During tunnel excavation, blasting dynamics cause substantial damage to surrounding rock mass in thin bedrock roof conditions, while roof thickness progressively increases along the advancing direction. Current support schemes lack differentiated designs to accommodate varying roof thicknesses across tunnel sections. Focused on the Qingdao Tangshan Road Tunnel, this study defined a damage variable through dominant frequency attenuation analysis during blasting excavation of the surrounding rock mass. A quantitative relationship between blasting damage and the distance to the blast center was established to assess the severity of roof rock damage. Using 3DEC discrete element software, a three-dimensional numerical simulation of the continuous blasting excavation process for 9 pilot tunnels and 5 sections was conducted, with rock mass mechanical parameters adjusted to generate critical data for support system optimization. The research findings indicate that arch crown excavation in sections 1 and 2 with thinner roof thickness resulted in a 10 mm increase in arch settlement values. These sections remained significantly affected by subsequent excavation activities, ultimately exhibiting final arch settlements exceeding 60 mm. The arch crown anchor cables demonstrate effective anchoring performance, successfully controlling surrounding rock settlement. After reinforcement replacement in sections 1 and 2, arch crown settlement reduced by approximately 10 mm. All support schemes exhibit abrupt changes in curvature in settlement curves at the critical roof thickness of 7.4 m, which is identified as the tunnel safety threshold. Numerical simulations guided optimized support parameters, yielding a combined bolt-anchor cable system for thin roof sections and single-layer initial support for thick roof sections. Both simulation and field monitoring confirm stabilized arch crown settlements at 45 mm across varying roof thicknesses, validating the schemeu2032s effectiveness in maintaining tunnel stability.
The water shock wave and seismic vibrations produced during underwater drilling and blasting operations pose significant risks to adjacent structures, aquatic ecosystems, and maritime safety. To facilitate a comprehensive multi-factor assessment and intuitive classification of construction impacts, this study establishes a detailed three-tier evaluation framework that integrates hydrogeological conditions, blasting parameters, and safety measures. Construction impacts are categorized into four levels:green, yellow, orange, and red. Addressing the inherent fuzziness and randomness in evaluation processes, this research introduces an integrated AHP-Cloud Model assessment methodology:the Analytic Hierarchy Process (AHP) assigns index weight coefficients to resolve multi-criteria weight subjectivity, while the Cloud Model allows for probabilistic conversion between qualitative impact categories and quantitative monitoring data via uncertainty mapping algorithms. Validation was performed utilizing the navigation channel improvement project in the Fuling-Fengdu section of the upper Yangtze River as a case study. The results demonstrate that the impact cloud droplets predominantly cluster within the medium impactu2018(orange) grade, with minor dispersion toward the high impactu2019(red) grade, exhibiting strong agreement with field monitoring data across river sections. This study confirms the efficacy of the AHP-Cloud Model for underwater blasting impact assessment, offering scientific insights to support adaptive construction planning and ecological conservation strategies.
Given the substantial explosive volumes and charges involved in underground room-and-pillar mining operations, blasting-induced damage to retained pillars becomes severe, compromising structural integrity and potentially triggering catastrophic failures. This study established a mathematical correlation between necessary pillar safety width and height while accounting for blasting damage effects, revealing how conventional designs that neglect such damage may dangerously overestimate both pillar dimensions and load-bearing capacity. A 20 mu00D780 mu00D780 m pillar structure from a representative mining area was taken as a case study. Utilizing parameters derived from laboratory uniaxial compression and Brazilian splitting tests, an ANSYS/LS-DYNA model of fan-pattern long-hole blasting was developed to analyze pillar damage and vibration characteristics under simultaneous initiation versus millisecond-delay initiation(25 ms and 50 ms). Findings reveal that simultaneous initiation causes stress wave superposition, resulting in unilateral damaged depths of 4~5 m, while delayed initiation reduces damage to approximately 3~3.5 m(25 ms delay) and about 2 m(50 ms delay). Additionally, a practical implementation scheme is proposed that combines a 50 ms interval delay with an optimized detonation sequence. This approach prioritizes creating localized free surfaces to direct energy dissipation toward excavated voids, reducing average surrounding rock damage depth to 1~1.5 m while decreasing pillar surface peak vibrations by approximately 16.6%. These findings provide practical guidance for pillar-width design and blasting damage control in room-and-pillar mining operations.
To address the secondary hazards, including flying debris, dust, shock waves, noise, and vibration, that accompany the open-pit shallow-buried explosion disposal of obsolete bombs, this paper proposes an integrated protective technology system. The system follows the main line of u2018source reduction, process attenuation, directional pressure relief, terminal interceptionu2019 and integrates multiple synergistic control measures: shaped-charge induced detonation is adopted to reduce the equivalent total explosive charge. Meanwhile, the hydrogel is used to wrap the explosive charge to lower the detonation gas temperature and impede fragment projection, and a decoupled charge pit constructed with blast-resistant fiber blankets and EPS foam is employed to reduce the peak gas pressure and achieve targeted pressure relief. Besides, the flexible protective nets are supplemented to intercept ejected stemming materials, thereby significantly mitigating the environmental impact of shallow-buried explosions. Experimental results show that the evaporation rate of hydrogel is significantly lower than that of an equal volume of water, effectively prolonging the endothermic cooling process. Under the same charge weight, the shaped charge has approximately twice the capability of a conventional charge in severing steel pipes. The centralized disposal practice of obsolete explosive articles in Wuhan further verifies that the integrated protective pit markedly narrows the dust dispersion range, with the maximum projection distance of stemming and packaging materials being 50 m, and no residual hardware was found at the site after disposal. The research findings can provide technical reference and engineering support for the safe disposal of obsolete bombs in confined sites adjacent to urban areas.
In mudstone interbedding geological formations, critical blasting parameters including the distance between blast holes and mud layers, borehole spacing, row spacing, and initiation delay intervals significantly impact explosive energy utilization efficiency and overall blasting performance in open-pit bauxite mining operations. To identify optimal blasting parameters for bench blasting in interbedded mudstone geology, representative rock samples were systematically collected from the target mining area, processed under standardized conditions, and subjected to comprehensive static mechanical testing to characterize fundamental geomechanical properties. Subsequently, a single-hole blasting simulation model for interbedded mudstone was developed using LS-DYNA to analyze damage characteristics and peak effective stress at varying distances (L) between the bottom of the blast hole and the mudstone interlayer, thereby determining the optimal L value. Furthermore, a multi-hole blasting simulation model for interbedded mudstone was established to extend the investigation. A comprehensive analysis was performed to evaluate damage characteristics, peak effective stress distribution, and peak vibration velocity under varying blast hole spacing (d1), burden (d2), and delay interval (T) configurations, ultimately identifying optimal parameter combinations. Field blasting experiments were subsequently conducted to validate the simulation findings. The results demonstrate that explosive energy dissipation becomes significant when blast holes are positioned near mud layers, with the optimal vertical distance from the hole bottom to the mud layer set at 1 m. For interbedded mudstone formations, the ideal blasting parameters are 3 m hole spacing, 2 m burden, and a 50 ms delay interval, achieving both effective rock fragmentation and minimized vibration impacts. These findings provide valuable guidance for precision blasting design in comparable open-pit mining operations with similar interbedded mudstone geological conditions.
