4. Deep leveling piles: The main purpose is to continuously monitor the compressive change of the stratum thickness from the surface to a single specific depth below the ground. The mechanism is to drill holes to a certain depth below the surface and place a steel tube, and then pour a cement mortar base at the bottom of the tube to closely combine with the stratum. Through automatic and real-time measurement of the vertical displacement change between the top of the steel tube and the surface, it can be automatically continuous Monitor the change in compression of the formation.