Rock Blasting Research Articles

Fluid/structure coupling in fracturing solids and particulate media

The objective of the paper is to present the essential issues related to an effective computational implementation of a continuum/discontinuum formulation of rock masses under various loading conditions, including fluid interaction for three classes of problems; fluid flow through fracturing rock masses, rock blasting and the transport of large particles through a fluid medium. The applicability of the methodology developed is illustrated through a selection of practical examples.

경암층 발파현장에서 진동예측 및 장약량산정

The blasting has a lot of economic efficiency and speediness but it can damage to a neighbor structure, a domestic animal and a cultured fish due to the blasting vibration, then the public grievance is increased. Therefore, we need to manage the blasting vibration efficiently. The prediction of the correct vibration velocity is not easy because there are lots of different kinds of the scale of blasting vibration and it has a number of a variable effect. So we figure the optimum line through the least-squares regression by using the vibration data measured in hard rock blasting and compared with the design vibration prediction equation. As a result, we confirm that the vibration estimated in this paper is bigger than the design vibration prediction equation in the same charge and distance. If there is a Gaussian normal distribution data on the left-right side of the least squares regression, then we can estimate the vibration prediction equation on reliability 50%(<TEX>${\beta}=0$</TEX>), 90%(<TEX>${\beta}=1.28$</TEX>), 95%(<TEX>${\beta}=1.64$</TEX>). 99.9%(<TEX>${\beta}=3.09$</TEX>). As a result, it appears to be suitable that the reliability is 99% at the transverse component, the reliability 95% is at the vertical component, the reliability 90% is at the longitudinal component and the reliability is 95% at the peak vector sum component.

断層活動に伴う水素ガス発生の検討－立坑発破・岩石破壊実験の結果－

断層活動に伴う水素ガス発生の検討－立坑発破・岩石破壊実験の結果－

Study into blast vibration and frequency using ANFIS and MVRA

Blast induced ground vibration is a crucial parameter in determining safe charge levels and minimising the damage to the surrounding structures. A number of empirical equations have been proposed for prediction of peak particle velocity (PPV), but no empirical formula has yet been established for the prediction of frequency. In order to minimise the blast damage and the blasting related loss, it is important to study the parameters influencing blasting. In the present case, the adaptive neuro-fuzzy interface system (ANFIS) model was used to predict the PPV and frequency using blast design, rock properties and explosive parameters from the Northern Coal Field open pit mine in MP, India. Results were also compared using multivariable regression analysis (MVRA) to further prove prediction capability. The ANFIS approach shows very good prediction capability for PPV and frequency. The coefficients of correlation between predicted and measured PPV and frequency are 0·9986 and 0·9988 respectively.

Theoretical Derivation of a Peak Particle Velocity–Distance Law for the Prediction of Vibrations from Blasting

I would like to suggest a theoretical justification for the mathematical structure of some laws for predicting the maximum particle velocity vibration from blasting operations in the light of some basic notions of elastic and anelastic wave theory. Within this point of view, in dimensionally correct expressions, the terms pertaining to the rock, to the blast and to the seismic wave become evident and recognisable. A law is presented that can be used to forecast the maximum particle velocity on the basis of some blast design and rock parameters. Four tests of the proposed law performed with real data sets seem to confirm fairly well its reliability.

Decomposition of Avicennia marina on an iron-smelting slag substrate

The present study, conducted near Newcastle, Australia, used a blocked analysis of variance experimental design to compare initial nutrient concentrations and decomposition rates of Avicennia marina (grey mangrove) grown on sand and rock blast furnace slag. There were no significant differences ( ANOVA; P > 0.05) in mean initial nutrient concentrations of total C, N and P for plants grown on the sand and slag substrates. A litterbag technique was used to estimate decomposition rates. After 360 days of incubation, repeated measures analysis did not identify significant differences between the substrates for the interaction term ‘substrate × time’ or the term ‘substrate’ for percentage weight loss or for C, N and P remaining. Avicennia marina on both substrates had nutrient characteristics and decomposition rates comparable to those found in the literature. Results suggest that initial nutrient concentration and decomposition rates are not dramatically influenced by the presence of slag.

Utilização de sismógrafos de engenharia como ferramenta no controle de qualidade de acessórios de detonação não elétricos

Nesse artigo, são apresentados os trabalhos realizados com o objetivo de verificar se a elevada dispersão dos valores de velocidade de partícula obtidos durante monitoramentos de vibrações decorrentes de desmontes de rocha com a utilização de explosivos, em mineração localizada no município de Limeira (SP), vinculava-se a variações nos tempos dos elementos de retardo dos acessórios de detonação em relação aos nominais. Os experimentos foram realizados em janeiro e junho de 2004. O procedimento adotado para estimar os tempos de retardo de acessórios de detonação não elétricos redundou em resultados que apresentam consistência, necessitando, porém, de estudos mais aprofundados. Os dados obtidos indicam a necessidade de considerar sua ocorrência quando da elaboração de planos de fogo, por suas implicações: ambientais, que inclui aspectos relativos à segurança e econômicas.

Dynamic Fracture and Strain Rate Behavior of Aggregates Used in Transportation

The static and dynamic uniaxial compressive strengths of coarse aggregate materials used in portland cement concrete (PCC) were determined under dry and saturated conditions for three blast furnace slags, three limestones, four dolomites, and two mafic igneous rocks. The slag aggregates exhibited the lowest compressive strength, followed by the carbonates (limestones and dolomites), and the mafic igneous rocks. Both the dry and saturated aggregates revealed a higher compressive strength under dynamic loads compared to the static loads. Based on the experimental data, a rate sensitivity parameter was defined to describe the increase in compressive strength as a function of strain rate. This parameter is deemed to have considerable relevance in evaluating the ability of a specific aggregate to resist dynamic loads such as in aggregate interlock in PCC cracks and joints, friction in asphalt, and also in the development of microfracture during rock blasting. Comparison of the compressive strength data to dens...

Fragmentation Energy in Rock Blasting

The theoretical explosive energy used in blasting is a common issue in many recent research works (Spathis 1999; Sanchidrian 2003). It is currently admitted that the theoretical available energy of the explosives is split into several parts during a blast: seismic, kinetic, backbreaks, heave, heat and fragmentation energies. Concerning this last one, the energy devoted to the breakage and to the creation of blocks within the muckpile can be separated from the microcracking energy which is devoted to developing new and/or extending existing micro cracks within the blocks (Hamdi et al. 2001; Lopez et al. 2002). In order to investigate these two types of energy, a first and important task is to precisely study the main parameters characterising the two constitutive elements of the rock mass (rock matrix and discontinuity system). This should provide useful guidelines for the choice of the blasting parameters (type of explosive, blasting pattern, etc.), in order to finally control the comminution process. Within the frame of the EU LESS FINES research project, devoted to the control of fines production, the methodology was developed in order to: (1) characterize the in situ rock mass, by evaluating the density, anisotropy, interconnectivity and fractal dimension of the discontinuity system and (2) evaluate fragmentation (both micro and macro) energy spent during the blasting operation. The methodology was applied to three production blasts performed in the Klinthagen quarry (Sweden) allowing to estimate the part of the fragmentation energy devoted to the formation of muck pile blocks on one side and to the muckpile blocks microcracking on the other side.

A Non-Ideal Detonation Model for Evaluating the Performance of Explosives in Rock Blasting

A new model to predict the non-ideal detonation behaviour of commercial explosives in rock blasting is presented. The model combines the slightly divergent flow theory, polytropic equation of state, simple pressure-dependent rate law and statistical expressions to model the effect of confinement on detonation. The model has been designated as DeNE, an acronym for the Detonics of Non-ideal Explosives. It is aimed at predicting the detonation state and subsequent rarefaction (Taylor) wave to provide the pressure history for different explosive, rock type and blasthole diameter combinations. It enables the prediction and comparison of the performance of commercial explosives in different blasting environments. The unconfined detonation velocity data has been obtained from the testing of six commercial explosives to calibrate DeNE. A detailed sensitivity analysis has been conducted to evaluate the model. The model has been validated using the results of hydrocodes as well as measured and published in-hole detonation velocity data.

Explosion Dynamics in Saturated Rocks and Solids

Non-elastic pore deformations and crack propagations are the principal causes of dynamic damage in rocks and soils. In the case of downhole blasting from wellbores, these two mechanisms compete with each other. Therefore, to carry out a mechanical analysis of rock blasting, a sufficiently complete model that takes these various mechanisms into account has to be developed. To address this issue, this paper proposes the use of an elastic–plastic model, which includes a yield condition with a non-associated plastic flow rule, the effects of pore fluid saturation, and a brittle failure criterion under extension. The results presented in this paper describe underground explosions with spherical motion (cavity growth under the internal pressure of detonated gases without leakage into the formation), typical for oil or water reservoirs. The governing equations are written in a Cartesian system of coordinates for the case of spatial dynamic medium deformation. For this case, Cartesian coordinates are more convenient than spherical coordinates because they avoid numerical difficulties connected with the non-divergent terms of the non-linear form of the Biot–Frenkel equations. The numerical method uses the Wilkins approach, which has been generalized for the model described in this paper. The dilatancy of the material during plastic deformation is neglected for simplicity. The numerical results show that, when using typical parameters for relatively “soft” porous skeleton, the plastic flow overcomes the brittle failure. An extension zone only appears near the cavity. The results also show the presence of the two Biot P-waves. The second Biot wave, however, is only seen in the case of an extremely high permeability rock. Furthermore, in the case of the first Biot wave, the saturating liquid and the solid skeleton particles are moving with different velocities in a 100 darcy rock and with the same velocity in a 0.01 darcy rock. Calculated radial particle velocities as a function of the scaled radius are close to measured velocities in rigid dense media but are larger than measured ones in clays. It is suggested that the difference is due to different levels of water saturation, assumed full saturation in the calculation, partial saturation in the experiments.

Further study on effect of concrete defense layer on evolution mechanism of stress-waves

The Taylor–Chen–Kuszmaul model, which regards the dynamic fracture process of brittle materials as a continuous accrual of damage, has been successfully applied to simulate rock blast and concrete penetration. This paper employs the TCK damage model to numerical study on the effect of perforated concrete defense layer on evolution mechanism of blast-induced stress waves. The numerical results reveal that the tensile damage near free boundary should be noteworthy under a higher blast loading, and the peak values of hydrostatic pressure beneath an artificial cavity are largely reduced. The effects of cavity dimensions and position on wave evolution and reduction are detailedly explored. One empirical formula is proposed to relate the decay factor of peak hydrostatic pressure to the dimensions and relative position of cavity.

A laboratory and full-scale study on the fragmentation behavior of rocks

Rock fines produced in rock blasting and crushing processes is a major problem for aggregate producers. Laboratory and full-scale studies were carried out to explore the possible relationship between fines production and water content of rock material. The Brazilian tensile test was selected for the laboratory study while a cone crusher machine was employed for the full-scale trials. Results of the laboratory work showed that the percentage of fines fraction produced was a function of the type of rock tested and the tensile strength of individual specimens. Different rocks produced various amounts of fines, but for the rocks investigated, a correlation between its strength and its fines generation could be attained. The influence of water content on production of fines was also examined and showed that increased water content reduces both tensile strength and fines generation in the laboratory. The impact of water content on aggregate production was also studied in full-scale but the results were not as clear as those of the laboratory tests.

Physicochemical characteristics of Ivo River, Ebonyi state, Nigeri

A study was carried out on the physiochemical characteristics of Ivo River in Ivo Local Government Area of Ebonyi State, Nigeria to determine the present level of pollution of the river water due to incidental industrial, agricultural and human activities. The results showed that pH, temperature, conductivity, total dissolved solids, dissolved oxygen, potassium, calcium, silica, sulphate and chloride which had value ranges of 7.2 – 7.4, 27 – 28.2 0C, 40.4-150&#956;s/cm, 22 – 39 ppm, 2.4 – 9.0 ppm, 0.07 – 0.17 ppm, 0.1 – 4.0 ppm, 1.007- 1.48 ppm, 4.55 – 65.88 ppm, and 31.62 – 47.13 ppm respectively, were below the maximum permissible standards. The range of value of turbidity (0.8 – 60.2 NTU), total suspended solids (6.1 – 19.14 ppm) and sodium (82 – 89 ppm) were above the standards of WHO but below that of Federal Environmental Protection Agency (FEPA) and Department of Petroleum Resources (DPR) standards. Good refuse and sewage disposal practices, proper management and control of industrial wastes emanating from rock blasting and lead-zinc mining should be encouraged in the area. International Journal of Natural and Applied Sciences Vol. 1(2) 2005: 145-149

Energy components in rock blasting

Ten production blasts and one single-hole confined blast have been monitored in two quarries in order to assess the measurable forms of energy in which the energy delivered by the explosive is transformed in rock blasting. The seismic field from seismographs readings, the initial velocity of the blasted rock face obtained from high-speed video camera records, and the fragment size distributions from image analysis of the muckpile material are used to determine the seismic wave energy, the kinetic energy and the fracture energy, respectively, transferred in the blasting process. The blasting data and the methods of calculation of the energy terms from those are described in detail. Heat of explosion and useful work to 100 MPa have been used as descriptions of the energy of explosives. The maximum total energy measured accounts for not more than 26% of the available explosive energy if this is rated as the heat of explosion, though lower figures are usually obtained. The values measured for each of the energy components range from 2% to 6% of the total energy available for the fragmentation energy, 1–3% for the seismic energy and 3–21% for the kinetic energy. For the confined shothole, the seismic energy was 9% of the heat of explosion. The uncertainty of the calculated energies is analyzed from the variability of the measured data. Particularly important influential parameters are the treatment of the fines tail of the fragment size distribution in the determination of the fragmentation energy, and the use of P or S wave velocity values, and whether these are determined from in situ or from laboratory measurements, in the calculation of the seismic energy.

Plasma Discharge Initiation of Explosives in Rock Blasting Application: A Case Study

A plasma discharge initiation system for the explosive volumetric combustion charge was designed, investigated and developed for practical application. Laboratory scale experiments were carried out before conducting the large scale field tests. The resultant explosions gave rise to less noise, insignificant seismic vibrations and good specific explosive consumption for rock blasting. Importantly, the technique was found to be safe and environmentally friendly.

Review article: Analysing the crack coalescence in brittle rock materials

The understanding of fracture has tended to follow great public disasters (e.g. over 200 US ships suffered due to catastrophic failure during WW II, later several jet air-craft damaged, destroying some bridges and buildings, etc). Rock fracture mechanics dates back to early 60-s and its application to rock blast problems, collapses deep gold mines in South Africa, earthquake disasters, etc. Pure shear mode (Mode I) or mixed tension and shear mode (Mode I and II) fracturing are the most important in rock mechanics and geophysics. The goal of this paper is to summarize the existing fracture criteria and the observed crack growth firstly from single flaws, secondly from multiply (two) flaws. Analysing the fracture propagations different types of coalescence can be determined and classified. Using these modelling and analysing the observed patterns, for example we could forecast the new failures after the earthquakes or calculating the stability of rock slopes, etc.

Managing Rock Blasting Work in Urban Environments

In recent years, controlled rock blasting methods have been used to excavate rock in shafts, tunnels, and chambers at many projects at urban locations throughout the United States. For engineers, blasters, regulators, project supervisors, and managers, controlling blast-induced vibrations and air overpressure and other risks associated with this blasting is becoming an ever increasing challenge. For urban work, explosives security, storage and handling systems, overbreak control, impacts of blasting on green concrete, community relations, and the availability of skilled labor also influence the outcome of the work. This paper presents practical methods regarding blast design and risk management practices that have been used successfully at high-exposure projects located in or near Boston; Atlanta; Portland, Ore.; Milwaukee, Wis., and other cities in the United States. Special focus is on practical blast design techniques that mitigate blast-induced vibration and air overpressure generated by shaft and tunnel blasts. Controlling blasting impacts on concrete of varying age and placement condition is also discussed.

Suggestions of rock classification methods for blast design and application to tunnel blasting

In this paper, the methods of general rock classification and blast design for tunnel excavation in Korea are reviewed, and efforts to develop a new classification method, reflecting the blasting performance, are presented. A series of test blasts were carried out at two tunneling sites of Central Inland Highway crossing the country. Long hole blasting was tested in rock mass whose RMR value is over 60. The blasting results were evaluated by measuring degree of fragmentation, advance rate, muckpile distribution, overbreak, etc. Based on the results of test blast, several patterns were proposed for two-lane highway tunnel. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.

Statistical models of brittle fragmentation

Recent developments in statistical models for fragmentation of brittle material are reviewed. The generic objective of these models is understanding the origin of the fragment size distributions (FSDs) that result from fracturing brittle material. Brittle fragmentation can be divided into two categories: (1) Instantaneous fragmentation for which breakup generations are not distinguishable and (2) continuous fragmentation for which generations of chronological fragment breakups can be identified. This categorization becomes obvious in mining industry applications where instantaneous fragmentation refers to blasting of rock and continuous fragmentation to the consequent crushing and grinding of the blasted rock fragments. A model of unstable cracks and crack-branch merging contains both of the FSDs usually related to instantaneous fragmentation: the scale invariant FSD with the power exponent (2−1/D) and the double exponential FSD which relates to Poisson process fragmentation. The FSDs commonly related to ...