Bechtel International Corporation

James D Grenia

A method of mining thick seam materials is performed by forming a pair of generally horizontal, vertically spaced, vertically aligned passes or drifts in one side of the thick seam. A number of contiguous vertical holes are drilled in the material from the lower to the upper drift to form a relatively large opening extending the length of the drifts. This large opening is then filled with low grade concrete to support the overburden and, after the concrete is set, a second pair of generally horizontal, vertically spaced, vertically aligned drifts are formed adjacent to the first mentioned drifts and the foregoing process is repeated. The above steps are continued until the entire seam of material has been removed. Each individual hole between an upper drift and a lower drift is formed by first drilling a relatively small diameter hole from the upper drift to the lower drift, following which a relatively large diameter reamer is then coupled to the drill shaft and the drill shaft is raised and rotated to cause the reamer bit to mine the materials from the bottom drift to the top drift, the materials falling into the lower drift and being removed in any suitable manner.

Method of mining of thick seam materials

A method is provided for the underground mining of thin seams of certain minerals, such as coal, particularly minerals capable of being bored or cut, employing walls formed in place. A relatively narrow substantially rectangular drift is cut in the seam, usually the entire height of the ore formation. The drift is then filled with low-grade concrete to form a wall. After the concrete has set to have sufficient compressive strength to provide support for the overburden, additional drifts are driven immediately adjacent to the wall and are joined behind the wall, so as to allow for air circulation around the wall and provide space to repeat the process. In this way, a plurality of tandem walls can be introduced through the working area of the seam. Between each tandem wall, a temporary barrier is erected, having manways with closeable doors therein as required, so that forced ventilation will travel the full length of one drift and return back through the companion drift. Additional walls may be established at lateral distances from the first wall, so as to define an area of the seam for longwall mining. Desirably, the walls are of a compressible material. After removal of the mineral or coal between the walls, upon subsidence of the overburden, the walls will be substantially compacted, so as to minimize surface unevenness.

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Concord, CA, United States of America

James D Grenia