Search Results (65)

Blasting-induced seismic waves are typically nonlinear and non-stationary signals. The EMD-Hilbert transform is commonly used for time–frequency analysis of such signals. However, during the empirical mode decomposition (EMD) processing of blasting-induced seismic waves, endpoint effects occur, resulting in varying degrees of divergence in the obtained intrinsic mode function (IMF) components at both ends. The further application of the Hilbert transform to these endpoint-divergent IMFs yield artificial time–frequency analysis results, adversely impacting the assessment of blasting-induced seismic wave hazards. This paper proposes an improved EMD endpoint effect suppression algorithm that considers local endpoint development trends, global time distribution, energy matching, and waveform matching. The method first analyzes global temporal characteristics and endpoint amplitude variations to obtain left and right endpoint extension signal fragment S(t)_L and S(t)_R. Using these as references, the original signal is divided into “b” equal segments S(t)₁, S(t)₂ … S(t)_b. Energy matching and waveform matching functions are then established to identify signal fragments S(t)_i and S(t)_j that match both the energy and waveform characteristics of S(t)_L and S(t)_R. Replacing S(t)_L and S(t)_R with S(t)_i and S(t)_j effectively suppresses the EMD endpoint effects. To verify the algorithm’s effectiveness in suppressing EMD endpoint effects, comparative studies were conducted using simulated signals to compare the proposed method with mirror extension, polynomial fitting, and extreme value extension methods. Three evaluation metrics were utilized: error standard deviation, correlation coefficient, and computation time. The results demonstrate that the proposed algorithm effectively reduces the divergence at the endpoints of the IMFs and yields physically meaningful IMF components. Finally, the method was applied to the analysis of actual blasting seismic signals. It successfully suppressed the endpoint effects of EMD and improved the extraction of time–frequency characteristics from blasting-induced seismic waves. This has significant practical implications for safety assessments of existing structures in areas affected by blasting. Full article

The roof slab, as a critical component for partitioning the vertical space within RC frame structures, can effectively mitigate the propagation of shock waves and reduce damage levels in adjacent rooms. This study employed finite element (FE) modeling to investigate the vertical propagation of blast waves and roof ejection velocity in RC frames. The model’s reliability was verified by reconstructing internal explosion tests on RC frames and close-in explosion tests on masonry walls. On this basis, two typical single-room RC frame structures that are vertically adjacent were designed, and numerical simulations of the internal explosion were conducted under four explosive equivalents and four venting coefficients. The propagation of shock waves, load characteristics in the vertically adjacent room, and the dynamic response of roof slabs were examined. The results show that shock waves propagated to the vertically adjacent room decreased by approximately two orders of magnitude for peak overpressure and one order of magnitude for impulse due to the obstruction of shock waves by roof slabs, respectively, compared to the source explosion room. For larger venting coefficients, abundant energy was released through the venting openings, making it difficult to form a quasi-static pressure with a long duration inside the source explosion room. In addition to the shock wave, the explosive ejection of roof slabs in the explosion source room will further exacerbate the damage to the vertically adjacent room. Peak overpressure and impulse propagated to the vertically adjacent room were reduced significantly by the increase in the venting coefficient, resulting in an attenuation of structural damage. Finally, empirical models incorporating the venting coefficient were established to characterize the attenuation coefficients of power parameters, demonstrating the predictive capability for peak overpressure, impulse, and roof ejection velocity in both the explosion source room and the vertically adjacent room. Full article

High temperatures can induce a range of physical and chemical alterations in radiation-protective concrete, potentially compromising its strength and significantly diminishing its radiation shielding capabilities. Therefore, it is very important to study the high temperature performance of radiation-proof concrete to ensure its safety and stability in extreme environment. In this study, the magnetite–serpentine radiation-proof concrete is designed with magnetite as coarse aggregate, serpentine as fine aggregate, and Portland cement and granulated blast furnace slag as mixture. The apparent characteristics, mass loss, ultrasonic pulse velocity, mechanical properties, shielding performance, and correlation of this concrete were analyzed through experiments. The results show that the damage degree and relative wave velocity have a good correlation in evaluating the relative mass loss, linear attenuation coefficient, compressive strength, and tensile strength after high temperatures. The compressive strength at 800 °C is 12.2 MPa and the splitting tensile strength is 0.48 MPa; the linear attenuation coefficient of specimen at 800 °C is reduced to 80.9% of that at normal temperature. Meanwhile, penetrating cracks appeared at 600 °C and spalling phenomenon appeared at 800 °C, and better thermal stability and favorable mechanical properties and shielding performance also occurred; thus, suitable radioactive and high temperature environment was determined. The results could provide scientific guidance for nondestructive testing and performance evaluation of shielding structure materials. Full article

The dynamic response law of the vibration cavity effect in the adjacent large-section rectangular coal roadways induced by deep-hole bench blasting vibrations was deeply revealed, and the prediction accuracy of the PPV in the coal roadway was improved. The vibration equations of the coal roadway were derived based on the stress wave propagation theory and the wave-front momentum conservation theorem. Based on coal roadway vibration monitoring data and numerical simulations, the cavity effect and vibration response characteristics of the coal roadway induced by deep-hole bench blasting under varying blast source distances and relative angle conditions were analyzed. A predictive model for PPV of rectangular coal roadway surrounding rock, incorporating the relative angle as one of the key influencing factors, was developed. The results showed that the presence of cavities and changes in the relative angle enhance the asymmetry of the dynamic response of blasting stress waves near the free surfaces of the surrounding rock on each side of the coal roadway, resulting in significant differences. Moreover, as the blasting distance decreases, the cavity effect tends to promote greater PPV differences on each side of the coal roadway. The prediction model exhibited improved accuracy by about 15.6% compared to the traditional Sadovski equation for the face-blasting side of the coal roadway. It demonstrates better adaptability and predictive capability. This research provides a theoretical basis for the dynamic response of adjacent large-section rectangular coal roadways and for preventing dynamic instability failures in open-pit mining. Full article

With the acceleration of urban renewal, directional blasting has become a common method for building demolition. Analyzing the time–frequency characteristics of blast-induced seismic waves allows for the assessment of risks to surrounding structures. However, the signals monitored are frequently tainted with noise, which undermines the precision of time–frequency analysis. To counteract the dangers posed by blast vibrations, effective signal denoising is crucial for accurate evaluation and safety management. To tackle this challenge, a dual denoising model is proposed. This model consists of two stages. Firstly, it applies endpoint processing (EP) to the signal, followed by complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to suppress low-frequency clutter. High-frequency noise is then handled by controlling the multi-scale permutation entropy (MPE) of the intrinsic mode functions (IMF) obtained from EP-CEEMDAN. The EP-CEEMDAN-MPE framework achieves the first stage of denoising while mitigating the influence of endpoint effects on the denoising performance. The second stage of denoising involves combining the IMF obtained from EP-CEEMDAN-MPE to generate multiple denoising models. An objective function is established considering both the smoothness of the denoising models and the standard deviation of the error between the denoised signal and the measured signal. The denoising model corresponding to the optimal solution of the objective function is identified as the dual denoising model for blasting seismic wave signals. To validate the denoising effectiveness of the denoising model, simulated blasting vibration signals with a given signal-to-noise ratio (SNR) are constructed. Finally, the model is applied to real engineering blasting seismic wave signals for denoising. The results demonstrate that the model successfully reduces noise interference in the signals, highlighting its practical significance for the prevention and control of blasting seismic wave hazards. Full article

The adjustment of delay time in open-pit bench blasting is a research hotspot in vibration control. Its core lies in utilizing the periodic characteristics of vibration waves to achieve the superposition and cancellation of wave peaks and troughs. However, due to the spatiotemporal variability in the propagation of blast-induced vibration waves, the optimal delay time determined for vibration control requirements at a specific protected area (monitoring point) makes it difficult to achieve the misalignment superposition effect simultaneously at multiple monitoring points. To address the challenge of multi-area vibration control in open-pit bench blasting, this paper proposes an adjustment method based on local delay adjustment. First, a spatiotemporal relationship model between blast holes with monitoring points is established to calculate vibration wave arrival times. This enables rapid hole identification during dense wave arrivals at monitoring points, with waveform separation achieved through initiation delay adjustments. Following the Anderson principle, reconstructed single-hole vibrations are superimposed according to the wave arrival sequence to validate control efficacy. Statistical analysis of concurrent wave arrivals across all-direction monitoring points identifies high-probability vibration hazard locations. Targeted delay adjustments for blast holes within clustering arrival periods at these locations enable comprehensive vibration reduction. Field data confirm that single-point control reduces peak vibration by >10.55% through simultaneously reducing the amount of waves in clustering arrival periods. Multi-point control resolves seven hazard locations across two directions, attaining 88.57% hazard elimination efficiency and 14.05% peak velocity attenuation. This method achieves vibration control through local delay adjustments while maintaining the fragmentation effect of the original scheme, providing a new approach to solving the challenge of vibration control in large-scale blasting areas. Full article

To investigate the influence of the in situ stress on the damage characteristics and fracture patterns of sandstone, this study designed a confining pressure loading device that simulates a deep high in situ stress environment. It allows for the coupled loading of blasting stress and in situ stress on rock specimens. Based on this, experimental research on three-dimensional rock blasting was conducted. A segmental analysis method was then applied, dividing the sandstone into stemming, charge, and bottom segments to refine the study. Using CT scanning, three-dimensional reconstruction, multifractal methods, and SEM scanning technology, the damage characteristics and failure modes of sandstone under the coupling of blasting stress and in situ stress were investigated from macroscopic, mesoscopic, and microscopic perspectives. The experimental research indicates that, under in situ stress, the rock’s ability to resist the effects of blasting stress waves and blasting gas is enhanced. With increasing in situ stress, the overall damage level of sandstone specimens gradually decreases and the damage characteristics in different segments of the specimen show significant variation. Under the same in situ stress, the damage level of the sandstone specimen decreases as the axial position shifts from the stemming segment to the charge segment, and then to the bottom segment. Additionally, with increasing in situ stress, shear fractures increase, the blasting fracture surfaces become progressively rougher, and the microscopic fractures in the sandstone transition from brittle cleavage fractures to brittle–plastic quasi-cleavage fractures. In some areas, the energy is insufficient to penetrate the grain boundaries, leading to a transition from transgranular fractures to coupled fractures and intergranular fractures. Full article

Optimizing structural resistance against blast loads critically depends on the effects of different explosive shapes, equivalents, and distances on the damage characteristics of reinforced concrete beams. This study bridges the knowledge gap in understanding how these factors influence damage mechanisms through close-range air blast experiments and LS-DYNA numerical simulations. Key damage characteristics, such as craters, overpressure, impulse, time-history displacement, and residual mid-span displacement of reinforced concrete beams, were thoroughly analyzed. Results show that cuboid-shaped explosives cause the greatest damage, with the most severe effects observed at shorter distances and higher charge weights, including an increase in mid-span displacement of up to 16.3 cm. The study highlights the pivotal role of explosive geometry, charge weight, and standoff distance in shock wave propagation and structural failure and proposes an optimized damage criterion to enhance predictive capabilities for reinforced concrete beams under blast loads. Full article

To investigate the propagation of stress waves in viscoelastic joints under blasting loads, and their impact on crack propagation and dynamic response in rock masses, a numerical model incorporating intersecting viscoelastic joints was developed using LS-DYNA. This study focuses on the influence of various joint geometric parameters, including thickness and angle, on stress wave propagation and damage patterns in rock. The Riedel–Hiermaier–Thoma (RHT) model was employed to simulate the dynamic behavior of rock, while the Poynting–Thomson model was used to describe the viscoelastic properties of the joint fillings. The simulation results provide detailed insights into the principal stress, displacement, and particle vibration velocity around the joints. Based on the stress wave propagation theory, the velocity transmission coefficients were calculated to quantify the attenuation of stress waves across the joints. The findings demonstrate that viscoelastic joint properties significantly affect the damage patterns in the rock mass. Specifically, the area of the crushed zone and the width of cracks on the blasting side are proportional to joint thickness, while crack propagation at the joint tips is governed by differences in principal stress. Moreover, the propagation of vibration velocity is notably weakened at the second joint, highlighting the critical role played by joint characteristics in stress wave dynamics. These results underscore the complex interaction between joint properties and stress wave behavior in rock masses, providing valuable insights for optimizing blasting designs and improving the safety of underground engineering projects. Full article

To investigate the dynamic wave propagation characteristics and dynamic response of heterogeneous layered slopes under a blasting vibration, a modeling method considering the slope’s layered dip angle and heterogeneity was proposed. Different dip jointed slope models were established using the Weibull random distribution function introduced to realize the stochastic distribution of rock mechanics parameters, representing heterogeneity. Taking the background project of the Sijiaying Yanshan Open-Pit Iron Mine as an example, through numerical simulation, the effects of different joint dip angles and rock hardness on the slope’s dynamic response were analyzed in detail. The sensitivity of the elastic modulus, cohesion, and friction angle to the slope dynamic response was also investigated. A comparative analysis of the amplification effects between a jointed slope and heterogeneous slope was conducted. Finally, the dynamic stability of the jointed slope and heterogeneous slope under a blasting load was analyzed. The results indicate that the Peak Ground Acceleration (PGA) of jointed slopes with dip angles of 45° and 60° is generally higher than that of slopes with a 0° dip angle and without joints. The smaller the rock mass heterogeneity, the smaller the PGA at the measuring points, and the less sensitive the PGA is to variations in the three quantities. Under the same physical and mechanical parameters of the rock, the amplification factor of jointed slopes is generally greater than that of heterogeneous slopes. Under the blasting load, the overall dynamic time-series safety factors of both slopes decrease first and then increase, with the safety factor reaching its lowest value at the location of the strongest blasting vibration wave. This study can provide guidance for the blasting design and safety protection of layered dip slopes and serve as a reference for the analysis of blasting impact laws in similar mines. Full article

This study investigates the local damage characteristics and influencing factors of steel box girder structures under explosive shock waves. The single-box, double-chamber steel box girder commonly used in urban road bridges was chosen as the research object. Based on model validation of the explosion test values of a 1:10 scaled-down model of the steel box girder, a 1:1 numerical model of the steel box girder structure was established. The research analyzed failure modes under varying explosive charge weights and detonation locations. The results showed that failure primarily occurred in the top plate, base plate, and internal partitions, with the top plate experiencing the most severe damage due to direct impact. The effectiveness of transverse and longitudinal partitions in mitigating damage was highlighted, with unpartitioned sections exhibiting up to a 70% increase in damage area. Additionally, stiffening ribs influenced the deflection of base plate cracks, with maximum offset distances ranging from 0.5 m to 1.5 m as explosive weight increased. These findings emphasize the critical role of structural features in enhancing the blast resistance of steel box girder bridges, providing valuable insights for improving protective designs against explosive threats. Full article

This paper presents a WENO-based upwind rotated lattice Boltzmann flux solver (WENO-URLBFS) in the finite difference framework for simulating compressible flows with contact discontinuities and strong shock waves. In the method, the original rotating lattice Boltzmann flux solver is improved by applying the theoretical solution of the Euler equation in the tangential direction of the cell interface to reconstruct the tangential flux so that the numerical dissipation can be reduced. The fluxes at each interface are evaluated using a weighted summation of lattice Boltzmann solutions in two local perpendicular directions decomposed from the direction vector so that the stability performance can be improved. To achieve high-order accuracy, both fifth and seventh-order WENO reconstructions of the flow variables in the characteristic spaces are carried out. The order accuracy of the WENO-URLBFS is evaluated and compared with the traditional Lax–Friedrichs scheme, Roe scheme, and the LBFS by simulating the advection of the density disturbance problem. It is shown that the fifth and seventh-order accuracy can be achieved by all considered flux-evaluation schemes, and the present WENO-URLBFS has the lowest numerical dissipation. The performance of the WENO-URLBFS is further examined by simulating several 1D and 2D examples, including shock tube problems, Shu–Osher problems, blast wave problems, double Mach reflections, 2D Riemann problems, K-H instability problems, and High Mach number astrophysical jets. Good agreements with published data have been achieved quantitatively. Moreover, complex flow structures, including shock waves and contact discontinuities, are successfully captured. The present WENO-URLBFS scheme seems to present an effective numerical tool with high-order accuracy, lower numerical dissipation, and strong robustness for simulating challenging compressible flow problems. Full article

Traditional seismic wave-based tunnel advanced geological forecasting techniques are primarily designed for drill and blast method construction tunnels. However, given the fast excavation speed and limited prediction space in tunnel boring machine (TBM) construction tunnels, traditional methods have significant technical limitations. This study analyzes the characteristics of different types of TBM construction tunnels and, considering the practical construction conditions, identifies an effective observation system and data acquisition method. To address the challenges in advanced forecasting for TBM construction tunnels, a method of ellipsoid positioning velocity analysis, which takes into account the constraints of three-component data directions, is proposed. Based on the characteristics of the advanced forecasting observation system, this method compares the maximum values on the spatial isochronous ellipsoidal surface to determine the average velocity of the geological layer rays, thereby enabling accurate inversion of the spatial distribution ahead. Utilizing numerical simulation, a model for the advanced detection of typical unfavorable geological formations is established by obtaining the wave field response characteristics of seismic waves in three-dimensional space, and the velocity structure of the model is retrieved through this velocity analysis method. In the engineering example, the fracture property, water content, and weathering degree of the surrounding rock are predicted accurately. Full article

Numerous studies have shown that explosive sequence loads can cause serious damage to underwater vehicles, especially the bubble surge in the later stage of the explosion, which poses a huge threat to the internal structure of the vehicle. This study explores the damage characteristics of cylindrical shell structures under complete sequence loads based on the Arbitrary Lagrangian–Eulerian (ALE) method. By conducting experiments on the surge characteristics near the damaged plate under explosive action and comparing them with numerical results, the effectiveness of the method is verified. Subsequently, the damage characteristics of single- and double-layered cylindrical shell structures under underwater explosion sequence loads (shock waves, bubbles, surges) were explored, and the failure modes of cylindrical shell structures under various loads were summarized. The results indicate that the damage of shock waves to single-layer cylindrical shell structures is most severe at a blast distance of 0.5 m. For double-layer cylindrical shells, increasing the blast distance will reduce the impact of bubble surge on the pressure-resistant shell. The stress and strain in the central area of the pressure-resistant shell also decrease, and the deflection and Z-direction velocity also decrease accordingly. This study laid the foundation for enhancing the impact resistance of underwater vehicles. Full article

In the bench method of tunnel excavation, the blasting impact from upper bench blasting poses significant risks to personnel and equipment. This study employed dynamic analysis software, ANSYS/LS-DYNA, and field testing to examine the propagation characteristics and attenuation behavior of tunnel shock waves. The findings revealed that, near the central axis of the tunnel, shock wave overpressure was lower compared to areas near the tunnel wall due to reflections from the wall. As the shock wave traveled a distance six times the tunnel diameter, it transitioned from a spherical wave to a plane wave. The attenuation coefficient for the plane wave ranged from 1.03 to 1.17. A fitting formula for shock wave overpressure attenuation, based on field test results, was proposed, and it showed good agreement with the numerical simulation results. This provided valuable theoretical insights for predicting shock wave overpressure during bench method tunnel excavation. Full article