Experimental Study On Cement And Fly Ash Improving The Southern Red Soils

China’s red clay is mainly distributed in the south,such as Yunnan,Guangdong,Guangxi,Hunan and Guizhou,the total exposure area is greater than 200,000 square kilometers.Red clay is a special materia with engineering performance of high water content,high liquid limit,high plasticity,and high porosity,the construction difficulty is big.Moreover,in the southern region,more rain and more coastal areas,t he long-term strength and stability of red clay decreased under the effect of dry and wet cycling.Therefore,the treatment before its development can improve the strength and stability,and use for the coastal embankment,seawall and other projects.Because of the diversity and complexity of the red clay in the south,different admixtures and curing agents have different curing effects.Therefore,the study on the ratio of southern red clay curing agent,the mechanical properties of solidified red clay and the analysis of strength and deformation characteristics under different factors,the effect of curing agent on curing effect and curing mechanism are important for guiding engineering practice..On the basis of summarizing the predecessors ’ research,the dissertation tests the curing soil of four curing agent ratio,and analyzes the factors influencing the engineering performance of solidified soil.The initial conditions such as mixing quantity of cement fly ash and curing agent,curing age,wet and dry cycle times were set up,and through the determination of the boundary moisture content,compactness,unconfined compressive strength,straight shear strength,compression,durability,etc,analyzed the solidified soil’s plasticity index,the max dry density,strength index,compressibility,resistance to wet and dry cycling ability,frost resistance and water stability,study the engineering characteristics of southern red clay in detail,and the results show that red clay has good compaction and high strength.A comparative study on the strength and durability of solidified soils and original soil was carried out.The main results are as follows:(1)The effect and change of curing agent,cement and fly ash on the plasticity Index and liquid index of southern red clay were analyzed through indoor single mixing and blending experiment.The primary formula of curing agent was obtained,and the mixture curing agent of 4 different ratios(4% cement +6% fly ash,6% cement +4% flyash,4% cement +6% ash +0.5% concentration curing agent,6% cement +4% flyash +0.5% concentration curing agent)was preliminarily determined.(2)The optimum moisture conte nt and maximum dry density of 4 different curing soils were found through the compaction test.Analysis of the effect of curing agent on the compaction properties of red clay,found in the same compaction work,the maximum dry density of solidified soils containing curing agent is greater than the original soil 0.02g/cm3,and the optimum moisture content is less than the original soil 3.1%~3.3%,solidified soil has good compaction.(3)Through the test of unconfined compressive strength and direct shear test,the effects of cement content,fly ash content and dosage of curing agent on unconfined compressive strength and shear strength of red clay are analyzed,and the results showed that the 7d unconfined compressive strength of 4 formula has has reached twice times more than original soil,the strength has reached a high level.Compound 10% mixture(4% cement +6% fly ash),0.5% concentration curing agent strength is 1.2 times of the same proportion of cement,fly ash solidified soil strength,and higher than the original soil strength 84.4k Pa.(4)The compressibility of solidified soils is analyzed by testing the compressive modulus and porosity ratio of the original soil and the 4 different ratio curing soils,which provide reliable parameters for the subseq uent engineering application simulation research.The results show that the compressive modulus of compacted red clay increases with the increase of the dosage of curing agent,which shows that the curing agent reduces the compressibility of red clay.(5)Experimental study on durability of 4 different proportioning cured soils and original soil show that mixing cement has an important effect on the water stability of solidified soil,which is beneficial to the formation of its early strength,and the increase of the amount of fly ash can increase its frost resistance,and the disintegration of the original soil is strong and the solidification soil is weaker and even not disintegrating.Comprehensive consideration of the technical performance,the strength of solidified soil(4% cement +6% fly ash +0.5% Concentration curing agent)is high,meets the needs of durability,and has good water stability,is the best formula to reinforce the southern red clay.(6)Using ABAQ US software to simulate the engineering application of solidified soil,the settlement and slope stability of the embankment filled with original soil and solidified soils were studied respectively,and the calculation shows that reinforcing the embankment of red clay with curing agent can reduce the settlement amount by 0.42 m,and the safety coefficient of seawall increases by 0.332.It was proved that the reinforcing red clay was obtained by the curing agent formula in this dissertation,which can satisfy the requirement of embankment deformatio n and stability,and it is a fine filler of coastal embankment,seawall and special foundation construction project.