Research On Prevention Mechanism Of Sulphate Saline Soil Subgrade Salt Expansion

Abstract:Saline soil takes more and more attention from people for its special nature. Research on saline soil gradually extended from the earliest agriculture to engineering. Domestic and international expansion on saline soil salts, dissolved trap, collapsible and corrosion studies have been relatively common. Its sodium sulphate saline soil containing soluble salts, such as occurs when the outside temperature deformation and thaw salt expansion. In Xinjiang extreme weather:large temperature, precipitation, evaporation under the influence, development and expansion of salt sulphate saline soil deformation caused serious impact on the local road works. The new road embankment built damaged by the salt migration and periodic salt-heave deformation. Longitudinal cracking occurs, uplift and take water occurred on the roads and eventually a shortening life.In this paper, sulphate saline soil is the main object. Combining with previous research, high and low temperature cycle test of saline soil salinity uneven distribution was done to study the sulfate salt expansion. Indoor and outdoor model test were done to test the partition above and channelize below structure.(1) Numerical analysis of the relationship between sulphate saline soil moisture, salinity, temperature and other factors and the salt expansion deformation was analyzed by coupling theory.(2) Physical parameter of the on-site soil samples was analyzed in laboratory. The main reason for the damage of sulpahate saline soil subgrade is the aggregate of sulfate to cement stabilized. Damage of sulpahate saline soil subgrade is caused by the Salt-frost heave under the temperature cycling outside. Deformation of salt expansion under different salinity and different spatial distribution was analyzed in temperature cycling test.(3) High and low temperature cycle test of sulphate saline soil were done to reveal the truth that the salt expansion of sulphate saline soil with salinity uneven distribution is greater than salt expansion of saline soils. When the overall salt content is consistent, the expansion of the soil with salt accumulation in the upper deformation is bigger than that salt accumulation in the lower salinity. During freeze-thaw cycles, the saline soil accumulated residual deformation, and it increases with the number of cycle increases.(4) The different barrier layers are set within the slope. The improvement can effectively discharge over saturated brine within the embankment。10-15°of V-type barrier layer which is better than other brine discharge.(5) Setting of subgrade insulation barrier layer and sparse drainage layer in sulphate saline soil roadbed can effectively control the rate of temperature change, the roadbed blocking capillary water rise and salt migration. The improvement can reduce the salt expansion roadbed deformation, reducing damage saline land area road effectively.(6) Field test of sulphate saline soil subgrade reaveled that the road is in a self-balancing stage. there is a certain lag of temperature in the roadbed. The deformation in the middle is more stable than the deformation on both sides.