A test
pile comprises a hollow
pile body. The lower portion of the
pile body is located underground, and the pile body is located above or beside an
underground pipeline. A test block
pipe is installed in the pile body. A cabin door is arranged on the pile body. A wiring board is installed in the pile body. A test block is installed in the test block
pipe. A
reference electrode is installed in the pile body. The test block, the
reference electrode and the pipeline are connected with the wiring board. The lower portion of the test pile is inserted underground, the test block is installed in the test block
pipe, the
reference electrode is installed in the lower end of the test pile, and therefore the lower portion of the test pile can be used as a reference pipe, and it is unnecessary to additionally install a reference pipe; installation and
layout are simple, and the cost of whole pipeline
cathode protection
engineering is also reduced. When the reference
electrode is calibrated, a
working electrode for calibration can be conveyed to an underground position through the test pile, the
working electrode is made to be close to the reference
electrode to be calibrated as much as possible, and calibration is more accurate; the reference
electrode to be calibrated can also be taken out to an overground position from the underground position along an inner cavity of the test pile, the reference electrode directly gets close to the
working electrode on the ground, calibration is conducted, and therefore calibration accuracy is improved; moreover, the reference electrode and the test block can be taken out from the underground position and are convenient to replace and maintain.