Study On Resistivity And Strengh Characteristics Of Lime Soil Modified By Red Mud

As a kind of waste in the alumina industry,red mud has caused great harm to the soil and groundwater,which seriously affects the living environment and living health of the human.Lime soil,also known as lime stabilized soil,is mixed with a certain amount of lime and water in the soil,which is widely used in road engineering,but its water stability,frost resistance and early strength are weaker than other inorganic bonding materials.If the lime soil can be modified by using the red mud,the performance of the lime soil can be improved.At the same time,the red mud can be used for secondary utilization,and a new idea is provided for the comprehensive utilization of each other.Based on the combination of AC resistance method and unconfined compressive strength test,the relationship between the resistivity and unconfined compressive strength of lime soil with the amount of red mud,the curing age and the moisture content,respectively was tested in this thesis.The internal structure change and reaction mechanism of lime soil were analyzed by XRD and SEM microscopic method,and established the fitting relationship between compressive strength and resistivity.The stress-strain-resistivity curve was drawn in the process of bearing pressure,the variation of compressive stress and resistivity with compressive strain is analyzed systematically,and the feasibility of resistivity in characterizing the compressive strength of modified lime soil is explored.To provide the theoretical basis for the practical road engineering.The main research contents and achievements of this paper are as follows:(1)The optimum amount of red mud mixed with lime soil is different at different ages.When the age was 7 days,the optimum amount of red mud was 42%,when the age was 14 days,the amount of red mud was 30% and 36%,the maximum strength was measured,and when the age was 21 days and 28 days,the optimum amount of red mud was 30%.The unconfined compressive strength increases with the age,increases first and then decreases with the increase of water content.When the water content approaches the optimal moisture content,the maximum compressive strength can be measured.(2)The addition of red mud makes the plate-like,piece-like and prism-shaped materials formed by hydration reaction in lime soil increase and fill the gap between particles,which makes the internal structure of the sample more compact.At the same time,the flocculation structure formed by hydration is attached to and around the surface of the material and particles,which increases the degree of cementation between the two,and makes the structure more stable and less vulnerable to damage.(3)Under different conditions,the effect of current frequency on the resistivity of red mud modified lime soil samples is basically consistent.The resistivity decreases with the increase of current frequency.When the current frequency f<50kHz,the resistivity decreases rapidly with the increase of the current frequency,and when the current frequency f > 50 kHz,the trend of the resistivity decrease slows down and tends to stabilize.In order to ensure the accuracy of the experiment,this paper selects the current frequency f=50kHz as the representative value for analysis.(4)The initial resistivity of red mud modified lime soil test sample was decrease gradually with the increase of red mud content,and increased with the increase of age.The relationship between red mud content and water content varied with different amount of red mud content: when the water content was less than the best moisture content.The initial resistivity of red mud-modified lime soil samples decreased with the increase of water content.When the moisture content was greater than the optimal moisture content,the initial resistivity of the lime soil without red mud increased slightly and then decreased continuously.When the amount of red mud gradually increased,the initial resistivity will increase with the increase of water content.(5)When the initial resistivity of red mud was less than the optimal content,the initial resistivity of red mud modified lime soil sample was linear with the unconfined compressive strength,and the fitting degree was higher.When the amount of red mud was larger than the optimal amount,the linear fitting degree was general at different curing ages.Under different age conditions,the initial resistivity and strength of calcareous soil with different amount of red mud were linear.Under different moisture content conditions,the relationship between initial resistance and strength is not obvious in calcareous soil samples without red mud,and the addition of red mud makes them have obvious negative correlation,and with the increase of unconfined compressive strength,The initial resistance tends to decrease.(6)Under the condition of different red mud content,in the elastic stage and strengthening stage of red mud improved calcareous soil during compression,the stress increases with the increase of strain,and the resistance decreases with the increase of strain.In the local deformation stage,the stress decreases rapidly after reaching the maximum value,and the resistance of the sample with 0% red mud content increases,and with the increase of the red mud content,the increasing trend will gradually weaken,when the red mud content c>24%,The resistance will continue to decrease slowly.Under different age conditions,the variation trend of stress-strain-resistance curve of calcareous soil samples with the same amount of red mud is basically the same,which is less affected by the change of age.Under different moisture content conditions,the resistance of the sample increases in different degrees in the local deformation stage,the lower the moisture content,the greater the increase range of the resistance,and the higher the moisture content,the smaller the increase range of the resistance.