Effective Treatment of Water Inrush and Shield Jamming in Double-Shield TBM Construction at China Hydropower Engineering Bureau III TBM2 Section of Lanzhou Water Source Project

On September 13, 2017, with approximately 2km remaining for tunnel breakthrough, the double-shield TBM encountered a water-bearing fractured fault zone that caused severe equipment jamming and significant water inrush. Initial mitigation measures involving shallow-hole grouting to stabilize the cutterhead face and deep-hole cement grouting reinforcement were implemented. However, the TBM still experienced excessive muck discharge, with 700m³ of material excavated during just 1.2m of advance. The massive volume of debris repeatedly overloaded and halted both the main and transfer conveyor belts, forcing extensive manual removal of muck that had overflowed into the shield interior. Meanwhile, water inflow intensified dramatically from initial minor seepage to multiple high-volume flows, ultimately reaching a total discharge rate of approximately 100m³/h and bringing tunneling operations to a complete standstill.