Asynchronous support changing construction method for super-large-area deep foundation pit in complex environment

The invention relates to the technical field of foundation pit support changing, in particular to an asynchronous support changing construction method for an ultra-large-area deep foundation pit in a complex environment. Comprising the steps that S1, a foundation pit is divided into a plurality of areas, the areas are enclosed through surveying and setting out, and the interiors of the areas are cleaned; s2, the elevation is designed, a foundation bed is constructed according to requirements, and a pipeline chamber is poured in the foundation pit; s3, expansive concrete construction is conducted on the main structure pipeline chamber; s4, a support changing platform is installed, and the support changing platform is divided into a first supporting platform, a second supporting platform and a third supporting platform according to the depth of the foundation pit; s5, foam concrete backfilling is conducted after the support changing platform is installed; s6, dismounting a platform plate, a horizontal jack and