Model Test of Grouting Escaping of Shield Tail Grouting and Research on Occurrence Conditions

The phenomenon of grouting escaping surrounding rock stratum that may occur during shield tail grouting can cause accidents such as incorrect grouting, segment floating, misalignment and cracking, and gushing, which has attracted extensive attention. By designing a self-made shield tail grouting model device for grouting escaping, the effects of grouting properties, gap thickness, and grouting pressure difference on whether or not grouting escaping occurs and the amount of grouting escaping are analyzed, and the critical conditions for no grouting escaping are discussed. The results show that: 1) The grouting pressure and the grouting escaping distance are linearly attenuated. When the grouting consistency is low, the amount of grouting escaping has an approximate linear positive correlation with the gap thickness and slurry consistency, and an approximate linear negative correlation with the shear yield stress of the grouting, and there is an approximate linear positive correlation between the grouting escaping distance and the grouting pressure difference. When the consistency increases, the above relationship will gradually transform into a nonlinear relationship; 2) The range analysis shows that the amount of grouting escaping is most affected by the thickness of the gap between the shield shell and the rock stratum, followed by the difference between grouting pressure and excavation surface pressure, and finally the properties of the grouting itself; 3) Based on the mechanical analysis model and calculation formula for the occurrence conditions of grouting escaping, the occurrence conditions and judgement methods of grouting escaping are obtained, which can be used to guide the preparation of grouting fluid during shield tunneling in stable surrounding rock stratum.