| Due to the high clay content of waste mud,the existing treatment methods such as press filtration and filtration encounter the technical bottleneck of slow dehydration,low strength of soil products and difficult backfilling.In other fields,flocculation is often used to accelerate dehydration,solidification is often used to improve soil strength,if the combination of solidification-flocculation-extraction filtration can achieve better dehydration and product strengthening effect.However,the mechanism of solidificationflocculation interaction has not been fully understood,and the dehydration and strengthening process after its combination with filtration needs to be studied.Therefore,this paper takes solidification-flocculation-vacuum filtration treatment of mud as the research object,and through the combination of flocculation,solidification and filtration testing,the dewatering characteristics of mud and the strengthening characteristics of soil products are studied,the properties of stage products are characterized,and the dehydration mechanism of mud is revealed.The effects of solidification hydration,filtration and dewatering and curing agent loss on the strengthening of soil products were discussed,and the strengthening mechanism of soil products after dehydration was elucidated.The main research contents and achievements of this paper are as follows:Firstly,the feasibility of solidification-flocculation-vacuum filtration treatment of waste slurry in pipe jacking project was discussed,and the test results showed that the slurry pretreated by solidification-flocculation or flocculation-solidification pretreatment can obtain a lower moisture content after vacuum filtration,among which the method of solidification-flocculation-vacuum filtration treatment of slurry has the highest dewatering efficiency,low filtration resistance,and the soil product has a certain strength,and the slurry with a moisture content of 400% can be rapidly reduced to 62% within 150 s.The 7-day unconfined compressive strength of the dehydrated product can reach 117.33 k Pa.In addition,compared with the mechanical filtration,flocculation and solidification treatment slurry commonly used in practical engineering,this method has lower cost,higher efficiency,and has good engineering application prospects,so it is feasible to use solidificationflocculation-vacuum filtration combined treatment of waste slurry in pipe jacking engineering.Secondly,the dewatering mechanism of solidification-flocculation-vacuum filtration waste slurry treated by top pipe is discussed.The test results show that the key factor of inter-group porosity,on the one hand,the addition of solidification agent can effectively adjust the electrical properties of the slurry,reduce the electrostatic repulsion of the slurry particles inside the floc,make the floc more solid,and strengthen the ability of the floc to resist compression deformation during the vacuum filtration process.On the other hand,solidification agents and flocculants can reduce the thickness of the bound water layer on the surface of the slurry particles or floc,increase the size of the pores between the groups during the vacuum filtration process,and thus improve the dewatering effect of the slurry.Finally,the soil product strengthening mechanism of solidification-flocculationvacuum filtration treatment of waste slurry was discussed.On the one hand,the same strengthening mechanism as conventional soft soil,the strengthening of soil products is related to its moisture content and the type and amount of curing agent,increasing the amount of solidification agent,and soil products with lower moisture content can be obtained after vacuum filtration,so that it has higher strength.On the other hand,because the waste slurry of the pipe jacking project has a high moisture content,therefore,when solidification-flocculation-vacuum filtration treatment slurry,the ionization and hydrolysis degree of the solidification agent is higher,and in the vacuum filtration process,the hydrolysate product is easier to be discharged with the tail water of the vacuum filtration,and some unhydrolyzed cement particles will also be lost,resulting in a reduction in the strength of the soil product. |
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