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The brittleness index is one of the most integral parameters used in assessing rock bursts and catastrophic rock failures resulting from deep underground mining activities. Accurately predicting this parameter is crucial for effectively monitoring rock bursts, which can cause damage to miners and lead to the catastrophic failure of engineering structures. Therefore, developing a new brittleness index capable of effectively predicting rock bursts is essential for the safe and efficient execution of engineering projects. In this research study, a novel mathematical rock brittleness index is developed, utilizing factors such as crack initiation, crack damage, and peak stress for sandstones with varying water contents. Additionally, the brittleness index is compared with previous important brittleness indices (e.g., B1, B2, B3, and B4) predicted using infrared radiation (IR) characteristics, specifically the variance of infrared radiation temperature (VIRT), along with various artificial intelligent (AI) techniques such as k-nearest neighbor (KNN), extreme gradient boost (XGBoost), and random forest (RF), providing comprehensive insights for predicting rock bursts. The experimental and AI results revealed that: (1) crack initiation, elastic modulus, crack damage, and peak stress decrease with an increase in water content; (2) the brittleness indices such as B1, B3, and B4 show a positive linear exponential correlation, having a coefficient of determination of R2 = 0.88, while B2 shows a negative linear exponential correlation (R2 = 0.82) with water content. Furthermore, the proposed brittleness index shows a good linear correlation with B1, B3, and B4, with an R2 > 0.85, while it shows a poor negative linear correlation with B2, with an R2 = 0.61; (3) the RF model, developed for predicting the brittleness index, demonstrates superior performance when compared to other models, as indicated by the following performance parameters: R2 = 0.999, root mean square error (RMSE) = 0.383, mean square error (MSE) = 0.007, and mean absolute error (MAE) = 0.002. Consequently, RF stands as being recommended for accurate rock brittleness prediction. These research findings offer valuable insights and guidelines for effectively developing a brittleness index to assess the rock burst risks associated with rock engineering projects under water conditions. [ABSTRACT FROM AUTHOR]

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 three-dimensional numerical model of a single blast hole is constructed, whereby the extent of blast-induced damage zone is delineated. 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. Key words: numerical modelling, FLAC3D, rock burst, underground mining. Les mines canadiennes de roches dures continuent d'atteindre les gisements plus profonds, ce qui pose de plus grands defis en matiere de securite, y compris le controle des eclatements de roches dans les mines. Les techniques de tir de relaxation (<< destress blasting >>) ont ete employees avec succes dans des mines souterraines dans le but de preconditionner la masse rocheuse fortement sollicitee pour limiter les risques d'eclatement de roche dans les mines profondes. Dans la presente etude, l'efficacite des tirs de relaxation est examinee par une comparaison entre les approches traditionnelle et alternative de la modelisation numerique. L'approche traditionnelle de la modelisation suppose une zone de dommage uniforme induite par explosion s'etendant sur tout le front de taille de la galerie en direction, tandis que la modelisation alternative, presentee ici, simule la zone de degats pour chaque trou de mine. Dans la premiere partie du present document, un modele numerique en trois dimensions d'un seul trou de mine est construit, auquel l'etendue de la zone de dommages causes par la detonation est delimitee. La derniere partie de cet article utilise les resultats du modele a trou simple afin d'examiner l'efficacite du tir de relaxation tel que pratique pour les galeries en direction dans les mines souterraines. Il est demontre par le biais de la comparaison des resultats par simulation numerique FLAC3D que l'approche traditionnelle de la modelisation peut mener a une indication trop optimiste de l'efficacite du tir de relaxation en comparaison avec la modelisation alternative, a laquelle s'applique une simulation plus precise des zones de dommages. [Traduit par la Redaction] Mots-cles : modelisation numerique, FLAC3D, eclatement de roche, exploitation de mine souterraine., Introduction When tunnels are excavated through competent rock mass under high stress conditions, rock bursts, especially strain bursts, can be a serious issue that poses a high risk to underground [...]

It is significant to monitor the leakage at the joints of the diaphragm walls of subway station foundation pits to check the weak links in the waterproof quality of the diaphragm wall structure. It is essential to take effective waterproof measurements timely to improve the overall waterproof quality of the diaphragm wall in the foundation pit to prevent accidents and reduce the operation and maintenance costs. This paper used ground penetrating radar (GPR) to detect the Lishan North Road Station section of Jinan Rail Transit Line R2 during construction. The abnormal waveform image is obtained after processing radar detection data with Reflexw software. This abnormal waveform image is used to identify the abnormal area. In order to accurately predict the location of leakage at the joint of diaphragm wall, MATLAB is used to calculate the average wave velocity amplitude and single channel signal of the electromagnetic wave velocity of geological radar at different mileages and draw the trend chart of average wave velocity amplitude with mileage and the corresponding relationship curve of electromagnetic wave amplitude and depth of radar. It is proposed that sudden changes in the area of the average wave velocity amplitude cause a change in the trend chart. Furthermore, the radar electromagnetic wave velocity amplitude curve is taken as the area where seepage may occur at the joints of the diaphragm wall, so as to determine the corresponding mileage and depth of the leakage area. On this basis, the grey correlation analysis for the analysis of the source of the water leakage at the joints of the diaphragm wall of the subway foundation pit is proposed. The research results show that the leakage water at the joints of the diaphragm wall of the subway foundation pit is not connected to the rivers around the foundation pit, which confirms that the construction of the subway station has not affected the groundwater resources around the station. The proposed approach has successfully predicted the location of the foundation pit leakage disaster and has been verified on the project site. The research results provide a reference for the monitoring and early warning of leakage at the joints of diaphragm walls in foundation pits with similar geological conditions. [ABSTRACT FROM AUTHOR]

Numerical modelling has long been used as a powerful tool for geomechanics mine design and analysis of such problems as ore dilution. Open stoping mining method with delayed backfill is generally employed for mining steeply dipping tabular ore deposits. Several authors reported that consideration of production blast vibrations on adjacent, exposed backfill faces is crucial for the effective backfill design for minimum ore dilution due to fill failure. In this study, it is shown that blast vibrations can be characterized with dynamic numerical modelling. A FLAC3D dynamic numerical model has been developed for a typical layout of a secondary stope that is being mined next to a previously mined and backfilled primary stope. The numerical simulations are validated by comparing predicted failure geometry with laser-surveyed stope profiles obtained with a cavity monitoring system. It is shown that blast-induced vibrations can be a primary cause for wedge-type failure of the backfill face. Key words: cemented rockfill, numerical modelling, vertical block mining, cavity monitoring survey. La modelisation numerique est utilisee depuis longtemps comme un outil puissant pour la conception geomecanique miniere et l'analyse de problemes tels que la dilution du minerai. La methode d'exploitation a chambres ouvertes avec remblayage reporte est generalement utilisee pour le minage de gisements tabulaires a pente abrupte. Plusieurs auteurs ont mentionne qu'il est crucial de considerer les vibrations causees par les sautages de production sur les faces de remblai adjacentes et exposees, ceci afin de concevoir efficacement le remblayage pour minimiser la dilution du minerai causee par la rupture du remblai. Dans cette etude, il est demontre que les vibrations des sautages peuvent etre caracterisees par la modelisation numerique dynamique. Un modele numerique dynamique avec FLAC3D a ete developpe pour representer un chantier secondaire typique qui est mine a cote d'un chantier primaire prealablement mine et remblaye. Les simulations numeriques sont validees en comparant la geometrie de rupture predite avec des profils de chantiers sondes au laser avec un systeme de suivi de cavite. Il est demontre que les vibrations induites par les sautages peuvent etre une cause principale des ruptures en coin de la face de remblai. [Traduit par la Redaction] Mots-cles: remblai rocheux cimente, modelisation numerique, minage en bloc vertical, surveillance de cavite., Introduction Many Canadian metal mines have adopted a sublevel stoping method or one of its variations, such as blasthole stoping, vertical crater retreat, or vertical block mining (VBM) for the [...]

This research work presents the rock mass characteristics and tunnel support system recommendations for hydroelectric power tunnels at Dasu dam site Pakistan. Two inverted U-shaped tunnels are proposed at the left bank of Indus river. The tunnels have inlet portals at an elevation of 773.00 m and outlet portals at an elevation of 758.00 m. The thickness of rock cover above the tunnels is between 100 and 200 m. Three types of rock are encountered at project site including Granulite, Amphibolite and Gabbronorite. Granulite rocks are encountered along the alignment of tunnels. Rock mass is classified using Rock mass rating (RMR) and Tunneling quality index (Q system). Support system is suggested based on values of Q and RMR. Correlation between Q-index and RMR is also derived. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Sublevel stoping methods with delayed backfill are employed for mining tabular steeply dipping ore bodies. Cemented rockfill (CRF) is a type of backfill with simple operation, moderate capital cost while acquiring good strength. CRF stope is subjected to blast-induced vibrations during production blasting in adjacent stopes. Excessive dynamic load may destabilise backfill stope that leads to dilution of precious ore. Blast-induced vibrations can be monitored to assess the stability of CRF and to determine the blast waveforms for a detailed analysis using numerical models. This paper aims to establish that excessive blast-induced vibrations are the prime cause of backfill dilution at the case study mine. A detailed methodology and results of monitoring blast-induced vibrations in backfill are also presented. Blast vibrations are monitored in a CRF stope using three dimensional geophones and blast vibration monitors. The monitoring results obtained are processed and analysed to produce results in terms of velocity components and vector sum of velocity components. The data is further processed to examine particle velocity vs. scaled distances of individual blastholes and the effect of rock/backfill interface [ABSTRACT FROM AUTHOR]

Backfilling is one of the most critical tasks for sublevel stoping mining methods with delayed backfill. Selection of the type of backfill is a significant component of backfill design at preliminary stage of mine development. This paper presents a state-of-the-art review of backfill practices with focus on backfill operations in North America. Major difficulties and solutions in backfill practice have been laid down in this review. Preliminary recommendations are made for the case study mine based on the knowledge gained from the literature review andin situobservations. [ABSTRACT FROM PUBLISHER]

Rockburst is an unstable failure of a rock mass which is influenced by many factors. During deep excavations, the presence of nearby geological structures such as minor faults, joints, and shear zones increases the likelihood of rockburst occurrence. A shear zone has been observed in the headrace tunnel in the Neelum Jhelum Hydropower Project, Pakistan, which has played an important role in major rockburst events in the project's history. A rockburst is a seismic event that involves the release of a great amount of energy as the dynamic wave radiated from the seismic source reaches the excavation boundary. In this paper, the FLAC 2D explicit numerical code has been used to simulate the dynamic phenomenon of rockburst near the shear zone in a headrace tunnel. The behavior of the rock mass around the tunnel has been studied under both static and dynamic loading. According to modeling results, rockburst significantly affected the upper left quadrant of the tunnel similar to the actual failure profile with a depth of approximately 5 m. The dynamic impact of rockburst has also affected the loading conditions of the support system in the adjacent tunnel. This study elucidates one of the most important rockburst controlling factors through numerical analysis and recommends yielding support measures that can withstand the dynamic impacts of rockburst in deep, hard rock tunnels. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]