Abstract: Plastic hose means, preferably of high pressure polyethylene admixed with a flame retarding agent and treated to render the same antistatic and characterized by a resistance to tearing of at least 15 N/mm.sup.2, an extension of at least 450 percent, a resistance to piercing of at least 1.5 J and a resistance to continued tearing of at least 17 N/mm, are disclosed, as is a process for using the hose means for filling the space between the rock face of a mine or tunnel and the supporting structure therefor.

Abstract: The generation of dust in a longwall mining operation is suppressed by covering the hanging wall of the mine with a plastic sheeting, the sheeting being pinned against the hanging wall by the support units used in the mine and being held in association the support units in the form of a flat package formed by folding the sheeting in a zigzag fashion along its entire length.

Abstract: A new process has been devised for the application of a mixture of calcium or magnesium chloride and a non-ionogenic wetting agent for the prevention of the spontaneous ignition of coal, especially during underground mining operations, by applying the same to the surface of the coal. The process involves boring of holes into the out-cropping coal and then forcing the mixture of calcium or magnesium chloride and wetting agent in an aqueous solution which contains 25 to 35% by weight of the mixture through the bore holes. A constant quantity of about 3 to 6 liters of solution per minute is pressed into the bore holes, the pressure being only sufficient to overcome the counter pressures occurring in the coal. The procedure greatly extends the time of effectiveness of the prevention of spontaneous ignition of the coal and eliminates to a large extent the expenditure of labor for supervision and retreatment of the surface of the coal now being experienced.