Search Results (35)

In deep mining engineering, grouting operations, although designed for reinforcement, inevitably induce microfracturing and associated microseismicity. Investigating the characteristics of grouting-induced microfractures in fractured rock masses is crucial for evaluating the grouting process and its effectiveness. Using the Wutongzhuang Mine as a case study, this paper first establishes mechanical criteria covering three stages—fracture filling, coupled permeation, and fracturing propagation—to analyze the process characteristics of grouting-induced microfractures. It reveals the mechanisms by which grouting pressure, in situ stress, and rock mass strength control fracture initiation and propagation. Furthermore, a grouting simulation method based on the Particle Flow Code (PFC) is proposed and summarized, constructing a “pipe-domain” fluid network considering fluid–solid coupling, thereby achieving a refined numerical reproduction of the entire grouting process. Addressing the complex geological conditions of the mine, three typical grouting modes are simulated and analyzed: grouting under conventional geological conditions, grouting under densely fractured conditions, and grouting near fault structures. The simulation results unveil their core influencing factors and behavioral characteristics: under conventional conditions, microfractures exhibit a “three-stage” evolution with the grouting process; under densely fractured conditions, the density of pre-existing fractures dominates the formation of complex fracture networks; and finally, fault structures guide fracture propagation, causing microfractures to cluster nearby. Subsequently, the development trends of microfractures under different grouting effects are clarified: after effective reinforcement, the rock mass strength increases, and the scope and quantity of fractures induced by subsequent grouting significantly decrease. The behavioral patterns under these different grouting modes are effectively validated through field microseismic monitoring, confirming the intrinsic relationship between the spatio-temporal evolution of grouting-induced microfractures and geological structures/grouting techniques. Finally, laboratory tests are conducted using a self-developed experimental apparatus, selecting grouting pressure, pore water pressure in the rock mass, and matrix grain size as variables. The mapping relationships between these variables and microseismic waveform characteristics, amplitude, etc., under different schemes are obtained, providing a basis for inverting the microfracturing process and evaluating grouting effectiveness. The research results provide multi-faceted references for characterizing the stability of fractured rock masses via microseismic monitoring and for optimizing grouting effectiveness. Full article

This paper provides an in-depth analysis of the microstructural characteristics and the chemical content of Polybutylene Terephthalate (PBT) composites that have different contents of Glass Fiber (GF). Blending of VALOX 420 (30 wt% GF/PBT) with unreinforced VALOX 310 allowed the composites to be prepared, with control of the concentration and distribution of the GF. The GF reinforcement and PBT matrix were characterized by an advanced microstructural spectrum and spatial analysis to show the influence of fiber density, dispersion, and chemical composition on performance. Findings indicate that GF content has a profound effect on microstructural properties and damage processes, especially traction effects in various regions of the specimen. These results highlight the significance of accurate control of GF during fabrication to maximize durability and performance, which can be used to inform the design of superior PBT/GF composites in challenging engineering applications. The implications of these results are relevant to a number of high-performance sectors, especially in automotive, electrical, and consumer electronic industries, where PBT/GF composites are found in extensive use because of their outstanding mechanical strength, dimensional stability, and thermal resistance. The main novelty of the current research is both the microstructural and chemical assessment of PBT/GF composites in different fiber contents, and this aspect is rather insufficiently studied in the literature. Although the mechanical performance or macro-level aging effects have been previously assessed, the Literature usually did not combine elemental spectroscopy or spatial microstructural mapping to correlate the fiber distribution with the damage mechanisms. Further, despite the importance of GF reinforcement in achieving the right balance between mechanical, thermal, and electrical performance, not much has been conducted in detail to describe the correlation between the microstructure and the evolution of damage in short-fiber composites. Conversely, this paper will use the superior spatial elemental analysis to bring out the effects of GF content and dispersion on micro-mechanisms like interfacial traction, cracking of the matrix, and fiber fracture. We, to the best of our knowledge, are the first to systematically combine chemical spectrum analysis with spatial mapping of PBT/GF systems with varied fiber contents—this allows us to give actionable information on material design and optimized manufacturing procedures. Full article

Formation MicroScanner Image (FMI) technology is a key method for identifying fractured reservoirs and optimizing oil and gas exploration, but its inherent insufficient resolution severely constrains the fine characterization of geological features. This study innovatively applies a Super-Resolution Generative Adversarial Network (SRGAN) to the super-resolution reconstruction of FMI logging image to address this bottleneck problem. By collecting FMI logging image of glutenite from a well in Xinjiang, a training set containing 24,275 images was constructed, and preprocessing strategies such as grayscale conversion and binarization were employed to optimize input features. Leveraging SRGAN’s generator-discriminator adversarial mechanism and perceptual loss function, high-quality mapping from low-resolution FMI logging image to high-resolution images was achieved. This study yields significant results: in RGB image reconstruction, SRGAN achieved a Peak Signal-to-Noise Ratio (PSNR) of 41.39 dB, surpassing the optimal traditional method (bicubic interpolation) by 61.6%; its Structural Similarity Index (SSIM) reached 0.992, representing a 34.1% improvement; in grayscale image processing, SRGAN effectively eliminated edge blurring, with the PSNR (40.15 dB) and SSIM (0.990) exceeding the suboptimal method (bilinear interpolation) by 36.6% and 9.9%, respectively. These results fully confirm that SRGAN can significantly restore edge contours and structural details in FMI logging image, with performance far exceeding traditional interpolation methods. This study not only systematically verifies, for the first time, SRGAN’s exceptional capability in enhancing FMI resolution, but also provides a high-precision data foundation for reservoir parameter inversion and geological modeling, holding significant application value for advancing the intelligent exploration of complex hydrocarbon reservoirs. Full article

This paper focuses on the study of the tensile fracture behaviour of prismatic notched specimens of cold drawn pearlitic steel, providing a macro- and micro-approach. Two types of notched samples with very different notch radius (sharp and blunt notches, PAA and PCC) and the same notch depth were studied, thereby allowing a study of the fracture behaviour under different levels of stress triaxiality (constraint) in the experimental specimen. The studied samples are machined from pearlitic steel wires taken from a real cold drawing chain, analysing the entire drawing process, from the initial base material (hot rolled bar; not cold drawn at all) to the final commercial product (prestressing steel wires; heavily cold drawn), including two intermediate stages in the manufacture chain. The aforesaid specimens were subjected to tensile fracture tests and analysed at macroscopic and microscopical level using the scanning electron microscope (SEM), thereby obtaining micrographs of the different areas appearing in the specimens under study and assembling full micro-fracture maps (MFMs) of the fractured area. The aim of the research is to analyse the macro- and microscopic changes produced by the variation in stress triaxiality state (constraint), along with the different fracture processes. The first relevant finding is the increase in fracture path deflection for higher drawing degrees, and for greater triaxiality levels associated with sharp notches. Another finding is the variation in area of the different fracture zones, i.e., outer crown (OC), fracture process zone (FPZ) and intermediate zone (Z_INT), which are characterised by their specific micro-mechanisms, micro-void coalescence (MVC), cleavage (C) and special (large) micro-void coalescence (MVC*). The higher the stress triaxiality level, the larger the area occupied by the Z_INT in the fracture process. The fracture behaviour tends to unify along with the degree of drawing, with less dependence on the state of triaxiality imposed on heavily drawn wires. Results have been obtained in which the increase in triaxiality, imposed by the smaller radius of curvature of the notch (sharp notch), as well as the greater degree of drawing of the wires, cause the fracture process to place the FPZ at the notch tip. It is demonstrated that the variation in stress triaxiality and the drawing degree can generate different locations of the fracture initiation zone (FPZ). Full article

Tuffaceous fillings are a significant component of the Permian Kuishan sandstone in the North China Platform, and their complex diagenetic processes have a notable impact on the development of clastic rock reservoirs. This study, based on microscopic analysis of reservoirs and combined with quantitative analytical techniques such as electron probe microanalysis, homogenization temperatures of fluid inclusions, micro-area carbon-oxygen isotope analysis, and laser Raman spectroscopy, investigates the influence of tuffaceous interstitial material dissolution on reservoir development in the Permian Kuishan sandstone of the Gaoqing buried hill in the Jiyang Depression, Bohai Bay Basin. The results indicate that the dissolution intensity of tuffaceous interstitial materials can be classified into three levels: strong, moderate, and weak. In the strong dissolution zone, associated fractures and dissolution pores significantly contribute to reservoir porosity, with a positive correlation between dissolution plane porosity and total plane porosity. The reservoir space is characterized by a network of dissolution pores and fractures. The moderate dissolution zone is marked by the development of authigenic quartz, feldspar, and clay minerals, which do not effectively enhance porosity and permeability. The weak dissolution zone contains well-preserved volcanic glass shards, crystal fragments, and clay minerals, representing non-reservoir development sections. Lithology, sedimentary facies, diagenesis, and fractures collectively control the quality of the Permian Kuishan sandstone reservoir in the Gaoqing buried hill of the Jiyang Depression, Bohai Bay Basin. The advantageous zones for reservoir development in this area can be effectively predicted using thickness maps of the Kuishan sandstone, planar distribution maps of sedimentary facies, and fracture prediction maps derived from ant-tracking and coherence algorithms. Full article

This study examines fracture-induced electromagnetic radiation (FEMR) to assess tectonic stress in the Ramon Crater, a geologically “stable” area in southern Israel. With its minor seismic activity, the Ramon Crater poses unique challenges for traditional methods of stress assessment. Here, we introduce FEMR as a novel approach for detecting regional stress orientations by capturing electromagnetic pulses from micro-cracks formed under stress. These FEMR pulses provide indirect but valuable indicators of stress directions on both local and regional scales, demonstrating FEMR’s capability to detect subtle stress changes even in low-activity regions. The findings show that FEMR offers a scalable and sensitive method for mapping stress orientations in stable tectonic environments, making it a promising alternative to conventional seismic techniques. This application of FEMR opens new avenues for understanding regional stress fields in areas with limited seismicity, providing critical insights into tectonic stress behaviors that influence faulting and fracture dynamics in such stable regions. Full article

Construction projects in deep underground engineering are associated with the recording of massive amounts of diversified signals during real time and continuous microseismic monitoring given the complexity and specificity of the construction environment. Before the analysis of source information and further prediction of possible disasters, it is generally necessary to perform onset time picking and detection of microseismic signals. To improve the accuracy and efficiency of these tasks, this paper proposes an advanced deep dual-task neural network, which sequentially integrates the two processes. In this method, a score map is used to label the onset time of micro-fracture waveforms to improve the picking accuracy. The proposed model can simultaneously handle the onset time picking and detection tasks of microseismic signals to achieve optimal performance. Based on the similarity of data structures, the output from the onset time picking section is imported into the detection section to classify different types of microseismic waveforms. The onset time picking and detection procedures can be seamlessly integrated, where the score map of the onset time can help improve the detection accuracy. The results show that this method has a good performance for the onset time picking and detection of microseismic waveforms that are polluted by noises of various types and intensities. A comparison of the proposed method with existing methods and applications in underground engineering projects helped demonstrate the excellent performance of this method. The proposed approach can accelerate the automatic processing of microseismic signals and has significant potential for the exploration of seismology and earthquake research. Full article

The Um Ara granites are a suite of granitoid rocks located in the southern part of the Eastern Desert of Egypt. The integration of various electron probe micro analyzer (EPMA) techniques, such as backscattered electron (BSE) imaging, X-ray compositional mapping, and wavelength dispersive spectrometry (WDS), has provided valuable insights into the alteration process of zircon in the Um Ara granite. The zircon exhibits high concentrations of non-formula elements such as P, Al, Ca, Fe, Ti, and REEs, suggesting that the alteration involved coupled dissolution-reprecipitation processes influenced by aqueous fluids. The negative correlations between Zr and the non-formula elements indicate that these elements were incorporated into zircon at the expense of Zr and Si, significantly affecting the distribution and fractionation of REEs in the original zircon. Based on the presented data and literature knowledge, the sequence of alteration events is proposed as follows: (1) initial zircon crystallization around 603 Ma accompanied by the formation of other U- and Th-bearing minerals like xenotime, thorite, monazite, and apatite; (2) long-term metamictization leading to fractures and cracks that facilitated fluid circulation and chemical changes; (3) a major hydrothermal event around 20 Ma that released a suite of non-formula elements from the metamicted zircon and associated minerals, with the enriched hydrothermal fluids subsequently incorporating these elements into the modified zircon structure; and (4) further low-temperature alteration during subsequent pluvial periods (around 50,000–159,000 years ago), facilitated by the shear zones in the Um Ara granites, may have allowed further uptake of non-formula elements. The interplay between hydrothermal fluids, meteoric water, and the shear zone environments appears to have been a key driver for the uptake of non-formula elements into the altered zircon. Full article

The influence of damping and friction performance of grinding wheels on precision grinding was explored for the first time. GO hybrid PU-modified PF copolymers were prepared by in situ synthesis and adopted as a matrix for fabricating grinding wheels. FT-IR, DSC, TG, and mechanical property tests showed the optimal modification when PU content was 10 wt% and GO addition was 0.1 wt%. Damping properties were investigated by DMA, and tribological characteristics were measured by sliding friction and wear experiments. The worn surfaces and fracture morphologies of GO hybrid PU–PF copolymers were observed by SEM. Distribution of components on the worn surfaces was explored by Raman mapping and EDS. The research results revealed that the PU component tended to be dispersed around the edges of corundum abrasives acting as a buffer layer of abrasive particles, which could provide micro-damping characteristics for abrasives, making the grinding force more stable during precision machining and facilitating a smoother surface quality of the workpiece. Full article

Pore structure and flow characteristics are key factors affecting oil recovery rates in heterogeneous tight conglomerate reservoirs. Using micron computed tomography (CT) and modular automated processing system (MAPS) techniques, the pore structure of downhole core samples taken from Mahu’s tight conglomerate reservoirs was analyzed in detail, and a two-scale digital core pore network model with both a wide field of view and high resolution was constructed based on these pore structure data; the digital pore model was corrected according to the mercury intrusion pore size distribution date. Finally, we simulated flow characteristics within the digital model and compared the calculated permeability with the indoor permeability test date to verify the dependability of the pore network. The results indicated that the pore–throat of the conglomerate reservoir in Mahu was widely distributed and exhibited significant bimodal characteristics, with main throat channels ranging from 0.5 to 4 μm. The pore structure showed pronounced microscopic heterogeneity and intricate modalities, mainly consisting of dissolved pores, intergranular pores, and microfractures. These pores were primarily strip-like, isolated, and played a more crucial role in enhancing pore connectivity rather than contributing to the overall porosity. The matrix pores depicted by the MAPS were relatively smaller in size and more abundant in number, with no individual pore type forming a functional seepage channel. The permeability parameters obtained from the two-scale coarse-fine coupled pore network aligned with the laboratory experimental results, displaying an average coordination number of two. Flow simulation results indicated that the core’s microscopic pore structure affected the shape of the displacement leading edge, resulting in a tongue-in phenomenon during oil–water flow. The dominant flow channel was mainly dominated by water, while tongue-in and by-pass flow were the primary microscopic seepage mechanisms hindering oil recovery. These findings lay a foundation for characterizing and analyzing pore structure as well as investigating flow mechanisms in conglomerate reservoirs. Full article

This article reports the elastoplastic and viscoelastic response of an industrially cured CAD/CAM resin-based composite (Brilliant Crios, Coltene) at different scales, spatial locations, aging conditions, and shading. Mechanical tests were performed at the macroscopic scale to investigate material strength, elastic modulus, fracture mechanisms and reliability. An instrumented indentation test (IIT) was performed at the microscopic level in a quasi-static mode to assess the elastic and plastic deformation upon indentation, either by mapping transverse areas of the CAD/CAM block or at randomly selected locations. A dynamic-mechanical analysis was then carried out, in which chewing-relevant frequencies were included (0.5 to 5 Hz). Characteristics measured at the nano- and micro-scale were more discriminative in identifying the impact of variables as those measured at macro scale. Anisotropy as a function of the spatial location was identified in all shades, with gradual variation in properties from the center of the block to peripheral locations. Depending on the scale of observation, differences in shade and translucency are very small or not statistically significant. The aging effect is classified as low, but measurable on all scales, with the same pattern of variation occurring in all shades. Aging affects plastic deformation more than elastic deformation and affects elastic deformation more than viscous deformation. Full article

Organic matter serves as the hydrocarbon-generating parent material for shale reservoirs, in which organic pores are also important reservoir spaces. Different types of organic matter have wide differences in hydrocarbon generation and pore-forming ability. Based on the occurrence state of organic matter, in the over-mature Marine shale organic matter mainly includes in situ and migrated organic matter. It has been extensively studied on in situ organic matter and organic matter migrating into inorganic pores, while there are few reports of organic matter migrating into microfractures. In this study, the over-mature Marine shale reservoir in the first sub-member of the Silurian Longmaxi Formation in the Luzhou area of the Sichuan Basin is taken as an example. Core observation, optical microscope, high-precision large-view scanning (MAPS, modular automated processing system) and mineral analysis scanning (QEMSCAN, quantitative evaluation of minerals by scanning electron microscopy) were conducted to observe the morphological characteristics of organic matter veins, and then analyze the genesis and pore-forming characteristics of such organic matter. The results show that: ① Organic matter veins (OM veins) are soluble organic matter with fractures as an effective channel, and OM veins in the study section is easy to form under the condition of micro-fractures in the shale sweet segment after organic matter generating oil and before gas generation ② Organic matter in the OM veins are less efficient in pore-forming, with sparse pores and smaller pore sizes. The occurrence of fractures varies greatly, including horizontal fractures, oblique fractures and high-angle fractures, which are mostly developed in the Long1₁¹ and Long1₁² layers. ③ The development of OM veins can indicate better reservoir conditions, that is, the layers have strong hydrocarbon generation intensity (strong pore-forming ability of organic matter) and high brittle mineral content (strong reservoir compressibility). The new findings in this paper reveal that OM veins are instructive for the determination of geological–engineering sweet spots in the Longmaxi Formation in the Sichuan Basin, and also provide guidance for future research on occurrence form and geological significance of different types of organic matter. Full article

The study of microfractures in shale is mainly based on qualitative description. Conversely, quantitative description of the parameters of shale microfractures can provide a quantitative basis for shale fracture characterization and shale physical properties. Nine shale reservoir samples of the Wufeng–Longmaxi Formation in the Jiaoshiba area were studied, using the backscattered two-dimensional multiscale resolution imaging technology, combined with high-resolution map imaging technology (MAPS), and thousands of images were obtained using scanning electron microscopy. Gray image analysis was used to extract microfracture information from images (2 × 2 cm multiresolution). The “maximum circle method” was used to calculate the length and aperture characteristics of the fractures. Parameters such as the area of the bedding fractures, the surface rate of the fractures, and the linear density of the fractures were obtained by the integration of apertures. The fracture length was between 2~7 mm, the aperture was between 1~6 μm, the linear density was between 1~6/m and the surface rate was 1%. The bedding fractures do not contribute much to the porosity of the shale reservoir; however, shale reservoirs with high porosity have a high development of bedding fractures and good permeability. The development of a bedding fracture is controlled by the lithology within shale reservoirs. Different types of lithology contain different bedding fractures, but they have a certain regularity. Moreover, the content of organic matter and TOC (total organic content) in the shale reservoir control the development of a bedding fracture, where a high organic and TOC content are accompanied by a high number of fractures. Full article

Bone structure metrics are vital for the evaluation of vertebral bone strength. However, the gold standard for measuring bone structure metrics, micro-Computed Tomography (micro-CT), cannot be used in vivo, which hinders the early diagnosis of fragility fractures. This paper used an unpaired image-to-image translation method to capture the mapping between clinical multidetector computed tomography (MDCT) and micro-CT images and then generated micro-CT-like images to measure bone structure metrics. MDCT and micro-CT images were scanned from 75 human lumbar spine specimens and formed training and testing sets. The generator in the model focused on learning both the structure and detailed pattern of bone trabeculae and generating micro-CT-like images, and the discriminator determined whether the generated images were micro-CT images or not. Based on similarity metrics (i.e., SSIM and FID) and bone structure metrics (i.e., bone volume fraction, trabecular separation and trabecular thickness), a set of comparisons were performed. The results show that the proposed method can perform better in terms of both similarity metrics and bone structure metrics and the improvement is statistically significant. In particular, we compared the proposed method with the paired image-to-image method and analyzed the pros and cons of the method used. Full article

The Gulong shale oil reservoir is situated in freshwater to slightly saline lacustrine basins mainly consisting of a pure shale geological structure, which is quite different from other shale reservoirs around the world. Currently, the development of Gulong shale oil mainly relies on hydraulic fracturing, while the subsequent shut-in period for imbibition has been proven to be an effective method for enhancing shale oil recovery. To clarify the characteristics of the fluid occurrence space and the variation in the fluid occurrence during saltwater imbibition in Gulong shale, this paper carried out porosity and permeability tests on Gulong shale cores and analyzed the fluid occurrence space characteristics and imbibition oil recovery based on nuclear magnetic resonance (NMR). In the porosity and permeability tests, T₂ distributions were used to correct the porosity measured by the saturation method to obtain the NMR porosity. Combined with the identification of fractures in shale cores using micro-CT and the analysis of porosity and permeability parameters, it was found that the permeability of the shale cores was related to the development of fractures in the shale cores. Through the testing and analysis of T₁-T₂ maps of the shale cores before and after saturation with oil, it was found that the shale mainly contained heavy oil, light oil, and clay-bound water, and they were distributed in different regions in the T₁-T₂ maps. Finally, the T₁-T₂ maps of the shale cores at different imbibition stages were analyzed, and it was found that saltwater mainly entered the minuscule inorganic pores of clay minerals during the imbibition process and squeezed the larger-sized inorganic pores containing light oil through the hydration expansion effect, thus expelling the light oil from the shale core and achieving the purpose of enhanced oil recovery. Full article