| 摘要 |
A method for coordinating the lifting velocity of a drilling rod and the amount of concrete poured into a borehole to cast a pile from the bottom towards the surface. The concrete is poured through a pipe which is part of the drilling rod. A positive pressure is maintained at the bottom of the drilling rod by analyzing the tensile force in the lifting cable. As a pressure develops at the bottom of the drilling rod, a force is generated and upwardly pushes the drilling rod. The force is due to the "piston effect" of the drilling rod geometry and reduces the minimal tensile force in the lifting cable.
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