Pressure Control Analysis Based on Mechanical Properties of Bolts During Grouting at Shield Tail

Abstract:

As to segments joined by bolts, two kinds of friction forces between segments and shear resistance of bolts are in balance with shear force produced by grouting pressure. It is believed that the friction force between segments takes effect before segments displacement happens, while shear resistance of bolts would be dominating afterward. The pressure acting on shield tunnel segments during grouting at the tail was studied by substituting the intrinsic void percentage with the equivalent void percentage of the soil to assess the influence of construction gap. Based on such a theory and derivation, a formula to calculate the pressure was established. It shows that the pressure on segments increases with the increasing of grouting pressure and grouting time period. By combining shear resistance of bolts with the pressure acting on the segments, the grouting pressure and time could be controlled by shear stress of the bolts,which indicates that with the shear stress determined,the shear stress should be less than the allowable stress so as to control the grouting pressure and time.

Key words:shield tunnel; tail void grout; tunnel segments; bolts; grouting pressure