| Silt is mainly distributed in the Yellow River Basin and the middle and lower reaches of the Yellow River and Haihe rivers in my country.Due to its special nature,it is a bad roadbed soil in road engineering construction.The reinforcement and improvement of silt has become one of the focuses of experts,scholars and engineering technicians.Traditional calcium-based soil curing agents such as cement and lime have been widely used in the reinforcement of various soils.With the development of science and technology,more and more soil curing agents are used in the curing of poor soils.The mechanism of action can be divided into inorganic curing agents,organic curing agents,ionic curing agents and biological enzyme curing agents,forming a wide variety of soil curing agent groups covering various soil types.With the development of material science,polyurethane-based high-molecular polymers(hereinafter referred to as polymers)have gradually been applied to soil reinforcement treatment,showing good results.This paper takes Zhengzhou Yellow River silt as the main body of research,uses polymer to solidify the silt,and through unconfined compression test and variable head penetration test to study polymer blending ratio,silt moisture content,and curing age The law of influence on the strength and permeability of polymer solidified silt;at the same time,based on the unconfined compressive test and permeability test,a water-immersed curing environment is set up to explore the influence of water erosion on the strength and permeability of the cured soil during the curing period.Using scanning electron microscopy test(SEM),energy spectrum test(EDS),X-ray diffraction test(XRD)and mercury intrusion test(MIP)and other modern test and analysis methods,the microscopic morphology and mineral composition of silt before and after polymer solidification And pore characteristics are analyzed,and the improvement mechanism of polymer solidified silt is explored.Use Plaxis 3D software to build a two-dimensional road model,analyze the stress distribution of the roadbed,the road surface settlement and the change of the pore water pressure,and explore the engineering performance of the silt after polymer solidification as the roadbed soil.Through a series of experimental studies,the main conclusions are as follows:(1)Polymer has a good curing effect on silt soil.The higher the blending ratio of polymer(5%～15%),the lower the moisture content of silt soil(8%～15%),and the longer the curing period.(1d～28d)The higher the strength of the solidified soil,the stronger the impermeability.(2)The water-immersed curing environment will weaken the strength and impermeability of the polymer solidified soil.Its strength change law is the same as that of the solidified soil under the standard curing environment,while the permeability coefficient change law is slightly different from that of the standard cured soil.It is manifested in the rate of change;the strength loss rate of solidified soil under water immersion curing environment is less than 40%.(3)The polymer can effectively adhere to the surface of the silt and fill between the particles of the silt,mainly through the functions of "wrapping","filling" and "bridging" to reduce the void ratio of the silt and improve the silt Density,thereby enhancing the strength and impermeability of the silt,no new compounds are formed in the process.(4)Numerical analysis results show that the polymer-cured silt has good performance as roadbed soil.Compared with 7% cement-soil roadbed,the settlement of polymer-cured silt roadbed is smaller than that of 7% cement-soil;water soaking during the maintenance period The environment will increase the settlement of the pavement,but this effect is very small;in the case of being soaked by groundwater during the service period,the incorporation of polymers will prolong the saturation time of the roadbed. |
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