Blast-induced Vibration Research Articles

Analysis of predictor equations for determining the blast-induced vibration in rock blasting

The paper proposes a new empirical correlation designed to complement the “site laws” currently used to evaluate the attenuation in the rock masses of vibrations induced by rock blasting. The formula contains a deformed exponential known as the K-exponential, which seems to well represent a large number of both natural and artificial phenomena ranging from astrophysics to quantum mechanics, with some extension in the field of economics and finance. Experimental validation of the formula was performed via the analysis of vibration data covering a number of case studies, which differed in terms of both operation and rock type. A total of 12 experimental cases were analysed and the proposed formulation exhibited a good performance in 11 of them. In particular, the proposed law, which was built using blast test data, produced very good approximations of the points representing the vibration measurements and would thus be useful in organising production blasts. However, the developed formula was found to work less well when a correlation obtained for a given site was applied to another presenting similar types of rocks and operations, and thus should not be employed in the absence of measurements from test data.

Neural network approach based on a bilevel optimization for the prediction of underground blast-induced ground vibration amplitudes

Due to its technical and economic advantages, the use of explosives in underground rock excavation is widely adopted. However, some safety and, especially, environmental issues arise when using this technique, mainly concerning ground vibrations induced by blasts. Thus, to minimize dynamic environmental impacts, prediction of blast-induced vibrations is imperative. In the last few years, artificial neural networks (ANNs) have been applied to model blast-induced ground vibrations. Nevertheless, ANN’s architecture, mainly the number of neurons in the hidden layer, has been selected manually concerning ANN’s performance parameters. To avoid over-fitting and reduce model’s complexity, this paper presents a bilevel optimization of ANN architecture, considering two transfer functions, based on the maximization of quality of the adjustment and model’s complexity, this last one as a penalty criterion. An ANN approach based on this bilevel optimization was successfully applied on a database of 1188 samples obtained from underground blast-induced ground vibration monitoring in a granitic rock mass. A residual analysis of the best-fitted model is performed to ensure the quality of the adjustment. It is demonstrated that the determined ANN model offers much higher generalization ability than the traditional prediction models usually used for blast-induced ground vibration amplitude predictions and other ANN architectures applied to ground vibration prediction.

Propagation Characteristics of Blast-Induced Vibration in Parallel Jointed Rock Mass

Propagation Characteristics of Blast-Induced Vibration in Parallel Jointed Rock Mass

Development of a blast-induced vibration prediction model using an artificial neural network

Development of a blast-induced vibration prediction model using an artificial neural network

Motion parameter estimation and measured data correction derived from blast-induced vibration: New insights

Motion parameter estimation is significant for obtaining all information from one recorded parameter by employing a desirable measured data correction method due to the noises produced by many uncertain factors in practical applications. However, few researches have paid attention to this issue in blast-induced vibration. In this study, a detailed overview focused on motion parameter estimation modes and measured data correction methods is developed. Then, a time-history signal described by a sine wave with a suitable sampling rate is employed to evaluate the integration and differentiation performances in the time domain and frequency domain, and a random-noisy signal is established to explore the noise effect on the integration and differentiation results. Based on the experimental monitoring of far-field and near-field blasting vibrations, an evaluation study of various baseline correction and de-noising methods is carried out. However, these measured data correction methods all have their own advantages and limitations. Even for some methods that perform very well, the procedure of data correction is complicated. To obtain accurately estimated motion parameters in blast-induced vibration, this paper proposes a novel measured data correction method of a zero-phase filter based on the power spectrum. The application results show that the method can be applied as not only a baseline correction method but also a de-noising method, and the zero-phase filter can effectively eliminate the signal time delay. Compared with the conventional data processing methods, the method’s desirable performance is verified to be robust, simple and flexible.

Complex Modeling of the Effects of Blasting on the Stability of Surrounding Rocks and Embankment in Water-Conveyance Tunnels

Blasting in water-conveyance tunnels that cross rivers is vital for the safety and stability of embankments. In this work, a tunnel project that crosses the Yellow River in the north district of the first-phase Eastern Line of the South-to-North Water Diversion Project was selected as the research object. A complex modeling and numerical simulation on embankment stability with regard to the blasting power of the tunnel was conducted using the professional finite difference software FLAC3D to disclose the relationships between the blasting seismic waves with vibration velocity and embankment displacement under different excavation steps. Calculation results demonstrated that displacement generally attenuated from the tunnel wall to the internal structure of rocks under the effect of blasting seismic waves. The tunnel wall was in tension, and tensile stress gradually transformed into compressive stress with increased depth into the rocks. The curtain-grouting zone was mainly concentrated in the compressive zones. For different excavation steps, the vibration velocity at different feature points was high at the beginning of blasting and then gradually decreased. The resultant displacement was relatively small in the early excavation period and slowly increased as blasting progressed. The effects of different excavation steps on the safety of surrounding rocks and embankment under blasting seismic waves were simulated. We found that the blasting-induced vibration velocity was within the safe range of the code and that the calculated displacement was within the allowed range. Numerical simulation was feasible to assess the safety and stability of engineering projects.

Multivariate statistical analysis approach for prediction of blast-induced ground vibration

Excavation of coal, overburden, and mineral deposits by blasting is dominant over the globe to date, although there are certain undesirable effects of blasting which need to be controlled. Blast-induced vibration is one of the major concerns for blast designers as it may lead to structural damage. The empirical method for prediction of blast-induced vibration has been adopted by many researchers in the form of predictor equations. Predictor equations are site specific and indirectly related to physicomechanical and geological properties of rock mass as blast-induced ground vibration is a function of various controllable and uncontrollable parameters. Rock parameters for blasting face and propagation media for blast vibration waves are uncontrollable parameters, whereas blast design parameters like hole diameter, hole depth, column length of explosive charge, total number of blast holes, burden, spacing, explosive charge per delay, total explosive charge in a blasting round, and initiation system are controllable parameters. Optimization of blast design parameters is based on site condition and availability of equipment. Most of the smaller mines have predesigned blasting parameters except explosive charge per delay, total explosive charge, and distance of blast face from surface structures. However, larger opencast mines have variations in blast design parameters for different benches based on strata condition: Multivariate predictor equation is necessary in such case. This paper deals with a case study to establish multivariate predictor equation for Moher and Moher Amlohri Extension opencast mine of India. The multivariate statistical regression approach to establish linear and logarithmic scale relation between variables to predict peak particle velocity (PPV) has been used for this purpose. Blast design has been proposed based on established multivariate regression equation to optimize blast design parameters keeping PPV within legislative limits.

Performance Evaluation of Moment-Resisting Steel Frame Buildings Under Seismic and Blast-Induced Vibrations

The paper is an attempt to evaluate the efficiency of passive control techniques such as base isolation system (e.g. Lead/Rubber Bearing) and fluid viscous dampers subjected to earthquake ground motions and underground blast-induced vibrations. Two moment-resisting steel frame buildings are analyzed to evaluate the structural responses under dynamic excitations. The effect of vertical irregularity on the performance of passive control techniques in mitigating the responses of the building is also studied. Non-linear dynamic analysis has been conducted on regular and irregular steel structures. The study investigates the effect of isolation period on the structural responses. The isolators are designed based on the design procedures developed by various researchers. The technical specifications of fluid viscous dampers have been selected from M/s Taylor Devices, USA. The structural responses and energy dissipated by these control techniques is evaluated and a comparative study is also carried out amongst control techniques under blast and seismic excitations. Both the selected passive control techniques have proved to be very effective in reducing the structural responses and forces induced in the building owing to ground-induced vibration.

Assessment of Blast-induced Ground Vibration using Different Predictor Approaches- A Comparison

Blasting is a mechanism of rock fragmentation. Usages of high explosive causes ground vibration, air noise, back breaks, over breaks as well as fly rock. Excessive blast-induced vibrations cause severe damage to nearby structures and residents in and around mine. So, it is essential to the precise prediction of ground vibration to reduce the ecological damage. Vibrations are expressed in terms of peak particle velocity (PPV). The aim of this study was to assess and predict the ground vibration at different explosive quantities and distances, applications of generalized regression neural network (GRNN) as well as empirical predictors were used. A total of fourteen blast events were collected at various strategic and valuable locations in the site, out of these ten blast events were considered for training and reaming for validate of the GRNN model. A three-layer GRNN with 2-14-1 architecture was developed and trained with Levenberg–Marquardt algorithm. Five emphircal predictor equations were proposed by the United States Bureau of Mines (USBM), Ambraseys-Hendron, Langefors- Kihlstrom, Central Mining Research Institute (CMRI) predictor and Bureau of Indian standard were applied to governing a relation between peak particle velocity and its influencing parameters. The obtained results reveal that the proposed GRNN model can predict the PPV accurately as compared to the other predictor models available. Obtained results were compared based on evaluation performance models such as coefficient of determination (R2) and mean square error (MSE) between monitored and predicted values of PPV. It was observed that GRNN approach provides high R2 (0.9988) and low MSE (0.0001) among all other empirical predictor approaches for accurate prediction of ground vibration.

Assessment of blast-induced vibration using various estimation models

Mining and quarrying activities cause vibrations that depend on blast-induced excavation. Today, competitive factors such as transportation costs and an expanding population result in much of the quarrying of raw materials falling within city limits or at least occurring very close to settled areas. Such situations can lead to various legal restrictions. Buildings and other sensitive structures are often present near limestone quarries, in which blast-induced excavation may be necessary. Because such structures may be affected by blast-induced vibration, their characterization is important in determining the effects on nearby built structures. However, due to differences in geological conditions and blast patterns, the amount of vibration that occurs without blasting in a given zone can be estimated by evaluating the results of vibration measurements from trial blasting. It is important that the vibration values that occur during the ongoing blasting are below the legal limit for areas near settlements. The prediction models are generated by binary regression analysis, based on the data set obtained from the trial blasting. The coefficients of the regression function are specific to the study field. These coefficients characterize the geological structure and other blasting pattern variables. However, for binary regression analysis, different approaches have been accepted for the reduction of variables in the literature. In this study, 22 blasting trials in a limestone quarry were monitored to produce 39 measurements of vibration directed towards a residential area located 396 m west of this quarry. The generated data set was evaluated using prediction models based on binary regression analysis, which have been previously accepted in the literature (USBM, Ambraseys-Hendron, Langefors-Kihlstrom and Indian Standards). From this evaluation, the USBM and Ambraseys-Hendron prediction models are found to have realistic estimates close to the values from the empirical data used in the prediction of blast-induced vibration. Correlation coefficients in the cross-validation of USBM and Ambraseys-Hendron estimation models were found to be 78%. Additionally, the correlation coefficients of cross-validation of the Langefors-Kihlstrom and Indian Standards estimation models were found to be 70%. The Langefors-Kihlstrom and Indian Standards estimation models are quite successful in predicting the charge per delay, which is a parameter included in the dataset, but if the amount of explosives per delay is increased, the results of these estimation models are far off from reflecting the real situation.

Dynamic model validation using blast vibration monitoring in mine backfill

Sublevel stoping mining methods with delayed backfill are employed for mining steeply dipping ore deposits at deeper horizons. Cemented rockfill (CRF) is used as a backfilling material for open stopes formed during mining. In primary-secondary mining sequence, blast vibrations are induced in CRF during the extraction of adjacent stopes. Higher magnitude of blast vibrations may destabilize CRF causing failure and dilution of precious ore. This paper presents a methodology for calibrating a FLAC3D numerical model, encompassing mine backfill with blast-induced vibration data recorded from field instrumentation. Two FLAC3D models are prepared, one for simulating the blasting process and the other is prepared for backfill stability analysis. The first model resulted in load vectors to be applied to backfill and rock interface. The second model showed that the backfill fails under the blast vibrations induced by the adjacent production stope. The results of the back analysis of fill failure are presented and discussed. The methodology may serve as numerical model calibration procedure for mine backfill.

Degradation of a discrete infilled joint shear strength subjected to repeated blast-induced vibrations

This paper presents the results of a series of numerical modeling experiments aimed at quantifying blast-induced degradation of shear strength of discontinuities. Near-field vibration history of a single-row production blast in a limestone quarry was used as input to the numerical model. For this purpose, two rock blocks, representing a stiff massive sulfide rock and a weaker limestone rock, were simulated using the 2D Particle Flow Code (PFC2D). Rock mass containing a single inclined joint was modeled as Mohr-Coulomb. The results show that the crack generation rate is increased in both samples after repetitive vibration loading. Joint shear strength degradation rate in the stiffer massive sulfide rock sample is higher than the softer limestone rock, which is attributed to the higher seismic impedance mismatch. The results show that even low-amplitude blasting vibrations (<80 mm/s), when repeated as in multi-hole blasts, can significantly degrade joint shear strength in the nearby pit walls.

The Ceneri Base Tunnel: Construction Experience with the Southern Portion of the Flat Railway Line Crossing the Swiss Alps

Abstract This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel (CBT), which is the southern part of the flat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross-passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approximately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast (D&B) excavation. The support consisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine (TBM) was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel (with an enlarged cross-section) passed underneath the A2 Swiss highway (the major road axis connecting the north and south of Switzerland) at a small overburden and through soft ground. Vertical and sub-horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D&B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel (at a vertical distance of only 4 m) required special excavation methods through reduced sectors and special blasting techniques in order to limit the blast-induced vibrations. The application of a comprehensive risk management procedure, the execution of an intensive surface survey, and the adaptability of the tunnel design to the encountered geological conditions allowed the successful completion of the excavation works.

Assessing and controlling of bench blasting-induced vibrations to minimize impacts to a neighboring community

Blasting is an important operation in mining production but is a source of concern due to its associated environmental impact; in particular, blasting-induced vibrations may cause structural damage and human discomfort. For decades, communities near open-pit mines have complained of blasting-induced vibrations. This study presents a methodology to predict, assess, and control ground vibrations in large open-pit mines operating close to a community. To conduct this study, 178 levels of blasting-induced vibrations were recorded in an area encompassing a large open-pit iron ore mine and a neighboring community located in the Quadrilátero Ferrífero, state of Minas Gerais, Brazil. Collected data were processed with multiple regression techniques to obtain the blasting vibration attenuation law to predict the levels of blasting-induced vibrations for the locality studied with knowledge of only the maximum explosive charge per delay and the distance to the blasting point. Brazilian and international admissibility standards of blasting-induced vibration, the minimum distance between the mine and community and the constants obtained from the regression were used to establish the maximum explosive charge per delay for an acceptable ground vibration level that would not cause structural damage and human discomfort. Finally, the proposed methodology was validated by comparing the predicted ground vibrations levels to measured values. The results demonstrate that this methodology can be applied to any open-pit mine to control blasting-induced vibration effects.

The effect of blast-induced vibration on the stability of underground water-sealed gas storage caverns

Underground water-sealed gas storage caverns have become the primary method for strategic storage of LPG. Previous studies of excavation blasting effects on large-scale underground water-sealed gas storage caverns are rare at home and abroad. In this paper, the blasting excavation for underground water-sealed propane storage caverns in Yantai was introduced and field tests of blasting vibration were carried out. Field test data showed that the horizontal radial velocity had a major controlling effect in the blasting vibration and frequencies would not cause the vibration velocity concentration effects. In terms of the influence of blasting vibration on adjacent caverns, the dynamic finite element model in LS-DYNA soft was established, whose reliability was verified by field test data. The numerical results indicated the near-blasting side was primary zone for the structural failure and tensile failure tended to occur in the middle of the curved wall on the near-blasting side. Meanwhile, the safety criterions for adjacent caverns based on stress wave theory and according to statistic relationship between peak effective tensile stress and peak particle velocities were obtained, respectively. Finally, with Safety Regulations for Blasting in China (GB6722-2014) taken into account, a final safety criterion was proposed.

Comparing blast-induced ground vibration models using ANN and empirical geomechanical relationships

Abstract Blasting remains as an economical and reliable excavation technique, but there are some environmental shortcomings such as the control of blast-induced vibration. The impacts of vibration over surrounding communities in a blast area have been investigated for decades and researchers have been using a myriad of empirical predictive attenuation equations. These models, however, may not have satisfactory accuracy, since parameters associated to geomechanical properties and geology affect the propagation of seismic waves, making vibration modeling a complex process. This study aims for application of an Artificial Neural Network (ANN) method and Geomechanical parameter relationships to simulate the blast-induced vibration for a Brazilian mining site and then compare them to the traditional approach. ANN had the best performance for this mine despite having demanded large datasets (as much as for the traditional approach), while geomechanical parameters like RQD and GSI may be used to deliver a fair approach even without seismic data. Also, ANN methods may be useful in dealing with a large amount of information to facilitate the simulation process when combined with other methods. Therefore, alternative prediction methods may be helpful for small budget mining operations in planning and controlling blast-induced vibration and helping mining in urban areas becoming a more sustainable activity.

Short-delay blasting with single free surface: Results of experimental tests

Delay blasting with relatively long-delay intervals is widely used in mining engineering since the former detonated blast-holes can produce new free surfaces for the later detonated blast-holes. With the application of electronic detonators, which have a minimum delay and a delay accuracy of 1 ms, a new blasting pattern using short-delay intervals is proposed in the present study in order to improve rock breaking and control blast-induced vibrations in cutting blasting with single free surface in underground mines. Theoretical analyses are firstly conducted to investigate the mechanisms of blasting crater formation and vibration reduction of short-delay blasting. Then a series of blasting crater tests with different delay intervals are performed to compare the characteristics of blasting craters and blast-induced vibrations produced by short-delay and simultaneous blastings. The results of crater sizes show that it is possible to form a common blasting crater only when the delay intervals are shorter than the formation time of a new free surface. It is also found that the short-delay blasting can effectively reduce PPV compared with the simultaneous blasting, particularly in the near-field. Spectral analysis indicates that there is less energy in the low-frequency content in short-delay blasting than simultaneous blasting. The possibility and feasibility of reducing vibration via short-delay blasting in underground mines are also discussed in this study.

New methodology to prevent blasting damages for shallow tunnel

From all of the environmental problems, blast-induced vibrations often cause concern to surrounding residents. It is often claimed that damage to building superstructures is due to blasting, and sometimes the building owner files a lawsuit against the company that perform blasting operations. The blast-vibration problem has been thoroughly investigated in the past and continues to be the subject of ongoing research. In this study, a tunnel construction has been performed by a construction company, according to their contract they must have used drilling & blasting method for excavation in tunnel inlet and outlet portal. The population is very condensed with almost tunnel below in the vicinity houses of one or two floors, typically built with stone masonry and concrete. This situation forces the company to take extreme precautions when they are designing blasts so that the blast effects, which are mainly vibration and aerial waves, do not disturb their surrounding neighbors. For this purpose, the vibration measurement and analysis have been carried out and a new methodology in minimizing the blast induced ground vibrations at the target location, was also applied. Peak particle velocity and dominant frequencies were taken into consideration in analyzing the blast-induced ground vibration. The methodology aims to employ the most suitable time delays among blast-hole groupings to render destructive interference of surface waves at the target location.

Assessment of blast induced vibrations based on regulatory criteria (a case study of limestone mines, Nigeria)

This study assesses the effect of blast-induced vibration on the environment. Measurements of six blasts were carried out with number of blast hole per blast ranging from 30 to 56. The distance between the locations of the vibrograph and the centre of the blast ranged from 0.8 km to 3 km. The vibrograph measured the peak particle velocities and air blast over pressure levels. Blast induced vibrations can cause human annoyance and damage to nearby structures. Hence, measurements of ground vibrations and air blast levels and use of published damage criteria are necessary to judge the design of the blasting operations, if it complies with the safe regulated levels. Blast induced vibrations at the Quarries were monitored from selected locations. All measurement obeys the USBMRI8485 and Office of Surface Mining (OSM) regulation criteria. Maximum PPV is 0.75 inch/s (168.75 mm/s) for the measured locations. The structures at the monitored locations were safe.

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF BLASTING-INDUCED GROUND VIBRATION FROM TUNNEL UNDERCROSSING A VILLAGE

To study the effect of blasting-induced vibration on ground buildings when tunnel undercrossing a village, a blasting vibration trial was carried out in Beizhuang tunnel in Henan Province, China. The safety blasting distance and reasonable explosive charge were pre-estimated according to empirical formula. The attenuation of ground vibration velocity was simulated using a 3D numerical model. Less explosive charge and longer distance to blasting source would result in lower ground vibration. When designed explosive charge was 54 kg, the safe distance was 42.26 m. While the distance between building and blasting source was about 37 m, the maximum explosive charge was 36.24 kg. The numerical results showed that the significantly horizontal affect region of blasting vibration was within 50 m to blasting source. Accordingly, effective vibration control is necessary to avoid disturbing human daily life during tunneling.