ISSN 1000-3665 CN 11-2202/P

    不同密实度条件下云南红黏土积水入渗特性研究

    Water-infiltration characteristics of Yunnan red clay under different density conditions

    • 摘要: 雨水入渗对斜坡渗流及稳定性影响显著,而土体的密实度与其入渗特性紧密相关。为研究不同密实度条件下的红黏土积水入渗特性,以云南省永仁县红黏土为例,利用自主设计的一维土柱积水入渗试验装置,对3组不同密实度(1.25 g/cm3、1.35 g/cm3、1.45 g/cm3)均质土柱进行常水头积水入渗试验。结果表明:(1)水头高度恒定条件下,红黏土密度越大,土柱内相邻传感器响应历时越久,监测点土体增湿过程越慢,含水率快速增长阶段的总历时随干密度增大分别增加25.8%、83.7%;(2)3组土柱入渗时程曲线均呈抛物线型增长,湿润锋垂直运移速率由较高的初始值迅速下降到0.03~0.05 cm/min后趋于稳定;(3)通过对红黏土积水入渗过程中湿润锋柱面形态的量化,分析得出在相同的入渗深度,密度越大,湿润锋水平程度指数越小,指数稳定时入渗深度越浅;(4)红黏土非饱和渗透系数随土体增湿逐渐增大,主要介于10−9~10−4 cm/s,当体积含水率小于18%时,3组红黏土渗透系数相差较小,当体积含水率大于18%后,密度对渗透系数作用明显,两者呈反比;土柱增湿至稳定状态后,含水饱和度在88.2%~94.9%,土体渗透系数均小于真空饱和试样渗透系数。研究成果为红土地区地质灾害的成因分析与治理提供理论基础。

       

      Abstract: Rainwater infiltration has a significant impact on slope seepage and stability, with the soil compactness exerting strong over infiltration dynamics. To investigate the water ponding infiltration characteristics of red clay soil under different densities, constant-head ponding infiltration test was carried out using an independently designed one-dimensional apparatus on three groups of homogeneous red clay samples from Yongren County, Yunnan Province, with different densities (1.25, 1.35, 1.45 g/cm3). The results show that at the higher dry densities, he response time of sensors increased, the humidification process slowed, and the duration of rapid water content increase was extended by 25.8% and 83.7% respectively with the increase of dry density. The infiltration time curve of the soil column in the three groups showed a parabolic growth, with the vertical migration rate of the wetting front decreasing rapidly from a high initial value to 0.03~0.05 cm/min before stabilizing. By quantifying the morphology of the wetting front column during laterite water infiltration, it is concluded that at the same infiltration depth, the higher the density, the smaller the wetting front horizontal degree index, and the shallower the infiltration depth when the index is stable. The unsaturated permeability coefficient of laterite increases gradually with soil humidification, mainly ranging from 10−9 cm/s to 10−4 cm/s. When volumetric water content is below 18%, the permeability coefficient of the three laterite groups has a minor difference; when the volumetric water content is above 18%, permeability is strongly and inversely related to density. When the soil column is humidified to a stable state, the water saturation ranges from 88.2% to 94.9%, and the permeability coefficient of the soil is lower than that of the vacuum saturated sample. This study provides a theoretical basis for the cause analysis and treatment of geological hazards in laterite areas.

       

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