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 object, the shield spoil is modified by adding the independently developed waste solid based gelatinizer (Cement-SlagGypsum-Alum, CSGA) and basalt fiber (BF), and the shield spoil modified by CSGA-BF is subjected to freezethaw 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 mechanism 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.