Survey-stage-based external water pressure monitoring structure for tunnel to be built

The utility model relates to the technical field of geological exploration, in particular to a prospecting-stage-based external water pressure monitoring structure for a proposed tunnel, which comprises a vertical prospecting hole with the lower end extending to the periphery of the section of the proposed tunnel, a vertical mounting pipe is arranged in the prospecting hole, and the lower end of the mounting pipe extends to the lower end in the prospecting hole. An upward lead is arranged at the upper end of the detection probe, penetrates out of the upper end of the mounting pipe and extends out of the upper end of the exploration hole to be connected with a data acquisition instrument; an expansion layer is further arranged on the outer circumferential surface of the lower end of the mounting pipe, so that the expansion layer can expand after being in contact with water and is attached to and supported on the inner circumferential wall of the exploration hole; a water permeable hole penetrating through the