高风能高输沙率沙砾质戈壁沙/砾释放强度和输移规律研究—以哈罗铁路南湖戈壁为例

The research on laws of wind-blown sand movement and formation mechanism of aeolian sand disaster in gobi areas with strong wind has been strengthened by domestic scholars in research of aeolian physics in recent years, which mainly focuses on the gravel gobi with high wind and low sand transport rate, yet it is less on the sandy gobi with both high wind and sand transport rate. The Hami-Lop Nor Railway runs through the Nanhu sandy gobi which develops on lacustrine plain, and the sand sources are extremely abundant on the land surface. At the same time, the gobi locates downwind the Baili and Yandun wind areas, and the high winds happen frequently. The sands/gravels are entrained locally by the strong wind, and the wind-blown sand/gravel flow develops. The wind-blown sand/gravel flow has high concentration and great intensity, which buries the roadbed and rail and exerts an enormous threat to the railway operational safety. In view of this, this project takes Nanhu Gobi as a study area, and attempts to study the sands/gravels entrainment intensity and the characteristics of aeolian transport over sandy gobi with both high wind and sand transport rate, aiming to quantitatively evaluate the entrainment intensity of sandy gobi under various wind speeds and sand contents; to reveal the interaction mechanism between wind speeds, wind-blown sand/gravel flux and their energy in different heights; to build the vertical structure of sand/gravel flux and kinetic energy; and to establish the models of wind-blown sand/gravel transport rate in gobi areas with both high wind and sand transport rate by field wind tunnel experiment and observation methods. This research is not only able to provide a scientific basis for the wind-blown sand/gravel control and prevention of Hami-Lop Nor Railway, but also enrich the studies on wind-blown sand physics in gobi areas with strong wind.

近年来在风沙物理学领域，我国学者加强了关于戈壁大风区风沙/砾运动规律和致灾机理的研究，但主要集中在高风能低输沙率的砾质戈壁地表，尚未对高风能高输沙率的沙砾质戈壁开展相关研究。哈（密）—罗（布泊）铁路穿越南湖湖积平原沙砾质戈壁，地表沙源极其丰富，同时，它又位于百里风区和烟墩风区下风向，风力强劲。大风作用下戈壁表面沙/砾就地释放，形成高浓度戈壁风沙/砾流，侵蚀掩埋哈罗铁路路基铁轨，对行车安全造成巨大威胁。本项目以哈罗铁路南湖戈壁为例，拟通过野外风洞实验和定位观测等方法，研究高风能高输沙率沙砾质戈壁沙/砾释放强度和输移规律，定量评估不同含沙量沙砾质戈壁在不同风速下的沙/砾释放强度，揭示不同高度风速与沙/砾流量和能量间的相互作用关系，建立沙/砾流量与能量垂直结构模式，构建输沙/砾通量模型。这不仅为哈罗铁路风沙灾害防治提供了科学依据，也丰富了戈壁大风区风沙物理学研究内容，具有重要的理论和实践意义。

南湖戈壁是典型的高含沙量沙砾质戈壁，大风作用下戈壁表面沙/砾就地释放，形成高浓度戈壁风沙/砾流，侵蚀掩埋哈罗铁路路基铁轨，对行车安全造成巨大威胁。本项目以哈罗铁路南湖戈壁为例，通过野外定位观测和风洞模拟实验等方法，研究高风能高输沙率沙砾质戈壁沙/砾释放强度和输移规律。通过研究，得出以下结论：.（1）哈罗铁路南湖戈壁段属于高风能环境，输沙势最大为1116VU，最大可能输沙量为2015 kg·m-1·a-1。（2）不同于高覆盖度砾质戈壁地表沙/砾的间歇性输移特征，沙质戈壁地表在大风条件下沙/砾输移具有连续性特征。（3）沙/砾跃移起动风速ut是沙漠地表的3.5倍，ut随跃移间歇性参数AP值的增大指数递减，沙/砾的起动主要受控于冲击起动风速，而非流体起动风速。（4）输沙/砾量随高度增加指数递减，沙/砾平均跃移层高度zq介于0.10-0.49 m，平均值为0.23±0.07 m，是沙漠地表的4倍，zq与地表沙/砾粒径及风速正相关，而与戈壁类型无关；（5）输沙率与摩阻风速间存在幂函数关系Q=ap/g[u* (u*2-u*t2)]b,幂指数b是一般戈壁地表的2.5倍。（6）高含沙量沙砾质戈壁沙/砾释放强度随风速增大而增大，呈线性关系。.研究结果表明哈罗铁路南湖戈壁段在大风作用下，戈壁地表就地起沙，输沙量大，风沙/砾流近饱和传输。因此，风沙防护工程应考虑借鉴沙漠地表防沙经验，以固沙措施为主，阻沙措施为辅，但应根据沙/砾跃移层高度相应提高固沙方格高度和规格。同时，哈罗铁路不同路段输沙方向及输沙量差异较大，要根据各路段风沙环境特征调整工程措施的走向和防护宽度。