Liquid and gaseous products are recovered from an in situ oil shale retort formed in a retort site in a subterranean formation containing oil shale. A void is excavated in the subterranean formation within the boundaries of the retort site and a zone of unfragmented formation is left in the retort site adjacent the void. A retort inlet is at one upper edge of the retort site and a retort outlet is at the lower edge of the retort site opposite the retort inlet. Explosive charges are placed in the zone of unfragmented formation and detonated in an asymmetrical time delay sequence for forming a fragmented permeable mass of formation particles which substantially fills the retort to the top boundary in the region of the retort inlet. A combustion zone is formed in the fragmented permeable mass adjacent the inlet and a retort inlet mixture comprising an oxygen-supplying gas is introduced into the fragmented mass for sustaining the combustion zone and advancing the combustion zone diagonally through the fragmented mass from the inlet toward the outlet. A retorting zone is on the advancing side of the combustion zone for producing liquid and gaseous products and the liquid and gaseous products are withdrawn through the retort outlet.

Process and device for sealing barrier constructions in subterranean galleries, especially in salt mines. In the process, a fluid sealing medium is filled into a hollow space and is maintained at overpressure relative to the pressure of a stressing medium. With the device, a hollow space is filled with a sealing medium, maintained below overpressure, and positioned between the part of the gallery to be protected and the part of the galley in which a stressing medium is present. The sealing medium is stressed with a preset pressure and at the pressure of the stressing medium. The hollow space has a pressure shaft, in which the sealing medium stands at a predetermined level. The part of which is located above the level of the sealing medium is connected with the gallery in which the stressing medium stands. Through this, it is ensured that a specific overpressure is always present in the hollow space. Losses of sealing medium are independently compensated through the column of sealing medium in the pressure shaft, which represents a supply of pressure medium.

Disclosed is a process for controlling subsidence during underground gasification of coal. Prior to the complete coal gasification step, holes are provided extending from the bottom to the top of the coal seam and these holes filled with heat resistant support material. Thereafter, the complete gasification process is carried out.

An explosive charging apparatus for charging explosive pellets to a bore drilled in a rock. The apparatus includes a body having coaxial pellet guiding first and second bores, the second bore being provided with a pellet supplying port. A cylinder is provided and has a piston with its rod extending into the second bore to force the pellet therein when the rod is advanced under an air pressure supplied to the cylinder. The rod is formed with an axial air passage opened to the second bore and adapted to be connected with a pressurized air source when the rod is advanced so as to supply air pressure to the second bore to thereby drive the explosive pellet to the first bore. The first bore is supplied with a lower air pressure which functions to feed the pellet in the first bore to the bore in the rock. The cylinder is associated with a pilot operated valve which receives a returning pilot pressure when the piston is fully advanced and an advancing pilot pressure when the piston is fully retracted.

In conjunction with the face mining of bituminous coal, previously excavated or some portions of the tunnel are collapsed in a manner to form a mass of debris into which a mixture of electrostatic filter ash and water is injected to stabilize the structure.