输沙量对海岸沙丘表面风沙流中不同粒径沙粒垂向分布的影响

 在我国海岸沙丘的典型分布区河北昌黎黄金海 岸，对不同输沙量下海岸沙丘表面风沙流中不同粒径组沙粒垂向分布的变化进行了野外观测。结果表明，在风速相近、物质组成一 致和下垫面性质相同情况下，随着风沙流总输沙量的增加，在非均匀沙床面上不同粒径组沙粒的垂向分布呈现出了不同的变化特点 。其中，随总输沙量增加粗沙输沙量总量并无增加，其输沙量下层减少、中层增加、上层减少，垂向分布转变为典型负幂函数模式 ；中沙在不同高度的绝对输沙量均有增加，相对输沙量下层（0~4 cm）减少、上层（4~60 cm）增加或基本持平，其垂向分布基本 符合指数递减规律，尤其是在0~60 cm高度内的分布随总输沙量的增加由负幂函数转变为指数函数；细沙输沙量总量和不同高度的 输沙量均有不同程度的增加，相对输沙量下层（0~6 cm）减少、上层（6~60 cm）基本持平或增加，垂向分布符合典型的指数函数 布模式。究其原因，主要应与不同风速气流的携沙极限以及不同粒径组沙粒的运动方式密切相关。

Influence of Total Sand Transport Rates on the Vertical Distribution of Different Sand Grain Sizes in Wind-sand Flow on the Coastal Dune

The data of vertical distribution of different sand grain sizes at different total sand transport rates, including the data of structure of wind sand flow and its grain size composition of sands at different heights,were measured on the crest of typical coastal transverse ridge along the Changli Gold Coast in Hebei Province, which is one of the most typical coastal Aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The results showed that under the conditions of near wind velocity and the same surface material and environment, with increasing total sand transport rates in the wind sand flow, vertical distribution of different sand grain sizes in the wind sand flow on the crest of coastal transverse ridge had different change features. With increasing total sand transport rates, the transport rate of coarse sands had no increase, the ratio of sand transport rates of different height layers in total sand transport rates decreased at the low height layer (0 ～2 cm) and high height layer (32～60 cm),and increased at the middle height layer (2～32 cm) .The vertical distribution of coarse sand transport rate in the wind sand flow could be expressed by the typical power function. The transport rates of middle sand at all height layers increased, the ratio of sand transport rates of different height layer in total sand transport rates decreased at the low height layer (0～4 cm) and increased at the high height layer (4 ～60 cm). The vertical distribution of middle sand transport rate in the wind sand flow could be expressed by exponential function.With increasing total sand transport rates, the transport rate of fine sands increased at different height layers,its ratio in total sand transport rates decreased at the 0～6 cm height layer and increased at the 6～60 cm height layer. The vertical distribution of fine sand transport rate could be expressed by the typical exponential function. These changes had a close relationship with the limit of sand grain size of wind flow transporting with definite wind velocity and transporting ways of sands with different grain sizes in the wind sand flow.