塔克拉玛干沙漠腹地垄间平沙地沙粒胶结体对沙面蚀积过程的影响及作用机制

The properties of bed surface play a very important role on the process of aeolian erosion and deposition on ground surface. The process of aeolian erosion and deposition of inter-dune corridor in the central Taklimakan Desert is affected not only by the coarse sand layer on ground surface, but also by the sand cemented bodies (SCD, for short). SCD is a kind of larger granular material with irregular shapes whose diameter reach the level of coarse sand, very coarse sand and gravel. They were made up of a mass of sands which be cemented together by a certain substance, with a density slightly lower than sand or gravel. Does it have a similar sand fixation effect like sand or gravel in the same diameter? What role does it play in the stability of inter-dune corridor? This has been reported less in the related literature at home and abroad. This study will conduct the SCD covering experiment with different coverage, diameter, particle shape and grain composition, in the wind tunnel and fields respectively, compared with the coarse sand or gravel covering and drift sand without covering. The aerodynamic characteristics of the bed surface covered with SCD will be analyzed based on the data of wind speed profile and sand transport rate profile near ground surface, and weight changes of sand plates, the main controlling factors of erosion/deposition mutual transformation on sand bed and related threshold conditions will be discussed, action mechanism of SCD covering on aeolian erosion and deposition on sand surface will be disclosed. The results will help for thoroughly disclosing the stability mechanism of the inter-dune corridors in Central Taklimakan Desert and provide some theoretical basis for application of SCD in sand-controlling engineering.

床面性质对地表蚀积过程起着非常重要的作用。对于塔克拉玛干沙漠腹地垄间平沙地来说，地表蚀积过程不仅受到粗沙层的影响，而且还受到沙粒胶结体（sand cemented bodies，缩写为SCD）的影响。SCD是由众多沙粒胶结而成的，外形极不规则，直径可达到粗沙至砾石级别，密度略小于沙或砾石。它是否具有类似于粗砂或砾石的固沙作用？对垄间平沙地的相对稳定有何贡献呢？本项目拟采用野外实验观测与室内风洞模拟的方法，开展不同覆盖度、不同粒径、不同粒形、不同颗粒级配的SCD覆盖流沙实验，并与相应的沙或砾覆盖和无覆盖（流沙）床面进行对比，测定地表风速廓线、风沙流结构、蚀积量变化，查明SCD覆盖床面的空气动力学特征，探讨不同因素对SCD覆盖床面蚀积过程的影响，阐明床面蚀积转化的阈值条件，揭示SCD对床面蚀积过程的作用机制。研究结果有助于全面认识垄间平沙地的稳定机制，也可为SCD在防沙工程中应用提供科学依据。

本项目以塔克拉玛干沙漠腹地垄间平沙地上天然发育的沙粒胶结体（sand cemented bodies，缩写为SCB）为研究对象，旨在研究其沙面稳定效应及作用机制。通过野外实验观测与室内风洞模拟，开展了不同的覆盖度、粒径、粒形、颗粒孔洞的SCB覆盖流沙实验，并与相应的沙或砾覆盖和无覆盖（流沙）进行对比，测定了地表风速廓线、风沙流结构、蚀积量变化。实验结果均证实：SCB的确能够影响沙面蚀积过程，而影响程度与SCB的覆盖度有密切关系，随着覆盖度越大，沙面逐渐由净风蚀状态向净堆积状态转变，临界覆盖度约30-40%；同时，在同等覆盖度情况下，SCB的粒径、外形和内部孔洞均可影响下覆沙面的蚀积状况，粒径越小、外形细高有明显边界（方向比率大）、有内部孔洞，则沙面输沙率越小，有利于固沙。这些研究结果有助于全面认识流动沙漠垄间平沙地的稳定机制，也可为SCB在防沙工程中应用提供理论依据和关键参数。此外，项目还对SCB的物质机械组成进行了深入研究，并推测了其可能发育环境特征及胶结物可能的化学反应，同时对其发育动力进行了初步探讨，研究结果为进一步研究其天然发育机制奠定了基础。