Studies of the effect of dynamic processes during explosive break-out upon the roof of mining excavations

Abstract

The stress state of a rock mess siEnificantly affects the indices for explosive breakout of mineral resources, while the nature of the explosion results' dependence upon rock pressure is not unique. It is well known that omnidirectional compression makes destruction proceeds while carryinE out explosvie operations or impacts upon the rocks, load-relief waves caused by the redistribution of static stresses, can initiate rock busts and can evoke an increase in the bulk of the destruction. At the present time, quantitative patterns in the process of dynamic rock-pressure redistribution have been studied comparatively little, althouEh they also are of siEnificant practical interest. In particular, the results of similar studies can be used to perfect the technology for conducting explosive operations at deep shaft levels and in regions where high tectonic stresses operate.In this work, the process of change in the stress state of a rock mass is considered during the instantaneous destruction of its near-face region. The effect of dynamic loads arising durinE the redistribution of rock pressure and explosions upon possible destruction beyond the edEe of the rock mass is also considered. The results of shaft experiments are presented based on determininE the rupturability of the roof rocks in underEround excavations. STUDY OF THE PROCESS OF DYNAMIC ROCK-PRESSURE REDISTRIBUTIONThe results of studyinE the mechanism of rock-pressure redistribution durinE an explosion are contained mainly in works devoted to questions of conductin E excavations in locations danEerous due to rock burst [1][2][3][4]. It is noted [i] that in an explosion, redistribution of the stress state and deformation of the rock surroundin E the charEe occurs. With the formation of a new, open surface in the rock mass, load-relief waves are formed, which leads to the transfer of the potential enerEy of bulk compression into kinetic enerEy of movement...particles of the rock are moved toward the surface of the rock exposure. As laboratory experimetns indicate, at a specific level of potential enerEy of compression, rock burst occurs. The seismic action of the explosions also plays a substantial role in the release of rock bursts [2,3].In a rock burst, limited destruction takes place near the exposed surface, which leads to a new stress redistribution.This, in turn, makes possible a new limited destruction in the near-face zone and contributes to further development of the burst [4].In the works pointed out above, the process of static-stress redistribution is described durinE explosive break-out in mining excavations. We note that analoEous effects have been recorded in a number of underEround nuclear explosions.The presence on seismoEr-m-of anomalous transverse waves is considered to be evidence of the relaxation of tectonic stresses durin E the explosion [5][6][7]. Estimates, made on the basis of laboratory experiments, of the amount of enerEy w~ich is Eiven off durin E an explosion in a stressed medium, confirm the mechanism of the radiation of transve...

Comparison of vibrations induced by excavation of deep-buried cavern and open pit with method of bench blasting

“…(8). The vibration waveforms of single delays and corresponding time−energy curves are shown in Fig.5 and Fig.6, respectively.…”

“…So, the energy distribution of all frequency bands varying with time b is given by Eq. (8), which is called timeenergy density function. In the actual application, through changing integral upper and lower limits in Eq.…”

“…ABUOV et al [8] indicated that remained rock mass near excavation work face could be damaged because of the quick unloading of in-situ stress during blasting. By theoretical analysis, CARTER and BOOKER [9] implied that vibration in the surrounding rock could be induced by the transient unloading of in-situ stress, and the intensity of vibration should increase with the unloading rate of in-situ stress.…”

Dynamic response of rock mass induced by the transient release of in-situ stress

“…The work of Abuov could be damaged because of the quick release of in-situ stress during blasting [24]. Carter and Booker thought that stress wave could be induced by the sudden release of in-situ stress [25].…”

Damage Evolution Mechanisms of Rock Induced by Blasting with the Aid of Empty-Hole Effect

“…Many other researchers established different tension-compression damage models, using various strength criteria. The rock mass tension-compression damage model is able to reflect the change law of rock mass unit damage type under blasting loading more accurately [21][22][23][24][25]. Meanwhile, many researchers have analyzed the effect of empty holes on rock damage [26,27].The above studies disclosed the influence of the empty borehole on fracture evolution and stress transmission in the rock mass under dynamic loading.…”