Abstract: During the backfilling of the underground structures for a subway station, if a cross strut needs to be removed, an extractable strut is usually installed below this cross strut. Conventionally, the extractable strut is not optimized for the deformation control. This paper presents a case history of the application of the extractable strut in the supporting of Xingtang Street Station structures for Suzhou Transit Line No.5. The locations of the vertical struts were evaluated. Several different struts plus extractable struts were compared. It is concluded that different strut arrangement resulted in different maximum bending moment and at different locations. For the backfilling of the subway station, the number of extractable struts should be minimized and even avoid as long as the maximum bending moment is within the tolerable limits. Although the reduction of the extractable will result in the increase of the bending moments in the supporting structures and increase the content of steel, the over construction cost is still cost effective.

Key words: Subway Station Excavation, Bracing Support, Bracing Replacement, Comparison and Analysis