Definition - What does Hydraulic Jack mean?
A hydraulic jack is a hydraulically powered jacking device consisting of a hydrostatic press with its pump and reservoir containing a supply of liquid, as oil, used for lifting, moving, or forcing objects or loads into place. These jacking devices provide the impetus to move the pipeline into place behind a cutting shield (mole), or microtunneling boring machine (MTBM) in a pipe jacking operation. This process is a standard trenchless construction technique and can be used in most soil types as it serves to avoid ground settlement and instability issues.
Trenchlesspedia explains Hydraulic Jack
During a pipe jacking operation, the cutting shield excavates a pathway through the earth. Powerful hydraulic jacks push pipe segments into place behind the cutting shield as the soil is removed. Thrust walls are constructed in the entry pit in order to provide adequate reaction for the force generated by the hydraulic jacks. It is also important to ensure that the thrust from the jacks is evenly distributed over the diameter of the pipe. The jacks are interconnected hydraulically to make this possible and a thrust ring actually transfers the thrust to the pipe.