某大型土石坝坝脚挡墙变形机理分析

Study on Deformation Mechanism of Retaining Wall at Foot of Large Earth-rock Dam

常见土石坝坝脚挡墙变形破坏机理主要有地基承载力不足、地基不均匀沉降、温度效应或自身抗滑(倾)稳定性不足等。某项目土石坝坝脚棱体排水改为挡墙后,挡墙变形特征与常见起因均不相符,变形仅在挡墙伸缩缝处可见,伸缩缝呈张开、闭合或错位等变化。研究发现,伸缩缝变形是因坝体固结沉降导致挡墙产生水平位移,并与相邻挡墙间形成水平位移差有关,位移差越大变形越严重;同时挡墙水平位移大小与坝截面高度、坝基所处水文地质条件等相关。土石坝下游棱体排水改为重力式挡墙后,除按规范要求设计计算外,还应计算挡墙间水平位移差,并考虑挡墙位移、排水不畅对坝体下游排水系统的影响。研究结果对正确分析坝脚挡墙变形机制和挡墙抗滑设计具有较好的参考价值。

The common deformation and failure mechanism of retaining wall at foot of earth-rock dam is mainly caused by insufficient bearing capacity of foundation,uneven settlement of foundation,temperature effect or insufficient anti-sliding stability.For a certain project,the retaining wall deformation characteristics are not consistent with the above causes after the drainage of the embankment foot of the earth-rock dam is changed to the retaining wall.The deformation is only visible at the expansion joints of the retaining wall,and the expansion joints are open,closed or misplaced.Through calculation and analysis,it is found that the expansion joint deformation is caused by the retaining wall horizontal displacement caused by the consolidation settlement of the dam,and the size of the deformation is related to the horizontal displacement difference between adjacent retaining walls.The larger the displacement difference is,the more serious the deformation is.At the same time,the horizontal displacement of retaining wall is related to the height of dam section,hydrogeologic conditions of dam foundation.Based on this,it is proposed that after the prism drainage of the downstream earth-rock dam is changed into gravity retaining wall,in addition to the design and calculation according to the standard requirements,the horizontal displacement difference between retaining walls should also be calculated,and the damage of retaining wall displacement and poor drainage to the downstream drainage system of the dam body should be considered.The research results have a good reference value for the correct analysis of deformation mechanism and anti-slip design of retaining wall at dam foot.