Hydraulic prestressing units: An innovation in roof support technology

The performance capabilities of hydraulic prestressing units (PSU) and the impact they have on the performance of various support systems are examined. The examination of PSU's includes, the range of support applications using the technology, load capacities, and their impact on overall support stiffness. Since the PSUs are transported into the mine in a collapsed form, they reduce the volume of the material that must be brought into the mine to construct the support system. The use of over-sized PSU's relative to the support size can provide for larger preloading capability, and also decrease the initial stiffness of the support if it is not fully pressurized to permanent shape.