| There is a wide distribution of silt in southeast coastal and the middle and downstream of the Yellow River in our country.Due to its poor physical and mechanical properties,it cannot be directly applied to the road base filling.The improvement technology of silt has become a hot and difficult research topic for experts and scholars at home and abroad.On the other hand,with the gradual acceleration of the process of industrialization and urbanization,the increment of industrial solid wastes is huge and environmental pollution is becoming increasingly serious.However,these potentially active industrial solid wastes can well improve the road performance of silt under the action of activators.Therefore,using industrial solid waste to improve silty soil conforms to the national strategic demand of "accelerating large-scale and efficient utilization of solid waste and improving comprehensive utilization capacity of complex and difficult solid waste".In order to further study the silty soil improvement technology of industrial solid waste,this thesis selects blast furnace slag as the main curing agent and takes the silt of An-He expressway in Henan province as the research object to carry out a series of systematic experimental studies on the improvement of silty soil by blast furnace slag for base material filling.The main work contents and achievements are as follows:(1)This thesis summarizes the general situation of Henan An-He expressway Project,and grasps the geographical location,climate,hydrology and engineering geological conditions of the project.The basic characteristics of soil in this area are studied through the laboratory soil test,and it was determined that the soil in this area is low liquid limit silt.(2)With the help of Design-Expert software,the optimal mixing ratio of granulated blast furnace slag with calcium hydroxide and sodium sulfate to improve silt was analyzed by single factor test method and response surface test method.The accuracy of the results was verified by variance analysis and test model fitting degree analysis,and the pairwise interaction between factors was studied by factor interaction analysis.The results show that the optimum mixture ratio of curing agent is: granulated blast furnace slag: calcium hydroxide: sodium sulfate=17.38∶9.56∶0.88.When the curing age is 7 days,the interaction between granulated blast furnace slag and calcium hydroxide,granulated blast furnace slag and sodium sulfate is more significant.The interaction between granulated blast furnace slag and calcium hydroxide was significant when the curing age was 28 days.(3)Aiming at the mechanical properties of solidified soil,unconfined compressive strength test,splitting strength test and California load ratio test were carried out to study the granulated blast furnace slag composite solidified soil under the optimal mix ratio and cement solidified soil with the same content.The results show that with the increase of curing agent content and curing age,the unconfined compressive strength and splitting strength of solidified soil also increase,showing a high correlation between them.The unconfined compressive strength and splitting strength of 12% granulated blast furnace slag composite solidified soil for 7 days are3.58 MPa and 0.48 MPa,respectively,which are higher than those of cement solidified soil with the same content.The CBR value of 12% mineral powder composite solidified soil is 116.8%,which is approximately 22.3% higher than that of cement solidified soil with the same content.(4)Aiming at the durability of solidified soil,the granulated blast furnace slag composite solidified soil and cement solidified soil with the same content under the optimal mix ratio were studied through water stability test and wet and dry cycle test.The results show that the water stability coefficient of the two kinds of solidified soil is less than 1,and the improvement of water stability of granulated blast furnace slag composite solidified soil is better than that of cement solidified soil.When the strength loss rate of granulated blast furnace slag composite solidified soil surges,the number of cycles is greater than that of cement solidified soil.Therefore,when the number of cycles is small,the resistance of granulated blast furnace slag composite solidified soil to wet and dry cycles is stronger than that of cement solidified soil.(5)From the microscopic point of view,the granulated blast furnace slag composite solidified soil was studied by scanning electron microscope test,energy dispersive spectrometer test and x-ray diffraction test.The results show that the microstructure of the composite solidified soil is very compact,the soil particles mainly contact with the surface,and there are almost no pores between the particles.The gel materials such as calcium silicate hydrate and calcium aluminate hydrate and crystal materials such as ettringite and calcite produced during the curing agent reaction together improve the overall strength of the solidified soil,and the newly generated berlinite also plays the role of cementing soil particles. |
