面板坝垂直缝失效后垫层区渗流细观研究

Meso Study on Cushion Seepage Field After Vertical Fracture Failure of Face Rockfilled Dam

面板堆石坝接缝止水是重要的防渗设施,一旦失效将导致集中渗流、渗透破坏等系列问题。目前对渗流问题的研究基本上基于有限元法,但其在求解离散颗粒物质的系统现象存在一定局限性,可求解颗粒介质的流动及固体力学大变形的颗粒流理论研究目前较少。鉴于此,以某面板坝为例,应用PFC2D软件采用粗网格流法对面板垂直缝失效后的垫层区渗流特性进行模拟,通过分析表明:该面板坝垂直缝单缝失效时,垫层区未产生明显的渗透破坏,颗粒流量在5%以内,最终颗粒重新排序后达到平衡状态;渗流关键要素颗粒流失量、渗透系数、流速及孔隙率等均随压力梯度呈正相关,且随着计算时步的增加,各渗流要素均有增大,但增幅大小各异,最终达到平衡状态。相关成果可为垫层区渗透稳定、管涌临界值等的确定提供参考,并对实际工程中有限元法模拟渗流问题奠定基础。

The joint sealing of concrete faced rockfill dam is an important anti-seepage facility.Once it fails,it will lead to a series of problems such as centralized seepage,seepage damage and so on.At present,the study of seepage is based on the finite element method,but it has some limitations in solving the systematic phenomenon of discrete particulate matter.There are few studies on particle flow theory which can solve the flow of granular medium and the large deformation of solid mechanics.In this paper,we take a concrete face dam as an example,the seepage characteristics in the cushion area after vertical fracture failure of face rockfill dam are simulated by using PFC2D software and coarse grid flow method.The results show that there is no obvious seepage failure in the cushion area after vertical fracture failure of concrete face dam,particle flow is within 5%,finally,the particles reach equilibrium after reordering.Particle loss,permeability coefficient,flow velocity and porosity are all positively correlated with pressure gradient,and with the increase of calculation time step,all seepage factors increase,but the increases are different.In the end,it achieves a balanced situation.The relevant results can lay a foundation for the study of seepage stability of cushion area and the critical value of piping failure,and it lays a foundation for the finite element method to simulate the seepage problem in practical engineering.