Treatment of quality defects of No. 6∼No. 8 tunnels of the Main Line in Shanxi Wanjiazhai Yellow River Diversion Project

Double-shield Tunnel Boring Machine (TBM) and liner with hexagon precast concrete segment are unsuitable for the tunnel construction under some unfavorable geological conditions, such as soil, karst, fault and soft rock etc. Since these unfavorable geological conditions are usually unavoidable during construction of a long tunnel, effective past-construction treatment is necessary to ensure the safety of tunnel operation. This paper aimed at the construction quality defects emerged in the soil tunnel sections of the No.6∼ No.8 tunnels of the Main Line in Shanxi Wanjiazhai Yellow River Diversion Project due to the special geological conditions and constructional quality problems, emphatically introduces the corrective countermeasures. Dislocated segments were reset by pulling open the segments, scooping out backfilled pea gravel and surrounding soil behind the segments, then pushing the segments back to their design positions. This method was safe, economical and fast. For the whole line of soil tunnels, all the cracks of segments, the joints between segments and the prepared holes in segments for grouting were sealed by combined application of rigid waterproof layers (cast-in-situ concrete or steel plate) and flexible waterproof layers (various non-toxicant chemical coating) to prevent seepage.