Mechanical Property and Microscopic Mechanism of Nano-SiO2-lime Stabilized Loess Subgrade
The stabilization method of loess has always been a study focus of subgrade engineering in loess area.Nano-SiO2 is an inorganic flocculent silicide characterized by the small size effect,surface energy effect and pozzolanic effect,thus attracting wide attention in soil stabilization.In order to explore the promotion effect and improvement mechanism of nano-SiO2 on the mechanical properties of lime stabilized loess,3 types of specimens are designed including 3％lime stabilized loess specimens,3％lime+nano-SiO2 comprehensively stabilized loess specimens,and 8％lime stabilized loess specimens.Based on the 3 types of specimens,the unconfined compressive strength test,resilience modulus test,California bearing ratio CBR test and SEM test are conducted to study the effects of curing agent content and curing time on the mechanical properties and microstructure of loess subgrade.The result shows that the introduction of nano-SiO2 sharply enhances the unconfined compressive strength,resilience modulus,and CBR of loess.0.2％nano-SiO2+3％lime stabilized loess achieves the same mechanical properties as 8％ lime stabilized loess.With the increase of nano-SiO2 content and curing time,the strength of loess subgrade increases gradually.The relationships of unconfined compressive strength,CBR and resilience modulus are established with regression fitting of the test data.SEM test shows that the addition of nano-SiO2 improves the aggregation form of soil particles,and fills the voids of soil particles thereby enhancing the mechanical properties of loess subgrade.Comprehensively considering the confined compressive strength,resilience modulus,CBR and economy,the mixture proportion of comprehensively stabilized loess is recommended as 3％lime+0.2％nano-SiO2.The nano-SiO2-lime stabilized loess technique provides an environmentally friendly and lower-cost stabilization approach for loess subgrade.
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