Research On Mechanical Properties Of Large Steel Slag Subgrade Soil

The steel production of our country has reached the magnitude of 1 billion tons a year.The steel slag is a by-product of the steelmaking process.The steel slag produced belongs to one kind of solid waste.The comprehensive utilization rate of steel slag in our country is very low,so if the "solid waste" can be used in the construction,the project cost can be effectively reduced.Therefore,it is of great engineering value and social significance to develop steel slag material for subgrade filling design and study its road performance.Based on the horizontal project "Experimental Study on pavement Performance of Steel slag road Materials",this paper proposes to take silty clay as the research object,add large dose of steel slag,and add a certain amount of cement as curing agent to improve the silty clay,analyze the physical and chemical properties of the material,design three kinds of materials through orthogonal test,and preliminarily draw up five kinds of mix ratio.CBR tests were carried out on compaction,limiting water content and bearing ratio of different mixtures to determine the optimal mix ratio of steel slag,cement and silty clay.The static triaxial test,dynamic triaxial test and freeze-thaw cycle test were carried out on the selected steel slag modified soil with the optimal mix ratio.The results show that the modified soil has good deformation resistance and freezeresistance,good stability,and greater strength than the original soil.Specific content:(1)According to the combination of previous research results and orthogonal test,five groups of mixing ratio of steel slag improved soil were drawn up.Through the indoor soil test,the compaction curve,liquid-plastic limit value and load-bearing ratio CBR value were analyzed,and the most mixing ratio of steel slag improved soil was finally determined: 45:2:53,and the next research was carried out.(2)Based on the triaxial compression test,the strength characteristics of the optimal mix under different water content and confining pressure conditions were studied,and the changes of shear strength,internal friction Angle and cohesion with water content were analyzed.The results showed that the shear strength of the improved soil was the maximum at the optimum moisture content.(4)The influence of confining pressure,compacting degree and vibration frequency of cyclic load on dynamic elastic modulus was explored,and the relationship curve between dynamic elastic modulus and dynamic strain was analyzed.All the working conditions showed a trend of decreasing gradually with the increase of the dynamic elastic modulus,and a single variable was controlled.The larger the three influencing factors,the higher the dynamic elastic modulus;According to the fitting analysis of the test points under each condition,the maximum dynamic elastic modulus of the slag improved soil increases with the increase of confining pressure,compacting degree and vibration frequency of cyclic load,and the relationship is linear.And the dynamic elastic modulus tends to be stable with the increase of vibration number.(5)The shear strength,internal friction Angle,cohesion and dynamic elastic modulus of the improved soil are all affected by the freeze-thaw cycle,and the soil performance index will be significantly reduced after the first freeze-thaw cycle.With the increase of freeze-thaw times,each index gradually tends to be stable,because the soil void does not change after freeze-thaw,and the structure does not change,so it tends to be stable.