Study On Strength Characteristics And Harmless Disposal Of Heavy Metals Of Tianjin Solidified Soil

The strength characteristics and heavy metal leaching amount of solidified soil are important aspects to be considered in engineering.In this paper,considering the moisture content of the dredged soil in Tianjin port,the solidification of the dredged soil was studied by using solidified materials,and a formula of high-strength solidified agent was developed,and its strength prediction formula was given.Based on the special heavy metal content of Xiqing dredged soil in Tianjin,the solidified material was used to repair the dredged soil,and the solidified scheme was developed to meet the requirements of backfill and green planting soil.The main research contents and achievements are as follows:?1?In view of the special physical and mechanical properties of the dredging soil near the port,slag powder and fly ash are used as cementitious materials to replace a certain amount of cement.Through the single mixing test and the unconfined compressive strength as the evaluation index,the representative level is selected.The optimal ratio of curing agent was selected by orthogonal test.The corresponding neural network prediction model is established,and the weight adjustment formula in BP algorithm is modified to improve the stability and convergence of the prediction model in the training process.Finally,taking the orthogonal test data as the training samples,taking the samples in the range of orthogonal test dosage as the test samples,using the trained neural network model to predict the strength of the solidified soil.?2?Taking the dredged soil near the port as the research object,slag powder and fly ash are used as cementitious materials to replace a certain amount of cement.Through the single mixing test and the unconfined compressive strength as the evaluation index,the representative level is selected.The optimal ratio of curing agent was selected by orthogonal test.In the experiment of the same proportion and different dosage,the optimal dosage of curing agent is optimized.Using NaCl,NaOH,Na₂CO₃ and tea as admixtures,a four factor five level response surface model was established,and a high-strength curing agent formula was developed.The curing mechanism was revealed through interaction analysis.Through residual analysis,variance analysis and fit analysis,the matching effect of response value and admixtures was verified to be ideal.?3?Taking Xiqing dredged soil as the research object,firstly,quicklime is used to reduce its water content,and sawdust is used for preliminary solidification.On this basis,cement and mineral powder+cement are used to study the solidification and passivation of heavy metals.In order to compare the curing effect of the two methods,heavy metal leaching test was carried out on the samples after treatment by atomic absorption spectrophotometry.Finally,a kind of curing agent which can effectively passivate heavy metals was obtained.