Abstract: In a propulsion process of buried pipe, an endless pipe to be buried is formed by sequentially curving a pipe material of long hoop shape made of a plastic material, and this endless pipe is successively inserted and propelled into the burying hole while forming the burying hole by propelling a leader in the ground.

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.

Abstract: A method and apparatus for laying pipes of low bearing force like a polyvinyl chloride pipe and others in the ground with a propulsion pipe laying method, wherein an excavation device to excavate a tunnel to lay pipes therein is propelled into the ground by a propulsion force exerted on a propulsion shaft joined behind an excavation device while the pipes to be laid are run over the propulsion shaft and propulsion shaft bodies are joined one after another to propulsion shaft bodies and the pipes are joined one after another to pipes. The propulsion shaft bodies have a supporting device on the outer periphery thereof which rigidly supports the inside surface of pipes run over the propulsion shaft. With this supporting power, pipes to be laid are propelled into the tunnel in accordance with an advancement of the propulsion shaft.