Study On Dynamic Characteristics Of Phosphogypsum Stabilized Soil Subgrade

The red clay roadbed is difficult to compact and the water stability is extremely poor.The traditional method is to discard and replace it,which not only affects the environment,but also increases the construction cost.The waste phosphogypsum is often reclaimed and buried or stacked on land,which not only takes up a lot of land resources,but also destroys a lot of vegetation.This paper takes red clay in Guiyang area as the research object,uses phosphogypsum,cement and lime as additives,uses indoor tests and numerical simulation methods,and uses soil mechanics and soil quality as the theoretical basis to carry out the mechanical and water stability properties of phosphogypsum stabilized soil.The test selects the best ratio,and on this basis,the dynamic characteristics are studied through dynamic triaxial tests,and the stress and deformation of the roadbed under the dynamic traffic load are analyzed through finite element.The main conclusions are as follows:(1)As the content of phosphogypsum increases,the unconfined compressive strength of mixed cementitious materials such as phosphogypsum decreases.The strength attenuation of cement phosphogypsum and lime phosphogypsum cementing materials after standard curing for 6 days+1 day of soaking in water are 15-30%and 40-50%,respectively,while that of 7 days of soaking in water is 40-50%and 45-55%,respectively.(2)With the increase of the content of phosphogypsum,cement and lime,the plastic limit,liquid limit and plastic index of phosphogypsum stabilized soil decrease.Cement:phosphogypsum:red clay=6:18:76 and 8:24:68 and lime:phosphogypsum:red clay=4:12:84 and 6:18:76 are the best.(3)The dynamic modulus increases with the increase of confining pressure,consolidation ratio and frequency,while the damping ratio decreases with the increase of confining pressure,consolidation ratio and frequency.The dynamic modulus,damping ratio and dynamic shear strain are used HD model representation.(4)Reducing the dynamic stress level and increasing the confining pressure can improve the ability of the roadbed to resist instability.The stable,critical and destructive curves are represented by ?p=(?·N?)/(1+?·N?)??p=a+bN and ?p=ANB,and respectively.The mean value of critical dynamic stress increases with the increase of confining pressure,and the critical dynamic stress is smaller than the static strength without vibration.The critical dynamic shear strength increases with the increase of confining pressure.(5)The maximum horizontal displacement and center settlement of the roadbed decrease with the increase of cement or lime content,and increase with the increase of the height of the roadbed.The maximum shear stress of the roadbed increases with the increase of lime or cement content,and with the increase of the height of the roadbed.