基于凝胶分形模型膨润土侵蚀质量的计算方法

Calculation of erosion mass of bentonite based on fractal model for colloids

地下水沿围岩裂隙对高放废物地质处置库膨润土缓冲/回填层产生侵蚀作用,膨润土的侵蚀质量与地下水流量密切相关。不同于砂粒,膨润土以凝胶形式赋存于地下水中,形成悬浊液。膨润土凝胶具有分形结构,基于膨润土凝胶的分形结构,导出膨润土的侵蚀质量(ms)与地下水流量(Vw)的理论关系,表示为ms=βVw^α,指数α表示为膨润土凝胶分维(D)的函数,α=D/(6-D).采用Borgesson等和Suzuki等对MX-80膨润土的侵蚀试验结果,验证膨润土的侵蚀质量与地下水流量的理论关系。膨润土凝胶的分维根据Svensson等的X-射线小角度衍射结果计算,膨润土在不同浓度NaCl溶液中的侵蚀质量与盐溶液流量的关系都符合基于膨润土凝胶分形模型的理论关系.

The water inflow into the deposition holes and tunnels in a repository will mainly take place through fractures in the rock and will lead to that the buffer and backfill will be wetted and eroded.If the counter pressure and strength of the buffer or backfill are insufficiently high,piping erosion will take place.An erosion model to estimate the erosion mass(ms)of bentonite buffer in saline solution for a certain water inflow rate during a certain time based on the fractal model for bentonite colloids is proposed as ms=βVw^α,in terms of a power law,Vw is the accumulated volume of water flow.The exponent parameter(α)is related to the fractal dimension(D)of bentonite colloids as α=D/(6-D).The relationship between the erosion mass(ms)and the accumulated volume of water flow(Vw)is verified by the experiments of MX-80 bentonite piping erosion in NaCl solutions by B?rgesson et al and Suzuki et al.The fractal dimension(D)of bentonite colloids is calculated according to the small-angle X-ray scattering(SAXS)of MX-80 bentonite by Svensson&Hansen(2013).