Front segmented bag type grouting steel pipe supporting system and construction method thereof

The invention relates to the field of foundation pit engineering, and discloses a preposed segmented bag type grouting steel pipe supporting system which comprises foundation pit fender posts, preposed segmented bag type grouting steel pipe piles, a reinforcement cushion layer, a basement structure and a force transmission belt. Each preposed segmented bag type grouting steel pipe pile comprises a steel pipe body, a pile tip and a bag, and each steel pipe body comprises segmented steel pipe joints and a steel sleeve; the lower end of the steel pipe body is provided with a grout outlet, and the outer side of the grout outlet is covered with a bag. The method comprises the following steps: constructing fender posts; digging a groove; measuring and placing a pile position; processing the steel pipe main body by sections; the first steel pipe section is vibrated in; lengthening the pipe joints of the segmented steel pipe; the steel pipe joint extension section is vibrated in; cement paste and gravels are filled i