Study On Soil Mechanicl Characteristics Of Cement With Doped Tailings Sands Based On Triaxial Test

Cement soil refers to a material that adds certain cement to the soil to improve the performance of the soil after hydration reaction.The cement-soil materials are easy to prepare,inexpensive and have excellent properties,and is widely used in various engineering constructions..However,cement soil itself has low strength and poor durability,so it needs to be improved.As a modern industrial steelmaking waste,iron tailings not only cause environmental pollution,but also occupy a large amount of land resources,so they need to be disposed of.This thesis studies adding iron tailings sand to cement soil to make iron tailings sand cement soil,the mechanical properties of iron tailings sand cement soil are discussed through laboratory experiments,which provides certain theoretical guidance for engineering application.This thesis mainly focuses on the study of iron tailings sand cement soil.The mechanical properties of the material are tested through various methods such as triaxial testing,dry-wet cycle testing,and freeze-thaw cycle testing.According to the test results,the influence of iron tailings content,cement content,age and confining pressure on the mechanical property of cement-soil is analyzed.Based on the stress-strain relationship,the constitutive model of Iron Tailings Cement soil is established.In addition,the mechanical properties of materials in complex environments were discussed through dry-wet and freeze-thaw cycles,and a strength damage model under these conditions is established.The specific findings are as follows:（1）The main failure mode of iron tailings cement soil is softening failure,and its strength is significantly affected by factors such as cement content,iron tailings content,age,and confining pressure.The addition of a certain amount of iron tailings in cement soil can improve its mechanical properties,and the optimal content of iron tailings is between 20%to 30%.The initial elastic modulus E₀of iron tailings cement soil and its relationship with confining pressure and iron tailings contentαThere is a functional relationship between.With the increase of iron tailings content,the initial elastic modulus E₀first increases and then decreases.Residual stress of iron tailings cement-soil is mainly affected by confining pressure,and there is a linear relationship between confining pressure and residual stress.Based on the E/E₀-Q/Q_maxgraphical relationship,a three-stage constitutive model was established and model parameters were determined.The provided constitutive model can better reflect the stress-strain relationship of iron tailings cement soil.（2）Through dry wet cycle tests,it was found that the strength loss of large volume cement is relatively low.Adding iron tailings will delay the dry wet cycle loss of cementitious soil,but its strength loss is similar to that of plain cementitious soil after multiple dry wet cycles.The decrease in strength of iron tailings cement soil is mainly manifested by a sharp decrease in cohesion.The stress-strain curves show some characteristics of hardening failure as the number of cycles increases.（3）Through freeze-thaw cycle testing,it was found that compared to plain cement soil,the cohesion of iron tailings cement soil showed a significant initial decrease and then stabilized.As the number of freeze-thaw cycles increases.The internal friction angle increases significantly compared with ordinary cement-soil.The shear strength of Iron Tailings Cement soil decreases significantly with the increase of freeze-thaw cycles,with the largest reduction in strength occurring after 3cycles.Unlike dry-wet cycling,the brittle characteristics of the material did not decrease with the increase in freeze-thaw cycles,and significant softening failure features still existed even after multiple cycles.（4）Using the relationship between ultimate deviatoric stress and C,φvalue and porosityη,cement volume content G_vand other parameters,A strength damage model for iron tailings cementitious soil under dry wet cycles and freeze-thaw cycles was established,and the calculated values were compared with the experimental values,the damage model can effectively estimate and predict the ultimate deviatoric stress and C,φvalues of iron tailings cement soil under the action of dry-wet cycle and freeze-thaw cycle.