小碎石与细土混合介质的导水特性

HYDRAULIC CONDUCTIVITY OF MIXTURES OF ROCK FRAGMENTS AND FINE EARTH

含碎石土壤的导水性质研究有利于这种多孔介质水分运动的模拟。本文采用室内定水头法和离心机法分别测定两种质地土壤（壤土、黏壤土）和三种岩性小粒径（2~10 mm）碎石构成的土石混合介质的饱和导水率和水分特征曲线,采用van Genuchten-Mualem模型计算各土石介质的非饱和导水率,分析碎石对土壤导水能力的影响。试验结果显示,风化程度低的碎石对黏壤土具有明显的增大饱和导水率的作用,且碎石含量愈高,增加的效果愈明显;而风化程度高的碎石对土壤结构无明显的改善作用,且对黏壤土具有减小饱和导水率的作用。风化程度低碎石介质的非饱和导水率随土壤水吸力的增加呈现了先大于土壤和土石介质的后迅速减小到低于土壤和土石介质的变化过程。风化程度低的河卵石和风化程度高的粉泥页岩碎屑分别构成的土石介质的非饱和导水率较土壤的低,而风化程度中等的片麻状花岗岩碎块构成的土石介质的非饱和导水率较土壤的高。近饱和状态下,碎石含量高的土石介质的非饱和导水率也相应的高,而较大的土壤水吸力下,土石介质的非饱和导水率呈现随碎石含量的增大而减小变化趋势。试验结论可为含碎石土壤水分平衡研究提供参考。

The study on characteristics of water conduction in gravelly soil is beneficial to modelling water movement in this porous type of medium.Saturated hydraulic conductivities and soil water characteristic curves of two soil samples,loam and clay loam,separately and three types of mixtures of fine earth and rock fragments,2～10 mm in particle size and different in lithologic characteristics,were measured in lab with the indoor constant water head method and centrifuging method.Unsaturated hydraulic conductivities of the mixtures were calculated using the van Genuchten-Mualem model,and effect of gravels on soil water transmitting ability was analyzed.Results show that introduction of gravels low in weathering degree into the clay loam significantly increased saturated hydraulic conductivity of the soil,and the higher the introduction rate,the more significant the effect.However,the introduction of gravels high in weathering degree did not improve much its soil structure,and rather decreased its saturated hydraulic conductivity.The unsaturated hydraulic conductivity of the medium of gravels low in weathering degree increased first with rising soil water suction and got over that of the soil-rock fragment mixtures and soils,and then dropped promptly down below that of the two groups of media.When soil water suction was near zero,the unsaturated hydraulic conductivity of soil-rock fragment mixtures high in gravel content was higher,whereas when soil water suction was great,the unsaturated hydraulic conductivity of the mixtures decreased with increasing gravel content in the soil.The findings may serve as reference to the study on water balance in gravelly soil.