Research On Engineering Properties Of Lignin Modified Silt In Seasonal Frozen Area

This paper relies on the project of "Key Technology Research on the Improvement of Seasonal Frozen Soil Subgrade by Industrial By-product Lignin" and the actual project of Songyuan-Tongyu Expressway,taking industrial by-product lignin as an improver,and the roadbed silt of Songyuan-Tongyu section as the research object.Macroscopic research on physical and mechanical indexes and road performance of lignin improved silt.The following results were achieved:1.The indoor particle analysis and mineral composition analysis results of the embankment soil of Songtong Expressway show that the particle size of the soil is small,the content of powdery clay particles is high,and the powdery particles are the highest,which is the representative silty of Songyuan section in Jilin Province,with compaction Good performance,high CBR,weak water retention and poor freeze-thaw stability.The lignin is specially selected from Luohe Huadong Lignin Co.,Ltd.,Henan Province,with a content of up to 45% to 55%,a small amount of water,yellowish brown,powdery solid,PH value of 10.35,alkaline.Through chemical composition analysis and data report,it is determined that the lignin belongs to the sodium lignosulfonate in the lignin sulfonate.2.The lignin is incorporated into the soil body,which causes significant changes in some physical and mechanical indicators of the soil body,mainly reflected in: reduction of liquid limit and plastic index,specific gravity,maximum dry density,optimal moisture content,clay content increase.From the freeze-heave test,with the increase of the number of freeze-thaw cycles,the height and volume of the lignin-modified soil decrease in the rate of freeze-heave,and eventually stabilize,and the change after the first freeze-thaw cycle is the largest.With the increase of the lignin content,the height and volume frost heave rates are significantly reduced,and the larger the content,the less the soil is affected by the freeze-thaw cycle,indicating that the addition of lignin can effectively inhibit the frost heave of subgrade soil.3.The triaxial compression test in the laboratory showed that the failure form of the lignin-modified soil specimen mainly showed strain hardening,which tended to be stable when the shear peak appeared.With the increase of lignin content,the cohesion and shear strength of lignin-modified soil decreased,and the internal friction angle did not change significantly.As the number of freeze-thaw cycles increases,the cohesion of the lignin-modified soil decreases,and the internal friction angle does not change significantly.The effect of curing age on the static parameters of lignin-improved soil is not obvious.4.The CBR test results show that with the increase of the lignin content,the CBR of the lignin-modified soil shows a decreasing trend.As the number of freeze-thaw cycles increased,the CBR of lignin-improved soil decreased,and stabilized 4 to 7 times.The first freeze-thaw cycle decreased the most.The higher the lignin content,the less the CBR of the lignin-modified soil is affected by the freeze-thaw cycle,and can meet the minimum requirements of the "Code for Design of Highway Subgrade".From the perspective of resilience,as the lignin content increases,the resilience of lignin-modified soil decreases.As the cyclic partial stress increases,the rebound modulus of the lignin-modified soil decreases and the sensitivity increases.As the confining pressure increases,the rebound modulus of the lignin-modified soil increases and the sensitivity increases.As the number of freeze-thaw cycles increases,the rebound modulus of lignin-modified soil decreases,and it stabilizes 4 to 7 times,with the largest decrease in the first time.After the freeze-thaw cycle is stabilized,the rebound modulus values of 3% and 6% lignin are higher than that of plain soil,and the combined amount of lignin is not more than 3%.5.For the construction of the test road,1% and 3% of the same kind of lignin and plain soil are used for comparison.The results show that lignin added to the soil can effectively suppress dust and water,and improve the construction environment and the ability of the subgrade soil to resist water erosion.The on-site compaction degree and deflection value can meet the relevant requirements of the construction code,can be used as a new roadbed filler,and have a positive effect on the actual project.