基于降雨染色示踪试验的大孔隙流特性研究

实际边坡土体内部存在大孔隙等优势通道,坡体内的水分运动常表现出优势流特性。为探究降雨作用下天然边坡土体内大孔隙的发育特征及优势流的空间响应规律,开展原状土柱的降雨染色示踪试验。通过染色信息标定水分浸润面积,根据“水分浸润面积比”这一参数评价土柱内部不同大孔隙的发育特征对优势流发展及水分入渗通量的影响。研究结果表明:原状土柱中优势通道的发育程度与空间变异性较强,优势通道类型以大孔隙为主,连通性与开启程度好的大孔隙,优势流快速通过,与周围基质交换能力弱,可快速多量地补给地下水;分布不规则、方向各异的大孔隙,优势流现象被削弱,与基质交换能力强,但随深度逐渐减弱;个别死端大孔隙,滞留水分较多,增强了与周围基质的水分交换能力,对优势流的运移作用不大。染色评价结果与土柱实测水分通量所得规律完全一致,准确揭示了原状土中大孔隙流的典型空间分布特征。

Research on Macropore Flow Characteristics Based on Rainfall Dyeing Tracer Experiment

Preferential channels such as large pores exist in actual slope soil where the water movement exhibits preferential flow characteristics. In this paper, we conducted a rain staining tracer test on undisturbed soil columns to investigate the development characteristics of large pores in natural slope soils and the spatial response rule of preferential flow under the action of rainfall. By calibrating the water infiltration area using staining information, we evaluated the influence of the development characteristics of different large pores inside the soil column on the development of preferential flow and water infiltration flux according to the parameter “water infiltration area ratio”. The research results revealed strong development and spatial variability of preferential channels in the undisturbed soil column. The preferential channel types are mainly large pores. To be specific, in large pores with good connectivity and opening degree, the preferential flow passes quickly, with weak exchanges with the surrounding matrix, hence replenishing groundwater quickly in large quantities; in large pores with irregular distribution and different directions, the preferential flow is weakened with strong exchange with matrix which yet gradually weakens with depth; in some dead-end large pores which retain more water, the water exchange with the surrounding matrix is enhanced, which is of little help to the migration of preferential flow. The results of the dyeing tracing evaluation are completely consistent with the laws obtained from the measured soil water fluxes of the soil column, which accurately reveals the typical spatial distribution characteristics of large pore flow in undisturbed soil.