bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessing Pillar Stability in Underground Stone Mines: Impact of Geological Structures and Stress Variations in the Appalachian Region
Authors: Elibol A. , Tuncay D. , Agioutantis Z. 
Published: August 2024

ABSTRACT:
Roughly 29% of fatalities in underground stone mines have been associated with roof and pillar collapses from the beginning of 2002. The S-pillar software can assess how a significant joint set intersecting a pillar impacts the pillar's stability, but the approach doesn't account for the relative positioning of geological structures concerning the pillars or in cases where multiple joint sets intersect a single pillar. This study delves into the Northern and Central Appalachian region's horizontal stress variations and their influence on the stability of underground limestone mine pillars by investigating their effect on the reduction of the load-bearing capacity of pillars and the potential increase of the risk of pillar failure. Discontinuity sets extracted from point clouds acquired by Light Detection and Ranging (LiDAR) sensor and the stress data obtained from the World Stress Map are investigated in conjunction with the region's geological history. The maximum horizontal stresses in the Northern and Central Appalachian regions align along the NE-SW direction, contributing to the formation of folds, faults, and discontinuities in the region. These geological phenomena are attributed to the Alleghenian orogeny, representing a pivotal moment in the region's geological history. The research goes beyond the factors such as overburden load and terrain configuration and analyzes the historical geological events that have shaped the area. Expanding analysis of pillar systems to examine varying topographies, geometries and modeling the discontinuities in the area, and adjusting geological information will enhance mine safety considerations. These collapses have occurred in geologically weak zones where a high frequency of discontinuities exists, resulting from a distinctive stress distribution. The paper will present possible correlations between stress distribution, tectonic processes, the Appalachian orogeny, and the geological discontinuities within the pillars and their overall integrity since a significant amount of pillar collapses associated with pillar stability issues have occurred within the Central and Northern Appalachian orogeny.

1. INTRODUCTION
Mining operations, particularly in underground stone mines, face significant challenges in ensuring the stability and safety of miners and pillars. A concerning statistic reveals that approximately 29% of fatalities in these mines result from roof and pillar collapses since 2002 (Centers for Disease Control and Prevention. (n.d.)).
Analyzing the Effect of Bolt Spacing on Coal Rib Stability Through Numerical Simulation
Authors: Xue Y. , Mohamed K. M. 
Published: August 2024

ABSTRACT:
Rib falls pose a major safety risk in underground coal mines, and there is currently no standardized approach for rib support design in the U.S. coal mines. To tackle this issue, a standalone application, Design of Rib Support (DORS), was developed for rib stability assessment and rib support design under development load. The last step of the rib support design in DORS was to calculate the bolt spacing from the recommended rib support density, bolt grade and number of bolts. Notably, the change of bolt grade and the number of bolts significantly affects bolt spacing, but it remains unclear how varying bolt spacing impacts the supported rib factor of safety (RibFOS). In this study, numerical simulations were conducted to analyze the influence of bolt spacing on coal rib stability. Initially, plane-strain 3DEC models were used to estimate the RibFOS of unsupported solid coal ribs, serving as a baseline for rib stability evaluation. Subsequently, 3D models were conducted for supported solid coal pillar ribs. A parametric study was conducted to investigate the influence of bolt spacing on the supported RibFOS under different conditions, such as varying overburden depths and bolt lengths. The simulation results show a general trend of reduced supported RibFOS with the increase in bolt spacing, and the trend can be further affected by varying conditions. The variation of supported RibFOS with bolt spacing can be quantified by normalizing the supported RibFOS to its values with a bolt spacing of 0.3 m. Finally, when the rib support density was maintained by varying bolt grade and bolt spacing, the influence of bolt spacing can still be observed in the results. Thus, it is essential to consider this bolt spacing effect in rib support design.

1. INTRODUCTION
Coal pillars are intentionally retained during mining to support overlying rock strata and prevent mine roof collapse and play a crucial role in maintaining the structural integrity of underground coal mines. When coal is extracted from a seam, the overburden load and/or abutment load tend to transfer and redistribute to the remaining pillars, leading to excessive pillar load. Coal ribs are the walls of coal pillars with free surfaces. Without rib support, the coal mass has low or no confinement, leading to lower strength and less constraint for deformation. The occurrence of rib falls presents severe safety risks, encompassing injuries, fatalities, and equipment damage. According to the Mine Safety and Health Administration (MSHA), statistics during the 10-year period between 2010 and 2019, rib-fall accidents contributed to 45.2% of the ground-fall fatalities (Rashed et al. 2022). Thus, rib falls pose a major safety hazard in U.S. underground coal mines.
Concept Feasibility and Predicted Behavior of Mining a Rock Tower with Drill-And-Blast Undermining Using Dynamic Three-Dimensional Discontinuum Numerical Models
Authors: Abousleiman R. , Contreras C. I. , Cremeens J. , Worsey T. , Rouse N. 
Published: August 2024

ABSTRACT:
The safety and efficacy of a proposed novel mining method - felling a mineralized rock tower away from an adjacent river and towards an existing open pit using a wedge-shaped "key-cut" blast pattern and post-split hinge – was analyzed by integrating site-specific and site-adjacent data to develop a into a dynamic three-dimensional discrete element method numerical model. These data included historic laboratory testing and geomechanical core logging from the adjacent open pit, Lidar scans and geomechanical spot mapping of the rock tower, local signature blast seismic data, and proposed blast-pattern. Static and dynamic model stages were run to assess the pre-blast, syn-blast, and post-blast deformation of the mineralized rock tower. Model sensitivities to mesh size, dynamic time-step, block size, and joint strength were assessed. Ultimately, model results indicated that the proposed mining method would likely result in 97 percent retention of the blasted material within the existing open-pit, and only 3 percent of material would be cast towards the adjacent river.

1. INTRODUCTION
The Dragon's Tooth rock tower is located near the base of an existing open pit at Mine A along the bank of a perennial river (Figure 1). The rock tower extends 50 meters (m) vertically above the open pit bottom and ranges in diameter from approximately 20 m at the crown to approximately 40 m at its basal contact with the adjacent open pit. The Dragon's Tooth and underlying material contain gold ore but were not mined with the completion of the open pit due to limited safe access for conventional open-pit mining equipment.
Successful mining of the Dragon's Tooth depends on limiting the casting and sliding of large blocks (i.e., blocks that require re-blasting) towards the river and the volume of fill required for access. This will afford more ore recovery and avoid blocking the river for a prolonged period. Mine A contacted Dyno Consult (DC) to develop a method to safely collapse the mineralized tower away from the river. DC developed a wedge-shaped "key-cut" blast pattern (Figure 2) and post-split hinge to topple the rock tower towards the open pit. The safety and efficacy of the proposed method was assessed using numerical models.
Stress Variations Controlled by Rock Composition in an Appraisal Well in the US: Evaluating Lithology, Stress Measurements, and Methods
Authors: Cruz Leonardo , Jimba Solomon , Affinito Ralph , Husain Zoya 
Published: August 2024

ABSTRACT:
We evaluate stress and lithology relationships, compare least-stress test methods, and assess stress-from-logs empirical equations, from a recently drilled and tested appraisal vertical well in the continental US. We perform multiple least-stress tests in several intervals spanning multiple lithologies, and including containment, injection, and producing zones. The presence of carbonates, including limestones and dolomites, is a better predictor of high fracture gradient than any other lithology. The least-stress magnitude in the salts is very close to the overburden stress. The shales exhibit the lowest least-stress magnitude among all lithologies, and when the shale intervals are compared to each other, the carbonate content seems to control the trend. The least-stress magnitude in sandstones is highly variable. The commonly used Eaton's equation performs relatively poorly predicting stresses in the non-shale lithologies, but the extended Eaton's equation, using Biot's coefficient equal to one, compares adequately to the stress calibration points in most lithologies. The relatively recent viscoelastic stress relaxation equation applied to shales performed slightly better than the Eaton's equation but laboratory data or applicable correlation data from similar lithologies/basins are needed to confirm this trend. Differences in the stress magnitudes from the least-stress test methods are probably related to poroelastic effect, test order, and operational related issues.

1. INTRODUCTION
Predicting in-situ stresses in sedimentary basins has significant value to the Petroleum and Carbon Capture and Storage (CCS) industry. In particular, knowledge of the magnitude of the least principal stresses has been used to prevent fracturing the cap rock in CCS projects, identify hydraulic fracture containment in Unconventional plays, and reduce wellbore stability issues during drilling operations, among other applications. Stress contrast, in sedimentary basins, is often observed from layer to layer within intervals where the mineral composition changes. These interlayer principal stress variations have been measured and reported before (i.e., Anderson et al. 1973, Hickman et al. 1985, Warpinski 1989, Ma and Zoback 2020), and at least two explanations have been proposed: elastic properties contrast and stress relaxation within shales and clay-rich intervals. Interestingly, in some basins, shale and clay-rich formations show higher stresses than adjacent formations such as the Piceance basin in Colorado (Warpinski et al., 1985) and the Paris basin in France (Magnenet et al., 2017), but in others, the stresses in shales are comparatively low such as the Canning basin in Australia (Bailey et al., 2021).
Rockburst Damage Characterization in a South African Gold Mine Subjected to High Horizontal Stresses
Authors: Masethe R. , Wienand G. , Adoko A. C. , Zvarivadza T. 
Published: August 2024

ABSTRACT:
Rockburst risk can often be reduced by selecting appropriate mining or excavation methods, sequences, strategically placing developments, and other infrastructure. However, owing to the uncertainties in rock mass properties and boundary conditions, rock engineering design necessitates dependence on ground control measures reinforced with burst-resistant rock support to ensure safety at the workplace. High horizontal stress at depth aids the rockmass to be self-supporting by clamping the rockmass. It reduces the gravity-driven damages that could be experienced at the excavation, as stress-induced damages might become significant when mining goes deeper. Significant seismic events (ML≥0.9) are usually associated with large damages near any excavation in the underground workings. We analyzed the damage mechanisms of large mining-related seismic events (0.9≤ML0≤ 3.0) located within the shaft. The study indicates that with the large energy release, damages were only observed with fewer stopes. This is not only influenced by the high horizontal stresses but also by the rockmass mineralogical and contrasting geomechanical properties. The rockburst analysis within active mine infrastructure indicates that 63% large seismic events did not cause any damage to the mine infrastructure or cause injuries within the WAF.

1. INTRODUCTION
Rockburst is a significant occurrence that has impacted numerous deep underground mines worldwide. Understanding this phenomenon is essential for managing such catastrophic events, which can lead to substantial increase in investment risk and loss of lives. It results from an overstressed rock mass or an intact, brittle rock and occurs when the stresses exceed the material's compressive strength. It is associated with excavation damage and is characterized by its destructiveness, suddenness, and complexity (Feng et al., 2012). However, due to uncertainties in rock mass properties and boundary conditions, rock engineering design must rely on ground control measures with burst-resistant rock support to ensure workplace safety. This ground control strategy is a norm in the deep gold South African mines. The rockburst phenomenon is driven by various factors, including mining depth, rockmass conditions, geological structures, and mining elements (e.g., abutments, pillars, etc.). In recent years, research has been increasingly addressing the global topic of reducing the challenges of rockburst. Its mitigation or prevention remains as one of the most crucial problems to be solved in underground rock engineering.
Analyzing Shale Gas Well Casing Deformation in Pittsburgh Seam Longwall Chain Pillars: A Case Study Integrating Numerical Methods and Field Monitoring
Authors: Tulu I. B. , Zhang P. , Su D. , Khademian Z. , Kim B. H. 
Published: August 2024

ABSTRACT:
In the Northern Appalachian region of the U.S., the coexistence of longwall coal mining and shale gas operations is a prominent feature. The gas wells in the vicinity of the longwall operations entail the potential for casing deformations arising from mining-induced subsidence and abutment stresses. Researchers at the Pittsburgh Mining Research Division (PMRD) of the National Institute for Occupational Safety and Health (NIOSH) have been employing a combination of field monitoring and calibrated numerical modeling methods to formulate engineering strategies for assessing the effects of longwall mining operations on gas well casing integrity and implementing measures to mitigate potential damage. This paper introduces the numerical modeling approach developed by PMRD researchers and verifies it by comparing the model's predictions of longwall-induced casing deformations with measurements from shale gas wells located in the gateroad chain pillar of the Pittsburgh coal seam longwall operation. The longwall panels adjacent to gas well chain pillars operate at a depth of approximately 313 meters, with a mining height of 2.1 meters and panel widths ranges between 450 to 480 meters. The gas well is constructed with fully cemented surface and intermediate casings, with the production casing left uncemented from the surface down to below the Pittsburgh coal seam. The model predicted that, following the first panel mining, the production casing would remain deformation-free, as the maximum predicted intermediate casing deformation falls below the annular space between the intermediate and production casing. This model prediction was subsequently confirmed through casing deformations monitored using a multi-finger caliper survey following the mining of the first panel.

1. INTRODUCTION
Pennsylvania is the second largest natural gas producer in the U.S., and since the 2005 shale gas boom, thousands of unconventional gas wells have been drilled through the Pittsburgh coal seam where the coexistence of longwall coal mining and shale gas operations is a prominent feature (Zhang et al., 2023). Pittsburgh coal seam longwall mines on average extract 460-m-wide and 4,000-m-long panels. The gas wells in the vicinity of these longwall operations entail the potential for casing deformations arising from mining-induced subsidence and abutment stresses, and if the deformations would be large enough to damage casing, that would lead to potentially hazardous conditions for the mine workers. The Pittsburgh Mining Research Division (PMRD) of the National Institute for Occupational Safety and Health (NIOSH) started a research project in 2016 to formulate engineering strategies for assessing the effects of longwall mining operations on gas well casing integrity and implementing measures to mitigate potential damage.
Experimental Assessment of the Energy Dissipation and Deformation Capacity of Ground Support Systems Under Dynamic Loading: Insights from LaRonde Mine Dynamic Drop Test Program
Authors: Durham C. , Caron M-E. , Falmagne V. , Brändle R. 
Published: August 2024

ABSTRACT:
Over its 30-year history, the design of ground support schemes at the LaRonde mine has evolved significantly to meet the demands of the rock mass while mining from surface to the current depth of over 3000 m. Over the past decade, seismicity and dynamic loading on ground support systems have become a focus of ground control management and one of the major challenges at LaRonde mine. In some rare occurrences, dynamic loading from seismic events have exceeded the capacity of ground support schemes. Furthermore, the ground control practices implemented to safely manage seismic conditions in development drives have been largely successful despite the operational challenges of a deep mine. Thus, as the mine progresses ever deeper, there is a continuous need to implement ground support schemes that are not only tougher but also more efficient to install considering the mine configuration and available equipment. As part of this endeavor, a dynamic testing program was developed at Geobrugg's testing facility, in association with Geobrugg and the Kittilä mine. The test program involved various elements of ground support schemes from LaRonde and Kittilä mines. This paper presents the testing program, instrumentation set up and results analysis process as well as testing results for three of the LaRonde tests. The testing program is intended to guide improvements in ground support schemes designs for deep mining environments.

1. INTRODUCTION
Deep underground mining environments present unique challenges for the design of ground support schemes, particularly in zones susceptible to stress-induced rock failure and rockbursting. Traditional ground support schemes, designed primarily to control gravity-induced rockfalls in blocky rock masses, have been found to be unsuitable for such environments. For the sake of consistency, the authors have adopted the terminology proposed by Windsor and Thompson (1992) as presented in Villaescusa et al (2023). A Ground Support Scheme is therefore defined as a combination of a surface support system, composed of plates, mesh, liner or shotcrete, with an internal reinforcement system consisting of rockbolts and cable bolts. In blocky ground, under static conditions, the design of a ground support scheme aims primarily at meeting the load demand and minimizing deformation to maximize the reinforcement function. In weak and highly deforming ground, ground support schemes require increased ductility to meet the deformation demand while retaining load capacity. Under dynamic conditions, the ground support schemes must also satisfy energy dissipation, rapid rock mass deformation demands and ensure load transfer from the rock mass to the reinforcement, and to the surface support. The ground support elements' load and deformation characteristics must be matched to enable this load transfer.
Fracture Initiation and Propagation Characteristics of SC-CO2 Fracturing in Hot Dry Rock: A Coupled Thermal-Hydraulic-Mechanical-Damage Numerical Model Based on Phase Field Method
Authors: Zhou Xiaoxia , Wang Tianyu , Ma Zhengchao , Zhang Xu , Hsu Maoya , Sun Yaoyao , Tian Shouceng 
Published: August 2024

ABSTRACT:
Hydraulic fracturing is a pivotal technique for harnessing geothermal energy from HDR. Conventional hydraulic fracturing encounters formidable challenges, including high fracture initiation pressure and simplistic fracture geometry. In contrast, SC-CO2 fracturing represents a novel and promising stimulation method capable of mitigating these challenges. However, limited work has been conducted on studying the fracture initiation and propagation of SC-CO2 fracturing. To have a clear understanding of how geological engineering parameters affect SC-CO2 fracturing, numerical simulations were conducted under some key parameters (horizontal stress difference, permeability, elastic modulus, etc.) based on the THM-D phase-field model. Furthermore, using breakdown pressure as the evaluation criterion, the primary control factors were determined. Results showed that the breakdown pressure in SC-CO2 fracturing is dominated by pore water pressure, thermal stress, and SC-CO2. Thermal stress and SC-CO2 could induce multi-directional fractures and reduce breakdown pressure. Decreasing the horizontal stress differences, permeability, injection temperature, and fluid injection rate is conductive to inducing more complex fracture morphology. The growth in coefficient of thermal expansion and elastic modulus promotes the number of the fractures. Horizontal stress difference and injection temperature play a more important role in fracture initiation. The study aims to uncover the potential of SC-CO2 fracturing in HDR.

1. INTRODUCTION
Hot Dry Rock (HDR) is a kind of geothermal resource where no water or only a small amount of fluid exists inside the rock and the average temperature of HDR is typically above 180°C. HDR geothermal resources represent a stable, efficient, and clean renewable energy source unaffected by seasonal variations, applicable across power generation, heating, agriculture, and other sectors (Zhang et al., 2018; Zhou et al., 2020). Enhanced Geothermal Systems (EGS) play a pivotal role in harnessing HDR, employing hydraulic fracturing to create artificial fractures within the HDR reservoir, establishing high-conductivity pathways, and enabling stable and efficient heat extraction. However, conventional hydraulic fracturing techniques encounter challenges such as limited fracture propagation, reservoir hydrothermal mineralization reactions, and pipeline blockages. Consequently, Supercritical Carbon Dioxide (SC-CO2) emerges as a promising, environmentally friendly, and efficient fracturing medium (Xu et al., 2022; Li et al., 2021; Chen et al., 2021). SC-CO2 not only enhances reservoir transformation outcomes but also facilitates carbon utilization and storage during the fracturing process.