Delineating subterranean solution channels using machine performance parameters in TBM tunnel post-grouting

摘要

Zagros Water Conveyance tunnel in western Iran crosses a broad and vast aquifer.This TBM burrowed tunnel has long drained the region's groundwater at an average rate of 416 lit/s.The groundwater is rich in hydrogen sulfide (H2S) gas.The gas reacts with the tunnel humidity and produces an acidic fume that penetrates the tunnel lining and decomposes its concrete and steel reinforcement,as well.The exact locations of these discharging conduits and their morphology are not known,since the TBM segmental lining conceals them.An elaborate post-grouting plan is on the drawing board to reclaim the aquifer but the cost of a systematic grouting is particularly high and at best scenario not conclusive.The scope of this paper is to discuss a series of carefully controlled field experiments in a 100 m pilot study area along the tunnel.It manipulates on the TBM performance parameters that were registered during the tunnel excavation stage.Based on this information,suitable field models are established that may be interpreted as being associated with either water or air-filled solution channels and open joints.The results are supported by in-situ permeability tests,where the suspected joints were theatrically identified and were cement grouted after construction phase.