Study On Failure Mechanism Of Wind-snow-in Duced Composite Erosion For Roadbed

The damage phenomenon caused by the wind-snow composite erosion of is usual inthe arid and cold regions such as Xinjiang province, Inner Mongolia autonomous region,Jilin province, Heilongjiang province and so on.Complex erosion is induced by manyfactors: annual strong wind days, dust storm days and snowing days are long in theseregions; furthermore, the average temperature is low and variation of temperature isobvious. In the special natural environment of arid and cold regions, the wind erosion ofroadbed is stem from the wind-draft sand storm. Because of the difference in temperatureleading to the snow melt into the roadbed, the damage of snow is mainly the freeze-thawaction caused by the moisture for the filler soil.Taking aeolian sandy soil roadbed as the research object, the failure mechanism of theaeolian sandy soil filling roadbed induced by the wind-snow composite erosion has beenresearched in this article.The trajectory of sand particles is studied by using wind tunnel experiments withhigh-speed camera shooting, which is influenced by design parameters of roadbed crosssection in the wind field. A single particle trajectory is traced and shooted by high-speedcamera before and after hitting roadbed slope, and the impact position, the impact angleand the impact velocity are analyzed under different roadbed section. When horizontalwind speed is constant and short roadbed is selected, most of the particles across the top ofthe roadbed directly or after hitting the top of roadbed. Moreover, the impact velocity willincrease as roadbed slope becomes steeper. However, when sand particles are blown tohigh roadbed, most of the particles hit roadbed slope many times and rebound to upwardwith energy loss, and then slide along the slope or landing directly in the slope toe. Asroadbed slope rate increases, the increase of the particles impact velocity is not obvious.Through the freeze-thaw cycling test with three temperatures, we study on the changlaw of the physical characteristics under the freeze-thaw action. Because of the lack ofcohesive force, the moisture of the filler soil moves slowly from the top to the bottom overtime under the action of gravity, however, the freeze-thaw action increases the migrationspeed of water, because of a new kind of power transfer of energy. The article studies the diffusion law of moisture under the freeze-thaw action. At the same time, the freeze-thawaction can make the soil porosity increase, which leads to the porosity of soil structure, sothe internal dry density decreases. But for sand soil, the deformation caused by thefreeze-thaw action is small.Through wind erosion test of freeze-thaw, the article studies the failure mechanism ofcomposite erosion induced by freeze-thaw and wind erosion has been researched. Take thevariable of shear strength as the measurement criteria, the different impact of wind-snowcomposite erosion is considered with the different position from the top to bottom, andfrom the slope surface to the interior. And the different impact degree for the differenterosion action also plays the important roles in the composite erosion action. For theaeolian roadbed under the certain size, the influence of composite erosion reducesgradually from top to bottom; what’s more, wind erosion damage is mainly for theshoulder slope, but the freeze-thaw erosion is more serious than wind erosion on bottom.For the filler soil with the increase of moisture content, the influence of wind erosionweakens, but the freeze-thaw action strengthens.