Microscopic Experimental Study On Composite Erosion Mechanism Of Embankment In Cold And Arid Regions

The Inner Mongolia Autonomous Region is located in the arid and cold Chinesenorthern area. Because of the windy, sand storm, snowy, low temperature, and extremetemperature variation, the desert highways have inevitably suffered from compositeerosions like wind carrying sand, wind drifting snow and wind driving raindrop under theharsh natural environment such as windy, snow storm and wind driving rain.Under the most unfavorable condition (without considering slope protection), thispaper mainly takes the aeolian sandy soil roadbed as the research object. With high speedphotography of wind tunnel test, the movement trajectories of wind carrying sand particles,wind drifting snow particles and wind driving raindrop particles are studied, and theinteraction between different particles carried by wind and roadbed side slope is investaged,including the impact position where particles hit roadbed side slope, the angle and theimpact speed of the particles at the impact moment. The influence of roadbed sectiondesign’s parameter, moisture of filler and the angle between center line of roadbed andprevailing wind direction are analyzed. For the same particles, when the wind speed isdetermined, roadbed model is a low one, the smaller the ratio of slope is, then most oflarge particles will bounce against hitting the upper of slope and continue to cross over theroadbed while most of the small particles will through the shoulder of slope; roadbed is ahigh one, the smaller the ratio of slope is, then most of large particles hit the roadbed slopeand will rebound along the up direction for several times, and with the loss of energy, mostof them will glide down the slope or after the rebound of particles, they will directly heapat the foot of roadbed slope. And most of the small particles often stick to slope’s surface.For the same particles, as roadbed models are the same,the increases of moisture of filler,cause most of the sand particles and snow particles stick to slope’s surface, the reduction ofraindrop particles damage to roadbed, quickly form the phenomenon roadbed scoured.Through changing included angles between the center line of roadbed and prevailingwind direction, using the high speed photography of wind tunnel test, we conduct somemeasurements on different angles. As roadbed models are the same, angles are different,when it is smaller, vortex formed on the surface of roadbed becomes weak, the less filler will be brought, the less sand particles pass over the roadbed and heap at the roadbed footafter they rebound against the slope shoulder,thus there will be less roadbed’s erosion. Theincrease of snow particles sticked onto the slope surface will cause freezing and thawingcycle damage to roadbed. The decrease of rain particles hitting on the roadbed foot will dosmaller damage to the roadbed.Through the influence of the penetration of melting snow into the inner part ofroadbed and freezing and thawing destroy, under different wind velocity flow field, thispaper focuses on the mechanism of the roadbed destroyed by freeze-thaw erosion and winderosion. And with the micro-scanning of stereomicroscope, taking Micrograph imageanalyzing system to refine roadbed soils’ microstructure parameters before and after thefreeze-thaw erosion and wind-erosion, the influence of the composed erosion are analyzedfor the interior of roadbed various testing layers in this paper. With certain water moistureand the increase of freeze-thaw circles, the serious erosion is to the roadbed surface. Withthe increasing depth of horizontal test layer, the erosion is weak. After the freeze-thaw, wecontinue to do the wind blowout erosion to the roadbed and conduct the crossing erosion tothe roadbed, the damage of roadbed’s surface is worse, especially serious to the shoulder ofthe slope.