Abstract:

 Bored tunneling of the project between the SongjiangNanjiang station and ZhongxiaoXinsheng station  in the Xinzhuang line of Taipei MRT was challenged by the conditions of driving through the underground structure of six panels of the retaining wall ,including the irregular continuous walls and noncontinuous base of foundation piles, beneath the existent tunnels of the Taiwan Railway （TR）and the Taiwan High Speed Rail （THSR）system.
As result of the limitation by the external environment condition, nonorthogonal between the tunnel alignment and the retaining wall or base of foundation piles.
For the safety reason, the construction procedure of this case adopted by the horizontal grouting to improve the soil condition around the domain of the retaining wall from the top head of the TBM, and coordinates with the glassfiber shotcrete method and the wellpoint method to excavate and break up the obstacles and wall bodies through the air chamber and an only approximately 85×55 cm channel enter a very narrow working space at the front of TBM. This article aims at the construction method and countermeasure adopted by this case, as well as the difficulty during the TBM driving through period, furthermore, the widely discussion of the dangerous condition occurrence, countermeasure and overcomes.

Key words: underground retaining wall  , horizontal grouting  , glassfiber shotcrete  , wellpoint