Study On The Characteristics Of Backfill Materials Of Early Strong Dredged Sediments’ Fluidized Backfill Soil In Pipe Trench

With the rapid rise of China’s modernization,the demand for trench engineering continues to expand.When using the traditional method of backfilling the trench,the narrow operating space will lead to the backfilling quality is difficult to guarantee.The trench construction often passes through the road.A large amount of dredged sediments is produced in China every year,which not only occupies a large amount of land but also pollutes the environment when it is treated by traditional methods.The characteristics of "high moisture content and poor engineering properties" lead to the difficult reuse of dredged sediments resources.Controlled Low Strength Materials(CLSM)is a new type of flow state backfill used to replace the traditional backfill.Its self-leveling and strength control characteristics are very suitable for backfill of pipe groove.This article with dredged sediments,sulphur aluminate cement,slag and water preparation early strength and moving of dredged sediments soil(hereinafter referred to as "fluidized backfill soil"),is studied,sludge moisture content of cement and slag replacement rate effects on the working performance of the flowing soil,and analyzes the sludge moisture content and slag replacement rate for the moving of the rule of variation of soil mechanics performance,The main work and achievements of this thesis are as follows:1)In order to study the working performance of fluidized backfill soil,the influences of dredged sediments moisture content,cement content and slag substitution rate on the working performance of fluidized backfill soil were studied by using single variable and equal amount substitution as the research parameters.The results show that there is a linear relationship between dredged sediments moisture content and cement content and fluidity when there is no slag in the preparation raw material,but when slag is added in the preparation raw material,the fluidity will increase linearly with the increase of dredged sediments moisture content and basically remain unchanged with the change of slag substitution rate.The density of fluidized backfill soil is small,which is beneficial to protect the pipeline,and there is a linear relationship between density and fluidity.The water retention of fluidized backfill soil becomes better with the increase of cement content or the decrease of slag substitution rate.The filling rate of fluidized backfill soil reaches more than 97%,which can effectively improve the construction quality when it is used in the backfilling of pipe ditches.2)to explore the mechanical properties of soil on the compressive strength test,analysis of the moisture content of sludge,slag replacement ratio and ages,respectively for the flowing soil,the influence of the compressive strength is when the sludge moisture content and the reduced slag replacement rate,the flow of the various ages soil compressive strength will increase linearly,when slag replacement rate less than 33.9%,fluidized backfill soil meets the requirements of rapid construction;The compressive strength increases with the increase of age and has a linear relationship with the logarithm of age.For examining dry wet stress effects on flowing soil compressive strength and conduct dry-wet cycling test,this thesis studies slag replacement rate for the strength of the flowing soil after dry-wet circulation loss rate and mass loss and get the rules,get after dry-wet circulation flow of the strength of the soil loss rate and mass loss increased with the increase of slag replacement rate increase,But in general,the compressive strength of fluidized backfill soil still meets the engineering requirements after the wetting and drying cycle.3)The apparent failure patterns of the fluidized backfill soil samples were observed and analyzed in combination with the slag substitution rate.It is found that when the water content and age of the dredged sediments remain unchanged,the increase of the slag substitution rate will lead to the decrease of the stiffness and brittleness of the fluidized backfill soil,and the increase of the deformation during failure.The top of the sample is conical and the bottom is flaky when it is damaged.The characteristics of the stress-strain curve of fluidized backfill soil are studied and divided into five stages according to their respective characteristics: the compaction stage,the elastic stage,the softening stage,the failure stage and the residual stage.The influences of the dredged sediments water content,the slag substitution rate and the age on the stress-strain curve are obtained: When the sludge water content and slag substitution rate decrease or the age increases,the peak stress on the stress-strain curve increases,the compaction stage shortens,and the slope in the elastic stage increases.