Study On Northern Yinshan Shallow Soil Freezing-thawing Feature Experiment

To give a further study on the wind-erosion mechanism in the northern area of yin-mountain under the condition of freeing–thawing variation and on soil-water-content in this area, researches inside and outside have been carried out and a numerical simulation calculation on soil temperature has been done, the following conclusions have been drawn:(1) soil temperature arises with initial water-content. Soil-water-content at plasticity-demarcation-line is the turning point of soil freezing temperature variation with water-content When the water-content larger than Soil-water-content at plasticity-demarcation-line soil freezing temperature is affected much less by the rising of water-content. The soil freezing-point's variation with soil-water-content is in accord with the equation: Y=ax3+bx2+cx+d.Sand- like soil's freezing point is higher and easily be frozen; fine-grained soil's freezing point is lower and difficult be frozen.(2) By large quantity of experiments,"a"and"b"in water-content erosion equation have been obtained, thus, a graph of unfrozen water-content varied with first-water-content has been presented. The powdered soil's pre-freezing water-content decreases with the soil temperature reduction. When the soil temperature is lower than 4℃,soil temperature is less affected by pre-freezing soil-water-content. The pre-freezing soil water-content increases with first soil-water-content. (3) A graph of day-period soil freezing and thawing has been drawn by the data got in northern yin-mountain experimental field research outside field during thawing season where it is found that the soil there have double-freezing layer and bi-directional thawing. The freezing-thawing extent is affected directly by long-term surface soil temperature below zero.Based on predecessors'research, a calculating model has been set up and a temperature variation graph has been made.