EXTRACTED DEPTH REFERENCE BENCHMARK Russian patent published in 2017 - IPC E21C39/00 

FIELD: mining engineering.

SUBSTANCE: extracted depth reference benchmark includes an estuarial tube, base and locking plugs connected to the indicators by steel cables. In this case, the estuarial tube is made of galvanized spring material along the diameter of hole, has a slot for its easy insertion into hole, protrudes on the 50-70 mm from hole to the level of fixing the worked out space in light and is the reference point for roof displacement for base and locking indicators. Base and locking plugs are made of spring wire, rolled up in the form of spirals with diameter D=8-10 mm with diluted ends of length L=12-14 mm at an angle α=145-155°, directed into the depth of hole. At the same time, the carrier steel cables of displacement indicators are pivotally mounted on the lower part of the spirals, keeping them on weight; and on the upper part ropes for extracting the plug from hole are mounted, the lower ends of which are fixed on corresponding displacement indicators diametrically opposite to the carrier cables, and have different colours. Displacement indicators are performed from the tubes entering into each other in the sequence of open-casts arrangement, have measuring scales, and, at the ends, openings for releasing and securing ends of cables and adjusting the position of indicator relative to estuarial tube.

EFFECT: simplification of measurements and design of reference benchmark and possibility of its reuse.

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