COMBINED OPEN AND UNDERGROUND WORKING OF MINERAL DEPOSITS IN MOUNTAINS AND HILLS Russian patent published in 2015 - IPC E21C41/00 

FIELD: mining.

SUBSTANCE: claimed process comprises the location of potential sliding surfaces and strengthening of rock hardness over said surfaces. Simultaneously with the pit overburden jobs for mining, deposit opening is executed under the highest part of the mountain or hill. Flattening of slopes, shoulders and walls of the pit occurs under effects of underground mining up their stability. Then, the potential sliding surface is flattened to up the stability of the entire rock massif. Pit wall stability criterion is assumed to be the mountain or hill inclination angle developed for a long time under integral action of the rock massif structure and properties, climatic effects and other specific features of developed territory. Underground mining in the zone of influence of the pit wall is carried in two steps. At the first step, pit wall are flattened for safe and efficient open working. At the second step, after termination of open working nearby the pit wall, overburden of residual reserves is performed by subsurface means. Note here that the pit nonworking wall is made approx parallel with the mountain or hill slope existing before starting the mining. The line is drawn towards the deposit at the boundary angle to intersection with the deposit from the point of the mountain or hill bed whereat curvature terminates and slope straight part starts and the slope is crossed by horizontal surface. Obtained intersection point is taken to be the boundary between open and subsurface working at their first step. Expected shifts caused by subsurface mining are calculated and plotted on vertical section. Obtained magnitudes of convergence from the slope contour to overburden are subtracted to get its contour after overburden. Works in the pit are continued with maintenance of the wall stability, or underground mining is made, or above described jobs are reiterated. Note here that the increase in stability is ensured by the pit wall mountain or hill slope flattening by turning the vectors toward the massif and by decrease in the load at potential sliding surface.

EFFECT: decreased efforts and costs of overburden works and harmful effects on ecology, higher stability of pit slopes and walls, accelerated development, lower losses of minerals.

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