Low density optimization of emulsion explosive to improve blasting quality (MNK Max70)

PT Multi Nitrotama Kimia is a mining service company engaged in providing blasting services and the largest sales of explosives in Indonesia. PT Pamapersada Nusantara jobsite Kideco Jaya Agung is one of the customers of PT Multi Nitrotama Kimia in the blasting service business unit. On a far more optimal side, the development of commodity price conditions and operational needs is a common concern. From these conditions, one of the best target cost controls for blasting and fragmentation is to make adjustments and improvement to the quality and quantity of the use of bulk products. The high use of bulk products at the Kideco Jaya Agung Jobsite is a particular concern, especially for rocks that require a high powder factor value, thereby increasing blasting operation costs. From this condition, PT Multi Nitrotama Kimia strives to optimize the bottom value of density product emulsion MNK Max70 using chemical improvement from the previous 1.15 gr/cc to 1.05 gr/cc. This improvement has brought good results, where optimization in terms of using bulks product and blasting quality such as fragmentation and Velocity of Detonation (VOD) values are still in accordance with product standards.

A review on the prediction and assessment of powder factor in blast fragmentation

Powder factor can be defined as the quantity of explosives (kg) required to break a unit volume or tonne (t) of rock. The prospect of excavating rocks by blasting is characterized by a specific consumption of explosives. In the past decades, researchers have come up with several precise approaches to predict powder factor or specific charge in blast operations other than through trial blast. Research in this area has focused on the relationship between rock mass properties, blasting material and blasting geometry to establish the powder factor. Also, the interaction between specific energy and particle size embodied in the theory of comminution that is less dependent on local conditions has been studied. In this paper, the various methods for powder factor estimation based on empirical and comminution theory modelling as well as machine learning approaches in both surface bench blasting and underground tunnel operations have been reviewed. The influence of intact rock properties on powder factor selection and the influence of powder factor selection on post-blast conditions have also been discussed. Finally, the common challenges that have been encountered in powder factor estimations have been pointed out in this regard.

Prediction of BlastInduced Ground Vibration (BIGV) of Metro Construction Using Difference Evolution AlgorithmOptimized Gaussian Process (DE-GP)

Rock blasting often has an irreversible impact on the surrounding environment and threatens the safety of life and property. Therefore, accurate prediction of blast-induced ground vibration (BIGV) is a prerequisite for safe construction. In view of the fact that traditional blasting peak particle velocity (PPV) empirical formulas cannot be accurately predicted, this study selected 88 sets of blasting monitoring data, based on distance from the blast-face, maximum charge per delay, total charge, hole depth, spacing, burden, stemming length, and powder factor being used as input variables and PPV being used as output variable to characterize BIGV. First, a nonlinear mapping relationship between input variables and output variable is established through the Gaussian process (GP). The differential evolution algorithm (DE) is used to optimize the hyperparameters σf, σn, and l of the GP, and a blasting PPV model based on the DE-GP is constructed. The proposed model is compared with the empirical formulas, least square support vector machine (LSSVM), artificial neural network (ANN), and GP model, and its prediction performance is evaluated by statistical indicators such as root mean square error (RMSE). Finally, the cosine amplitude method (CAM) is used to analyze the sensitivity of blasting parameters. The results show that the DE-GP algorithm for blasting vibration velocity prediction has higher precision and accuracy, which is significantly better than other models, and is the closest to the measured PPV. Distance from the blast-face, total charge, and maximum charge per delay have a greater impact on the prediction of PPV, while stemming length and powder factor have a smaller impact on the prediction of PPV. The DE-GP model proposed by this research has certain reference value for the prediction and control of PPV in blasting construction.

Safe Blast Design for Efficient and Sustainable Underwater Excavation: Art Meets Science!

Most of the dredging work associated with harbor, port, channel deepening, and other related operation requires underwater blasting due to the characteristics of material being dredged / moved. Underwater blasting is typically used to remove rocks for deepen harbours and channels, creating channels and levees, installing conduits, and other more specialised blasting operations that shall be completed below sea. Usually, such dredging work occurs in deep-water of varying between 16–20m in order to remove just few meters of rocks. Hence, this type of blasting activity needs high level of skill and familiarity than equivalent activities carried out above the surface of water because of aqueous layer over the its rock. Therefore, the factors such as selection of drilling parameters and drilling equipment, selection of appropriate explosives and accessories, usage of correct powder factor, determination of safe explosive charges per delay and selection of suitable personnel are studied carefully for accomplishing the successful underwater blasting operations. In addition to the above, the system shall also address the proper design for the underwater blasts to excavate the rock to the required depth keeping in view the permissible allowances of minimum and maximum depth and fragment size required. While adopting underwater blasts, adequate safety measures are also defined for safety of men, other vessels in the blasting zone and structures from blasting vibrations. Here, the authors broadly outline their approach with respect to underwater blasting using the existing blasting technology, with a case study.

Experimental Investigation on Influencing Factors of Rock Fragmentation Induced by Carbon Dioxide Phase Transition Fracturing

Carbon dioxide phase transition fracturing is a novel physical blasting technique, which is gradually used in mining and underground space engineering. The improvement of its rock breaking efficiency is the key concern in the application. In this paper, field experiments of CO2 phase transition fracturing were conducted. Based on the strain monitoring and fracturing crater volume measuring, the variation of CO2 filling amount and shear sheet thickness on rock fragmentation of CO2 phase transition fracturing was investigated. The experimental results indicated that the fracturing crater is shaped as an elliptical cone that is longer in the jet direction and shorter in the vertical jet direction. With the increase of the CO2 filling amount, the excavated crater volume gradually increases, but the growth rate gradually decreases. The powder factor is constant within a certain charge amount, and after exceeding this charge amount, the powder factor of CO2 increases significantly. As the shear sheet thickness increases, although the consultant peak stress gradually increases, its growth rate is still unchanged. The crater volume and its growth rate gradually increase in the same situation. Moreover, with the shear sheet thickness increase, the CO2 powder factor decreases continuously, and the decline rate remains unchanged.

Influence of natural discontinuities and mechanical properties on the fragmentation of marble by blasting in Central Africa

This research focuses on the influence of natural discontinuities and mechanical properties in the fragmentation of marble by blasting. These natural discontinuities and mechanical properties are the parameters which are difficult to control and which considerably influence the fragmentation of marble after blasting. This paper aims at predicting the fragmentation of the Bidzar quarry rock, the only marble quarry in Central Africa, while improving the knowledge on it. This quarry has been facing problems of fragmentation of marble blocks for decades, which requires secondary firing and incurs enormous costs. The Kuz-Ram method was used for this study. The dip of the discontinuity planes, the compressive strength, the distance between the discontinuities and the density of the discontinuities are the operational parameters that were used to study the influence of natural discontinuities and the mechanical properties of the rocks on the fragmentation after firing. This work consists precisely in studying the pullability as a function of the dip of the discontinuity planes, then the fragmentation as a function of the powder factor, the compressive strength and the drilling mesh. The results of this study were compared with those of the other authors. Qualitative and quantitative studies were carried out in order to highlight the influence of natural discontinuities and mechanical characteristics on fragmentation. The fragmentation pattern of the Bidzar quarry was examined and compared with those obtained in other regions of the world, namely, Northern Europe, Central America, South-East Asia and West Africa. The variation in the intensity of fragmentation caused on the one hand by differences in the dips of the firing planes and their compressive strength, and on the other hand by the variation in the drilling mesh was also discussed. The prediction test was carried out with seven plans of existing discontinuities in the Bidzar quarry and at different mesh sizes in order to estimate the distribution of the fragments of marble thatcan through the crsuher after being fired. Several suggestions were put forward for the evaluation of the fragmentation. Three practical tables were created to predict the result of the shot. The specific graphs, which were proposed to analyse fragmentation in this quarry, made it possible to assess the quantity of fragments passing through the crusher after firing. Predicting fragmentation by considering the dip of the firing planes and the powder factor can effectively optimise the fragmentation of the rocks by blasting and achieve the desired result.

PRELIMINARY ASSESSMENT OF THE EFFECTS OF BLAST DESIGN FACTORS ON FRAGMENTATION AT LAFARGE KANTHAN LIMESTONE QUARRY, CHEMOR, PERAK

The results of blasting affect every other downstream operation in quarrying and mining process. Factors influencing blast results can be classified as either controllable or non-controllable. If desired fragmentation is to be obtained, the controllable factors (blast geometry and explosive properties) must be sufficiently designed to match the non-controllable ones (geological factors and legislative constraints). This study investigates the influence of blast design parameters on rock fragmentation. Six different blast designs were studied and analyzed. Rock samples were obtained from each face to evaluate the uniaxial compressive strength (UCS). Images of muck pile were captured using suitable digital camera. The images were uploaded into the WipFrag software to analyze the fragmentation resulting from the blasting. The particle size distribution of each blast was obtained, and the mean fragment size correlated with the blast design parameters. The percentage cumulative passing for gyratory crusher with the feed size of 1500 mm ranges between 92.8 to 100%. The stiffness ratio, powder factor and uniaxial compressive strength have high correlation with mean fragment size. The stiffness ratio increases with mean fragment size with a correlation coefficient of 0.89. The mean fragment size becomes finer with increase in powder factor with a correlation coefficient of 0.76. Powder factor also has a high correlation with the uniaxial compressive strength of the rock. The higher the uniaxial compressive strength of rock, the higher the powder factor needed for a specified fragment size. In this study, spacing to burden ratio has a very weak correlation with the fragment size. All the studied blast events produced good fragmentation with a uniformity index varying from 2.097 to 2.525.

Comprehensive Evaluation of Blast Casting Results Based on Unascertained Measurement and Intuitionistic Fuzzy Set

In order to make a scientific and accurate evaluation of blast casting results, according to the characteristics of blast casting-dragline stripping system, effective casting rate, looseness coefficient, limit vibration velocity, powder factor, fragmentation distribution, muck pile shape, boulder generation, damage degree of coal seam step, and dust pollution are selected as the evaluation indicators of blast casting results, and a classification standard is established. The unascertained measure theory was adopted to determine the membership degree of influencing factor indicator, which expanded the expression method of fuzzy information of evaluation indicators. The Analytic Hierarchy Process was used to determine the subjective weight of indicators, the entropy weight method was used to determine the objective weight of indicators, and the intuitionistic fuzzy set was used to express the range of the comprehensive weights of indicators. An evaluation model of blast casting results was constructed based on unascertained measurement and intuitionistic fuzzy set. The measured and processed data of blast casting in Heidaigou Open-Pit Coal Mine were calculated by the evaluation model. Besides, the sensitivity of indicator weights to the evaluation result of blast casting results was also analyzed. The results show that the blast casting results are level III (well). The effective casting rate ranks first in terms of the influence on the evaluation result, followed by damage degree of coal seam step, muck pile shape, looseness coefficient, powder factor, dust pollution, limit vibration velocity, and boulder generation/fragmentation distribution, and it was proved that the weight fluctuation of the evaluation indicator has no obvious correlation with weight.