Study on Deterioration Characteristics of Modified Slurry Shield Spoil Based on Freeze-thaw Cycle Test
Modifying the muck discharged from a shield tunnel into subgrade material will significantly increase the utilization efficiency of resources,but the freeze-thaw conditions will create safety hazard.By using a shield tunnel of Heping Avenue in Wuhan as the example and using the spoil from large-diameter slurry shield as the study ob-ject,the shield spoil is modified by adding the independently developed waste solid based gelatinizer(Cement-Slag-Gypsum-Alum,CSGA)and basalt fiber(BF),and the shield spoil modified by CSGA-BF is subjected to freeze-thaw cycle test,in order to investigate how the parameters such as amount of basalt fiber and number of freeze-thaw cycles will affect the appearance deterioration characteristics,mechanical properties and microscopic damage mecha-nism of improved shield spoil.As the results indicate:Under the effect of freeze-thaw cycle,the volume of modified spoil changes in a wave-like pattern,and it generally exhibits volume expansion.As the number of freeze-thaw cycles increases,both the unconfined compressive strength and modulus of elasticity of the modified shield spoil decrease non-linearly.Adding a proper amount of basalt fiber will increase the friction at the reinforcement-soil interface,which is important to frost resistance of spoil.However,excessive amount of fiber will degrade the strength of the specimen.When the number of freeze-thaw cycles is 9,the compressive strength and modulus of elasticity of the modified shield spoil stabilize,and the pores become interconnected.
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