Clay buffer is a key component of the engineered barrier system (EBS) for geological disposal of higher activity radioactive waste. Experimental observations indicate the possibility of buffer erosion at the interface with host rock due to interactions with groundwater. Existing models for clay erosion are very limited in terms of addressing the hydro-chemical effects, while the assessment of the long-term performance of clay buffer requires robust predictive models covering expected environment conditions and multiphysics phenomena involved in the erosion process. The work presented here is a step towards such a predictive capability, which considers clay expansion, detachment of clay particles and transport of detached particles by groundwater within a single modelling framework. The effects of solution chemistry and flowrate on the penetration, extruded mass and particle release rate of clay buffer are investigated in this paper. A series of experimental data are used to validate the swelling and erosion model developed in this study. The results show that the extrusion distance, which is controlled by both clay swelling and detachment processes, is nearly linearly dependent on the water flowrate irrespective of the water chemistry. Similar linear dependence of the erosion rate on water flowrate is observed for flowrates less than 10⁻⁵ m/s. Higher water flowrates are shown to induce nonlinearly increasing erosion rates in accordance with experiments. A flowrate threshold is found above which the erosion behaviour of compacted bentonite can be significantly affected. A concept of tolerance time for clay buffer is introduced as a failure criterion. The results indicate that the coupled effect of water chemistry and velocity requires further investigation for ionic concentrations below 1 mM.

粘土缓冲液是用于高活度放射性废物地质处置的工程屏障系统 (EBS) 的关键组成部分。实验观察表明，由于与地下水的相互作用，在与主岩的界面处可能发生缓冲侵蚀。现有的粘土侵蚀模型在解决水化学效应方面非常有限，而粘土缓冲长期性能的评估需要强大的预测模型，涵盖侵蚀过程中涉及的预期环境条件和多物理场现象。这里介绍的工作是朝着这种预测能力迈出的一步，它在单个建模框架内考虑了粘土膨胀、粘土颗粒的分离和地下水对分离颗粒的输送。溶液化学和流速对渗透的影响，本文研究了粘土缓冲剂的挤压质量和颗粒释放率。一系列实验数据用于验证本研究中开发的膨胀和侵蚀模型。结果表明，由粘土膨胀和脱离过程控制的挤出距离几乎线性地依赖于水流量，而与水化学无关。对于小于 10 的流速观察到侵蚀速率对水流速的类似线性相关性 与水的化学性质无关，几乎线性地依赖于水的流速。对于小于 10 的流速观察到侵蚀速率对水流速的类似线性相关性 与水的化学性质无关，几乎线性地依赖于水的流速。对于小于 10 的流速观察到侵蚀速率对水流速的类似线性相关性^-5 米/秒。根据实验表明，较高的水流速会引起侵蚀率的非线性增加。发现了一个流速阈值，高于该阈值会显着影响压实膨润土的侵蚀行为。粘土缓冲的容许时间概念被引入作为失效准则。结果表明，水化学和流速的耦合效应需要进一步研究离子浓度低于 1 mM 的情况。