Local deepening structure under building foundation

The utility model relates to a local deepening structure under a building foundation, and belongs to the technical field of building construction, the local deepening structure comprises a cushion layer, a flow guide layer and a drainage well, the cushion layer is circumferentially laid on the slope surface of a sump, the flow guide layer is circumferentially laid between the cushion layer and the slope surface of the sump, and the drainage well is arranged at the bottom of the sump. The drainage well is formed in the soil layer and communicated with the diversion layer and the outside, seepage water of the permeable layer in the soil layer of the water collection pit flows into the drainage well through the diversion layer, accumulated water on the cushion layer flows into the drainage well along the slope surface of the cushion layer, water pumping equipment is installed in the drainage well, water deposited in the drainage well is pumped out, and the drainage well is communicated with the diversion layer.