Construction monitoring device and method for deep foundation pit adjacent to existing railway

The invention relates to the technical field of settlement monitoring, in particular to a monitoring device and method for construction of a deep foundation pit adjacent to an existing railway, the monitoring device comprises a plurality of vertically-distributed monitoring mechanisms, and each monitoring mechanism comprises a monitoring pipe, a monitoring plate rotationally arranged on the monitoring pipe and a transmission assembly arranged in the monitoring pipe; the inner wall of each monitoring pipe is fixedly connected with at least one partition plate, the inner wall of each monitoring pipe is slidably connected with at least one pressure column, the space between each pressure column and the corresponding partition plate is filled with compressible fluid, each monitoring pipe is provided with a monitoring piece used for monitoring the pressure of the compressible fluid, and the multiple monitoring pipes are axially spliced; the monitoring plate is arranged on the peripheral side of the monitoring pipe