| Freeze-thaw soil is one kind of geological disasters. It can produce a series ofdisasters, which doing harm to people’s life, production and construction. Give someexamples, freeze-thaw diseases exist in10%of the road section in cold regions ofnorthern northeast. What’s more, disease sections in some individual lines reach60-70%.Serious freeze-thaw disasters of Qinghai-Tibet highway bring about huge difficulties tosafety transport, road maintenance and construction. According to the investigation ofHokkaido region in Japan, freeze-thaw soils takes up40%of all the reasons of slopecollapse accidents. Therefore, it is extremely necessary to go into research onfreeze-thaw.Freeze-thaw action is such a role that when temperature change periodically, it cancause frozen soil freeze and melt repeatedly, resulting in disturbance, deformation evendamage of soil or rock. Freeze-thaw erosion is formed by low temperature change, iceand snow. Freeze-thaw role is the main cause of freeze-thaw erosion.With the process offreeze-thaw, volume state of soil particles or debris particles change from expansion tocontraction. When expanding, soil particles are lifted upwardly perpendicular to theslope direction; being contracting, soil particles drop vertically along the gravitydirection; and the soil particle on the slope will move a small distance downward fromoriginal position after each freeze-thaw cycle. Over the long haul, obvious creepphenomenon of soil slope can be observed due to freezing at night and melting at noon,especially in spring melt season. In addition, soil particles will squeeze mutually whenvolume expands; sometimes when the volume contracts, if there is a gap between soilparticles, the upper soil particles will lose support, then the downward creep can also becaused. Even if the slope can’t go so far as to unstable, soil’s density and strength stillcan decrease.This paper studied freeze-thaw erosion of vegetation slope basing on the project"slope freeze-thaw erosion mechanism and its protective study in cold regions" incooperation with Kitami Institute of Technology of Japan. The test slope was located infrozen soil testing ground of this university, the test slope was composed of four intervals, which are out-soil hydroseeder interval, out-soil hydroseeder+3d(three-dimensional) nets interval, turf-banked interval, and turfing+3d nets intervalrespectively. Through field tests of slope water content ratio, soil temperature, heavecapacity and shift amount of three cycles, actual movement of vegetation slope duringfreeze-thaw process was captured, dynamic processes of freeze-thaw of soil wasobtained. The study results showed that soil quality, temperature, vegetation coverage,water content and their changes were vital to soil’s heave capacity and shift amount.Different distribution of slope water content ratio and temperature difference leaded tothat heave capacity of slope toe was greater than that of slope crest. The bigger heavecapacity the larger down slippage. Due to frozen surface not parallel to the slope, shiftupward along the slope took place early in the frozen. Maximum of shift amountachieved10.2cm through three freeze-thaw cycles by accumulating year after year. shiftwas closely related to heave capacity, lawn growth that is root development. In addition,vegetation had obvious inhibition frost heaving role, and different slope protectionvegetation had different effect. This study is of great significance in guiding engineeringpractice, enriching design and construction theory when conducting management ofcutting slope in alpine region. |
PDF Full Text Request