Study On The Mechanical Properties Of The Improved Soil By Iron Tailings Under Freeze-Thaw Cycle Conditions

The Northeast is one of the typical seasonal frozen soil regions in my country,and silty clay is widely used as a road base in the Northeast.The road base formed by silty clay has good initial strength and can experience several seasonal temperatures.After the effect of change,its strength has dropped significantly.The constant traffic load throughout the year is also increasing the degree of road damage.At the same time,the amount of iron ore mining is increasing with the development of the country,but how to deal with the massive accumulation of iron tailings A series of problems,if it can replace aggregates for road construction,on the one hand,it saves resources,on the other hand,it solves the problem of iron tailings occupying a large amount of land.On the basis of collating and combining relevant domestic and foreign researches,this paper explores the static and dynamic characteristics of iron tailings modified soil under freeze-thaw cycles and establishes a damage model.The static characteristics research includes mass loss,static strength and frost heave and thaw settlement.The study of dynamic characteristics includes dynamic strength,dynamic strain and dynamic modulus tests and the establishment of damage models.The static characteristics,frost heave and thawing rate and dynamic characteristics of the iron tailings modified soil and the undisturbed soil are compared.The results of the study are as follows:(1)The freeze-thaw cycle has a significant impact on the iron tailings modified soil.As the number of cycles increases,the mass loss rate increases,while the static strength decreases rapidly.It stabilizes after 7 freeze-thaw cycles.The gap with the undisturbed soil is gradually reduced to between 0.18MPa-0.21 MPa,and the frost resistance is better.(2)The frost heave and thaw settlement test showed that the frost heave rate and thaw settlement rate of the iron tailings improved soil were lower than the original soil.Tend to 0 after the cycle.(3)The dynamic strength of the iron tailing sand modified soil is relatively stable after four freeze-thaw cycles.At a confining pressure of 150 k Pa,the initial dynamic strength of the iron tailing sand modified soil is better than 50 k Pa and 100 k Pa,but as the number of freeze-thaw cycles increases,the When the pressure is 150 k Pa and100 k Pa,the difference of dynamic strength gradually decreases and stabilizes between330 k Pa-360 k Pa,and does not change with the change of confining pressure.(4)When the confining pressure is 100 k Pa,with the increase of dynamic stress,the dynamic strain of the sample's dynamic strain increases nonlinearly.It shows that the stress-strain curve of the iron tailing sand modified soil conforms to the hyperbolic relationship proposed by Hardin et al.With the increase of freezing and thawing times,the dynamic stress required for the iron tailing sand modified soil to reach the same dynamic strain gradually decreases.After the second freeze-thaw cycle,it starts to level off and is no longer affected by the number of freeze-thaw cycles.(5)At a confining pressure of 100 k Pa,with the increase of dynamic strain,the dynamic modulus of the iron tailings-improved soil decreases rapidly and then becomes stable.After 7 freeze-thaw cycles,the maximum dynamic elastic modulus of the iron-tailing sand-improved soil decreases by approximately 20%.The freeze-thaw damage model established at the same time can analyze and predict the effect of freeze-thaw cycles on the dynamic characteristics of the iron tailing sand improved soil within a certain range,and provide an assessment of the actual use of the iron tailing sand improved soil as a roadbed in this environment Reference value.