Search Results (5)

Addressing the stability control challenges of roadways with composite roofs in the No. 34 coal seam of Donghai Mine under high-strength mining conditions, this study employed integrated methodologies including laboratory experiments, numerical modeling, and field trials. It investigated the mechanical response characteristics of the composite roof and developed a synergistic control system, validated through industrial application. Key findings indicate significant differences in mechanical behavior and failure mechanisms between individual rock specimens and composite rock masses. A theoretical “elastic-plastic-fractured” zoning model for the composite roof was established based on the theory of surrounding rock deterioration, elucidating the mechanical mechanism where the cohesive strength of hard rock governs the load-bearing capacity of the outer shell, while the cohesive strength of soft rock controls plastic flow. The influence of in situ stress and support resistance on the evolution of the surrounding rock zone radii was quantitatively determined. The FLAC^3D strain-softening model accurately simulated the post-peak behavior of the surrounding rock. Analysis demonstrated specific inherent patterns in the magnitude, ratio, and orientation of principal stresses within the composite roof under mining influence. A high differential stress zone (σ₁/σ₃ = 6–7) formed within 20 m of the working face, accompanied by a deflection of the maximum principal stress direction by 53, triggering the expansion of a butterfly-shaped plastic zone. Based on these insights, we proposed and implemented a synergistic control system integrating high-pressure grouting, pre-stressed cables, and energy-absorbing bolts. Field tests demonstrated significant improvements: roof-to-floor convergence reduced by 48.4%, rib-to-rib convergence decreased by 39.3%, microseismic events declined by 61%, and the self-stabilization period of the surrounding rock shortened by 11%. Consequently, this research establishes a holistic “theoretical modeling-evolution diagnosis-synergistic control” solution chain, providing a validated theoretical foundation and engineering paradigm for composite roof support design. Full article

Anchor bolts, such as rock bolts and concrete anchors, are widely used in civil, geotechnical, and mining engineering for anchorage and ground support. They are used in retaining walls, dry docks, dams, mines, and prestressed concrete structures. Evaluating the grouting condition of anchor bolts is essential to ensure the safety of these applications. Spectrum techniques have been used to develop non-destructive methods for estimating the grouting quality of grouted anchor bolts. The spectrum methods include fast Fourier transform, time–frequency analysis, wavelet transform analysis, and empirical mode decomposition. In this study, we introduce the parameter-optimized variational mode decomposition (VMD) method for the spectrum analysis of impact echo signals of anchor bolts. This method overcomes the difficulty of conventional spectrum methods that cannot separate highly coupled natural modes for advanced analysis. The parameter-optimized VMD method enables the generation of a new evaluation index for quantifying bolt grouting conditions, which has the potential to significantly enhance the quality evaluation of anchor bolts compared with conventional analysis of natural frequencies. This study uses impact response to establish a new benchmark for the integrity diagnosis of anchor bolts, paving the way for more accurate and reliable safety assessments. Full article

This study offers insights into the management of intervention works aimed at conserving and revitalizing historical structures, focusing on the Bârnova Monastery in Iași, Romania. The study begins by contextualizing the broader challenges associated with preserving heritage churches and monastic buildings, elucidating the architectural characteristics and structural aspects typical of traditional Romanian Orthodox churches. Subsequently, the study delves into a detailed case analysis centered on the restoration of the medieval Bârnova Monastery, particularly its paramount structure, the Saint George Church, erected in the XVII century. This church exemplifies the traditional Orthodox architectural and structural norms prevalent during the medieval period. Through a structural diagnosis, the study identifies the vulnerabilities of the Saint George Church, which have been exacerbated by the impact of approximately 24 earthquakes of magnitudes exceeding 6.0 throughout its history. In response, a multifaceted approach to strengthening was devised, involving a combination of grouting and the installation of steel rods within vertically drilled galleries spanning the entire height of the walls. The adoption of this integrated strengthening strategy proved advantageous, significantly enhancing the seismic resilience of the church while simultaneously addressing the preservation needs of its historical features. This case study not only contributes to the body of knowledge on conservation and revitalization practices but also offers valuable insights into the effective management of intervention works for safeguarding heritage structures against seismic risks. Full article

Regenerated rice, characterized by single planting and double harvesting, saves labor and costs, significantly contributing to global food security. Hyperspectral imaging technology, which integrates image and spectral data, provides comprehensive, non-destructive, and pollution-free vegetation canopy analysis, making it highly effective for crop nutrient diagnosis. In this study, we selected two varieties of regenerated rice for field trials. Hyperspectral images were captured during key growth stages (flush, grouting, and ripening) of both the first and regenerated seasons. Utilizing a two-dimensional convolutional neural network (2D-CNN) as a deep feature extractor and a fully connected layer for nitrogen content prediction, we developed a robust model suitable for estimating nitrogen content in regenerated rice. The experimental results demonstrate that our method achieves a mean squared error (MSE) of 0.0008, significantly outperforming the back-propagation (BP) network and multiple linear regression by reducing the MSE by 0.0151 and 0.0247, respectively. It also surpasses the one-dimensional convolutional neural network (1D-CNN) by 0.003. This approach ensures accurate nitrogen content prediction throughout the growth cycle of regenerated rice, aiding in yield and economic benefit enhancement. Full article

When a building façade does not meet its performance requirements, the integrity and safety of the structure may be compromised, resulting in the reduction of the building’s service life. Ceramic tiles are a commonly applied cladding solution due to their aesthetic value and durability. However, as soon as ceramic claddings are installed, the claddings are subjected to various degradation agents, thus starting a degradation process in which different anomalies occur sequentially and simultaneously over the years. This study intends to find patterns of incidence of anomalies in distinct areas of the façade and to map the risk of occurrence of a given anomaly. For that purpose, 345 ceramic claddings are analysed (46 buildings, corresponding to 81,500 m²) in the region of Brasília, Brazil. Four main defects are identified based on visual inspections and using auxiliary diagnosis techniques, namely (i) detachment of ceramic tiles; (ii) cracking; (iii) grout failure; (iv) efflorescence. The results reveal that the detachment is the most frequent defect. The sensitivity maps proposed allow identifying a certain pattern in the occurrence of defects on ceramic claddings, revealing that continuous walls, transition between floors, and the top of the building are areas critically vulnerable to defects. The results obtained allow mapping the sensitivity of each part of the ceramic claddings to a given defect, aiding the detection and diagnosis of the degradation condition when carrying out inspections on new façades. Full article