Experimental tests show that velocities of seismic vibrations from quarry blasts generally lower as delay intervals between large-scale blasts are increased. At the same time, a seismically safe delay interval is governed by geological conditions, which vary appreciably within an open pit mine field, and by geotechnical conditions of mining. This study was aimed to obtain theoretical formulas of vibration velocities, compressive stresses and relative strains in rock mass as functions of the delay interval based on the mechanism of seismic waves induced by short-delayed blasting in jointed rock mass. These formulas were to be justified. After review of reference sources, the mechanism of blast-induced seismic waves in jointed rock mass was developed. According to this mechanism, high-velocity collisions of fractured and intact blocks under the action of pressure from detonation products generate elastic waves. The theoretical research allowed formulas for the delay interval dependence of the vibration velocities, compressive stresses and strain rates in rock mass in the seismic impact zone of blasting. The comparison of the mathematical and numerical analysis results with the actual practice data validates the formulas of vibration velocities as function of blast-to-blast delay intervals. These formulas make a framework for the development of regulations for blasting at minimized seismic impact on guarded objects in different geological and geotechnical conditions.
Опыт ведения взрывных работ в карьерах указывает на неодинаковую интенсивность сейсмического излучения в различных направлениях относительно сторон взрываемого блока. Это связано со многими факторами, в том числе с параметрами массовых взрывов, различными физико-механическими свойствами и параметрами трещиноватости массива горных пород, наличием тектонических разломов вблизи взрываемого блока. В работе установлена зависимость скорости сейсмовзрывных колебаний при массовых взрывах на карьерах в изотропном и анизотропном сложноструктурном горном массиве в различных направлениях относительно сторон взрываемого блока. Обоснованы, приведены формулы расчета, проведены численные расчеты скорости сейсмовзрывных колебаний в различных направлениях относительно взрываемого блока в изотропном и сложноструктурном массивах. Доказана правомерность формул. Формулы определения скорости сейсмовзрывных колебаний можно использовать для оценки влияния параметров массового взрыва, параметров естественно нарушенного массива горных пород на охраняемые объекты, а также для разработки методов снижения сейсмического действия взрыва при ведении взрывных работ на карьерах благодаря численному изменению параметров массового взрыва. Перспективным направлением является исследование влияния закладочного массива и выработанного пространства на скорость сейсмовзрывных колебаний при ведении взрывных работ в рудниках. Ключевые слова: массовые взрывы; сейсмовзрывные колебания; скорость колебаний; формулы расчета; трещиноватые массивы; тектонические разломы; численные расчеты; правомерность. Для цитирования: Тюпин В. Н. Параметры сейсмического действия массовых взрывов в изотропном и сложноструктурном горных массивах карьеров // Горный информационноаналитический бюллетень. -2021. -№ 12. -С. 47-57.
Generalization of the abundant experimental and theoretical research accomplished by Russian and foreign scientists in the 20th–21st centuries enables distinguishing between a few action zones of blasting, namely, crushing zone (fine grain crushing), radiating cracking zone, induced-fracture zone, shaking zone (residual stress after blasting), and blast-induced load zone. In the crushing zone, overgrinding takes place, which has an adverse influence on efficiency of processing of uranium, for instance, or granular quartz. The radiating cracking zone size in blasting in fractured rock masses governs the quality of drilling and blasting. The induced-fracture zone determines stability of rock mass and, consequently, safety of production processes both in surface and underground mines. In the shattering zone, fractured rock mass experiences residual stresses, which induces new fractures and rock falls, or dynamic events due to lithostatic pressure in rockburst-hazardous rock mass. This article aims at the experimental and theoretical determination of geometrics of blast-induced impact zones in different geological and geotechnical conditions with a view to developing appropriate actions toward abatement of the adverse effect exerted by these zones on geomechanical and technological processes in the course of mining. The theoretical formulas are given for the radii of the crushing, radiating cracking, induced fracturing and residual stress zones. Reliable applicability of the formulas in actual mining is proved by comparison of the calculations with the full-scale testing data. To mitigate the crushing zone impact, it is possible to charge the wellhead interval with a radial air gap, which decreases density of charging. Arrangements toward reduction of the zones of induced-fractures and residual stresses are proposed. Energy of the man-mane zone of residual stresses after blasting can be targeted at activation of raise driving with raise borer 2KV.
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