Opposite stopes

(Figure) The scheme for the specification of the direction for the crosscut

OPPOSITE STOPES (EN: entries, counter faces; DE: Gegenorter; FR: contre-tailles; ES: contratajos; RU: встречные забои) is the method for the conducting of the underground mine working simultaneously from the two sides, with the subsequent rendezvous of the stopes in the intended point. This method is used for the decreasing of the durations of the construction of the underground built structures, and during the development of the deposits (during the unsealing or preparation of the new horizons within the underground mine, and during the slicing of the excavation fields and places).

For the conducting of the mine workings for the opposite stopes, they determine the direction of the movement for each stope within the horizontal and vertical planes according to the coordinates of the points of the mine surveying reference networks, they transfer this direction into the reality, and they verify it systematically. They fixate the direction or axis for the mine working, which is being constructed, using the three plumbs, or they fixate this direction, using the ray of the laser pointer for the directions. For the geodetic and mine surveying substantiation of the opposite stope, they also use the explosion-proof portable mine surveying gyrocompasses, light ray rangefinders, and optical theodolites.

The conducting of the opposite stope is simplified in case of the rendezvous along the guide (along the useful minerals within the hanging wall or footwall of the deposition), because besides the responsible direction of the rendezvous (which is perpendicular to the axis of the breakthrough), there emerge the free directions. The existence of the free directions excludes or decreases the influence of the individual sources of the error, and simplifies the methodology of the mine surveying survey.

The major sources for the inaccurate rendezvous of the opposite stope within the projection onto the horizontal plane are the errors of the measurement of the angles and lengths of the lines within the polygonometric or theodolite passways of the reference networks, and also the errors of the orientation of the underground mine surveying networks (see the Figure).

The rendezvous of the stopes within the vertical plane depends on the errors of the leveling passways, of the trigonometric leveling, and of the transfer of the heights from the Earth's surface into the underground mine. The error of the rendezvous (of the breakthrough) is determined by the magnitude of the divergence of the axes of the mine workings, which are being constructed, within the horizontal and vertical planes.

They present the highest requirements for the precision of the rendezvous of the stopes during the conducting of the mine workings with the simultaneous erection of the capital lining, with the construction of the foundations for the equipment of the trunk conveyors, or of the supports for the railway tracks. In these cases, there is tolerated the divergence of the axes of at most several centimetres.