Movable support based on development of underground space above subway and construction method thereof

The invention relates to a movable support system arranged at the beam end of a supporting beam on a subway protective pile, a prestressed beam type underpinning structure and a foundation pit supporting structure based on development of an underground space above a subway and a construction method thereof. The movable support system comprises a plurality of underpinning piles and underpinning beams, wherein the underpinning piles and the underpinning beams are arranged in an abutting mode in sequence, and the underpinning beams are slidably connected with the underpinning piles. One side of each underpinning pile is provided with a pile body guard wall filled with concrete. A U-shaped waist beam arranged horizontally is embedded in each pile body guard wall. The end of each underpinning beam is arranged in an opening of the corresponding U-shaped waist beam. A gap is reserved between the end of each underpinning beam and a corresponding web plate. The construction method comprises thefollowing steps of S1, c