| The large amount of sediment produced by dredging of urban rivers and lakes has been an important research topic due to its high organic matter content,complex pollutant composition and poor engineering properties.In this study,four kinds of different liquid limit natural river lake pollution sediments were used,and cement and phosphogypsum were used as curing agents for curing test.The solidified chemical was measured by physical-chemical index and unconfined compressive strength test.The microscopic test analyzes the key influencing factors and the mechanism of solidification strength of the river mud pollution.The main research contents and conclusions of the thesis are as follows:（1）The stress-strain characteristics of the solidified sludge were investigated.The results show that the failure strain of the solidified sediment is mainly concentrated between 3%and 7%,which is a power function relationship with the unconfined compressive strength.Destructive strain decreased with age,and the reduction of failure strain was mainly concentrated before 28 days curing time.The relationship between deformation coefficient E50 and strength is discussed,and the influence of phosphorus-gypsum dosage and the curing time on the relationship is obtained.（2）The strength properties of the solidified sediment were studied.The results show that the physico-chemical properties of the sediment have a significant effect on the regular pattern of strength development and strength by employing cement-phosphorus gypsum for solidification.The effects of the amount of phosphogypsum and the curing time on the strength of the sediments of different physico-chemical properties were compared and analyzed.There is a significant linear relationship between the water-cement ratio 1/R and strength of the solidified sediment,and the influence of the amount of phosphogypsum and the curing time on the linear relationship is obtained.There is a correlation between the change rate of water content of the solidified sediment and the strength,which is affected by the initial water content of the sediment.（3）Through the microscopic test and mineral composition analysis of the solidified sediment,the macroscopic mechanical properties and microstructure characteristics were combined to analyze the mechanism of solidification strength.The research results show that the action mechanism of phosphogypsum-cement solidified sediment is mainly divided into the cementation of hydration products and the compaction and reinforcement of ettringite;The main difference between the solidification of organic high liquid limit sediment and low liquid limit sediment is that the shape and quantity of hydration products are different,which leading to the difference in strength development law and strength. |
