Abstract: A propulsion method of a pipe to be buried without soil discharge comprising the steps of drilling the ground with the tip of an excavator propelling in the ground, taking the drilled soil into the excavator, discharging the taken soil to the ground side by compacting the soil on the outer circumference of the excavator, and burying the pipe progressively in the hole formed behind the excavator; being characterized in using an excavator equipped with a tip part having a diameter larger than the outside diameter of the pipe to be buried and a rear part having nearly the same diameter as the outside diameter of the pipe to be buried.

Abstract: A protective tube is vertically buried in the ground, and sinking elements for generating magnetism are buried at plural positions at different depths in the ground outside the side wall of this tube. Magnetic sensors capable of detecting magnetism are disposed in the tube to detect the magnetism generated by the sinking elements, and the depth position of the sinking elements in the ground is measured according to the detected signal, so that the fluctuations by settlement or uplift of the ground may be known by each bed differing in depth. A plurality of magnetic sensors are fixed to the side wall surface of the tube, corresponding to the individual sinking elements.