The invention relates to the technical field of
building construction methods, and discloses a pit-in-pit supporting structure which is applied to the periphery of a foundation pit, soft foundation soil is arranged in the foundation pit, the pit-in-pit supporting structure comprises a plurality of stirring piles, a reverse pressing plate, a steel plate, joint bars and a steel
pipe support, and the reverse pressing plate comprises a horizontally-arranged
concrete cover plate and a vertically-arranged concrete
purlin beam. A plurality of mixing piles are arranged on the periphery of the inner side of a foundation pit and are obtained by mixing and solidifying a curing agent and soft foundation soil, a
concrete cover plate is laid above the mixing piles, a concrete
purlin beam abuts against the sides, close to the foundation pit, of the mixing piles, and a steel plate is fixed to the sides, close to the foundation pit, of the concrete
purlin beam. One end of the joint bar is inserted into the mixing
pile, the other end of the joint bar is anchored into the
back pressure concrete cover plate and used for fixing the
back pressure concrete cover plate to the mixing
pile, one end of the steel
pipe support is welded to the steel plate on one side of the foundation pit, and the other end of the steel
pipe support is welded to the steel plate on the other side of the foundation pit.