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We document the tectonic and metamorphic evolution of thrust nappes of the eastern island of Elba. The area exposes a natural cross section of the Northern Apennines hinterland, from the metamorphic basement units to the overlying continent- and ocean-derived nappes. We integrated mapping, analysis of structures and microstructures, and the interpretation of drill core logs with lithostratigraphic, metamorphic, and geochronological constraints, producing a novel geological map of eastern Elba (1:5'000 scale). We show that the area experienced polyphase Oligocene - Pliocene contractional tectonics marked by in-sequence and out-of-sequence thrusting accompanied by folding and overprinted by faulting in the Pliocene. Magmatism occurred during contraction with post-magmatic thrusting ultimately coupling HP-LT and LP-HT units. Drill core logs allow for the first time the reconstruction of the N-dipping character of the Zuccale Fault, which represents the youngest (late Miocene - early Pliocene) large-scale structure in the area.

Significant uncertainties remain regarding the field assessment of the peak shear strength of rock joints. These uncertainties mainly originate from the lack of a verified methodology that would permit prediction of rock joints’ peak shear strength accounting for their surface area, while using information available from smaller samples. This paper investigates a methodology that uses objective observations of the 3D roughness and joint aperture from drill cores to predict the peak shear strength of large natural, unfilled rock joints in the field. The presented methodology has been tested in the laboratory on two natural, unfilled rock joint samples of granite. The joint surface area of the tested samples was of approximately 500 × 300 mm. In this study, the drill cores utilised to predict the peak shear strength of the rock joint samples are simulated based on a subdivision of their digitised surfaces obtained through high-resolution laser scanning. The peak shear strength of the tested samples based on the digitised surfaces of the simulated drill cores is predicted by applying a peak shear strength criterion that accounts for 3D roughness, matedness, and specimen size. The results of the performed analysis and laboratory experiments show that data from the simulated drill cores contain the necessary information to predict the peak shear strength of the tested rock joint samples. The main benefit of this approach is that it may enable the prediction of the peak shear strength in the field under conditions of difficult access.HighlightsThe peak shear strength of two large-size rock joint samples is predicted based on small-size drill cores simulated on their joint surfaces.The results obtained show that the simulated drill cores contain the necessary information to predict the peak shear strength of the tested samples.A sufficient number of simulated drill cores needs to be used to reduce the statistical uncertainty of the predicted values of peak shear strength.The rock joint aperture needs to be accounted for and measured directly in the borehole under the prevailing level of normal stress.The main benefit of this approach is that it may enable the prediction of the peak shear strength in the field under conditions of difficult access.

This book offers a reference for the interpretation of natural and induced fractures in cores. The natural and induced fracture data contained in cores provides a wealth of information once they are recognized and properly interpreted. Written by two experts in the field, this resource provides a much-needed tool to help with the accurate interpretation of these cores. The authors include the information needed to identify different fracture types as well as the criteria for distinguishing between the types of fractures. The atlas shows how to recognize non-fracture artefacts in a core since many of them provide other types of useful information. In addition, the text's illustrated structures combined with their basic interpretations are designed to be primary building blocks of a complete fracture assessment and analysis. The authors show how to recognize and correctly interpret these building blocks to ensure that subsequent analyses, interpretations, and modeling efforts regarding fracture-controlled reservoir permeability are valid.

Rock quality designation (RQD) characteristics for assessing the degree of rock mass fracture make it a key parameter in rock grading or other rating systems. Traditional core characterization relies on subjective manual visual inspection by geologists. Currently, convolutional neural networks are used in borehole images to classify intact and nonintact cores in core rows for automatic RQD estimation. Classification networks cannot predict the exact locations of the intact cores, and drill core characterization is not intuitive. Alternatively, an attention mechanism combining channel and spatial attention modules is proposed to improve the YOLOv5 algorithm for drill core characterization. The model was trained on 657 artificial core tray images generated by the developed preprocessor to accurately predict the bounding boxes of the intact cores on the row centerline, and the automatic RQD calculation of the row was implemented with the developed postprocessing program. Our method performed RQD estimation on 602 new granite rows and 180 new quartz sandstone rows, with average error rates of 1.27% and 1.12%, respectively. It processed 50 m of cores on average in 1 s on a GPU. Furthermore, this method provides an innovative method for automatically processing and quantifying geological image databases.HighlightsDrill core images are automatically analyzed to estimate the RQD of the rows.An attention mechanism combining channel and spatial attention modules is proposed.YOLOv5 is combined with an attention mechanism for detecting intact cores.The proposed method is tested on granite and quartz sandstone images, yielding an average error rate of 1.24%.

SiCf/SiC composites have promising applications in aerospace industries. SiCf/SiC composite micro-holes are important components, such as gas film holes on turbine blades. However, micro-hole machining in the SiCf/SiC composite is challenging because of its excellent mechanical and physical properties and poor machinability caused by micro-hole constraints. Therefore, a novel brazed diamond abrasive core drill was designed to achieve high self-sharpness by continuously losing blunt diamond grits and exposing sharp diamond grits. The wear and self-sharpness of the developed drill were investigated and compared with those of an electroplated diamond core drill during ultrasonic vibration-assisted drilling of SiCf/SiC composite micro-holes. The material removal behaviors of SiCf/SiC composites, including drilling forces, exit tearing, hole dimensions, hole wall quality, and the wear of core drills, were also studied. The developed core drill demonstrated reduced drilling force and a significantly prolonged lifetime. Further, it achieved superior drilling performance, drilling accuracy, and micro-hole quality.

This Second Edition has been brought up-to-date and incorporates modern developments in coring techniques and core handling. All aspects of cores are covered including cutting and recovery; wellsite handling and logging; recognition of coring damage; laboratory analysis; logging and sampling; preservation and storage. Logging and interpretation are dealt with in detail, encompassing structural and engineering investigations in addition to sedimentology. Emphasis is laid throughout on those features most important to the economical development of geological resources.

This book is based on the standard lithostratigraphy and method of engineering description of Chalk developed over many years. Also important are over 3000 onshore and offshore chalk-cored boreholes undertaken by the author over more than 30 years. In addition, typical lithologies and weathering profiles representing the Chalk formations likely to be encountered in the various onshore and offshore construction projects are illustrated using field exposures, rotary core samples and geophysical borehole wire-line logs. There will be geological settings where information on the Chalk is poor and unexpected lithologies and stratigraphies may be found. This book will enable geologists to work from first principles to construct a lithostratigraphy and define weathering boundaries.

The increase in environmental awareness, energy saving, and carbon reduction means that demand for advanced materials for high-tech industries is increasing. Composite materials are widely used in structural components for various industrial applications because they feature light weight, high strength, corrosion resistance, and high durability. For final assembly processes for these composite material structural components (CMSCs), hole-drilling using a twist drill (TD) is a fast and inexpensive process. A step elliptical sphere-core drill (SESCD), which is a special compound drill, is composed of a TD and an elliptical sphere-core drill (ESCD). It prevents chip jamming and reduced thrust force (non-edge thrust) at the exit hole better than a step sphere-core drill (SSCD). Studies also show that CMSCs can delaminate during drilling if the thrust force is too great. This study determines the difference in the critical thrust force (CTF) for a SESCD and a TD for drilling composite materials. The results show that the CTF for a SESCD is increased by ~ 75% if s > 0.84 over that for a TD for various values of β (the ratio between the thickness of the ESCD ( t ) and the radius of the ESCD ( c )). This design for a SESCD increases the drilling quality of composite materials and provides direction for future tool innovation.

The objective of this study is to systematically examine the drilling efficiency and performance of various core drill bits in lunar rock formation using the discrete element method (DEM) and drilling experiments conducted in a lunar vacuum environment. This research aims to establish a scientific foundation for selecting core drill bits for lunar deep drilling operations. To achieve this, four distinct core drill bits were designed. Subsequently, a numerical model of lunar rock was constructed and the load characteristics and drilling efficiency of each bit during the drilling process were analyzed using DEM. Drilling and coring tests were then performed in both atmospheric and lunar vacuum environments, thereby validating the numerical simulation results and providing a comprehensive evaluation of the actual performance of the core drill bits. The study revealed that the carbide-tipped core drill bit with octagonal prisms design resulted in the core disking due to a significant rise in temperature, underscoring the critical importance of temperature control in maintaining core integrity. While the carbide-tipped core drill bit with cutting edges demonstrates exceptional drilling efficiency and coring quality, its inherent fragility and rapid wear of the cutting edges present considerable challenges for practical application. The diamond-impregnated core drill bit is unsuitable for drilling operations under lunar loads and power limitations due to its high weight-on-bit (WOB) requirements. In contrast, the PDC core drill bit exhibits excellent drilling stability, low rotary torque requirements, minimal temperature-rise effects, and significantly enhanced penetrating speed in the lunar vacuum environment, making it a recommended choice for lunar rock drilling. This study provides substantial theoretical and experimental support for the development of lunar drilling equipment and the formulation of effective drilling strategies. Highlights An improved HMB contact model was used in the numerical simulation calculations. Simulated lunar rock drilling tests were conducted in both atmospheric and vacuum environments, and a comparative analysis was performed with the numerical simulation results. Among the four self-designed drill bits, the PDC bit was identified as the most suitable for lunar rock drilling through comparative selection.

Lithology identification is a critical aspect of geoenergy exploration, including geothermal energy development, gas hydrate extraction, and gas storage. In recent years, artificial intelligence techniques based on drill core images have made significant strides in lithology identification, achieving high accuracy. However, the current demand for advanced lithology identification models remains unmet due to the lack of high-quality drill core image datasets. This study successfully constructs and publicly releases the first open-source Drill Core Image Dataset (DCID), addressing the need for large-scale, high-quality datasets in lithology characterization tasks within geological engineering and establishing a standard dataset for model evaluation. DCID consists of 35 lithology categories and a total of 98,000 high-resolution images (512 × 512 pixels), making it the most comprehensive drill core image dataset in terms of lithology categories, image quantity, and resolution. This study also provides lithology identification accuracy benchmarks for popular convolutional neural networks (CNNs) such as VGG, ResNet, DenseNet, MobileNet, as well as for the Vision Transformer (ViT) and MLP-Mixer, based on DCID. Additionally, the sensitivity of model performance to various parameters and image resolution is evaluated. In response to real-world challenges, we propose a real-world data augmentation (RWDA) method, leveraging slightly defective images from DCID to enhance model robustness. The study also explores the impact of real-world lighting conditions on the performance of lithology identification models. Finally, we demonstrate how to rapidly evaluate model performance across multiple dimensions using low-resolution datasets, advancing the application and development of new lithology identification models for geoenergy exploration.