Wind Tunnel Simulation Study On The Effects Of Soil Root Content On Wind Erosion

As one of the most important external agent at the surface of earth, wind erosion has caused serious damage to the surface. The process of wind erosion is the phenomenon that the wind carried the sand movement and persecution on the surface of the material. Soil erosion is widespread in the arid and semi-arid regions of the world. Soil erosion leads to the loss of soil nutrients and the decrease of land productivity. It has caused different degree of damage and even catastrophic damage to human survival environment. Plant is an important influence factor of wind erosion. Plants can increase the aerodynamic roughness and increase the wind speed, which can effectively reduce the erosion of wind-blown sand flow. Previous studies about the effects of plant on reduce wind erosion are mainly on the ground. On the effects of plant roots on soil erosion is rarely reported. However, the roots of plants are most closely related to the soil, it not only can improve the stability of the soil layer structure, but also can reduce the direct erosion of sand and sand flow on the surface material. The root system in the soil has an important influence on the soil resistance to wind erosion. Therefore, we should further explore the relationship between root content and wind erosion in soil under different wind speed, clarify the relationship between wind erosion factors. These studies have important theoretical and practical significance in the prevention and control of soil erosion in the arid and semiarid regions of northern China.In view of this, we have carried out a wind tunnel simulation experiment. In the experiment, we designed three kinds of simulated roots and two typical soils in the arid regions of northern China. We have carried out wind erosion experiments on the soil samples under the wind speed of six groups. We have measured and discussed the relationship between wind speed and soil erosion, and the relationship between root system and soil erosion. According to the experimental results, we have constructed the model of soil root anti wind erosion. According to the experimental results, we believe that:(1)The grain size composition of typical loess is mainly composed of silt(37.16%), coarse silt (35.31%) and very fine sand (23.03%), and the content of fine sand and medium sand is very small; The aeolian sandy soil particle size distribution range is larger, and the fine sand content up to 34.65%, silt(21.18%), very fine sand (17.22%), medium sand (13.426%), coarse silt (13.47%), and the content of coarse sand is least for 0.06%; The sand used in the experiment is mainly fine sand (72.63%), and the content of medium sand and fine sand were less than 16.2% and 11.16% respectively.(2)We have measured the wind velocity profile of the net wind bed surface condition and the sand carrying wind bed surface. The wind velocity profile is fitted with a logarithmic function, and the wind velocity profile in wind-blown sand flow is fitted by power function. In the absence of sand, the wind velocity profile is a straight line. In the case of sand, the wind velocity profile is a convex curve. The structure of the wind-blown sand flow is similar to that of the Gobi wind-blown sand flow structure in the experiment. The sediment yield reached a maximum at a certain height, and increased with the increase of wind speed.(3)Under the condition of any wind speed which is larger than the critical wind erosion, the relationship between wind erosion rate and friction wind speed can be described by the three power function. With the increase of wind speed, the erosion rate of the sample increases; There is a significant linear relationship between soil wind erosion rate and root system content. Under the same wind speed, the more root content in the soil, the lower the erosion rate of the sample; However, when the soil contains a certain amount of root content, wind erosion rate will be more volatile. Through the analysis, we can conclude that there are two aspects of the effect of flow around phenomenon, which will affect the amount of soil erosion. The fast movement of turbulence, which has carried large numbers of fine material, is likely to increase the amount of soil erosion; The soil anti-erosion model can be expressed by the power function relation between wind erosion rate and friction wind speed and root content.It can be concluded that wind erosion is mainly determined by wind speed. The carrying capacity of the wind to the particles determines the ability of erosion and transport capacity of wind-blown sand. Under certain conditions, improve the ability of soil erosion resistance. Therefore, we should raise the importance of plant roots, reasonably arrange the plant density, and give full play to the anti-wind erosion efficiency of root system. These theories can be used in the implementation of windbreak biological engineering and soil conservation tillage in arid area etc.