Rock fracturing mechanisms by blasting

Abstract

Optimizing blast fragmentation and reducing the damage from it are two important research subjects in this field. Detonation and explosive charge induces three sets of tension cracks in the monolith rock. Radial tension cracks are formed under the influence of the pressure wave whose cylindrical propagation induces tension. Along with the explanation of how radial cracks are formed, formulation is given as to how their length can be calculated using laboratory and drill and blast parameters. Cracks subparallel with the free surface (face) are related with amounts of absorbed and recoverable strain energies. The distance between subsequent cracks can be calculated using the results of simple load-unload laboratory tests. Third sets of tension cracks are formed as a result of excessive deformation of the beam or cantilever formed by radial cracks. Once the length of the cracks and the distance between them are known, it is possible to apply these results for estimation of fragment sizes and blasting pattern design.

Improvement of Thick Coal Seam Gas Drainage Efficiency Using Highly Pressurized Multidischarge CO2 Gas Fracturing Technique

“…The interaction between high pressure gas and the coal seam at different levels leads to plastic failure around the borehole. Researchers commonly refer to this zone as the crushing zone . In this segment of the study, we establish an approximately linear relationship between discharge pressure and the crushing radius of the fracturing borehole (Figure ).…”

Improvement of Thick Coal Seam Gas Drainage Efficiency Using Highly Pressurized Multi-Discharge CO2 Gas Fracturing Technique

“…Such a high pressure gas induces borehole wall failure and coal body fragmentation. The interaction of various levels high pressure gas impact loading with coal seam causes varying degrees of plastic failure around borehole, where the coal between the radial cracks is sheared and many researchers identify this zone as the crushing zone (Yorbica and Lapcevic, 2018). In this part of study,  The linear relationship between discharge pressure and crushing radius of fracturing borehole is identified (Table 7), and  The volumetric strain of coal seam induced by various levels of discharge pressure is presented (Figure 10a), accordingly, an empirical relations between discharge pressure and permeability of coal seam are proposed (Eqs.31 and 32),  Actually, the discharge pressure not only causes deformation and failure of coal body, but also forms high gas pressure zone around fracturing borehole (Figure 11), because of the result, a gas pressure gradient in coal seam is built up.…”

Compressive–tensile rock markings

“…To explain the Dong Men Yu rock markings we therefore turn to a related topic, the effects of explosives on rock, which has been well researched and provides the required details (e.g. McHugh, 1983;Donzé et al 1997;Esen et al 2003;Banadaki & Mohanty, 2012;Guerra et al 2013;Torbica & Lapčević, 2014, 2018. As in percussive impact, explosion represents a rapid release of high energy absorbed at a very focused point.…”

“…An explosive charge placed in rock, in tunnelling or mining, is typically of cylindrical shape. Upon detonation a pressure wave propagates cylindrically around the explosive charge (Torbica & Lapčević, 2018). Seen in section, the shock wave it creates travels in a circular pattern through the rock until it is countered by the need to expand the surrounding rock mass (Fig.…”