| Due to the characteristics of lightweight,self-leveling,and no need for vibration and compaction,fluidized fly ash is often used in abutment backfill to solve the problem of vehicle jumping at bridge heads.However,traditional fluidized fly ash is difficult to be widely promoted and applied due to its high cost,and existing research is mostly limited to the perspectives of mix design,durability,and static performance.There is a lack of research on its dynamic characteristics as a subgrade filler for abutment back.Based on the Shandong Provincial Transportation Science and Technology Plan project "Research on Engineering Characteristics and Application Technology of Liquid Fly Ash in Road Bridge Transition Section"(2021B117),this paper has developed a low cost,energy-saving and environmentally friendly desulfurization gypsum fly ash fluid light soil,which further has stimulated the activity of fly ash and has enhanced its strength by using desulfurization gypsum;Through indoor experiments,its fluidity,static and dynamic characteristics,cumulative plastic deformation and other properties have been systematically studied;Combining with practical engineering applications,the construction technology and key points for construction quality control of desulfurized gypsum fly ash flowing light soil abutment backfill have been proposed.The specific research content includes:(1)Through tests of fluidity and unconfined compressive strength,the effects of cement content,desulfurization gypsum/fly ash mass ratio,silt content,and age(standing time)on the compressive strength(fluidity)of desulfurization gypsum/fly ash flowable lightweight soil have been studied,The optimal mix ratio is 8% cement content,1:1 fly ash/desulfurized gypsum,60% silt content and 0.34 water solid ratio.The development process of its stress strain curve has been revealed using stress strain relationship tests,and a constitutive model for uniaxial compression has been presented.(2)Based on the MTS universal material testing machine,dynamic characteristics and cumulative deformation tests have been conducted to reveal the overall change rule of the hysteretic curve of desulfurized gypsum fly ash flowing lightweight soil and the change type of the cumulative plastic strain loading times curve.The effects of various raw material content,vibration frequency,cycle times,dynamic stress amplitude,and other factors on the dynamic elastic modulus,damping ratio,and cumulative deformation have been analyzed,and a cumulative plastic strain prediction model has been proposed.(3)Based on the actual engineering application of the reconstruction and expansion project of the Jitai section of the Beijing-Taiyuan Expressway,the layered pouring construction technology and key points for construction quality control suitable for desulfurization gypsum fly ash fluid light soil have been proposed.Postconstruction settlement observation has been conducted on the test section,and the accumulated settlement of the test section in the second half of the construction period has been 13.8 mm.A technical and economic comparison analysis has been made with common backfill materials.The results showed that the application of desulfurized gypsum fly ash fluid light soil had good effects and significant cost advantages.The research in this paper has provided an effective,feasible,economical,and environmentally friendly abutment backfill material for treating vehicle bumps at bridge heads,and has provided reference for its application in engineering scenarios such as subgrade widening,pipe trench backfilling,and retaining structures.This is of great significance for improving the service quality of roads and promoting the innovative development of comprehensive utilization of bulk solid waste. |
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