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Directional fracture controlled blasting technology plays a significant role in rock blasting engineering, in which the shaped charge forms are usually utilized. The energy-gathering form of shaped blasting still has no unified and strict standard currently, which can be optimized to save charge materials and improve blasting efficiency by a furthe...
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Citations
... Additionally, [22] discussed fracture creation, considering rock mass joints; for simultaneous holes, they suggested that cracks propagate along the lines between boreholes with larger filled joint strengths. Furthermore, [23] studied crack formation and damage to the surrounding rock, considering shaped charge form and short time delay blasting schemes. In the study by [24], which focused on no delay (simultaneous blasting), it was indicated that the number of simultaneous blastholes has a much smaller influence on vibrations than site constants. ...
When researching rock blasting, the design parameters typically used for analysis are the geometric and charging parameters. This study focuses on a different approach based on the effect of timing, specifically the role of delays in the initiation sequence. Data were obtained from the results of full-scale blasts. The experimental setting and location allowed us to consider all parameters, other than the number of delays, as constants. The experimental results were analyzed, relating the delay variables to the fragmentation and KPIs of downstream operations. It was found that increasing the number of delays per unit of blasted rock and reducing simultaneous adjacent holes produces finer fragmentation, reduces the amount of fines, facilitates secondary operations, and reduces the risk of flyrock.
... The JWL equation of state is programmed as the material model in most commercial codes, such as LS-DYNA, AUTODYN, and ABAQUS. In addition, LS-DYNA successfully simulated rock blasting in previous studies [36,37]. The JWL expression is [35]: ...
The effect of detonator placement on rock fragmentation by blasting was studied in the Kevitsa open-pit mine. Considering rock mass properties, explosives properties, and blast parameters, a comprehensive analysis of 37 production blasts confirms that the middle detonator yields finer fragmentation than the bottom detonator in the full range of investigated sizes. Meanwhile, using the LS-DYNA code, a bench model with a single blasthole was built in a three-dimensional setting. A single detonator placed at two different positions-the middle and bottom-of the explosive column was analyzed in this study. By analyzing principal stress states on the plane through the blasthole axial and vertical to the bench face, the numerical results show that the middle detonator creates a stress concentration area near the bench face characterized by triaxial tension, while the bottom detonator does not. Furthermore, the middle detonator generates a larger stress concentration area with biaxial tension near the bench face than the bottom detonator. Considering that triaxial and biaxial tensions are more favorable to fragmentation than uniaxial tension, it can be concluded from simulation results that these areas with triaxial tension and biaxial tension in the middle detonator are a significant factor contributing to achieving better fragmentation, compared to the bottom detonator. The middle detonator position has replaced the bottom detonator position in the Kevitsa mine.
... Also [22] discuss fracture creation, considering also rock mass joints: for simultaneous holes they state that cracks propagate along the lines between boreholes with larger filled joint strengths. [23]Yin et al., (2021) study crack formation and damage to the surrounding rock could considering shaped charge form and short time delay blasting scheme. [24] study no-delay (simultaneous blasting): their work indicates that the number of simultaneous blast-holes has a much smaller influence vivrations than site constants. ...
When researching rock blasting, the design parameters used for the analysis are usually the ge-ometric and charging ones. This study is based on a different approach, and focuses on the effect of timing, in specific the role of delays in the initiation sequence. The data come from the results of full-scale blasts. The experimental setting and location allowed to consider all parameter other than the number of delays as a constant. The experimental results are analyzed relating the delay var-iables to fragmentation and KPIs of downstream operations. It is shown how increasing the number of delays per unit of blasted rock and reducing simultaneous adjacent holes produces finer fragmentation, reduces the amount of fines, facilitates the secondary operations and reduces the risk of flyrock.
... He et al. 19 conducted single-and double-hole blast loading tests on granite samples to investigate the dynamic failure process between adjacent boreholes when using decoupling charges. Yin et al. 20 reported that the optimum blasting and fracturing effect of the surrounding rock mass can www.nature.com/scientificreports/ be achieved by uncoupled-shaped charge technology. ...
For shaped charge blasting projects in mining, civil engineering, and similar fields, it is proposed to modify the charge structure by combining slotted tubes and shaped charge liners to obtain a new type of charge structure. This aims to achieve directional rock breaking through the focused action of the shaped charge. The influence of different slotted pipe materials on the directional rock-breaking effect of concentrated energy using a new charge structure is explored through theoretical analysis combined with model test study, high-speed camera, stress–strain gauge, and other equipment. A comparison is made between slotted pipes made of aluminum, kraft paper, and PVC, with the cutting width of 2 mm. Based on the characteristics of the cracks formed after blasting, the new charge structure made of aluminum slotted pipe produces a penetrating crack that is almost consistent with the pre-cracking direction. Based on the corresponding characteristics of successively released blasting energy, the guiding and convergence effect of the new charge structure made of aluminum slotted pipe on the explosion energy is greater than that of the new charge structure made of the other two types of slotted pipe material. According to the strain data measured after blasting, the peak arrival time of the strain peak in the direction of the slotted pipe on one side of the shaped hood is shorter than that in the other two directions, and the peak strain is greater than that in the other two directions while having a better energy gathering effect. Based on the findings, the new charge structure with directional energy concentration has a damage reduction effect. Furthermore, the material of aluminum slotted pipe is found to be better than PVC slotted pipe, whereas the material of PVC slotted pipe is better than kraft paper slotted pipe in achieving directional rock breaking.
... In recent years, top-cutting technology based on the "top-cutting short-wall beam theory" has been applied and promoted in many domestic mines. This technology uses directional polygraphic blasting technology before the coal seam is retrieved to pre-crack the top plate along the side of the mining area in the retrieval roadway (Meng et al., 2020;Yin et al., 2021). Then, after the coal seam is retrieved, the top plate will automatically cut down along the pre-cracking slit to form the roadway gang under the action of mine pressure, thus realizing "roadway formation". ...
In order to solve the problem of stress concentration on the roof of the mining trench, reduce the risk of sudden collapse of the roof overburden and disturbance, improve the control effect of the surrounding rock of the roof cutting and retaining roadway, and reduce the construction cost of mining tunnels, a new type of pouch sealing technology has been developed. By using on-site testing methods, the optimal sealing material ratio was optimized, and the crack propagation law and roof cutting effect of the 11503 W working face in Zhaizhen Coal Mine, Shandong Province were studied under hole spacing of 0.7, 1.0, and 1.1 meters and different sealing methods. The results show that using 1.5 m single pouch sealing technology in the blasting test, when the water cement ratio of the sealing material is 1:1, the required sealing strength and sealing temperature can be achieved, and there will be no punching phenomenon. When the spacing between holes is 1 m, the blasting effect is optimal, with a single hole effectively reaching a cutting seam length of about 0.5 m. There are obvious through cracks in the cave, with a total length of about 7 meters. After using the new pouch sealing technology for blasting, the displacement and bottom drum volume on both sides of the tunnel are lower than those of the traditional yellow mud sealing method, and the bottom drum volume is reduced by 37% and 53%, respectively. Based on comprehensive theoretical analysis and on-site experiments, the optimal hole spacing is determined to be 1 m, and the pouch sealing effect is good.
... Wang et al. 31 conducted penetration tests of shaped charges into concrete specimens, and found a quadratic correlation between the penetration depth, crater diameter, and jet velocity. Yin et al. 32 demonstrated that decoupling bilateral-grooveslot-shaped charge blasting resulted in the best blasting effect, as indicated by long directional cracks, few nondirectional cracks, and minimal damage to the surrounding rock. Bhagat et al. 33 proposed a directionally controlled blasting technique for railroad tracks, which allows blasting works to be carried out without affecting the train counterparts (2-3 m from the slope). ...
The shape of a charge liner used in shaped charges with a combined liner will greatly influence the blasting effect. In this study, we examined how combined charge liners with different shapes affected directional rock blasting, and we assessed the influence mechanism. The numerical simulation results showed that among the three shaped charge liners, liners with arc and triangular shapes performed significantly better than the flat‐top liner, and the triangular liner was slightly superior to the arc‐shaped liner. Model testing indicated that principal cracks in the arc‐shaped and triangular liners developed along the combined energy‐gathering direction, while the principal cracks of the flat‐top liner deviated 32° from the axis. Therefore, the directional cracking effect of arc‐shaped and triangular liners was superior to the flat‐top liner. According to the peak strain values on the liners, the peak strain in the combined energy‐gathering direction was greater than that in the slot and nonenergy‐gathering directions, and the order of the peak strain of the three liners followed arc‐shaped liner > triangular liner > flat‐top liner. The directional blasting effect of the triangular liner was slightly better than the arc‐shaped liner. In conclusion, the findings of this study suggested that the best directional rock‐blasting effect was achieved when the shape of the combined charge liner was triangular.
... The key to this technology is the application of an energy-gathering device, as shown in Fig. 1. The device is designed as a tubular device with symmetrical V-shaped energy-gathering grooves on both sides (Yin et al. 2021). ...
With the increase of coal seam mining thickness, the caving height of stope roof, the mining-induced stress increase, and the control difficulty of gob-side entry retaining increase. To apply the gob-side entry retaining (GER) technology in thick coal seams, optimize the support method and reduce the deformation, based on directional energy-gathering blasting technology and roadside filling technology, gob-side entry retaining with synergistic roof cutting and roadside filling (GER-RCRF) is proposed. Through theoretical analysis, numerical simulation and field experiments, the mechanism and effect of the method are analyzed. The results show that due to the stress relief of roof cutting, the pressure of the solid coal rib and the roadside filling of the GER-RCRF is reduced, and the stress concentration area shifts to the deep rock mass. Under the condition of roof cutting, the stress of roadside filling is distributed in a “single peak”, and with the width increases, the peak stress first increases and then decreases, and then increases and then decreases. Meanwhile, the roof cutting height should be based on the broken and expansion effect of the rock strata, considering the key stratum effect of the rock layer. The stress of the surrounding rock is further reduced when the overlying key strata is cut off. Finally, the GER-RCRF has successfully reduced the stress of roadside filling, roof and solid coal rib, optimized the stress environment of surrounding rock, and successfully realized the purpose of gob-side entry retaining. The field test verified the effectiveness of GER-RCRF. The stress of roadside filling and the deformation of surrounding rock are significantly reduced. The research results provide a certain degree of scientific basis for the successful application of gob-side entry retaining in thick coal seam.
... In 1983, the effect of shaped charge jet penetration was introduced in rock blasting with a linear-shaped charge to control the growth of rock fracture by Bjarnholt et al. (1983). When the linear-shaped charge is ignited, the shaped charge jet penetration immediately acts on the borehole wall in the direction of the open slot of the shaped charge, and thus radial cracks initiate and propagate outwards in the desired direction, ultimately creating a smooth fracture surface (Luo and Shen 2006;Yin et al. 2021). To ensure the formation of shaped charge jet, an explosive with a high velocity of detonation (VOD) is needed. ...
... Fracture control blasting using a combined notched borehole and time sequence control was proposed by Li et al. (2021a), and it was numerically demonstrated that the quality of the excavation profile could be ensured with low construction costs when using this technique. Apart from these, new fracture control blasting techniques such as Bilateral Cumulative Tensile Explosion (He et al. 2003;Zhang et al. 2020), Elliptic Bipolar Linear Shaped Charge Blasting (Li 2013), Bilateral-Groove-Slot Shaped Charge Blasting (Yin et al. 2021), etc., were recently developed. However, a complicated combination of special boreholes and cartridges is generally used in these new-developed techniques, which greatly increases the procedure and costs of rock blasting. ...
Fracture control blasting produces rock fractures in the desired direction, which is significant for the stability of excavation structures in rock engineering. The present study proposes a new method of fracture control blasting using air–water coupling. This method utilizes the difference of explosion stress transfer between air and water, which guides the explosion energy consumption in fracturing rock on water-coupling side, i.e. rock in the excavation zone, and thus the rock in the excavation zone is properly fragmented, and the reserved rock is well protected from damage. Based on the plane strain assumption, the transmission and propagation of explosion stress in the excavation and reserved rock with this method are first theoretically analyzed. Then, fracture control blasting using air–water coupling is numerically studied utilizing the LS-DYNA program. The numerical model is first developed and calibrated in the simulation with the laboratory-scale air-coupling and water-coupling blasting tests. Then, the successive processes of pressure attenuation, fracture evolution and energy consumption under air–water coupling blasting are numerically investigated. Thereafter, the effects of the air–water ratio and decoupling ratio on the performance of fracture control are numerically investigated. The theoretical and numerical results show that good performance of fracture control can be obtained using air–water coupling blasting.
... However, the reflection and transmission of stress waves when confronting discontinuities and boundaries complicates the propagation process immensely. And the propagation of stress waves is actually the interaction with the rock masses and discontinuous structural planes [51,52]. Fig. 2 illustrates the pressure propagation process after blasting within the 0-14-14 model. ...
The propagation of seismic waves induced by blasting changes significantly at rock discontinuities such as joints and faults, many studies have focused on the mechanism of wave propagation at joints. However, in deep rock masses, high in-situ stress is non-negligible, and the interaction between confining stress and discontinuity under blasting disturbance remains poorly understood. To explore the role of confining stress and discontinuity on the dynamic responses and damage mechanism of rock masses, this paper employed the dynamic finite element method and a series of numerical models were subsequently developed. The Riedel-Hiermaier-Thoma (RHT) model was used to simulate the blast-induced damage of rock. Under blasting disturbance, the propagation of stress waves and damage patterns within the rock at different discontinuity orientations and different confining stress magnitudes were presented. Around the discontinuity, the principal stress distribution and displacements were presented and the dynamic stress intensity factor (DSIF) of the discontinuity tip was obtained to analyze the extension mechanism of the discontinuity. Numerical results show that the discontinuity, the magnitude and direction of confining stress significantly contribute to the damage patterns of rock masses, and the guiding effect of high confining stress on cracking will be weakened due to the existence of discontinuity.
... This study used the LS-DYNA software, which is widely used for blasting simulations, to simulate dynamic and non-linear problems. The arbitrary Lagrangian-Eulerian (ALE) formulation was employed to investigate blast-induced pressure and its interaction with various materials [25][26][27]. The ALE formulation contains both Lagrangian and Eulerian formulations to utilize the advantages of each approach [28]; it allows the mesh to move independently from the material flow, and each element in the mesh can contain mixtures of different materials [29]. ...
Cut blasting is one of the most essential processes to reduce blast-induced vibration in tunnel blasting. The long and large-diameter uncharged hole boring (LLB) method is an example of one of the cut blasting methods, which utilizes large-diameter uncharged holes drilled in the tunnel face. In this study, blasting simulations were performed to analyze its blasting mechanism, and the LLB method and the traditional burn-cut method were simulated to compare their blasting efficiency. A 3D numerical analysis using LS-DYNA code, a highly non-linear transient dynamic finite element analysis using explicit time integration, was used to simulate the blasting process, and a Johnson–Holmquist constitutive material model, which is optimal for simulating brittle materials under dynamic conditions, was used to simulate the rock behavior under blasting. The modified LLB method showed a 3.75-fold increase in the advance per round compared to the burn-cut method, due to the increased formation of long and large-diameter uncharged holes compared to blast holes. This modified LLB method used 30% less explosives, so its failure range was approximately 1.25 times less than that of the burn-cut method, but its advance was approximately 4 times larger than the burn-cut method, which was similar to the original LLB method. This confirmed that the modified LLB method is significantly more efficient in terms of increased blasting efficiency (particularly the advance per round) as well as reduced blast-induced vibration, compared to the traditional cut blasting method.
