DEVELOPMENT METHOD OF PILLARS OF DRILLED GRAVEL BOREHOLES OF PERMAFROST ZONE Russian patent published in 2011 - IPC E21C45/00 

FIELD: mining.

SUBSTANCE: method involves mining activities performed during summer season by water jet by means of devices installed in underground cavities pre-drilled from surface of the well along longitudinal axes of pillars at certain distance from each other with pulp lifting to the surface and its supply via pulp line to flushing device in order to extract useful component and laying of dehydrated flushing remainders formed during washout process of sands so that distributed filling masses are formed. Pillar recovery is performed in two stages during two years. During the first year the pillars are recovered partially so that gaps are left between cavities washed out between them, which are developed using the same method in the next year; at that, in order to strengthen compression properties of filling masses, they are frozen with natural cold during winter period.

EFFECT: avoiding execution of underground mine workings at pillar extraction; possibility of selective development of technogenic deposit; arrangement of dehydrated flushing remainders in the worked out space and its complete use; avoiding cavings in the ground surface; recovery of rock mass continuity and stabilisation of its temperature mode; minimum contamination of environment; eliminating the necessity for execution of recreation works.

2 dwg