川西非饱和混合土土水特征曲线研究

Research on Soil-water Characteristic Curve of Unsaturated Mixed-soil in Western Sichuan

川西地区地质构造和气候条件复杂,交通荷载和降水入渗经常会引发处于非饱和状态的混合土公路路基变形过大或滑坡破坏,非饱和土的工程性质主要与其吸力值紧密相关。为掌握川西非饱和混合土矿物成分与初始干密度对其土水特征曲线的影响规律,针对川西山区3种崩坡积混合土,采用滤纸法和压力板仪法相结合的试验方案,缩短试验时间,测得各自在不同初始干密度下的土水特征曲线,并通过微观特征来分析宏观现象,探究混合土特征因素的影响机理。试验结果表明:矿物成分对土水特征曲线有显著影响,亲水矿物含量越高,基质吸力越大且曲线走势越平缓;反之,含有较多石英矿物和较少黏粒时,基质吸力通常较低;在相同基质吸力条件下,干密度越大,土体含水量也越大;同时,干密度对土水特征曲线的影响程度随着含水量的减小而增大。最后,采用Van Genuchten(VG)模型拟合川西混合土土水特征曲线,其拟合参数与颗粒级配、非饱和程度相关,拟合曲线与试验曲线吻合较好。

The geological structure and climate conditions are complicated in the western area of Sichuan, the deformation or landslide damage of the non-saturated mixed-soil roadbed were often caused by the traffic load and rainfall infiltration. Engineering properties of unsaturated soil were closely related to the matrix suction. In order to investigate the effect of mineral composition of unsaturated mixed-soils and dry density on the soil-water characteristic curve in western Sichuan, soil-water characteristic curves of three typical unsaturated mixed-soils in western Sichuan were measured by filter paper method and pressure plate method under different dry densities. The macro phenomenon was analyzed to explore the influence mechanism of the characteristics of the mixed-soil by dint of microscopic characteristics. The results show that mineral composition has a significant effect on soil water characteristic curves. The higher the content of hydrophilic minerals in the soil is, the greater the matrix suction will be, and the smoother the curve will be.On the contrary, when there is high quartz content and low clay content in the soil, the corresponding matrix suction is usually low. Under the same matrix condition, the larger the dry density is, the larger the soil water content can be. The effect of dry density on the soil-water characteristic curve increases with the decreasing water content. Van Genuchten （VG） model is used for fitting the mixed-soil water characteristic curve, and the fitting parameters are related to the particle size distribution and unsaturated degree. Hence, the fitting curves are in line with the experimental curves. The results can provide the theoretical basis for the analysis of the structure of saturated mixed-soil in Western Sichuan.