Mine props

A mine support which includes:

• a mine prop comprising a cutting device and a cuttable plunger, the cutting device including a sleeve having first and second ends and cutting means which is fixed to the sleeve and which presents cutting edges transverse to the sleeve axis and a plurality of axially oriented openings between the cutting edges, and a vacant space defined in the sleeve on that side of the cutting means towards the second end of the sleeve, the cuttable plunger projecting from the first end of the sleeve with at least a portion of the plunger extending within the sleeve to the cutting means, wherein when compressive loading applied to the mine prop is of sufficient magnitude to cause the cutting device and plunger to telescope together, the cutting edges of the cutting means cut axially through the cuttable plunger to form a plurality of plunger segments which pass through the openings into the vacant space where they are restrained within the sleeve;
• and
• a preload unit operable to place the mine prop under an axial preload force between a hanging wall and a footwall of a mine working.