坝基帷幕防渗性能衰减的数值模拟

Numerical simulation of anti-seepage performance attenuation of dam curtain

大坝长期运行条件下,帷幕受到坝基水的侵蚀作用,其矿物组成的溶失使得帷幕细观结构发生改变,进而引起防渗性能衰减,可能造成渗流安全隐患.为反映帷幕防渗性能衰减机理及其造成的影响,依据地下水动力学、溶质运移以及化学动力学的相关理论,建立了渗流场、化学场以及固相介质细观结构等多物理场耦合的数学模型,以帷幕中的主要组成Ca（OH）2作为目标矿物,研究其溶失引起的帷幕自身孔隙度和防渗性能改变以及对渗流等的影响.模拟结果表明,模型能较好地反映帷幕细观结构改变发生的部位及其程度.同时,模型还可预测由于防渗性能衰减而引起的渗流量的增加以及幕后目标离子浓度的变化.

The interaction between dam curtain and groundwater made the mineral dissolved during long term operation of the dam.The mesostructure of the curtain was changed,which caused its anti-seepage performance weakened and some safety hidden danger.In order to reflect the mechanism of the anti-seepage performance attenuation and its effect degree,a multifield coupled model composed of seepage field,chemical field and solid medium,is built up based on groundwater dynamics,solute transport and chemical kinetics.The variation of dam curtain and flow field is analyzed by thinking of Ca（OH）2 dissolution.The results show that the model can simulate the location and extent of the mesostructure variation of the curtaion.And it could also predict the increase of the leakage and the decrease of Ca2＋behind the curtain due to its attenuation.