三峡库区紫色土柑橘园土质道路路面侵蚀的研究

The Three-gorge Reservoir area is one of the most appropriate ecological zones for citrus planting in China. Many hillside roads have been constructed in citrus orchards in order to satisfy the demands of orchards management and citrus transportation. However, there have no studies on road types, pavement structure, road erosion status and characteristics of these hillside roads. Therefore, the aims of this study were to (1) measure and analyze soil physical properties, mechanical properties and hydrological characteristics of unpaved purple earthen roads by collecting a series of samples; (2) monitor the processes of runoff and sediment yield on earthen road surface under simulated rainfall conditions and analyze different expressions of erosion and sediment yield processes on typical earthen pavements; and (3) study coarsening processes of purple soil on the unpaved earthen roads and clarify their driving mechanism based on rainfall simulation tests and measured data under natural rainfall conditions. This study would provide a theoretical basis and technical guidance to road erosion control in citrus orchards in the Three-gorge Reservoir area.

三峡库区是我国柑橘的最适宜生态区之一，退耕紫色土坡地是主要的柑橘园用地类型，为了方便果园管理和柑橘运输，山坡道路在柑橘园内被大量修建，但有关库区柑橘园道路类型、路面结构特征、道路侵蚀现状及侵蚀特征等方面的研究还未见报道。本项目以库区紫色土柑橘园土质道路为研究对象，在对研究区道路类型及侵蚀现状野外踏勘的基础上，采集系列样品对路面土体的物理性质、力学性质及水文特性进行测定和分析，开展野外模拟降雨试验对路面产流产沙过程进行动态监测，结合天然降雨观测资料，研究路面土体粗化过程，揭示紫色土土质道路侵蚀产沙规律，探索不同路面侵蚀产沙差异性表现，阐明路面土体粗化过程驱动机制，为三峡库区柑橘园道路侵蚀防治提供一定的理论依据和技术指导。

土质道路是当前我国山区农业生产与生活的主要道路，也是发生水土流失最严重的土地利用类型之一。三峡库区为解决移民就业及提高农民收入大力发展了柑橘种植业，为了方便果园管理和柑橘运输，山坡道路在柑橘园内被大量修建，但有关库区柑橘园道路类型、路面结构特征、道路侵蚀现状及侵蚀特征等方面的研究还极为缺乏。本项目以位于三峡库区腹心地带申家河流域内的紫色土柑橘园土质道路为研究对象，通过野外走访与调查，确定研究区土质道路主要以裸露土质路面、草皮路面和泥结碎石路面为典型道路路面类型；定点观测与采集系列土体样品分析了路面土体和柑橘园土壤的物理性质、力学性质及水文特性；开展野外模拟降雨试验研究了土质道路路面产流产沙规律。结果表明：①土质道路路面土体容重远高于相邻柑橘园土壤，土壤含水量、稳定入渗率低于同时期柑橘园土壤，路面土体在0.1-1.0 mm之间的粒径含量远高于柑橘园土壤，草皮路面土体和柑橘园土壤粘聚力远大于裸露土质路面；②开始产流时间随前期含水量的增大呈指数函数递减变化，路面产流率随降雨历时的延长而增大，路面产流初期径流含沙量都很高，但都很快下降并随降雨历时的延长而逐渐趋于平稳；③裸露土质路面的平均侵蚀速率分别是草皮路面和泥结碎石路面的1.72和2.85倍，集中的路面水流、车辙及路面上方来水股流的冲击力为路面土体粗化的主要驱动力。这些研究成果为三峡库区柑橘园道路侵蚀防治提供科学依据和技术指导。