Study On Road Performance Of Lime Phosphogypsum Stabilized Red Clay Under Dry-wet Cycle

Red clay soils are widely distributed in Guizhou,and due to their special engineering properties,they can cause undesirable engineering problems such as roadbed settlement and shoulder collapse when used as roadbed fillers;phosphogypsum,as an industrial waste,takes up land and pollutes the environment when disposed of in piles.In this paper,the red clay soil in Duyun City,Guizhou Province,and phosphogypsum in Fuchuan Wengfu Mine,Guizhou Province,are used as research objects.Indoor tests are conducted to analyse the strength characteristics,water stability properties and dynamic characteristics of the mixture under dry and wet cycles,and the feasibility of using this mixture as roadbed filler is verified through construction of test roads,construction quality inspection and post-work monitoring as well as numerical simulation.The main findings are as follows:(1)Through existing research,this paper uses the ratio of lime: phosphogypsum:red clay = 8:46:46 to carry out strength tests.The test results show that with the increase of the number of wet and dry cycles,the unconfined compressive strength of the mix with and without OTS-02 admixture decreases continuously,among which the twice wet and dry cycles have the greatest influence on the unconfined compressive strength.With the increase of age,the lateral limit compressive strength of the mixture gradually increased,7d age mixture lateral limit compressive strength is more than 80% of the age of 28 d,the age of more than 7d lateral limit compressive strength growth slowly.The initial unconfined compressive strength of the admixture with OTS-02 is approximately twice that of the mixture without the admixture.After five wet and dry cycles,the two strengths are relatively similar.The cohesive force c of the mixture increases with the number of wet and dry cycles and then decreases rapidly,the internal friction angle decreases after five wet and dry cycles,but the decrease is within 3°.The change in cohesion c is greater than the internal friction angle.(2)Under the wet and dry cycle conditions,the mix is tested for water stability.The test results show that the water stability of the mix without admixture is poor,and the addition of 10% OTS-02 admixture can significantly improve the water stability of the soil.The greater the degree of compaction,the greater the water stability coefficient.As the number of wet and dry cycles increases,the water stability coefficient of the mix decreases,and the first wet and dry cycle has the greatest effect on the water stability coefficient.(3)As the mix is used as a road base filler,it is affected by the vehicle load and is studied for its dynamic properties.Experimental studies have shown that the dynamic stress,dynamic shear modulus,damping ratio and dynamic strain of the mix can be fitted with the H-D model.The three factors of surrounding pressure,wet and dry cycles,frequency on the dynamic shear stress are the relationship between the size of the surrounding pressure > wet and dry cycles > frequency.(4)A large number of indoor test research results,lack of practical engineering verification,this paper applies the indoor research results to engineering.Lime phosphogypsum stabilised red clay soil ratio design method,road base construction process and quality control measures are proposed.After the test road construction monitoring,lime: phosphogypsum: red clay = 8:46:46(mixed with OTS-02 admixture)mix is better than phosphogypsum: red clay = 2:8(mixed with OTS-02 admixture)mix.The numerical simulated settlement values are similar to the actual construction measured settlement values,further verifying that this mix can be used as a road base filler.