随着经济社会的高速发展以及工程建设项目的快速递增,大量生产建设项目扰动地表并破坏原地貌植被,大范围且不平衡的挖填活动使得多余的土石混合堆积,尤其在山区工程建设形成的多余土石混合介质,堆积在沟道和河道上游及边坡,在强降雨条件下易发生严重水土流失,甚至造成滑坡、泥石流等灾害。以人为重塑工程堆积体为研究对象(坡度25°),通过模拟降雨试验,开展极端降雨条件下(降雨强度为2.5 mm/min)不同坡长(3,5,6.5,12 m)及砾石质量分数(0,10%,20%,30%)共同作用对堆积体流速空间分布特征及产沙特性影响的研究。结果表明:(1)坡长12 m时流速在降雨全过程始终处于波动状态,随砾石质量分数增大,波动幅度减小,而坡长3,5,6.5 m下的流速随产流历时呈先递增后趋于稳定的变化趋势。中下坡位平均流速是中上坡位的1.12~1.54倍,随着坡长增大,平均流速递增17.81%~335.94%,含砾石堆积体平均流速较纯土堆积体降低22.88%~54.67%,砾石质量分数比坡长对流速影响更显著。(2)纯土堆积体平均侵蚀速率随坡长显著增大,递增幅度达7.88%~87.67%,而含砾石堆积体随坡长增大在3~5 m呈下降趋势,降低9.10%~28.86%,但随后又显著增大,存在1个临界坡长。坡长为6.5,12 m的堆积体平均侵蚀速率较3 m增大22.33%~122.48%。砾石具有显著降低堆积体坡面侵蚀效果,其减沙效益达到24.99%~59.54%,且砾石对堆积体平均侵蚀速率影响的贡献是坡长的1.13倍。(3)堆积体坡面中上坡位流速对侵蚀速率影响大于中下坡位,平均侵蚀速率与流速之间呈极显著相关,流速可作为平均侵蚀速率的表征参数,其线性拟合关系较好(R2=0.67~0.95)。研究成果进一步深化了土壤侵蚀学科内涵,可为生产建设项目工程堆积体侵蚀预测模型提供数据基础,同时也为阐明工程扰动坡面侵蚀内在机制提供理论依据。
Large number of production and construction projects disturb the surface and destroy the original surface vegetation with the rapid development of economy and society and the rapid increase of engineering construction projects. Large-scale and unbalanced excavation and filling make excess soil and rock mixed and accumulated. The excess soil-rock mixed media formed in the construction of mountain projects are accumulated in the upstream and slope of ditches and rivers, which is prone to serious soil and water loss under heavy rainfall conditions, and even cause disasters such as landslides and debris flows. This study took the artificially remolded spoil heaps (with a slope degree of 25°) as the research object, and carried out the research on the influence of slope length (3 m, 5 m, 6.5 m, 12 m) and gravel content (0, 10%, 20%, 30%) on the spatial distribution characteristics of velocity and sediment yield characteristics of spoil heaps under extreme rainfall conditions (with a rainfall intensity of 2.5 mm/min) through the simulated rainfall test. Results showed:(1) The flow velocity was in a fluctuating state during the whole rainfall process, and the fluctuation amplitude decreased with the increase of gravel content and mass fraction under slope length by 12 m. However, the flow velocity under the slope length of 3 m, 5 m and 6.5 m increased at first and then tends to be stable with the runoff duration. The average velocity of the middle and lower slope was 1.12 to 1.54 times that of the middle and upper slope. With the increased of the slope length, the average velocity of the flow increased by 17.81% to 335.94%, and the average velocity of spoil heaps with gravel was 22.88% to 54.67% lower than that of the pure spoil heaps. The mass fraction of gravel had more significant effect on the flow velocity than the slope length. (2) The average soil loss rate of pure spoil heaps increased significantly with the slope length, with an increment of 7.88% to 87.67%. However, the gravel-bearing spoil heaps decreased with the increasing of slope length from 3 to 5 m (decreased by 9.10% to 28.86%), but then increased significantly. There is a critical slope length. The average soil loss rate of spoil heaps with slope length of 6.5 m and 12 m is 22.33% to 122.48% higher than that of slope length of 3 m. Gravel could significantly reduce the slope erosion of spoil heaps, and its sediment reduction efficiency reached 24.99% to 59.54%. The contribution rate of gravel to the average soil loss rate of spoil heaps was 1.13 times of the slope length. (3) The impact of flow velocity on the soil loss rate in the upper and middle slope of the spoil heaps was greater than that in the lower and middle slope. There was a significant correlation between the average soil loss rate and flow velocity. The flow velocity could be used as a characteristic parameter of the average soil loss rate, and its linear fitting relationship (R2 was 0.67 to 0.95). The results further deepen the connotation of soil erosion discipline, which can provide data basis for the prediction model of spoil heaps erosion of construction production and construction projects, and also provide theoretical basis for clarifying the internal mechanism of engineering disturbance slope erosion.
李魁, 王文龙, 李建明.工程堆积体流速及产沙特征对坡长及砾石作用响应[J].水土保持学报,2023,37(5):48~56,102复制