Study On Mechanism And Efficiency Of Salt-Freeze Thaw Cycles Of Salt-Frost Heave Prevention Road Structure

Saline soil is widely distributed in southern Xinjiang,and the engineering disasters caused by saline soil are also serious.The damage of urban roads in southern Xinjiang due to seasonal salt-freeze thaw cycles is an important topic that needs to be studied urgently.The deformation monitoring and experimental study on the damaged sections of Daxue Road and Tarim Avenue,which were newly built in Alar City,southern Xinjiang,show that the main reason for the road damage is that the cement stabilized base is subjected to seasonal salt-freeze thaw cycles,and the salt-frost heave deformation of the cement stabilized base occurs after the water and salt migration and accumulation of the road structure.This paper studies and puts forward the design scheme of salt-frost heave road structure,applies the water-salt-temperature multi-field coupling environment simulation experimental system to carry out the salt-freeze-thaw cycle test of salt-frost heave road structure,and studies the salt-freeze thaw cycles mechanism of salt-frost heave road structure.Real-time monitoring system is used to monitor the water-salt-temperature change and saltfrost heave deformation in road structures under different environmental conditions,and the law of material strength attenuation in each structural layer after salt-freeze thaw cycles is analyzed.Combined with SEM microscopic characterization analysis method,the mechanism of salt-freeze thaw cycles in road structures is studied and summarized,and the disaster prevention efficiency of salt-frost heave-proof road structures is evaluated.The main results are as follows:(1)The temperature gradient of each structural layer of road shows an increasing trend with the increase of subgrade height.Under the action of 20 salt-freeze thaw cycles,the maximum volume moisture content of subgrade soil is 36.5% when the environmental water and salt concentration is 0%.When the concentration of water and salt in the environment rises to 1%,its electrical conductivity reaches the maximum of 2.293,which has the greatest influence on the redistribution of water and salt in subsoil.The maximum increment of its volume moisture content is 9.8%,and the maximum increment of electrical conductivity is 1.843,indicating that lower salt concentration is more conducive to the migration and accumulation of water and salt in subsoil.(2)In different environmental water and salt concentrations,the final deformation of road structure samples shows the characteristics of cumulative increase due to the salt-freeze thaw cycles.When the concentration of environmental water and salt is 0%,the road structure sample only undergoes minor frost heave deformation.With the increase of environmental water and salt concentration,the salt-frost heave deformation of road structure sample increases.(3)The strength attenuation analysis of the materials in each structural layer of the road shows that with the increase of salt-freeze thaw cycles,the strength of asphalt concrete pavement materials decreases significantly,indicating that its load-bearing capacity is weakened;The bearing ratio of graded crushed stone stabilized base material shows a decreasing trend;The strength of aeolian sand cushion material decreases due to the continuous increase of salt crystals;In the subsoil,the CBR values of the soil samples participating in salt-freeze thaw cycles are all lower than those of the soil samples without freeze-thaw cycles(3.3%),which do not meet the requirements of subgrade filler bearing ratio.(4)In the aspect of blocking water and salt migration,the conductivity and water content of each structural layer of the road vary greatly from bottom to top and show a decreasing law.In different environmental water and salt concentrations,the salt-frost heaving deformation produced by the salt-frost heaving road structure is less than that of the original road structure,which shows that the salt-frost heaving road structure has good resistance to sulfate erosion,and the salt-frost heaving disease is effective,which is more suitable for the salinized road environment in southern Xinjiang.