RMZ – MATERIALI IN GEOOKOLJE

Physicotechnical substantiation of parameters of blasting operations in deep ...405objects safety in case of trapeze- andrhomboid-shaped blast block at an angleof blasthole rows inclination α =90 ° , α = 120 ° are presented in Table 1.The analysis of the findings shows thatwhen a trapeze configured block isblasted, three protected objects standseismic load and two are destroyed,and when an elongated rhomb configuredblock is blasted, the whole groupof protected objects stand seismic load.It has been established that blastingmethod, including drilling of blastholerows in a block of definite configuration,their charging and short-delayedblasting, in which case the blastholesrows are commuted in a block havingan elongated configuration viewin plan with narrowed opposite ends atan angle of 45 ° ≤ α ≤ 135 ° to a beelineto one of the chosen protected objects,provides reducing seismic load on protectedobjects:• in the direction of commencementof blasting the rows – twice;• to the left and to the right of the explosionfield in 120 ° sectors - fourtimes.Successive detonation of blastholerows with delay from the nearest holein the direction from the protected objectresults in redistribution of releasedseismic energy in such a manner thatthe maximum flow of seismic energyis directed towards the side oppositeto the protected object. This facthas been determined experimentally.When length of rows in the blastholeblock is reduced, a number of blastholerows are increased to maintain the totaltarget weight of blasted BE and a totalnumber of rows, that leads to decreasein extent of seismic load and concurrentincrease in seismic load duration.The two said factors allow of adjustingflow of seismic energy on protectedgroup of objects so that the shock effecton the nearest object could be minimaland the other nearby objects could bepractically safe.Using the open pit space for miningof ore deposits outside the pit contourenables to implement advantagesof combined open-and-undergroundmining method to the full. At thesame time, conventional approach todesign and operation of deep openpits does not take into considerationchanging mining methods in view ofdevelopment of underground mine.In this regard, researches have beenconducted to determine safe parametersof arch pillar separating openand underground mining operations.In calculations it is deemed that rockis the elastoplastic solid medium. Toensure stability of the arch pillar solidit is required that seismic load doesnot cause irreversible deformations.The condition of maintenance of rockstability is written as follows:U ≤ U o(17)RMZ-M&G 2012, 59