Method and apparatus for preventing rock fragments from entering or collapsing into a blast hole

An apparatus for location within a collar region at an open end of a blast hole for preventing surrounding loose rock fragments from falling or collapsing into the blast hole, the apparatus including:

• a sheet of resiliently flexible polymeric material including a pair of spaced apart longitudinally extending side edges and a pair of spaced apart laterally extending end edges, the sheet having a flat form and a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends, one end of the curved sheet being insertable within the open end of the blast hole, wherein, in the curved form, the side edges of the sheet are free and the sheet biases towards the flat form, whereby an external surface of the curved sheet is biased against an internal surface within the open end of the blast hole and forms a barrier preventing surrounding loose rock fragments from falling or collapsing into the open end of the blast hole, wherein the sheet tends, from the curved form, to assume a resting state in which the sheet is in the flat form.