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Cracks formation diagram under different blast hole spacing when PBH is a round hole. (a) H = 50 cm. (b) H = 60 cm. (c) H = 70 cm. (d) H = 80 cm. (e) H = 90 cm. (f) H = 100 cm. (g) H = 110 cm. (h) H = 120 cm.
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To make sure the integrity and stability of surrounding rock structure during blasting excavation of important structural planes in deep underground caverns, two kinds of fine blasting methods, timing sequence control fracture blasting network and notch blast hole, are innovatively combined and the formation of cracks between smooth blasting holes...
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Citations
... Zhou et al. [11] proved through experiments that the quality and flatness based on smooth blasting are better than presplitting blasting. Li et al. [12] innovatively and comparatively analyzed the formation of cracks between different delayed detonation light blast holes and different shaped detonation gun holes (PBH). Liu and Liu [13] proposed an improved optimization model for tunnel smooth blasting parameters built on the coupling of GA algorithm and ISVR algorithm. ...
The use of polyenergy water pressure controlled blasting technology in tunnel construction is gradually being promoted, and the technology is often used in hard rock, and the mechanism of rock breaking in fractured sandstone strata is still lacking systematic research. The above mechanism was investigated using a combination of field experiments and ANSYS/LS-DYNA numerical simulation, and the results showed the following: (1) In the case of joint-hole blasting, the concentrating jet formed by the concentrating tube can effectively achieve controlled directional blasting of fractured sandstone. (2) The use of gun clay to seal the hole can effectively improve the stability of the blasting effect, reduce the waste of explosive gas, and effectively extend the duration of action. (3) The water bag enhances the blasting effect through the water wedge effect in the broken surrounding rock and also has the function of energy storage, which can effectively improve the blasting effect when combined with the gun clay. (4) The rock-breaking mechanism of polyenergy hydropressure smooth blasting in fractured sandstone geological conditions is the dual rock-breaking action of “polyenergy jet + water wedge action.” (5) In this article, based on the analysis of blasting mechanism, the deployment method of polyenergy hydropressure smooth blasting is designed and has been well applied in engineering practice.
... Горная порода при этом приобретает дополнительную скорость в направлении движения взрывной волны. Из анализа представленных ниже материалов исследования, в этой связи, объяснима существенная разница измеряемых параметров фронта взрывной волны в противоположных граничных точках в сравниваемых модельных образцах конструкций зарядов [11,12]. Представленные ниже табличные данные и закономерности базируются на численном решении динамических задач геомеханики методом сглаженных частиц SPH, в том числе на исследовании внутрискважинных детонационных волн и их различных аспектов взаимодействий. ...
The modern requirements of the market economy and the increasing complexity of the field development conditions require new scientific and technical approaches in deep quarries and mines in the complex development of subsurface resources. As you know, the dominant mining paradigm in drilling and blasting is associated with the technique of drilling wells and boreholes of a circular shape (cavity) with the placement of explosives in it. However, in mining science and practice, the variety of mining conditions has long required the creation of methods for the destruction of rocks with an asymmetry in the distribution of explosion energy in space and its maximum concentration in certain directions. In this regard, we consider a conceptual direction based on a fundamentally new mechanism of action of the explosion of known groups of parallel-converged borehole charges, which effectively expand their use in various mining applications. The development of a new mechanism of action of the explosive process with the use of a computer program and numerical simulation of calculations made it possible to use the change in the shape and design of the charge as a means of increasing the share of the energy flow of the explosive explosion in a certain direction. The design of the deconcentrated charge is shown as a means of increasing the fraction of the energy flow of the explosive explosion in a given direction, which leads to a significant increase in the efficiency of the directed explosion and, in particular, minimizes its action in the opposite," legit", direction. Based on the results of the research, a method of blasting operations is proposed to neutralize the influence of anomalies in the state of the massif on mining operations by the explosive method. The method includes the appropriate tools, characterized by an unconventional design of the borehole charge and using a mechanism for influencing the anomalous states of the array with a combination of its explosive features.
... In this simulation, the explosive and air were defined as ALE grids, and the Lagrange algorithm was performed for the rock mass and stemming. Using the keyword * CONSTRAINED_LAGRANGE_IN_SOLID, the fluidsolid coupling algorithm was defined to realize the transfer of blasting energy from the detonation products to the rock mass and stemming [38,39]. Nonreflecting boundaries were applied to the model surface in addition to the working face to reduce the influence of stress wave reflections on the simulation results [40,41]. ...
To overcome the problems of poor cutting effects in hard rock roadways, a cut blasting technique with large diameter charges was developed; that is, the cut holes employ 50 mm diameter blast holes and 45 mm diameter explosive sticks, while the other holes adopt 42 mm diameter blast holes and 35 mm diameter explosive sticks. First, the effect of charge diameter on damage range and cut cavity formation was analyzed. Next, simulation of wedge cut for different charge diameters was conducted to reveal the stress wave developments and compare the stress field intensities. Finally, field tests were conducted to verify the viability of this technique. The results indicate that large diameter charges can increase the damage range around cut holes to improve the fragmentation degree of the rock mass in the cut cavity and significantly enhance the cavity formation power to better expel the rock mass fragments. The stress wave evolution of wedge cut was visualized using numerical simulations, which confirmed that the use of large diameter charges in cut holes increases the stress field intensity in the cut cavity and hence increases the damage degree of the rock mass. In this study, the use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. Therefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes.
... For the explosive, the 2# rock emulsion explosive is selected, its material type is HIGH_EXPLOSIVE_BURN, and the state equation of explosives is selected without considering the JWL equation of the explosive product composition. e values of explosive material parameters are selected according to the simulation experience in [28,29]. e specific parameters are shown in Table 4, where A, B, R 1 , R 2 , and ω are material parameters; E 0 is the initial specific energy; p is the pressure; and V 0 is the initial specific volume of the explosive before detonation. ...
... e specific parameters are shown in Table 4, where A, B, R 1 , R 2 , and ω are material parameters; E 0 is the initial specific energy; p is the pressure; and V 0 is the initial specific volume of the explosive before detonation. e specific form of the JWL equation of the state when the explosive is exploded [28][29][30] is ...
In this paper, the quantitative evaluation of the explosion effect based on the fuzzy comprehensive evaluation method is proposed to describe the qualitative evaluation results. The selected state characteristic parameters are expressed by two kinds of membership functions, fuzzy normal and triangular distribution membership functions, and preliminary evaluation results are obtained. The validity index of the maximum membership principle is used to assess the accuracy of the evaluation results of two algorithms, and a relevant approaching degree is chosen to optimize the results. The entire evaluation process selects eleven indicators to form an evaluation set, including the boulder yield, root rate, flying distance of flyrock, explosive consumption, postcracking distance, detonator unit consumption, vibration velocity, loose coefficient, cast distance, throw rate, and blasted volume per meter of hole. Part of the indicator parameters are derived from field test monitoring, and another part of the indicator parameters are derived from numerical simulation. The simulation process uses the user-defined material interface function provided by LS-DYNA. And the numerical model of slope blasting is established by embedding the evolution relationship of tensile and compressive damage into the elastoplastic constitutive material. The evaluation method proposed in this paper is used to evaluate the postexplosion effect of Zijin Mountain gold-copper mine slope cast blasting. The results demonstrate that the fuzzy normal distribution membership function can correlate the state characteristic information and evaluation index effectively, and the working condition after explosion can be reflected accurately. Additionally, the influencing factors can be ranked by the importance degrees according to the calculated value of the evaluation index.
Based on the theory of empty hole effect of cutting blasting, the Hopkinson effect and Saint–Venant principle are integrated to establish a two-dimensional calculation model of dynamic stress evolution of the holes wall, and then the dynamic fracture mechanism and damage distribution mode of the rock mass in the cutting area under the action of longitudinal waves are predicted. The results of the calculation and numerical simulation are verified by experiments, and the results show that: The time-varying stress function of the circular cavity wall conforms to the periodic dynamic evolution of the trigonometric function, and the theoretical calculation is consistent with the simulation results. Through the calculation of the round holes cut model and the square empty hole cut model, the change of the shape of the holes in the cut area changes the failure form of the surrounding rock mass. The circular empty hole wall is affected by the stress wave to produce "interval ring" destruction, and the effect of the reflected stretch wave is inhibited. The large range of rock mass in the square empty hole wall produces tensile and shear failure, and the rock mass collapses inward under the influence of the second stage stress. Among them, the empty space utilization rate of the square empty hole model is about 8.5 times that of the circular holes model. Vibration monitoring in the center of the cutting area shows that the vibration effect of the circular empty hole is larger than that of the square empty hole, and the proportion of rock breaking energy is lower.
Influences of high in-situ stress generally need to be considered when excavating deep underground caverns. The dynamic fracture behaviors of rocks under blast loads were investigated by using the rock-anchored beam excavation in underground powerhouses of Shuangjiangkou Hydropower Station in Sichuan Province, China as the engineering background. To solve the problems of the poor blasting breakage effect of rocks and the difficulty in protecting surrounding rocks during excavation, mechanical properties of granite under static and dynamic loads were investigated and the sequential controlled fracture blasting (SCFB) method was adopted during in-situ tests. Based on the Riedel-Hiermaier-Thoma constitutive model and the strength criterion, software LS-DYNA was employed to simulate the dynamic propagation of blasting-induced cracks. The contour shaping effect obtained via numerical simulation is generally consistent with the test results. The results show that SCFB can to some extent control the direction of crack initiation and rock fracture behavior of the blasthole wall cracks and the spacing of successive bursting holes is about 10 times the diameter of the blastholes when the cracks between the blastholes are shaped the best effect. Moreover, the magnitude and direction of principal in-situ stress can both affect the propagation path and length of blasting-induced cracks. The results of the research on the excavation and construction of deeply buried underground caverns have a certain reference value.
Detonation methods are significant to the construction efficiency, smoothness of the contour surface and the stability of the rock mass. In this work, based on dynamic finite element method, numerical models for crack initiation and propagation under different detonating sequence types were firstly established. Then parametric analysis was carried out to study the effect of the blasthole spacing and detonation delay time on the crack propagation. Finally, the effect of blasting wave interaction and stress distribution under different detonation sequence types were studied. The results show that the initial and propagation of the directional fracture is dependent on the blasthole spacing and delayed detonation time. The main cracks generated from detonation have the tendency of linear propagation along the concentric line for small spacing. Based on the wave propagation theory, the optimal range of detonation delay time can be calculated. The branch cracks generated and main cracks deviate from the concentric line if the delay time is out of the optimal range.
In recent years, various regions are vigorously promoting road infrastructure construction, and the tunnel is one of the essential ways of road infrastructure in mountainous areas, but the traditional smooth blasting has problems such as large disturbance of surrounding rock, easy to exceed and underdog, high dust concentration, etc., which delays the construction process of tunnel drilling, time-consuming and laborious. To solve these problems, this paper, relying on the newly built Guantian tunnel project of the ZJHZQ-9 section of Zhangjiajie to Jishou-Huaihua railway Project, studied the stress propagation law of rock blasting, vibration and displacement changes generated by seismic waves and analyzed them through theoretical analysis and numerical simulation, and drew the following conclusions: (1) Based on the basic theory of rock blasting, the principle of shaped charge action and forming mechanism of shaped charge jet are introduced. The effect of water medium and mortar on rock breaking in the blasting process and the movement law of mortar in the hole are analyzed; (2) ANSYS/LS-DYNA software was used for numerical simulation, and the blasting stress propagation law and surrounding rock damage were analyzed. The results showed that the stress propagation of the shaped water pressure smooth blasting was outstanding, and there was an obvious stress concentration phenomenon at the water bag, which verified the shaped energy jet effect of the shaped energy tank; (3) ANSYS/LS-DYNA software was used for numerical simulation, and the changes of vibration velocity and displacement of blasting simulation were analyzed respectively. The results showed that the vibration velocity of shaped charge hydraulic smooth blasting was the smallest, indicating that the water medium had certain energy storage and buffering effect, while the displacement change was on the contrary. Under the joint action of water bag and mortar, the water wedge enlarges the surrounding rock fissures so that the displacement variation of the shaped water pressure smooth blasting is the largest; (4) Through the field engineering application, the direction and width of blasting cracks correspond to the simulation results, which verifies the accuracy of the simulation.
During the blasting excavation of deep underground caverns, the effects of the structural surface on crack propagation are usually considered in addition to the clamping effects of high in situ stress. Based on the notched borehole and timing sequence control (TSC) fracture blasting method, this paper studies the effects of different borehole shapes on the degree of damage of the surrounding rock and profile flatness of the rock anchor beams and the effects of different filled joint characteristics on the blasting crack propagation rules. The results show that the damage depth of the surrounding rocks by round hole smooth blasting is approximately twice that by notched hole smooth blasting, by which the profile formed is flatter. The notched primary borehole (PBH) remains a strong guidance for crack propagation in a rock mass with filled joints, while the stress concentration effects of the round target borehole (TBH) cannot fully guide the cracks until they fall within a certain distance between the PBH and TBH. It is favourable for cracks to propagate along the lines between boreholes with larger filled joint strengths and larger angles between boreholes.
In order to solve the directional fracture controlled problem of blasting construction in key parts or specific areas of some projects, two refined directional blasting methods, namely, time sequence controlled (TSC) blasting and notched blasting, are innovatively combined, and numerical comparison research of three kinds of compound blasting methods has been carried out. The results indicate that, for TSC blasting, the optimum delayed denotation time is a certain period of time when the explosive stress wave of the earlier detonated blasthole (EDB) propagates to the wall of the later detonated blasthole (LDB) that away from the EDB. In the TSC-notched blasting with four blastholes as a group, when the LDB and EDB is notched separately, the corresponding directional fracture length is 33.3 d and 45.2 d (d is the blasthole diameter), and the directional fracture length is 52.4 d as the blastholes are all notched. If it is needed to consider both the crack propagation effect and the construction costs, we suggest that the TSC-notched blasting with the notched EDB and the round LDB should be carried out, by which the quality of the profile could be ensured with a low construction cost.
