Deep foundation pit inner support system bottom-layer supporting beam early dismounting structure and construction method

The invention discloses a deep foundation pit inner support system bottom-layer supporting beam early dismounting structure and a construction method. The construction method comprises the steps thata cushion layer is laid at the bottom of a foundation pit; basement bottom plates and a post-cast strip on the cushion layer are arranged at intervals, force transmitting structural steel is arrangedin the extending direction of the post-cast strip and sandwiched between the basement bottom plates on the two sides of the post-cast strip, and plain concrete is arranged between the basement bottomplates and a foundation pit protection wall. The deep foundation pit inner support system bottom-layer supporting beam early dismounting structure is convenient to install and economical and practical, and material taking is convenient; and meanwhile, the floor rigidity is enhanced, the foundation pit horizontal load is effectively transmitted, the construction period is shortened, cost is saved,and obvious economic benefit