三种被动式积沙仪积沙效率的野外实验研究

A FIELD EXPERIMENTAL STUDY ON THE SAMPLING EFFICIENCY AMONG THREE KINDS OF PASSIVE SAND TRAPS

积沙仪积沙效率的高低直接影响近地表输沙率的测定 ,从而影响着风沙地貌的研究和风沙工程设计。对目前三种常用积沙仪在相同条件下 (同一下垫面、相同风速 )的积沙进行了野外观测。结果表明 :①相同条件下 ,楔形积沙仪积沙量远远大于其它两种 ;②近地面积沙量随高度分布上 ,楔形积沙仪能更好地反映风沙流结构 ;③与其它两种积沙仪相比 ,楔形积沙仪所采集沙子中的小粒径颗粒含量明显多于其它两种积沙仪结果 ,而较大粒径颗粒的含量呈相反趋势。造成这些差异的原因在于楔形积沙仪采用的流线型构造和网状结构 ,从而对风沙流的阻挡程度较小 。

The sampling efficiency of sand traps affects directly on the measurement of the rate of aeolian sand transport near the ground surface, and thus influences the both studies on the aeolian geomorphology and the protecting engineering against sand drift. However, many kinds of sand traps are being used in China and at abroad, and their sampling efficiencies are not identical each other. So it is of importance to compare their sampling efficiencies in both wind tunnel measurement and field observation so as to select a best kind. This paper compares the sampling efficiencies of three kinds of sand traps used worldwide by the field experiments in Taklimakan Desert under the same conditions (the same underlying surface and the same wind speed). The results are as follows: (1) The quantity of sand trapped by a wedge shaped sand trap is much more than that by other two kinds, i.e., for 38%～63% and 58%～84% of the former respectively. (2) In the distribution of the trapped sand quantity with height near the ground surface, the drifting sand field can be preferably revealed. In the sand samples trapped by a wedge shaped sand trap, the content of fine sand is obviously higher but the course one lower than that trapped by other two kinds. These differences are caused by the streamlined and the wetted designs of the wedge shaped sand trap, which can reduce the resistance pressure on sand drift.