Earth Pressure and Internal Forces of Tunnel Lining in Jet Grouting Reinforced Mud Stratum

In this study, field measurements of the earth pressures and the main reinforcement strains were carried out at three shield tunnel linings in mud stratum reinforced by vertical jet-grouted piles during tunnel construction and post-construction. The measured strains were used to back-calculate the linings’ internal forces. The measured earth pressures and the back-calculated internal forces were compared to corresponding design values. The results indicate that the earth pressure and the internal forces increased rapidly, before exhibiting a fluctuating decrease and finally a long-term slow change, after lining assembly. The vertical jet-grouted piles were beneficial to mobilise the soil arching effect and led to the real earth pressure on the lining significantly smaller than the full overburden pressure, even with a relatively shallow buried depth. The vertical jet-grouted piles intensified the influence of backfill grouting on the earth pressure and caused the lining segments near the backfill grouting holes to continuously bear more radial pressure in the long-term. The resultant internal forces during lining assembly were large, and the Conventional Model failed to consider this element of the internal forces. The findings can provide a reference for the design and the construction of similar projects.