Effect of silica micropowder-quicklime on strength properties and microstructure of expansive soils
[Objective]In order to study the effect of silica micronized powder-lime on the amelioration of expansive soils,[Methods]taking Nanyang expansive soil as the research object,unconfined compressive strength test,consolidated undrained triaxial shear test,scanning electron microscope test(SEM)and X-ray diffraction test(XRD)were carried out to analyse the strength characteristics and microstructural changes of expansive soil and mineral composition under the action of different amounts of doped silica micropowder and quicklime,and the SEM was quantitatively and statistically analysed using MATLAB software.[Results]The results show that:the peak unconfined compressive strength of composite improved soil under the opti-mal dosage is 2.139 MPa,which is increased by 751.32%compared with that of the plain soil.The cohesion of composite im-proved soil under the optimal dosage is c=494.6 kPa,which is significantly greater than that of the plain soil,c=38.59 kPa.The correlation coefficients of the fractal dimensions of different silica micronized powders in expanding soils are all calculated to reach 0.9 or above.[Conclusion]The results show that the unconfined compressive strength and shear strength of expansive soil under the action of silica fume-lime are obviously improved,which is better than either single-factor improvement,and the opti-mal mixing ratio is 15%silica fume doping and 4%lime doping,at which time the porosity and fractal dimension are the smallest,with good fractal characteristics and the most stable structure.The research result can be used to guide the design and construction of infrastructure projects in expansive soil areas,which has important scientific significance and practical application value.
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