西藏派墨公路不同砾石磨圆度开挖坡面土壤侵蚀特征研究

STUDY ON SOIL EROSION CHARACTERISTICS OF EXCAVATED SLOPES WITH DIFFERENT GRAVEL GRINDING ROUNDNESS ON PAI-MO HIGHWAY, TIBET

西藏派墨公路穿越生态极为敏感脆弱的雅鲁藏布大峡谷国家级自然保护区,公路建设导致地表裸露,引发水土流失,造成严重生态问题。派墨公路沿线堆积体由于成因不同,导致开挖坡面砾石磨圆度差异较大,研究不同砾石磨圆度开挖坡面土壤侵蚀特征能为建立青藏高原地区含砾石坡面土壤侵蚀预测模型和防治水土流失提供基础理论依据。通过室内人工降雨模拟试验,探究了不同砾石磨圆度开挖坡面微地形、入渗过程、产流过程、水动力学特性和产沙过程变化特征。结果表明:卵石坡面在降雨过程中,形成以卵石为中心遍布坡面的深切环形小细沟,导致卵石周围土壤侵蚀较为严重。与砾石坡面相比,卵石坡面平均入渗率偏高11.3%,初始产流时间延长28.1%,径流率偏小9.4%。卵石坡面水流流态为层流,流型为急流,相较于砾石坡面,其雷诺数和阻力系数偏小,弗劳德数和平均流速偏大。砾石坡面比卵石坡面更早发生细沟侵蚀,但卵石坡面稳定侵蚀速率比砾石坡面大2.1倍,其总产沙量比砾石坡面高20.1%。

The Pai-Mo Highway in Tibet crosses the Yarlung Zangbo Grand Canyon National Nature Reserve, which is extremely sensitive and fragile ecologically. The construction of the highway has led to the exposure of the ground, triggering soil erosion and causing serious ecological problems. The soil erosion characteristics of excavated slopes with different degrees of gravel rounding can provide a basic theoretical basis for establishing a predictive model for soil erosion on gravel-containing slopes and preventing soil erosion in the Qinghai-Tibet Plateau region. Through indoor artificial rainfall simulation tests, the micro-topography, infiltration process, flow production process, hydrodynamic characteristics and sand production process of different gravel grinding roundness excavation slopes were investigated. The results show that the pebble slopes, during rainfall, form small, deep circular furrows centred on the pebbles all over the slope, resulting in more severe soil erosion around the pebbles. Compared to gravel slopes, the average infiltration rate on pebble slopes is 11.3% higher, the initial flow production time is 28.1% longer and the runoff rate is 9.4% smaller. The pebble slope has a laminar flow regime and a rapid flow pattern, with a lower Reynolds number and drag coefficient and a higher Froude number and mean flow velocity than the gravel slope. Fine gully erosion occurs earlier on gravel slopes than on pebble slopes, but the steady erosion rate is 2.1 times greater on pebble slopes than on gravel slopes, and their total sand production is 20.1% higher than on gravel slopes.