Study On Application Of Fluidized Waste Soil Backfilling Foundation Pit Side Wall

At present,many scholars have studied fluidized waste soil as a new type of backfill material,but there is still a lack of further research on its performance when it is applied to foundation pit sidewall backfilling projects.At the same time,it is considered to use steel slag to replace part of cement to prepare fluidized soil.This test to save construction costs is not yet complete.At present,when backfilling the side walls of foundation pits in my country,materials such as cohesive soil,coarse sand,stone powder and slag are used,but they are not easy to compact.As a new type of backfill material,fluidized waste soil has high fluidity and strong self-tightness..Therefore,in view of the difficulty of compactness due to the narrow backfill space,large backfill depth,and special-shaped cross-sectional structure when backfilling the side walls of the foundation pit,this thesis uses the waste soil generated during construction and industrial waste steel slag as the main materials,and uses them prepare fluidized waste soil,and from the four perspectives of construction workability,mechanical properties,durability and permeability,it is explored whether the backfill effect is good and whether it can meet the engineering requirements.This article mainly starts from the two perspectives of steel slag replacement rate and moisture content.The main work and conclusions are as follows:(1)The construction and workability test research of fluidized waste soil under different steel slag substitution rate and moisture content mainly start from four perspectives of fluidity,density,water retention and filling performance.The test results show that by adjusting the steel slag replacement rate and moisture content,fluidized waste soil with up to standard fluidity,controllable bleeding rate,density conforming to specifications,and good filling performance can be prepared.Increasing the replacement rate of steel slag and increasing the moisture content will improve the fluidity of fluidized waste soil.The impact of moisture content on the fluidity is far greater than that of steel slag replacement.And according to the mixing site of the fluidized waste soil,the water content requirements are different.When further applied to the sidewall backfilling project of foundation pits,different steel slag replacement rates should be selected according to the backfilling environment.In addition,studies have found that the density of fluidized waste soil can reflect its fluidity to a certain extent.(2)Experimental research on unconfined compressive strength of fluidized waste soil with different steel slag substitution rate,moisture content and age.The test results show that the 28 d unconfined compressive strength of the fluidized slag studied in this thesis is in the range of 90～398k Pa.The strength of fluidized waste soil can be controlled by adjusting the steel slag substitution rate and moisture content.And based on the minimum strength of the backfill,there is an optimal steel slag replacement rate,which reduces the construction cost while ensuring the normal construction.Through the 7d and 14 d strength of the fluidized waste soil,the 28 d strength can be effectively predicted.(3)Research on dry-wet cycle test of fluidized waste soil under different steel slag substitution rate,moisture content,and cycle times.The test results show that the anti-dry-wet cycle ability of fluidized waste soil is related to its steel slag replacement rate.As the steel slag replacement rate increases,its anti-dry-wet cycle ability will become weaker and weaker.In order to ensure that the backfill area is normal after the construction is completed,the replacement rate of steel slag should not exceed 66.7%.(4)Experimental research on the permeability of fluidized waste soil with different steel slag replacement rates and ages.The test results show that under the same test conditions,either reducing the steel slag replacement rate or extending the age can effectively reduce the permeability coefficient.However,as the replacement rate of steel slag decreases and the age increases,the rate of decrease of the permeability coefficient will gradually slow down.By analyzing the influencing factors of the fluidized waste soil’s permeability coefficient,mathematical expressions for predicting the change of fluidized waste soil’s permeability coefficient considering the age and the replacement rate of steel slag were established.