Dynamic performance of cemented rockfill under blast-induced vibrations

In this thesis, a new methodology for the design of CRF under static and dynamic loading conditions is developed. First a comprehensive literature review of the backfill material is accomplished which included a review of CRF operations and laboratory testing programs. This is followed by a review of numerical modelling studies performed on CRF. Based on the findings from literature review, two numerical models for CRF are developed using FLAC3D code. One of the models considers stopes to be inclined at about 67 degrees and the other considers vertical stopes. The numerical models are then used to study different aspects of CRF practice including the loading conditions, blast-induced vibrations from adjacent production stopes, vertical block mining method, CRF properties, CRF placement method and segregation. A case study mine CRF model is then constructed in accordance with site conditions and the geomechanical data provided by the mine. The case study mine numerical model is calibrated with in-situ stress measurements previously conducted at the case study mine. Mining and backfilling sequence is simulated with the calibrated model and the secondary stope is mined out in three lifts. In-situ blast vibration monitoring experiment in CRF is performed at the case study mine. Two geophones are installed: one inside CRF and the other on the surface of the CRF, and all three production blasts of the adjacent secondary stope are recorded. The detailed procedure, installation and results are presented in the thesis. The results are also used for numerical model calibration. To calculate damping coefficient for the model and blast load magnitude an equivalent cavity model is constructed. The equivalent cavity model is applied with reduced borehole pressure and the model is compared with charge-weight scaling law. The blast load and damping coefficients are extracted from equivalent cavity model and applied as input parameters for the CRF model. The numerical model is calibrated using blast load and damping coefficients obtained from the equivalent cavity model by computing the blast vibrations at a location similar to the one on site. The model is calibrated for all three blast lifts and results are presented. Finally, a CRF failure control study is carried out which encompasses the base case scenario of a planned stope at the case study mine, selective mining strategy for mining high grade ore, strategy of leaving an ore skin, tactically varying CRF properties vertically in CRF. In addition a parametric study is conducted to improve CRF stability by varying CRF properties and possible trends are presented. All results compare static loading versus blast loading scenario on CRF. The results include comparison of backfill stresses and profiles of peak particle velocity. Results of all analyses are presented along with the findings, conclusions, suggestions for future work and statement of contribution.Dans cette thèse, une nouvelle méthodologie pour la conception de CRF sous des contraintes statiques et dynamiques est développée. Premièrement, un examen de la littérature existante à été accompli. Les opérations minières employant le CRF sont examinées ainsi que les programmes d'essai en laboratoire et les études de modélisation numérique effectuées pour le CRF. Basés sur l'examen de la littérature existante, deux modèles numériques pour le CRF on étés développé en utilisant FLAC3D. Le premier modèle considère un pendage de 67 degrés pour les chantiers, lorsque l'autre considère des chantiers verticaux. Ces modèles numériques sont ensuite utilisés pour l'étude de différents aspects de la pratique du CRF tels que les conditions de chargement, les vibrations de tir, les propriétés du CRF, la méthode de placement du CRF, ainsi que la ségrégation du CRF. Un modèle pour la mine de l'étude de cas est ensuite construit en tenant en compte les conditions du site ainsi que les données geo-mecaniques fournies par la mine. Le modèle pour la mine de l'étude de cas est calibré selon les mesures des contraintes in-situ effectués à la mine. La séquence d'abattage et de remblayage est ensuite simulée avec le modèle numérique calibré et les chantiers secondaires sont extraits en trois étapes. Les vibrations de tir in-situ sont mesurées à la mine de l'étude de casé. Deux géophones sont installés : un à l'intérieur du CRF et l'autre à la surface du CRF, et les trois sautages de production du chantier adjacent sont enregistrés. La procédure de l'installation et les résultats obtenus avec le géophone sont présentés dans la thèse. Les résultats sont utilises pour valider le modèle numérique. Le chargement de tir ainsi que les coefficients d'amortissement sont extraits d'un modèle de cavité en calculant les vibrations de tir à la même position que celle du site. Le modèle est validé pour les 3 étapes de l'abattage du chantier et les résultats sont présentés. Finalement, une étude sur le contrôle de stabilité du CRF est effectuée. Cette étude englobe un scenario de base d'un chantier planifié à la mine de l'étude de cas, une stratégie d'abattage sélectif du minerai de haute teneure, une stratégie ou une couche de minerai est laissée dans le chantier, et une variation verticale planifiée des propriétés du CRF. De plus, une étude paramétrique est conduite pour améliorer la stabilité du CRF en variant les propriétés du CRF. Les tendances possibles sont présentées. Tous résultats comparent le chargement statique avec le chargement dynamique sur le CRF. Les résultats incluent une comparaison des contraintes du remblai ainsi que le profile de la vitesse de crête des particules. Les résultats de toutes les analyses sont présentés avec les constatations et conclusions

Role of ergonomics in the selection of stemming plugs for surface mining operations

Stemming plugs are one of the widely used accessory in surface mining operations. Stemming plugs assist conventional stemming material in gas retention and help in better fragmentation and explosive utilization. Effective use of the stemming plugs results in economic benefits and enhance the efficacy of the project. Economic and productive viability of stemming plugs have been conducted in depth by different researchers. Addition of stemming plugs to a new system requires ergonomic challenges for operators conducting drilling and blasting operation. Induction of a newer product in already established system is subject to overall positive feedback. This work investigates ergonomics of three different stemming plugs introduced to a limestone quarry in Pakistan. The stemming plugs were evaluated based on extra time needed, workers feedback, failures during operation, recovery time after failure and number of extra equipment required to carry out the operation. Points based matrix was established with likeliness of each plug and based on overall scores stemming plug 1 was most acceptable followed by stemming plug 3. Stemming plug 2 was disliked by operation and did not reach the level of acceptability of operators. This work will help stemming plug making industry in adapting to best practices by incorporating ergonomics of plugs in designing. Literature shows no previous work on ergonomics of stemming plugs

Tunnel Portal Construction using Sequential Excavation Method: A Case Study

Portal excavation in soft rock is one of the most challenging tasks in the construction of underground facilities. Significant convergence, collapses and surface settlement are usually associated with portal construction. Alluvium is loose unconsolidated material and most often tunnels constructed through tend to destabilize. In this study, portal excavation design has been analyzed using the finite element based computer program known as Phase2. The method of top heading and benching was not a suitable approach, keeping in view the previous experience. Subsequently, a different design of sequential excavation method (SEM) was proposed. Minimum convergence, minimum surface settlement, and machinery constraints were considered to be the vital importance for selection of final design. The results of finite element method (FEM) analysis showed that the finally selected SEM design has a roof convergence of 4 mm for the heading and full face excavation has 25 mm. These values were comparable with the ones obtained from a 5-pin convergence station, installed during the portal excavation (0.5 m inside from the portal). No or very little surface settlement was shown by the numerical model and actual field observation. Consequently, a proper SEM design based on numerical modeling allowed a successful construction of a large portal in alluvial deposits

Tunnel Portal Construction using Sequential Excavation Method: A Case Study

Portal excavation in soft rock is one of the most challenging tasks in the construction of underground facilities. Significant convergence, collapses and surface settlement are usually associated with portal construction. Alluvium is loose unconsolidated material and most often tunnels constructed through tend to destabilize. In this study, portal excavation design has been analyzed using the finite element based computer program known as Phase2. The method of top heading and benching was not a suitable approach, keeping in view the previous experience. Subsequently, a different design of sequential excavation method (SEM) was proposed. Minimum convergence, minimum surface settlement, and machinery constraints were considered to be the vital importance for selection of final design. The results of finite element method (FEM) analysis showed that the finally selected SEM design has a roof convergence of 4 mm for the heading and full face excavation has 25 mm. These values were comparable with the ones obtained from a 5-pin convergence station, installed during the portal excavation (0.5 m inside from the portal). No or very little surface settlement was shown by the numerical model and actual field observation. Consequently, a proper SEM design based on numerical modeling allowed a successful construction of a large portal in alluvial deposits

Study on the efficiency of destress blasting in deep mine drift development

Canadian hard rock mines continue to reach deeper deposits, which poses greater challenges to mine safety including rock burst control. Destress blasting techniques have been successfully employed in such underground mines with the aim of preconditioning highly stressed rock mass to mitigate the risk for rock burst occurrence in deep mines. In the present study, the efficiency of destress blasting is examined through a comparison between traditional and alternative numerical modelling approaches. The traditional modelling approach assumes a uniformly distributed blast-induced damage zone extending over the entire drift face, whilst the alternative modelling approach, presented herein, simulates the damage zone for each individual blast hole. In the first part of this paper, a 3-D numerical model of a single blast hole is constructed, whereby the extent of blast-induced damage zone is delineated under various conditions to consider influential factors, such as mining depth (in-situ stress) and inherent heterogeneity of rock mass strength. The latter part of this paper uses the single-hole model results to examine the efficiency of destress blasting as practiced in drift development in deep mines. It is demonstrated through comparison of FLAC3D numerical simulation results that the traditional modelling approach may lead to an overly optimistic indication of destress blasting efficiency when compared with the alternative modelling approach, in which a more precise simulation of the damage zones is applied.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Synergetic Effect of Different Plant Growth Regulators on Micropropagation of Sugarcane (Saccharum officinarum L.) by Callogenesis

The response of different plant growth regulators on callus induction and regeneration on three sugarcane genotypes (YT-53, CP-77-400, and NSG-59) was evaluated. Different concentrations of 2,4-D alone and in combination with other plant growth regulators (Kinetin and BAP) were used for callus induction. Kinetin along with IBA, BAP and NAA were analyzed with respect to shoot induction, while NAA and IBA were used for root induction. The best callus response in terms of number of days, callus fresh weight, and frequency in YT-53 was observed on MS media provided with 2,4-D (3 mg L−1) + Kinetin (0.5 mg L−1), while in NSG-59 the best response was on MS+2,4-D (4 mg L−1) + Kinetin (0.5 mg L−1), and in CP-77400, MS+2,4-D (5 mg L−1). For shoot induction, 2 mg L−1 Kinetin was found to be the best for YT-53 and NSG-59, while 1 mg L−1 BAP was found to be the best for CP-77-400 in terms of number of days, shoot numbers, and shoot length. The best media for root induction in terms of number of days, root numbers, and root length was 1 mg L−1 NAA + 1 mg L−1 IBA for YT-53, while this was 3 mg L−1 NAA for NSG-59. The highest root frequency and maximum root length in the minimum number of days was observed in CP-77-400 on MS media provided with 2 mg L−1 NAA

Impact of Shear Zone on Rockburst in the Deep Neelum-Jehlum Hydropower Tunnel: A Numerical Modeling Approach

Rockburst is a hazardous phenomenon in deep tunnels influenced by geological structural planes like faults, joints, and shear planes. Small-scale shear-plane-like structures have damaging impact on the boundaries of the tunnel, which act as barrier and accumulate high stresses. A shear plane combined with high stress conditions is very dangerous in deep excavations. Such a shear plane exposed in the side wall of the right headrace tunnel in the Neelum-Jehlum Hydropower Project. This project is constructed in the tectonically active Himalayas under high stress conditions. The influence of a shear zone on rockburst occurrence near the tunnel is studied. The FLAC3D explicit code simulated the shear zone in the right tunnel, revealing that the stresses are concentrated near the shear zone, while no such stress concentration is present in the left tunnel. The Rock mass got displaced near this shear zone. Modeling results confirm that the presence of shear zone in side wall of the right tunnel has a major influence on rockburst occurrence. A shear slip along this plane released huge amounts of accumulated energy, causing human fatalities and property damage. A comparison of numerical simulation with empirical rockburst criteria validates the actual conditions and help us to understand the phenomenon of stress concentration near the shear zone and its impact during deep tunneling

Real-Time Diesel Particulate Matter Monitoring in Underground Mines: Evolution and Applications

Diesel exhaust is a major cause of large number of occupational diseases. Acute and continuous exposure to DPM can cause numerous health issues including respiratory disease, lung disease, heart disease, etc. The NIOSH and the IARC consider DPM as ‘probable carcinogenic’ and ‘carcinogenic’, respectively. In large underground M/NM mines, DPM regulatory compliance is challenging. This paper primarily focuses on the evolution and application of real-time DPM monitoring in mining. This study discusses different monitors performance, their applications, and prospects of DPM monitoring in mining. This paper also presents an overview of core issues of using diesel equipment in underground mines and summarises existing DPM regulations in US and other countries

An Appropriate Model for the Prediction of Rock Mass Deformation Modulus among Various Artificial Intelligence Models

The rock mass deformation modulus (Em) is an essential input parameter in numerical modeling for assessing the rock mass behavior required for the sustainable design of engineering structures. The in situ methods for determining this parameter are costly and time consuming. Their results may not be reliable due to the presence of various natures of joints and following difficult field testing procedures. Therefore, it is imperative to predict the rock mass deformation modulus using alternate methods. In this research, four different predictive models were developed, i.e., one statistical model (Muti Linear Regression (MLR)) and three Artificial Intelligence models (Artificial Neural Network (ANN), Random Forest Regression (RFR), and K-Neighbor Network (KNN)) by employing Rock Mass Rating (RMR89) and Point load index (I50) as appropriate input variables selected through correlation matrix analysis among eight different variables to propose an appropriate model for the prediction of Em. The efficacy of each predictive model was evaluated by using four different performance indicators: performance coefficient R2, Mean Absolute Error (MAE), Mean Squared Error (MSE), and Median Absolute Error (MEAE). The results show that the R2, MAE, MSE, and MEAE for the ANN model are 0.999, 0.2343, 0.2873, and 0.0814, respectively, which are better than MLR, KNN, and RFR. Therefore, the ANN model is proposed as the most appropriate model for the prediction of Em. The findings of this research will provide a better understanding and foundation for the professionals working in fields during the prediction of various engineering parameters, especially Em for sustainable engineering design in the rock engineering field