The damage and safety assessments of the arch dam subjected to underwater explosions have been significant topics in recent years. However, the majority of current research is on summarizing arch dam failure patterns, with no established criteria or methods for rapid assessment of explosion-induced failure to arch dams. In light of this, the failure mechanism of the arch dam prototype was revealed. And the critical sections and the most unfavorable moments of the arch dam after detonation were clarified, combined with the earlier underwater explosion model test. The energy transferred from underwater explosions into the arch dam was calculated theoretically, leading to the development of an energy-based prediction method and failure criteria of macroscopic cracks in arch dams. Then, the critical safety distances for macroscopic cracks were investigated based on this method. The crown cantilever and the arch ring near the dam crest are the two critical sections of the arch dam subjected to underwater explosion, according to the results. The resulting vertical cracks and horizontal cracks correspond to failure possibilities of the arch system and the cantilever system, respectively. The critical safe distances of horizontal cracks are approximately 40 m, 75 m, and 150 m for explosive equivalents of 3000 kg, 5000 kg, and 15000 kg, respectively. The critical safety distances of vertical cracks for explosive equivalents of 3000 kg, 5000 kg, and 15000 kg are approximately 20 m, 50 m, and 80 m, respectively.

Strong blasting disturbance caused by blasting load and high in situ stress is a key problem for weak and broken rock excavation in underground tunnels. Advanced grouting can help control rock blasting damage. However, the effect of in situ stress on grouted rock damage is unclear, which may increase the difficulty of subsequent blasting design and support. This study investigates the influence range of grouted rock under the coupled effect of blasting load and in situ stress using both theoretical and numerical methods. The propagation characteristics of blasting stress waves in the near field of the blasting source and the redistribution law of in situ stress are first presented to investigate stress changes during blasting excavation of grouted rock. A model to calculate the safety velocity (SV) is then proposed to study the effects of the lateral pressure coefficient and magnitude of in situ stress on grouted rock. The blasting influence range can be inferred from SV and peak particle velocity. Finally, a numerical model of an underground tunnel was built to analyze the blasting influence range of grouted rock under different in situ stress conditions. The results indicate that in situ stress redistribution causes initial shear damage and that the range increases with increasing in situ stress magnitude. The distribution characteristics of in situ stress have a guiding effect on the blasting influence range, which is larger in the direction perpendicular to the maximum in situ stress. SV is the smallest when the lateral pressure coefficient is 2 and the polar angle is 55 degrees. Thus, both the magnitude and the lateral pressure coefficient should be considered in blasting design for advanced consolidation grouting of rock.

Ground vibration induced by rock blasting is a critical challenge in engineering. Controlling seismic energy that quantifies the overall vibration intensity is essential for ensuring safety and efficiency. In this study, a seismic energy calculation model constrained by the fracture boundary was proposed, establishing a unified interface to characterize the seismic energy radiation. Using a combined approach of theoretical analysis, field experiments, and numerical simulations, the control mechanisms of three key parameters were elucidated. The results indicate that the decoupling coefficient operates via a load-control mechanism. By creating a cushioning effect, it modulates the source input function and decreases the energy conversion efficiency, thereby reducing the proportion of radiated seismic energy. The free surface functions through a propagation-control mechanism. It imposes a geometric truncation on the fracture boundary, effectively blocking radiation paths in specific directions. Furthermore, the initiation position controls seismic energy through a direction-control mechanism that actively modifies the seismic energy distribution. It dominates the wavefield directionality and enables energy to be redirected away from sensitive areas through wave superposition. On the basis of these findings, practical guidelines are proposed, including an optimal decoupling coefficient range of 1.28–1.67 and strategies for optimizing free surface orientation and initiation methods. These insights provide a scientific basis for balancing vibration control and excavation efficiency.

To investigate the blasting-induced rock fragmentation mechanism under arcuate free face (AFF) conditions at the pilot shaft formed by raise boring, the following analysis was performed. First, an analytical model was established within the framework of explosive stress-wave theory to explain tensile failure induced by wave reflection at the AFF. The formulation was then applied to quantify the dynamic stress response on the blast-facing side and estimate the associated reflected tensile fracture range. Subsequently, two-dimensional (2D) particle flow code (PFC2D) simulations were performed to examine how AFF curvature radius and burden control fracture development and fragmentation performance. Finally, single-hole blasting experiments with AFF configurations were carried out to verify the analytical and numerical results. The results indicate that a larger AFF curvature radius promotes the expansion of the reflected tensile fracture range and improves fragmentation, as evidenced by increases in both the fragmented area within the crater zone and the proportion of fractures developing toward the free-face side. With increasing burden, the reflected tensile fracture range and the fragmentation indicators first increase and then decline. The best fracturing performance is obtained at a burden curvature coefficient (BCC) of 0.57, corresponding to a burden of 80 mm. The proposed theoretical formula for determining the reflected tensile fracture range under an AFF provides a theoretical basis and reference for designing blasthole patterns during pilot shaft enlargement blasting. These findings are primarily applicable to common engineering conditions involving homogeneous rock masses without significant in situ stress; their applicability under extreme conditions requires further verification.

Accurate estimates of rock mass mechanical parameters are important for safe and efficient construction. Wave-velocity-based methods have been widely used for rock mass evaluation; however, their field application in blasting construction environments often requires reliable first-arrival picking and high-quality sensor deployment or synchronization, which can be difficult to achieve during routine excavation monitoring. This study presents a site-calibrated engineering estimation framework for evaluating the equivalent elastic modulus of rock masses using the attenuation of P-wave pulse rise time in blasting vibration records. The P-wave pulse rise-time attenuation rate was used as the main waveform-based indicator. On the basis of pulse-broadening behavior, equivalent P-wave attenuation, and the elastic-wave velocity–modulus relationship, a physically constrained empirical relationship between this indicator and the equivalent dynamic modulus was established. Numerical simulations were conducted under selected mechanical and blasting conditions to calibrate the relationship and examine its sensitivity within the investigated parameter ranges. The results show that the attenuation rate decreases systematically with increasing equivalent dynamic modulus, and that this trend remains generally consistent under the examined Poisson’s-ratio range and selected blasting configurations. Field vibration data from three engineering projects were analyzed as preliminary field applicability demonstrations. The observed ranges of rise-time attenuation rates are broadly consistent with the representative modulus levels of the investigated rock masses. These findings suggest that the proposed approach may provide a rapid, non-contact, and site-calibrated reference for preliminary rock-mass stiffness assessment during routine blasting vibration monitoring.

Understanding the generation mechanisms and extension behaviors of blast-induced cracks is crucial for improving rock fragmentation efficiency. Various types of cracks, such as radial, circumferential, and spalling cracks, are generated during blasting excavation, each exhibiting distinct extension behaviors. However, limited attention has been paid to the influences of in-situ stress on the extension behaviors of these cracks. In this study, the generation mechanisms of different blast-induced cracks are theoretically analyzed. Subsequently, the extension behaviors of radial, circumferential, and spalling cracks are numerically reproduced under various in-situ stresses. Furthermore, optimization schemes for blasting excavation under high in-situ stress are proposed. The findings reveal that the extension behavior of spalling cracks remains largely consistent across varying in-situ stress conditions, owing to the stress relief associated with prior excavation activities. In contrast, the generation of radial and circumferential cracks is governed by the in-situ stress conditions. Under equiaxial in-situ stress, circumferential cracks are limited to lower stress levels, whereas in an anisotropic stress field, they occur exclusively along the axis of the maximum principal stress. Moreover, as the in-situ stress increases, the average damage and fractal dimension of radial and circumferential cracks decrease, indicating a suppression of crack propagation. Circumferential cracks intersect with radial cracks and play an important role in blast-induced rock fragmentation. As the peak pressure and duration of the explosive loading increase, more circumferential cracks are generated, thereby enhancing the fragmentation of rock masses under high in-situ stress. However, a higher peak pressure generally results in an excessively large crushed zone, which reduces the efficiency of explosive energy utilization. Consequently, increasing the duration of the explosive loading, rather than its peak pressure, is recommended to improve rock fragmentation during blasting excavation in deep rock masses

In the blasting excavation of inclined thin-layered rock masses, the presence of interfaces between rock layers adversely affects the stability of the retained rock mass. However, the distribution characteristics of blastinduced damage in such rock masses are still unclear. In this study, the generation mechanisms of blastinduced damage are investigated based on the dynamic stress field in layered rock masses. Subsequently, onsite blasting experiments and numerical simulations are conducted to analyze the distribution characteristics of blast-induced damage. Furthermore, the evolution of blast-induced damage under smooth blasting and presplitting blasting is discussed to provide references for blasting excavation in inclined thin-layered rock masses. The results indicate that during blasting excavation in inclined thin-layered rock masses, damage is generated in the vicinity of the blasthole when the strain energy induced by blasting stress waves reaches the critical threshold. As the distance from the blasthole increases, the stress waves attenuate rapidly and fail to meet this threshold. However, when the stress waves encounter an interface, sliding and splitting between adjacent rock layers are likely to occur, resulting in additional damage in the layered rock mass. The thickness and inclination angle of rock layers both influence the distribution of the dynamic stress field, thereby further changing the distribution of blast-induced damage. As layer thickness and inclination angle increase, the average damage degree of the retained rock mass decreases, whereas the damage depth increases. Due to the presence of interfaces, a greater portion of the explosive energy from the buffer blastholes is consumed in rock fragmentation, resulting in less energy being transmitted into the retained rock mass. In inclined thin-layered rock masses, damage within the retained rock mass induced by smooth blasting is mainly caused by the buffer blastholes and smooth blastholes. As a result, the damage depth induced by smooth blasting is smaller than that induced by presplitting blasting. Therefore, smooth blasting is recommended for blasting excavation in inclined thin-layered rock masses.

Surface blasting vibration attenuation induced by underground blasting serves as the foundation for controlling underground blasting vibration. However, conventional attenuation models neglect stratigraphic complexity's impact on surface vibration propagation patterns, yielding poor prediction accuracy. Therefore, based on analysis of geometric properties of propagation planes in different orientations, seismic wave theory was employed to quantify variations in actual wave paths and abrupt velocity changes at rock interfaces caused by heterogeneous stratigraphy. This led to the development of a new predictive model for surface blast vibrations. Furthermore, the influence of wave superposition effects within the near-surface low-velocity layer on model accuracy was investigated through numerical simulation. Subsequently, underground blasting experiments were carried out to validate the feasibility and superiority of the model. It was found that the propagation planes of underground blasting vibration in different directions had geometric similarity. Within these planes, heterogeneous layer interfaces induce variations in seismic paths and abrupt velocity changes, causing attenuation asymmetry in surface with the ource-to-surface vertical line as axis. While, the superposition of waves has less effect on the attenuation law. The proposed attenuation model demonstrated strong performance in the test data, achieving correlation coefficients 26%, 20%, and 11% higher than those of the proportional distance model and two elevation-effect models, respectively. Thus, it can be seen that the model in this paper has good feasibility and superiority.

The prediction and control of fragment size distribution remain significant challenges in rock blasting. Based on thermodynamic energy-balance theory, this study reveals that bench blasting fragmentation is co-dominated by the synergistic effects of local kinetic energy (LKE) and strain energy (SE). An analytical KSE (Kinetic-Strain Energy) model is rigorously derived by explicitly incorporating the geometric attenuation of strain rate, kinematic confinement, and a Damköhler number-based time-scale coupling to quantify the efficiency of energy conversion under transient loading. Through three-dimensional Finite Element Method (FEM) simulations and time-history analysis of fragmentation energy density, the spatial transition mechanism is elucidated, characterized by a progressive shift from LKE-dominated crushing to SE-dominated spalling as the standoff distance increases. The proposed KSE model is validated against four full-scale production bench blasting tests at the Changjiu Shenshan limestone mine. Statistical evaluations reveal that the KSE model achieves remarkable predictive robustness with R2 > 0.978 and an RMSE of less than 21.01 mm, outperforming the classical Kuz-Ram and modified KCO empirical models. Notably, it accurately predicts the median fragment size with a maximum error of 7.62% and fundamentally resolves the systematic underestimation of fine fractions. Furthermore, the critical strain rate thresholds governing the transition of dominant fragmentation mechanisms are quantitatively identified.

As a high-order statically indeterminate structure, the stability of high arch dam primarily depends on the dam foundation and abutment. Especially, non-uniform contraction between both banks of river valley often imposes a potential threat on normal performance of the high arch dam. An intelligent interval prediction model is innovatively proposed to evaluate long-term safety of the high arch dam under abnormal abutment deformation. Firstly, valley contraction characteristics are numerically simulated by boundary displacement method, combined with monitoring time series. The rapid embedding technique of cohesion model is taken to indicate structural damage evolution of the high arch dam. Subsequently, a mechanism-driven statistical model is constructed considering with internal and external factors of valley deformation. An intelligent interval prediction model is also established to improve model accuracy and quantify inherent uncertainty. Afterwards, dam cracking risk under the abutment abnormal deformation is estimated based on reliability theory. Finally, the effectiveness of the proposed method is verified by the monitoring time series and the numerical simulation of Jinping I high arch dam. The results indicate that the physical factors of the abutment deformation can be reasonably separated and the cracking risk of the high arch dam can be scientifically evaluated during long-term operation.

This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control. First, the viscoelastic rock mass parameters corresponding to the engineering rock mass quality classification were determined based on wave theory of Kelvin medium. Then, a calculation model was obtained for the millisecond-delay cut blast vibration in Kelvin media using the Starfield charge superposition principle. Further, the influence of the delay time on the cut blast vibration was quantitatively analyzed and a method for calculating the reasonable cut blasting millisecond delay time is proposed according to the principle of dimensional analysis. Finally, field tests were used to verify the applicability of the method. The results show that 5 ms to 20 ms is a better detonator delay time range and cut blasting vibration can be effectively controlled using the delay time calculated by the calculation model described in this paper.

Revealing the modal evolution law of the damaged high arch dam under explosion is an important basis for damage identification and location, and of great significance to the anti-explosion safety of dams. In this work, the modal evolution law of high arch dam caused by horizontal cracks under explosion is investigated by theoretical analysis and numerical methods based on the typical damage modes in the explosion model experiment of the arch dam. An improved modal assurance criterion (IMAC) is proposed to reconstruct the vibration mode sequence of the arch dam with horizontal cracks to eliminate the interference of new local modes of substructure. The modal sequence factor and mode localization factor are proposed to quantify the degree of the change of mode. The mode transition and mode localization characteristics under horizontal cracks induced by explosion are studied. The results show that the large depth and penetrating horizontal cracks may lead to special modal characteristics of the high arch dam, including the mode transition and mode localization in the vertical beam direction. These cracks also make the modal sequence and vibration mode of the damaged arch dam change significantly. The proposed mode localization factor based on the reconstructed modal sequence is sensitive to the horizontal cracks of high arch dams, which can provide a reference for crack identification and location of similar structures.

The shape memory effect induced by thermally exciting shape memory alloy (SMA) provides an active constraint method for structural reinforcement. To investigate the axial compression performance and failure mechanism of SMA strips confined concrete columns, axial compression tests and real-time acoustic emission (AE) monitoring were performed on concrete columns with diverse pre-strain levels and constraint methods. The results reveal that the constraint of SMA strips improves the mechanical properties and inhibits the brittle failure. Based on the correlation between AE characteristic parameters and stress-time curves, the internal failure of confined specimens is classified into three stages: micro-crack initiation, crack stable development and macroscopic crack formation. The rise angle value grows and average frequency value reduces as the damage progresses, manifesting that the shear crack is in the stable propagation stage. The b-value generally diminishes as the load rises, illustrating that the cracking level inside the specimen is continuously increasing. Moreover, compared with the PC40-50-40 specimen, the AC40-50-40 specimen generates highly active AE signals. The distribution of AE damage events indicates that active constraint significantly accelerates the initiation and propagation of cracks in concrete columns during compression loading.

Accurately identifying blast-hole marks and calculating the half-hole ratio is essential for evaluating the effectiveness of drilling-blasting methods. To overcome the inherent limitations of manual measurements and traditional digital imaging methods, this paper proposed an encoder-decoder structure, called BMSegNet, for accurate detection of blast-hole marks. Ablation experiments demonstrated that the BMSegNet outperformed other deep learning models in pixel-level extraction and detailed characterization of blast-hole marks, achieving a mean intersection-over-union of 83.32 %. Further analysis of the pixel distribution, length, and width of blast-hole marks from the test set confirmed the model's robust performance in identifying blast-hole features. In addition, the half-hole ratio was calculated based on the segmentation results and the minimum enclosing polygon method to analyze the blasting quality. The proposed method offered a fast, objective, and end-to-end solution for identifying blast-hole marks and calculating half-hole ratios, significantly reducing detection difficulty and construction time.

Owing to the inherent high risks and operational constraints associated with explosives, the development of controlled and safe experimental methods for equivalently simulating explosive loading has become a critical experimental technical objective. A simulation method, equivalent impact of water entry (EIWE), was proposed for equivalently simulating blast triangular-like pressure loads in a borehole on the basis of principles and advantages of water media in transmitting pressure. The pressure characteristics of the EIWE method, which involves instantaneous water-entry impact induced by a flat-bottomed hammer, were studied through numerical simulations. Then, a water entry impact experiment using a drop hammer was carried out to verify the feasibility and reliability of the EIWE method. Finally, the ability of the equivalent load to induce a rock dynamic stress field and explosive cracking was verified via numerical simulation. The results indicate that the water-entry impact of a flat-bottomed hammer can induce an instantaneous pressure load with a triangular-like distribution in a borehole. Its load-time history is similar to the characteristics of conventional explosive shock loads and follows the same pattern as the measured impact pressure time history in the laboratory. For the induced equivalent load, the peak load increases with the impact velocity, whereas the duration of the load pressure increases as the diameter of the water-facing surface decreases. The reduction in the impact noncoupling coefficient in a borehole significantly decreases both the peak pressure and its duration. These findings provide valuable technical references for the simulation of controlled equivalent explosive loads in laboratory settings. The EIWE method can induce similar radial and tangential dynamic stress fields, as well as explosive cracks, in the surrounding rock mass outside the borehole. This demonstrates the feasibility and rationality of using such a load to equivalently simulate the explosive loading pressure inside a borehole.

Accurately and promptly identifying rock fragments and particle size distribution after blasting is crucial for rock transportation and aggregate control in hydraulic and hydropower engineering. Manual screening and traditional edge detection methods suffer from subjectivity and inefficiency, resulting in considerable processing time. Images of rock fragments post-blasting, captured in open-air conditions, present challenges due to overlapping fragments, complicating intelligent recognition. To address this, an instance segmentation model, RDT-FragNet, is designed for rock fragment segmentation. RDT-FragNet is a hybrid model that integrates the Deformable Convolutional Network (DCN) and the Transformer Attention Mechanism (TAM). The DCN-Transformer structure adaptively preserves global and local features, enhancing the segmentation and recognition of rock fragment edges. Comparative analyses and rigorous ablation studies demonstrate RDT-FragNet's competitive advantages. RDT-FragNet outperforms other advanced models in both quantitative metrics and visual results. The visualization results and the characteristic and maximum particle size of rock fragments closely match the actual situation. The robustness and applicability of the RDT-FragNet model are validated using images from two additional engineering projects. This research introduces an intelligent, efficient, and objective method for rock fragment analysis in open-air settings.

The detection and evaluation of rock mass joints and fractures are essential in assessing the stability of engineering rock masses and mitigating geological hazards. To address the challenge of intelligent extraction and quantification of fractures, a deep learning-based complex rock fracture segmentation network, termed CRFSegNet, has been developed and combined with multiple feature computation methods. Ablation experiments and multi-model comparisons are conducted on a self-constructed dataset comprising fractures induced by natural processes and blasting. CRFSegNet performs competitively in terms of visualization and evaluation metrics in comparative experiments, with an average intersection-over-union of 83.90 %. The network effectively captures the intricate characteristics of fractures, demonstrating the approach's robustness and competitiveness. Fracture characteristics, such as length-dip, surface fracture rate, and fractal dimension, are obtained based on the segmentation results and the proposed characteristic calculation method. By analyzing the feature acquisition of four images, it is found that the results based on CRFSegNet are basically consistent with the actual situation, which shows that the proposed method is an effective approach for intelligent recognition and feature acquisition.

This paper presents a study on the compressive behavior of novelly designed cruciform cold-formed steel (CFS) built-up columns with web V-stiffeners. The built-up columns were composed of four identical single-limb, and connected by longitudinally arranged high-strength bolts and filler plates at the webs. Eight specimens were prepared for compression tests, with varying lengths, initial loading eccentricity, and cross-sectional forms. The bearing capacity, load-displacement curves, and failure modes of specimens were obtained. The failure modes of the concentric and eccentric compression specimens were local-distortional interaction buckling and localdistortional-flexural interaction buckling, respectively. Subsequently, finite element models of the specimens were developed and validated to provide a base for conducting parametric studies with different slenderness ratio, web height-to-thickness ratio, and initial loading eccentricity. Finally, the design methods in the Chinese code GB50018-2002 and the AISI S100-16 specifications for predicting the resistance of built-up columns were evaluated by using experimental and numerical results. The corresponding assessments on the design approaches adopted in European code were also preliminary discussed. The study shows that the current AISI S100-16 specifications are unstable for predicting the resistance of built-up columns, while the provisions in the Chinese code GB50018-2002 are overly conservative. Hence, a reliable design procedure is proposed based on the Effective Width Method (EWM) in the Chinese code. The strength predictions of the proposed design procedure match well with those experimental and numerical results.