Supporting system and device for soil between piles of expansive soil deep foundation pit

The invention relates to expansive soil iron deep foundation pit engineering construction, in particular to an inter-pile soil supporting system and device for a deep foundation pit of an expansive soil stratum through bored grouting row piles. The expansive soil deep foundation pit is provided with an inter-pile soil supporting and reinforcing device support on a supporting pile; after a support of the inter-pile soil supporting and reinforcing device is installed, phi 8 welding reinforcing meshes are installed and shaped to serve as a temporary fixing structure; the method comprises the following steps: mounting prefabricated steel belts, mounting the steel belts on pre-mounted supports, mounting the steel belts on the supports, mounting the steel belts on the supports, fixing the steel belts by using phi 10 bolts, firmly binding the steel belts and reinforcing meshes at the middle positions of piles by using binding wires, and enabling the horizontal plane of the pre-bent steel belts to be perpendicular to