Dikes constructed from sand generally have a sand core and clay layers on the slopes and the crest to protect the core against erosion. In extreme hydraulic conditions, several failure mechanisms can lead to destruction of the clay layers, exposing the sand core to water. When water overtops the dike and the protective cover of the land-side slope or the crest fails, water flows over the core and erodes the sand. The dike starts to breach, and eventually the land behind the dike is flooded. The rate at which the dimensions of the breach grow influences the rate of inundation of the polder. Reduction of the inundation rate may be achieved by retarding the breaching process. This may reduce the number of casualties, resulting in increasing safety for the inhabitants. In order to achieve, for instance, a safety level ten times higher, mortality has to decrease by a factor of 10. The breaching process can be retarded by reducing the erosion velocity of the sand core. Experiments were executed to investigate the effect on the erosion velocity of adding bentonite to sand. The results of these experiments showed a significant reduction of the permeability and erosion velocity of the sand–bentonite mixtures compared with those of pure sand. The effect of adding bentonite on the breaching process was investigated by applying the Bres model (breach erosion in sand dikes model) to a sand dike tested in a large-scale field experiment (Zwin'94). It was found that adding a small percentage of bentonite reduces the rate of breach growth and the inundation rate in the polder. For the Zwin’94 dike it was determined that 5·4% of bentonite is sufficient to reduce the inundation rate below a threshold value of 0·5 m/h, leading to a significant increase in safety.

中文翻译：

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延缓堤防的破坏过程

用沙子建造的堤坝通常在斜坡和山顶上有一个砂芯和黏土层，以保护砂芯不受侵蚀。在极端水力条件下，多种破坏机制可能导致粘土层破坏，使砂芯暴露于水。当水超出堤防并且陆地侧斜坡或山顶的保护层失效时，水会流过岩心并侵蚀沙子。堤防开始破裂，最终堤防后面的土地被淹没。漏洞尺寸的增长速率会影响the的淹没速率。可以通过延迟破坏过程来降低淹没率。这可以减少人员伤亡的数量，从而提高居民的安全性。为了达到例如十倍的安全水平，死亡率必须降低10倍。破损过程可以通过降低砂芯的侵蚀速度来延迟。进行了实验，以研究将膨润土添加到沙子中对侵蚀速度的影响。这些实验的结果表明，与纯砂相比，砂-膨润土混合物的渗透性和侵蚀速度显着降低。通过将Bres模型（在堤坝模型中发生Breach侵蚀）应用于大规模现场试验（Zwin'94）测试的堤坝，研究了添加膨润土对破坏过程的影响。发现添加少量的膨润土会降低reduces裂的发生率和and虫的淹没率。