Abstract: Kerogen and other combustible matter can be extracted from an area of oil shale or tarsand by drilling boreholes in a selected pattern through the overlying soil and rock without removing it. Each borehole mouth is tightly closed by a cover provided with an air inlet pipe and a gas exhaust pipe. In the covers of one or several boreholes, the inlet pipe is centrally guided and longitudinally movable in an upward and downward direction, and a laser beam generated by a laser source is inroduced into the upper end of the pipe and directed centrally to its bottom where it is diverted toward the borehole wall by a mirror assembly. The laser beam moved along the borehole wall irradiates the oil shale or tarsand and ignites the combustible matter contained therein which liquefies and evaporates. Combustion spreads from the initially ignited bore to the remaining bores in the area through the fissures in the formation and likewise serves to liquefy and evaporate the kerogen there.

Abstract: Reinforcing the rock walls of a cavity comprises drilling long holes into the rock at predetermined distances and grouping and to a predetermined depth, inserting a bar-shaped tension member of high tensile strength into each of these holes and fixing their end of each member in the inner end of the respective hole. The tension members are subsequently elongated by biasing their outer ends against the cavity surface by known tension means such as screw nuts or wedges, thereby compressing the rock and preventing cracks from developing. In order to convert such cavities into tight containers, an impervious pliable sheet material is laid close to the cavity wall and held there by fastening it to the protruding ends of the tension members.

Abstract: The method of converting clayey or silty soil into stable and solid underground columns or piles suitable for carrying a building structure, comprises first the drilling of bores of a diameter considerably smaller than the external diameter of the column or pile to be created, to a predetermined depth, and secondly directing a focused laser beam gradually across the entire surface of each bore by mechanical and optical means, in such a manner that each point of the bore surface is irradiated and heated at an intensity sufficient for converting the soil surrounding the bore into a solid permanent mass of a predetermined thickness measured from the bore surface, which mass retains its strength and is resistant to moisture and temperature.