Evaporation of saline colloidal droplet and deposition pattern

The dynamic process of the evaporation and the desiccation of sessile saline colloidal droplets,and their final deposition are investigated.During the evaporation,the movement of the colloidal particles shows a strong dependence on the salt concentration and the droplet shape.The final deposition pattern indicates a weakened coffee-ring effect in this mixed droplet system.The microscopic observation reveals that as evaporation proceeds,the particle motion trail is affected by the salt concentration of the droplet boundary.The Marangoni flow,which is induced by surface tension gradient originating from the local evaporative peripheral salt enrichment,suppresses the compensation flow towards the contact line of the droplet.The inhomogeneous density and concentration field induced by evaporation or crystallization can be the major reason for various micro-flows.At last stage,the distribution and crystallization of Na Cl are affected by the colloidal particles during the drying of the residual liquid film.

水-土特征曲线的分段对估测非饱和渗透系数的影响（英文）

目的:在采用统计法估测非饱和渗透系数的过程中,探讨水-土特征曲线分段的不同方法和不同数量对估测结果的影响。创新点:比较在体积含水量区间和土吸力区间分割水-土特征曲线对估测非饱和渗透系数的影响;最终建议在土吸力区间分割水-土特征曲线。方法:采用现有模型和数学公式,对比不同类型土质(单峰和双峰水-土特征曲线)估测和实验测量的非饱和渗透系数。结论:1.传统的在体积含水量区间分割水-土特征曲线会造成对低吸力区域的非饱和渗透系数的估测不够精确。2.综合比较单峰和双峰的水-土特征曲线及2种不同分割水-土特征曲线的方法,发现在分段大于40片时,估测结果非常接近实验结果。因此,在采用统计法估测土体的非饱和渗透系数时,建议在土吸力区间对水-土特征曲线进行分割,且分割数量应该大于40。

Effect of the uncertainty in soil-water characteristic curve on the estimated shear strength of unsaturated soil

Most failures or instabilities of geotechnical structures commonly result from shear failure in soil. In addition, many infrastructures are constructed within the unsaturated zone. Therefore, the determination of shear strength of unsaturated soil is crucial in geotechnical design. The soil-water characteristic curve(SWCC) is commonly used to estimate the shear strength of unsaturated soil because the direct measurement is time-consuming and costly. However, the uncertainty associated with the determined SWCC is rarely considered in the estimation of the shear strength. In this paper, the uncertainties of SWCC resulted from different factors are reviewed and discussed. The variability of the estimated shear strength for the unsaturated soil due to the uncertainty of SWCC associated with the best fit process is quantified by using the upper and lower bounds of the determined SWCC. On the other hand, the uncertainties of the estimated shear strength due to different initial void ratios or different confining pressures are quantified by adopting different SWCCs. As a result, it is recommended that the measured SWCC from the conventional Tempe cell or pressure plate needs to be corrected by considering different stress levels in the estimation of the shear strength of unsaturated soil.

孔径分布函数对水分在非饱和土体中迁移的作用（英文）

目的:了解孔径分布函数对水分在非饱和土体中迁移的影响,并提出相关数学模型,量化非饱和土体在不同吸力作用下的渗透系数。创新点:从孔径分布函数出发探讨土体的工程性质,以日常生活中所用的阀门模型解释非饱和土体在不同吸力作用下的渗透系数。提出采用非饱和土渗透系数的实验数据,间接估算土体的孔径分布函数。方法:从物理模型推导相关数学公式,并用实验结果对数学公式进行验证。结论:孔径分布函数主导非饱和土的渗透系数;孔径分布函数是连接土体两大水力特性(包括水土特征曲线和渗流方程)的桥梁。孔径分布函数对水分在土体中迁移的作用可以用日常生活中使用的阀门模型简单描述。基于阀门模型,土体的孔径分布函数也可以由土体的非饱和渗透系数的相关实验数据间接估算得到。