Study On Characteristics And Prevention Measures Of Subgrade Frost Heave Of Carbonate-saline Soil

Highway is a zonal structure, the highway network is staggered crossing the country.Due to the special climate condition in China northern region, subgrade frost heaving become a common defect of the road.In Nong’an County of Jilin Province, there are large areas of saline soil,as subgrade frost heaving become more and more serious because frost deformation of the carbonate-saline soil recently.Through determination of the natural temperature of the different depth soil in sampling time of field and determination of the basic properties of the granulometric composition,mineral composition,natural moisture content,natural density,liquid and plastic limits,PH values,organic matter content,dissolving salt content,cation exchange capacity to obtain the material composition and fundamental physicochemical properties of the test soil in sampling point;completed the vertical frost and normal frost heave experiment where is no load of the cylinder specimen which is different moisture content(16%、20%、24%),different salt content(0.95%、1.50%、2.0%)、different strike solidity(85%、90%、95%),then completed the ultrasonic velocity test who though the freeze-thaw cycles,analysised the influence of moisture content、salt content、strike solidity and cycle time of freeze-thaw to ultrasonic velocity.Specific as follows:1、In order to master Nong’an area of carbonate saline soil vertical frost caused by changes in the height,the experiment by microcomputer control of asphalt mixture performance test system to simulate the carbonate saline soil specimens of different temperature environment, by measuring the amount of frost heaving, find out the maximum frost heaving content of the different specimens under the different temperature. Test showed that provides control direction in a certain extent, there is a direct ratio relation of the carbonate saline soil frost heave rate, water rate and compaction degree, but overall, the frost heaving is more obvious of the specimens which is water content high, salt high and high strike solidity, and there will increase violent of the specimens in 5℃~-7℃, which also governance carbonate saline soil subgrade frost heave.2、In order to master the numerical of normal frost heave force of the carbonate saline alkali soil in Nong’an area, the test by computer control of asphalt mixture performance test system to simulate the carbonate saline soil specimens of different temperature environment, through the function of automatic induction system recorded carbonate saline soil specimens produced by vertical frost heaving force, through the formula to calculate the normal frost heave force. The test shows that:there is a correlation between the normal frost heave force and the frost heaving rate.3、Complete the test of ultrasonic velocity to master the compressive strength of Nong’an area of carbonate-saline soil specimens who though the different freeze-thaw cycles.The experiment shows that the ultrasonic velocity is the fastest in the times of 0~5 freeze-thaw cycles, and the rate of the increase of the number of the freeze-thaw cycles increases, the final ultrasonic velocity tends to balance, until it is not changed. This also provides a theoretical basis for the study of the freeze-thaw cycle.4、Through the above experimental results are collated and analyzed, summed up the previous experience of Nong?an area carbonate saline soil subgrade frost prevention measures are put forward.