强,也最容易产生破坏。冲坑形成后主要对隧洞底板和边墙弯矩的对称性及数值影响较大,对轴力及剪力影响较小。受内外水压力控制的差异,相对于检修工况,运行工况下冲坑对结构安全的影响更加明显,冲坑导致截面抗弯刚度显著减小,随着冲坑深度增加,抗弯承载力逐渐减小,工程运行中应重点关注运行工况下底板混凝土的冲刷情况。

The hydraulic tunnel will have cracks,wear,falling blocks,scour holes and other defects during long years of operation,which will greatly affect the safety of the project.In view of the causes of scour holes in the lining bottom plate of hydraulic tunnel and their impact on the structural safety,numerical simulation of hydraulic characteristic parameters of tunnel section was carried out,the causes of scour holes in the lining bottom plate were analyzed from the hydraulic point of view,and the impact of different scour hole depths on the stress of the lining structure under operation and maintenance conditions was analyzed.Combined with monitoring data and simulation results,the bearing capacity of the section at the location of the scour hole was checked.The results show that the velocity and turbulent kinetic energy of the tunnel floor are both large,and the tunnel floor is most vulnerable to high-speed water erosion and damage during operation.After the scour hole is formed,it mainly affects the symmetry and numerical value of the bending moment of the tunnel bottom plate and side wall,and has little influence on the axial force and shear force.Due to the difference of internal and external water pressure control,compared with the maintenance condition,the impact of scour holes on the structural safety under the operating condition is more obvious.The scour holes lead to a significant reduction in the flexural rigidity of the section.With the increase of scour hole depth,the flexural bearing capacity gradually decreases.During the project operation,attention should be paid to the scour of the bottom plate concrete under the operating condition.