Blast-induced Vibration Research Articles

Blasting techniques applied to control vibrations, flyrock, and slope damage while ensuring compatibility with fragmentation

Blasting operations in mines near communities are of increasing social concern and scientific investigation due to the potential structural damage and human discomfort caused by blasting induced vibrations. Therefore, a technical-scientific approach is necessary to conduct these activities safely and sustainably compatible with fragmentation requirements of the scale of production. This paper presents a case study of an open-pit mine located in Brazil, where blasts are frequently carried out near a community. Additionally, controlling flyrock is extremely important in this mine due to the proximity of people to the blasting sites, as well as controlling the slope damage. Thus, it became necessary to develop a methodology for the application and combination of techniques and simulation fo blasting-induced vibration and wall control, flyrock and fragmentation such as attenuation law, signature holes, decking charge techniques, pre-split holes. The proposed methodology was effective, validated, and is recommended for open-pit mines operating near communities.

Analysis of vibration signals near ground surface during blasting excavation of a tunnel in fractured rock

This study aims to analyze the vibration signals near the ground surface due to the underneath drilling and blasting activities in a fissured rock tunnel. Blasting induced vibration on the ground surface was continuously monitored in a fissured rock tunnel drilling and blasting excavation project in field. Wavelet packet analysis of the vibration signals using Matlab was carried out for signal denoising, differential blasting delay time interval identification, and three-way time-frequency energy analysis. The results show that within a 30 m range from the palm face, the dominant frequency bands of blasting-induced vibrations on the ground surface were concentrated in the range of 0–130 Hz. Two prominent peak frequency bands were identified at 31.25–39.063 Hz (low-frequency band) and 93.75–101.56 Hz (high-frequency band), accounting for 12% of the total energy. Among the three directions of ground surface vibrations, the energy decay was the most significant in the x-direction (tunnel excavation direction), which amounted to 54.29% of the overall energy decay with increasing distance. The energy decay within the 50–80 Hz range was the most pronounced (more than 90%), when the angle between the vibration propagation direction and the fissure or joint direction was 75°. The conclusions provide the insights in the attenuation of blast-induced vibrations in fissured rock and can potentially assist in the design of blasting vibration control.

Attenuation of blast-induced vibration on tunnel structures

The blast-induced vibration during excavation by drilling and blasting method has an important impact on the surrounding structures. In particular, with the development of tunnel engineering, the impact of blasting vibration on tunnel construction has attracted extensive attention. In this paper, the propagation attenuation characteristics of blast-induced vibration (PPV, peak particle velocity) on different tunnel structures were systematically studied based on the field monitoring data. Initially, the attenuation characteristics of blasting vibration PPV on the lower bench surface, the side wall of the excavated tunnel and the closely spaced adjacent tunnel were investigated. Subsequently, the capacity of several widely utilized empirical prediction equations to estimate the PPV on tunnel structures was examined, along with a comparative analysis of their prediction accuracy. The research findings indicate that it is feasible to predict the PPV on the tunnel structures using empirical equations. The attenuation characteristics of blasting vibration PPV are different in different structures and directions. The prediction accuracy of the empirical equations varies, while the discrepancies are minimal. The principal variation among these equations lies in the site-specific coefficients k, β, λ, highlighting the differential impact of structural and directional considerations on the predictive efficacy. Based on the empirical equation and safe PPV provided by the blasting vibration safe standards on tunnels of China (GB6722-2014), and considering the influence of all structures and directions, it is determined that the safe distance of blasting vibration in the tested tunnel project should be larger than 20.28–18.31 ​m, 18.31–16.16 ​m, and 16.16–13.75 ​m for blasting vibration frequency located in ≤10 ​Hz, 10–50 ​Hz, and >50 ​Hz.

Study on blast-induced vibration of single-hole cylindrical charge

It is essential to study the blast-induced vibration of cylindrical charge so as to reduce ground vibration level and protect the surrounding environment. In this paper, the Heelan model is used to study the generation and propagation mechanisms of blasting vibration induced by single-hole cylindrical charge. It shows that the superposition of vibration waves induced by explosives in different positions of the cylindrical charge causes the increase of peak particle velocity ( PPV) in the region along the propagation direction of detonation waves. The vector peak particle velocity ( VPPV) versus distance for different stemming lengths ( SL) indicates that the linear attenuation between the VPPV and the exponential of distance appears only over a certain distance. Hence, the traditional formula for PPV prediction is suitable just in the middle and far field, not in the near field. The influences of charge length, detonation velocity and initiation pattern on the blast vibration are also investigated. The generation of Mach waves is determined by the relationship of scale between velocity of detonation ( VoD), P-wave velocity, and S-wave velocity. Over a certain value, the charge length doesn’t affect maximum VPPV, but affects the range of VPPV with relatively large values. Moreover, the bottom and top detonator positions have similar consequences on vibration control in the far field as the influence of limited charge length on blast vibration can be ignored. The VPPV of the middle initiating is almost twice as much as the other two detonator positions in the far field. Thus, in practical blasting, the middle initiating needs to be avoided.

Characteristics of blasting vibration induced by short-delay cylindrical charges based on Heelan model

As the electronic detonators can control the detonation error within 1 ms, short-delay blasting was nowadays proposed to replace multi-hole simultaneous blasting to reduce the vibration hazards. In this study, the Heelan model was used to study blast-induced vibration of short-delay cylindrical charges. The influence of delay time on the vector peak particle velocity ( VPPV) of superimposed vibration waveforms was analyzed and the calculating formula of the shortest delay time between adjacent holes based on vibration reduction was established. It is found that as the delay time increases, the overlapping area of VPPV becomes further away from the explosion source. The main influencing factors for the shortest delay time between holes include the distance between the monitoring point and the explosion source, the difference between P wave and S wave velocities, and the duration of S wave in the first and second explosion holes. As the distance from the explosion source increases, the shortest inter hole delay time based on vibration reduction also increases. The research results have guiding significance for the control of blasting vibration in underground mines.

Spatial Variation Law of Blasting Vibration in Layered Strata under Blasting Excavation of Subway Tunnel

Blasting vibration generated from blasting excavation of subway tunnel may endanger the adjacent structures buried in strata. To guarantee their safety and stability, it is crucial to understand the spatial variation law of blasting vibration in strata. In this paper, the blasting excavation of the large cross-sectional tunnel of Wuhan Metro Line 8 is studied. Three-dimensional finite element simulation is performed using the dynamic finite element program LS-DYNA, and its validity is verified by the field monitoring data. The spatial variation law of blasting vibration in layered strata is investigated through analyzed the distribution characteristic of blasting vibration in three directions, including the direction along the axis of the large cross-sectional tunnel, the direction perpendicular to the axis of the large cross-sectional tunnel, and the direction along the depth. A prediction model for blasting vibration velocity, which considers the impact of elevation differences, is established through dimensional analysis, enabling the prediction of blasting-induced vibrations at various depths in the layered strata.

Tracking of horizontal alignment of the long and large diameter uncharged hole in NATM tunnel

The long and large diameter uncharged hole boring (LLB) method is a cut blasting method that minimizes blast-induced vibrations by creating long and large diameter uncharged holes at the excavation face of tunnels prior to tunnel excavation. Drilling in this method typically uses a 50 m long with a 382 mm diameter hammer bit in the horizontal direction at the tunnel face. However, the significant weight and uni-directional rotation of the rod head, as well as variables such as geological characteristics, machine conditions, and inexperienced operators result in significant deviation from the target borehole alignment that hinders the vibration-dampening effect of the uncharged holes. Furthermore, since there is no method to verify the alignment of the boreholes until main tunnel construction, borehole misalignment is often not discovered until weeks after construction, which requires tunnel construction to cease until the equipment can be remobilized and an additional borehole be created, causing significant delays and increased costs for the entire tunnel project. In this study, the borehole alignment tracking and ground exploration system (BGS) is developed to predict and monitor the quality and alignment of boreholes for cut blasting methods such as the LLB methods immediately after boring. The BGS was subsequently tested at a subway construction site to evaluate its performance in the field. The measurements yielded by the BGS were compared with manually measured boring positions at every 5 m along the borehole. Although the BGS showed a maximum deviation of approximately 12% at a local point where the hole surface was relatively rough, the accuracy for the final boring position was approximately 97%, demonstrating excellent precision of the alignment tracking system. The BGS demonstrates excellent performance in predicting ground conditions and the boring quality of a cut hole immediately after drilling, and shows promise in various other applications for monitoring borehole alignment.

Blast Mitigation of Reinforced Concrete Structures Incorporating Shear Walls in Modern Building Designs

Material science advancements have resulted in the development of high-strength concrete and steel reinforcement, allowing more efficient and stable buildings against natural and manmade disasters. Increasing security concerns and the potential threat from terrorist activities have led to the safety and resilience of structures against blast loads in modern construction. The present study investigates the performance of reinforced concrete shear walls in mitigating blast-induced vibrations. The study examines four different reinforced concrete buildings based on their shapes, namely square, rectangular, C-shaped, and L-shaped, to understand the blast behaviours with and without shear walls. The study presents a methodology to protect the regular and irregular buildings equipped with shear walls against blast loads at varying standoff distances of 100 m, 200 m, 300 m, and 400 m, respectively. The study also compares the efficiency of passive control dampers and shear walls in enhancing the buildings’ performance against blast vibrations. The best placement of the shear walls is also evaluated for all the selected buildings. The study also considers the effect of shear wall thickness in mitigating blast-induced vibrations in multi-storey buildings. The study also discusses the design guidelines and reinforcement detailing of shear walls to protect buildings against detrimental blast effects.

Dynamic stability of concrete structures with varying sections to underwater contact explosion: A case study of gravity dams

Concrete structures with varying sections are widely used in the fields of ocean engineering, hydraulic engineering and civil engineering. And the damage mechanism of variable-section structures to underwater contact explosion, which involves localized damage by explosion impact and instability by overall structural vibration, is very complex. The gravity dam is taken as an example, the coupled analysis model for gravity dams under underwater contact blast is established, a prototype test on the dynamic response of a gravity dam under underwater explosion is conducted to verify the reliability of the fluid-solid interaction method, and the reliability of the concrete dynamic damage model adopted in this paper is validated by a small-scale field test on the internal blast damage of a gravity dam. The damage mechanism of gravity dams subjected to underwater contact explosion is analyzed. A stability analysis method for gravity dams to underwater contact explosion is proposed, which allows simultaneous consideration of the dam stability in the blast-induced vibration phase and the static phase after damage. The dynamic stability performance of gravity dams to underwater contact explosion is analyzed. And a stability assessment criterion that could be used to assess the safety level of dams at various stages is presented.

Frequency spectrum characteristics of blast-induced vibration with electronic detonators in ground blasting

With the wide application of electronic detonators in blasting engineering, further study of frequency spectrum characteristics under precise delay time is essential for blasting design and safety evaluation. In this paper, the frequency spectra induced by blasting vibration under different delay times and distances are calculated, the frequency distribution and energy characteristics of various frequency bands are then investigated, and the demonstration is conducted using numerical simulation and electronic detonator blasting experiments. The results show that the low-frequency vibration proportion increases, and the dominant frequency shifts to a lower frequency compared with the vibration frequency distribution of single-hole blasting when using a very short delay time (≤5 ms). However, when a short delay time (6–12 ms) is used, the low-frequency shift to high frequency, reducing the energy ratio of low-frequency bands. And there are certain differences in the delay time to reduce PPV at different blasting center distances. A shorter delay time (6–8 ms) in the nearer region and a longer delay time (10–20 ms) in the intermediate and farther regions better reduce blasting vibration. Finally, considering multiple influencing factors, the 7–12 ms delay time is recommended to protect structures in the blasting area factors.

Empirical prediction of blast-induced vibration on adjacent tunnels

The blast-induced vibration during excavation by the drilling and blasting method has an important impact on the surrounding buildings/structures and auxiliary equipment. In particular, with the development of tunnel engineering, the impact of blasting vibration on tunnel construction has attracted extensive attention. Based on literature data statistics, this paper first explored the performance of several commonly used empirical equations in predicting the propagation and attenuation characteristics of blasting vibration on adjacent tunnels. Secondly, the relationships between the empirical parameters of the blasting vibration prediction equation and the geological strength index (GSI) of tunnel surrounding rock were discussed, and two new blasting vibration prediction equations based on site rock GSI were established to approximately predict blast-induced vibration on adjacent tunnels. Finally, the application feasibility of the established prediction equation in practical engineering was discussed based on field test data. The research results show that under the condition of multiple groups of data, the prediction performance of various prediction models does not differ significantly. With the increase of the GSI of the surrounding rock mass of the adjacent tunnel, the site coefficients β and k of the blasting vibration prediction equation in predicting PPV (peak particle velocity, resultant velocity) both show a decreasing trend as a whole. The site coefficient k is generally within 3,000. Two new empirical prediction equations of blasting vibration propagation and attenuation on adjacent tunnels under different site conditions were established: Eq. (14) for PPV and Eq. (15) for PPVi (max) (maximum value of the three component velocities; i = x, y, z represent peak component particle velocity). The verification analysis of five sites shows that these two equations have a certain practical application value. Compared with other empirical equations, these two equations do not need regression fitting blasting vibration data, they only used the GSI of the site rock mass, and they are more easy to use in the field when there is a lack of monitoring data.

Experimental research and energy analysis of a new type of dry ice powder pneumatic rock breaking technology

When the traditional drill and blast method is applied to rock crushing projects, it has strong vibration, loud noise and dust pollution, so it cannot be used in densely populated areas such as urban public works. We developed a supercritical CO2 true triaxial pneumatic rock-breaking experimental system, and conducted laboratory and field tests of dry ice powder pneumatic rock-breaking. The characteristics of the blast-induced vibration velocity waveform and the evolution of the vibration velocity and frequency with the focal distance were analyzed and discussed. The fracturing mechanism of dry ice powder pneumatic rock breaking is studied. The research results show that: (1) The vibration velocity induced by dry ice powder pneumatic rock breaking decays as a power function with the increase of the focal distance; (2) The vibration frequency caused by dry ice powder pneumatic rock breaking is mainly distributed in 1–120 Hz. Due to the dispersion effect, the dominant frequency of 10–30 Hz appears abnormally attenuated; (3) The traditional CO2 phase change fracturing energy calculation formula is also applicable to dry ice pneumatic rock breaking technology, and the trinitrotoluene (TNT) equivalent of fracturing energy is applicable to the Sadovsky formula; (4) Dry ice powder pneumatic rock breaking is shock wave and high-energy gas acting together to fracture rock, which can be divided into three stages, among which the gas wedge action of high-energy gas plays a dominant role in rock mass damage.

Effect of plan irregularity on the performance of steel buildings subjected to blast-induced vibrations

Effect of plan irregularity on the performance of steel buildings subjected to blast-induced vibrations

Characterization of Blighia sapida seed extracts.

Blighia sapida, commonly known as the ackee, is a member of the Sapindaceae family. The tree is native to the forests of West Africa and was brought to the Caribbean and later Florida, where it is cultivated as an orchard crop in some areas. Arilli of the fruit are processed to make canned ackee in brine whereas the seeds, raphe and pods are discarded. Physiochemical studies were conducted on extracts of the seed. Qualitative analysis detected the presence of phenolics and reducing sugars. Aqueous extracts of the seeds (ASE) exhibited free radical scavenging activity and had an inhibitory concentration of 2.59 mg/mL. Gas chromatography mass spectrometry led to the identification of several metabolites including amino acids and fatty acids. Hypoglycin B was isolated utilizing ion exchange chromatography. Fourier transform infrared spectroscopy of hypoglycin B detected a band resonating at 3070 cm-1 which may be attributed to the methylenecyclopropane moiety of hypoglycin B. The seeds had a lipid content of 5.72 ± 0.25 % (w/w). The ackee seed oil (ASO) had a saponification value of 152.07 ± 37 and a carotenoid content of 23.7 ± 1.8 mg/kg. The ackee seeds are a source of bioactive components.

A new approach to reduce blasting-induced vibration in tunnel blasting by utilizing the initiation time scatter of detonator

The charge weight per delay is one of the major variables in empirical models for predicting the peak particle velocity in tunnel blasting. In many instances, the corresponding initiation times of the detonators often overlaps. The overlaps occur because of the initiation time scatter of each of the detonators. The overlap, in turn, causes an increased charge weight per delay, which consequently causes an increase in the blast-induced vibration. In this study, a novel technique is introduced for development of a blasting pattern exploiting the initiation time scatter of the detonators. The initiation time of 423 detonators was measured using a vibration monitoring instrument and a high-speed camera. From the data obtained, a standard deviation of the initiation times of the detonators was determined. The probability of overlap of the initiation times of the detonators was calculated using a Monte Carlo simulation. After simulating both a new blasting pattern utilizing the initiation time scatter of the detonator and the conventional blasting pattern 10,000 times each, it was determined that, in the new blasting pattern, the number of sets in which four or more blastholes initiated simultaneously decreased from 17,595 to 1604. Moreover, the probability that four or more blastholes initiated simultaneously in a blasting round decreased from approximately 70% to 12%.

IMPACT OF THE LAYERING OF BLAST-INDUCED DAMAGE FACTORS IN THE HOEK–BROWN FAILURE CRITERION ON THE BENCH DAMAGE MONITORING OF MINES

The process of creating a slope in a rock mass using the excavation and blasting methods consistently leads to stress release in the rock mass, resulting in a certain level of fracture and disturbance. Blast-induced vibrations can also influence the quality of the rock mass remaining after the blasting, as well as the stability and bench damage monitoring (BDM) of mines. A damage factor (D) is included in the Hoek–Brown failure criterion to compute the disturbance of a rock mass in creating a slope. Choosing the value and thickness of the blast zone for the Hoek–Brown criterion is crucial in the safety analysis and BDM of mines. However, the selection is still a crucial technical challenge in this criterion. Employing nonlinear layering, the present study divides the rock mass behind a blast hole into several layers with decreasing D values applied to each layer. The numerical simulation was conducted using the FLAC finite difference software for bench vibration assessment and damage monitoring by checking the peak particle velocity (PPV) in the bench face with different geometries. Behind the blast hole, five different layers of D were considered through which the Hoek–Brown properties of the rock mass declined nonlinearly during the execution of the model. Since the disturbance threshold of PPV was assumed to be 120 mm/s, the toe and middle parts of the small benches were in the disturbance threshold, while for the medium and high benches, only the bench toe was within the disturbance threshold.

Statistical analysis of blast-induced vibration near an open pit mine

Statistical analysis of blast-induced vibration near an open pit mine

Assessment of the Blasting Efficiency of a Long and Large-Diameter Uncharged Hole Boring Method in Tunnel Blasting Using 3D Numerical Analysis

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.

Vibration Energy Comparison Helps Identify Formation Time of New Free Surface in Urban Tunnel Blasting

Cut blasting creates new free surfaces that facilitate rock breaking and reduces blast vibration. However, the time when the new free surface is formed is not clear in on-site blasting practices. This paper proposes a method to identify this formation time through a vibration energy comparison. Firstly, a variational mode decomposition method identified the initiation time sequence of high-precision detonators from the observed blast-induced vibration wave. Based on the superposition of the single-hole waves extracted from the single-free-surface blasting test, we constructed a predicted wave that shared the initiation time sequence with the observed one. The Hilbert transform found the accumulated energy curves of the two waves separately. By comparing the linear correlation of the two curves, we identified the new free surface’s formation time to improve the blast design. The tunnel-blasting case showed that 64.5 ms was required to form the new free surface. In the actual blasting, each cut hole used 1.0 kg of explosives. The maximum vibration velocity was 0.90 cm·s−1, which met the control target of less than 1.0 cm·s−1.

Combined blast and vibratory machines effect on in-service structures

Large cement storage towers are commonly exposed to both quarry production blasting and the excitations from vibratory plant. Several seismographs were placed in the quarry to monitor blast-induced vibrations in the vicinity of the cement plant. Moreover, two ultra-sensitive vibration acquisition stations were installed respectively, at the bottom and at the top of the cement storage tower. Both stations were synchronized allowing them to be set on the same time scale. An advanced processing procedure was adopted in order to separate the effect of each excitation (i.e. blasting and vibratory machines). The wall displacements/strains were then estimated at both ends of the tower. The frequencies associated with the vibratory machines showed a noticeable dominance comparing to the waves linked to the blasting activities and eventually higher than the natural frequency of the structure. Ultra-high excitation frequencies led to the amplification of the vibrations induced from the vibratory machine for both events. Vibrations from the production shots as well as those from the vibratory machines has been found to have minor effect on the structural integrity of the tower, with induced strains fall below the critical thresholds that may cause cracking within the tower’s walls.