The bounding effect of the water retention curve on the cyclic response of an unsaturated soil
The bounding effect of the water retention curve on the cyclic response of an unsaturated soil
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DOI：
10.1007/s11440-022-01724-0
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发表时间：
2022-10
期刊：
影响因子：
5.7
通讯作者：
A. Azizi;Ashutosh Kumar;D. Toll
中科院分区：
文献类型：
--
作者：
A. Azizi;Ashutosh Kumar;D. Toll
公路、铁路地层土的保水特性由于反复的交通荷载和周期性的降雨事件而不断变化。这是很重要的，因为这种土壤的累积变形和弹性模量在循环荷载下受到水保持特性的深刻影响。本文讨论了粘土砂在反复循环加载和润湿阶段下的循环和保水响应。结果表明：试验土的累积永久应变和弹性模量与吸力水平有关，而土体的主湿润保水曲线则反映了循环加载和润湿过程中所测吸力的变化。发现这种保水曲线的边界效应依赖于孔隙比，在循环加载下，随着饱和程度的增加，由于应变的积累，吸力甚至会增加。这与通常观察到的随着饱和程度的增加而减少的吸力相矛盾。考虑到观察到的边界效应，建立了孔隙率依赖的保水模型，并用于预测重复循环加载和润湿过程中测量的吸力。由孔隙率依赖的持水模型预测的吸力值与实验数据吻合较好。然后将预测的吸力用于半经验公式中，以获得累积的永久应变和弹性模量。当使用依赖于孔隙率的持水量模型预测的吸力值时，模型预测与实验数据之间的相关性更好。研究结果表明，公路和铁路地层循环特性的预测框架需要考虑孔隙率对土壤保水曲线的边界效应。
The water retention properties of soils present in formation layers of roads and railways continuously vary due to repeated traffic loads and periodic rainfall events. This is important because the accumulated deformation and resilient modulus of such soils under cyclic loading are profoundly affected by water retention properties. This paper discusses the cyclic and water retention response of a clayey sand subjected to repetitive cyclic loading and wetting stages. The results show that the accumulated permanent strains and resilient modulus of the tested soil are dependent on the suction level while the main wetting water retention curve of the soil dictates the variation of the suction measured during cyclic loading and wetting. This bounding effect of the water retention curve is found to be dependent on the void ratio where the suction can even increase due to the accumulation of strains under cyclic loading while the degree of saturation increases. This contradicts the suction reduction typically observed with an increase in the degree of saturation. A void ratio dependent water retention model is developed accounting for the observed bounding effect and employed to predict the measured suction during repetitive cyclic loading and wetting. The suction values predicted by the void ratio dependent water retention model are in good agreement with the experimental data. The predicted suctions are then used in semi-empirical formulations to obtain the accumulated permanent strains and resilient modulus. A better correlation between model predictions and experimental data is achieved where the suction values predicted by the void ratio dependent water retention model are used. The results imply that predictive frameworks proposed for the cyclic behaviour of road and railway formation layers require water retention counterparts that incorporate the bounding effect of void ratio on soil water retention curves.