Experimental Study On Freezing And Thawing Cycles Of Natural Saline Soil By Large-sized Device

Select the Lop Nur region S235 kilometers along different natural saline soil for the study, carried the basic test of the nature saline soil, and using the freeze-thaw cycles devices to explore frost and thaw condition Saline Soil Salt- heaving variation, variation of the internal temperature, water and salt migration rule and shear strength variation. The results showed that:473Km sand at low liquid limit clay salt content of 5.89%, is a strong chlorine saline soil; 532 Km at low liquid limit clay and salt content of 3.58%, is a sulfurous saline soil. After washing, the salt content of fines significantly more than saline soil before, saline soil liquid and plastic limits bigger than before.selected Sand,low liquid limit clay and low liquid limit clay freezing and thawing cycle test, in conditions of freeze-thaw cycles under two soil samples, five times before the freeze-thaw cycles of salt-frost accumulation significantly, sixth, seventh reduce the accumulation of even a drop phenomenon. Sand, Low Liquid Limit Clay accumulation of salt- frost is about 7.61 mm, low liquid limit clay accumulation of salt- frost is about 2.87 mm, sand low liquid limit clay salt- frost heaving was significantly greater than the maximum amount of low liquid limit clay, and it has a more significant salt- frost heaving are additive. Low liquid limit clay to the heating process is relatively sensitive to thaw collapse occurred shorter time, low liquid Clay melt sand trap occurs relatively long time.Changes of temperature during the freeze-thaw cycle is: an upper soil temperature fluctuation clear, and the lower part of the soil temperature changes to a lesser extent, temperature fluctuations substantially parabolic curve.Due to Sand, Low Liquid Limit Clay gravitational field effect greater than the water temperature field so,the upper water shift is not obvious, but in the role of the temperature field, salt solution polymerization flow up to the cold and the precipitated salt crystals, making salt upward migration more apparent. Heating process due to salinity and soil particles formed cemented body blocking the down passage. Lead to the low liquid limit clay water-salt up to migrate performance significantly.Sand, Low Liquid Limit Clay soil cohesion at different heights along inversely "S" t ype distribution, with thawing increase the number of layers 1, 2 cohesion increases, 4,5,6 layer cohesion changes little; low liquid limit clay soil cohesion with each freeze-thaw cycles have reduced tendency to increase, and the top is smaller than the underlying cohesion. Low liquid limit clay and sand, Low Liquid Limit Clay showed similar levels at "3" type.