| Loess is widespread in China,and the loess in the natural state has a certain strength and stability,but the strength and the stability of the loess are sharply reduced with water,so the loess is generally used for stabilizing treatment when the loess is used in the project.Lime-blast furnace slag stabilized loess has high strength and stability and is widely used in pavement base and foundation treatment.However,the systematic study on the strength characteristics and stability mechanism of loess is seldom carried out.This paper mainly studies from the following aspects:The lime-blast furnace slag stabilized loess with different proportion is used to make cylindrical sample,and the samples are cured in standard curing box for 3 days,5 days,7 days,28 days,90 days,180 days and 365 days,and then the unconfined compressive strength test(UCT)of different curing age samples was carried on exploring the influence of inorganic binder content,ash slag ratio,porosity and curing time on the unconfined compressive strength(UCS)of stabilized loess.The test results show that UCS increases with the increase in binder content or curing time,and it gains strength rapidly within the first 7 days of curing.At same binder content,UCS increases with the decrease in L/S ratio or porosity.Finally,the correlations of UCS with binder content,porosity,and curing time were derived,which exhibited reasonable correlation coefficients R~2.The split tensile strength test(STT)is carried out for stable loess with different proportion and curing age of 3 days,5 days,7 days,28 days,90 days and 180 days respectively and the effects of inorganic binder content,lime/slag ratio,porosity and curing time on the splitting tensile strength(STS)of stable loess are obtained.The test results show that STS increases with the increase in binder content or curing time,and it gains strength rapidly within the first 7 days of curing.At same binder content,STS decreases with the increase in L/S ratio or porosity.Finally,the correlations of STS with binder content,porosity,and curing time were derived,which exhibited reasonable correlation coefficients R~2 more than 0.95,and thus the above results can provide reference for the projects.According to the Mohr-Coulomb theory,a simple calculation method of internal friction angle and cohesion of stable loess based on UCT and STT tests is proposed.According to the analysis of the test data of STS and UCS,it is concluded that the ratio of STS/UCS(ζ)is a constant(ζ=0.1062),which is independent of the curing age,the content of stable materials and the porosity of lime-blast furnace slag stabilized loess;the internal friction angle is only related toζ,and the internal friction angle of stabilized loess is obtained by usingζ.Based on the test data of UCS,Based on the UCT data,a simple formula for calculating the cohesion of stable loess is given.and the reliability of the proposed method is verified by triaxial test,and the method of determining c andφis feasible.The formation mechanism of lime-blast furnace slag stabilized Loess Strength and the change of its microstructure in different curing ages are analyzed by SEM and EDS.In the early stage of curing,cation exchange and hydration are mainly occurred,which are manifested as the reduction of water film thickness on the surface of soil particles,the agglomeration of soil particles and the formation of a small amount of cementitious materials;In the later curing stage,a series of pozzolanic reactions and carbonation occurred in the lime-blast furnace slag stabilized loess,which were manifested as the hardening of cementitious materials and the generation of hard crystals,so as to bring the lime-blast furnace slag stabilized loess to a higher activities and completeness. |
