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The cumulative damage effects of surrounding rock under single full-face blasting and multiple full-face blasting of a large cross-section tunnel are comparatively studied in this paper. The damage processes of the single and multiple full-face blasting of the tunnel are simulated by the established rock damage model embedded into the LS-DYNA computer code through its user subroutines and a cumulative damage simulation technology in the LS-DYNA. The simulation results are verified against field test data. The results demonstrate that the numerically predicted peak particle velocity (PPV) of the surrounding rock under multiple full-face blasting is more consistent with field test data than that under single full-face blasting, which indicates the advantages of multiple full-face blasting in comparison to single full-face blasting in simulating the blasting process of a tunnel. The maximum damage depth in the middle of the tunnel invert is mostly affected by multiple full-face blasting. Both the maximum damage depth and the maximum PPV occur in the middle of the tunnel invert under single and multiple full-face blasting. Based on the defined damage threshold Dcr and the modeled maximum damage depth of the surrounding rock, the influence of initiation sequence on the critical PPV for rock damage is analyzed, and a critical PPV of rock damage is proposed to provide a safety criterion for tunnel blasting excavation.

With the deterioration of mining conditions, the stability of roadway has become an important research topic for safe and efficient production in coal mines. To protect the gob-side roadway from dynamic mining disturbance under the condition of thick and hard roof so as to ensure the stability of roadway, an innovative method of combined deep hole blasting (CDHB) is proposed. The CDHB method consists of directional energy-gathering blasting and non-directional blasting. By means of theoretical analysis, numerical simulation and field test, the mechanism and effect of the method to protect roadway are analyzed. The research results show that due to the pressure relief principle of the directional energy-gathering blasting technology, the coal mass stress on the side of coal pillar in the roadway is reduced, and the stress concentration area is far away from the roadway. At the same time, owing to the principle of broken expansion filling of non-directional blasting, the collapsed gangue can fill the goaf and support the roof, thus reducing the coal mass stress in front of the working face and at the side of the roadway coal pillar. Finally, the combination of the two blasting methods successfully reduces the coal mass stress of the two sides of the roadway in front of the working face, optimizes the stress environment of the roadway and achieves the goal of protecting the roadway. The effectiveness of the CDHB method is verified by field tests, in which the stress and deformation of the surrounding rock of the roadway are significantly reduced. The research results provide a scientific basis for roadway deformation control under similar conditions.HighlightsA new CDHB method is proposed based on characteristics of rock.Protecting roadway by pressure relieve and increasing coefficient of broken expansion.Comprehensive monitoring showed that CDHB method effectively protects gob-side roadways.

Underwater blasting, often known as submarine blasting, is used for a wide range of purposes. This includes harbor and channel widening, trench excavation for establishing oil and gas pipelines and communication cables, demolition operations, and substructure construction. Particularly, underwater rock blasting is the most difficult and least understood source of vibration, which may have a significant impact on the safety of neighboring buildings and structures, especially berthing structures. The main aim of the study is to design the blasting patterns and monitor the blast vibrations on substructures during real blasting. Furthermore, it is designed to monitor vibration movements and manage them in order to protect the coastal environments from the blasting effects and ensure the safety of various building structures, as well as to maintain the blasting efficiency. Dredging occurs in deep water, with depths ranging from 16 to 20 m, to remove only around 5 m of rock. As a result of the aqueous layer above the rock, this sort of blasting action demands a higher level of competence and understanding of the related activities performed above the surface of the water. The measuring and monitoring of underwater blast-generated vibration in the coastline structures at Nhava Sheva Port, Navi Mumbai, Maharashtra, were discussed in this study. When using underwater explosives, proper safety precautions are taken to protect workers, other vessels in the blasting zone, and buildings from blasting vibrations. With a case study, the authors provide a thorough overview of their approach to underwater blasting utilizing existing blasting technologies.

Accurate prediction of ground vibration caused by blasting has always been a significant issue in the mining industry. Ground vibration caused by blasting is a harmful phenomenon to nearby buildings and should be prevented. In this regard, a new intelligent method for predicting peak particle velocity (PPV) induced by blasting had been developed. Accordingly, 150 sets of data composed of thirteen uncontrollable and controllable indicators are selected as input dependent variables, and the measured PPV is used as the output target for characterizing blast-induced ground vibration. Also, in order to enhance its predictive accuracy, the gray wolf optimization (GWO), whale optimization algorithm (WOA) and Bayesian optimization algorithm (BO) are applied to fine-tune the hyper-parameters of the extreme gradient boosting (XGBoost) model. According to the root mean squared error (RMSE), determination coefficient (R2), the variance accounted for (VAF), and mean absolute error (MAE), the hybrid models GWO-XGBoost, WOA-XGBoost, and BO-XGBoost were verified. Additionally, XGBoost, CatBoost (CatB), Random Forest, and gradient boosting regression (GBR) were also considered and used to compare the multiple hybrid-XGBoost models that have been developed. The values of RMSE, R2, VAF, and MAE obtained from WOA-XGBoost, GWO-XGBoost, and BO-XGBoost models were equal to (3.0538, 0.9757, 97.68, 2.5032), (3.0954, 0.9751, 97.62, 2.5189), and (3.2409, 0.9727, 97.65, 2.5867), respectively. Findings reveal that compared with other machine learning models, the proposed WOA-XGBoost became the most reliable model. These three optimized hybrid models are superior to the GBR model, CatB model, Random Forest model, and the XGBoost model, confirming the ability of the meta-heuristic algorithm to enhance the performance of the PPV model, which can be helpful for mine planners and engineers using advanced supervised machine learning with metaheuristic algorithms for predicting ground vibration caused by explosions.

The vibration characteristics induced by different kinds of blastholes, such as presplitting blastholes, smooth blastholes, and production blastholes, are quite different. Figuring out the vibration differences of different kinds of blastholes and the inherent causes are of great significance for the safety control of blast vibration. In this study, taking the excavation of a dam foundation as a case study, the inherent causes of vibration differences induced by presplitting blastholes, smooth blastholes, and production blastholes are investigated and discussed with both theoretical analyses and numerical simulation methods. In addition, onsite blasting experiments are conducted to verify the vibration characteristics differences. The results show that the explosion pressure applied on the hole wall of the presplitting and smooth blastholes are much smaller than those applied on the production blastholes. Thus, the inner blasting effects (i.e., the rock breakage and plastic zone around the blasthole) of the presplitting and smooth blastholes are relatively weaker. On the other hand, the outer blasting effects (i.e., the rock breakage induced by the reflection of blast waves at the free surface) of the presplitting blasthole are negligible because of their substantially larger burden thicknesses relative to the other blastholes. Therefore, much more explosion energy of the presplitting blasthole is converted into vibration energy than the other two kinds of blastholes. However, the vibration energy conversion and the plastic zone development of the smooth blastholes and production blastholes are approximately at the same level due to the balance of their inner and outer blasting effects. The measured peak particle velocities (PPVs) and dominant frequencies induced by different kinds of blastholes show good agreement with the above theoretical and numerical conclusions. It can be drawn that the inherent causes of the vibration characteristics differences induced by various blastholes lie in the differences in the blasting parameters, which determine the proportions of the inner and outer blasting effects.HighlightsThe inner and out blasting parameters of different kinds of blastholes in dam foundation blasting excavation were defined based on the mechanisms of rock breakage by blasting.The blasting vibration responses of rock mass under different blasting parameters were investigated to figure out the inherent causes of vibration characteristics differences of various blastholes.Horizontal smooth blasting experiment and horizontal presplitting blasting were carried out to verify the vibration characteristics differences induced by various blastholes.We suggest adjusting the inner and outer blasting parameters of blastholes based on the distances of the structures from the explosive sources to minimize the disturbance caused by blasting to structures.

In this research, a directional reduction charging structure was proposed to solve the problems caused by drilling and blasting method such as serious damage to surrounding rocks, working face low contour flatness and serious over-under break of root base c. Drilling and blasting tests, numerical calculations and field applications were designed and performed for the verification of the blasting advantages of charge structure. Test results showed that the peak positive strain along the protection direction of directional protection shaped charge was significantly smaller than that of ordinary charge, where PVC material presented the strongest effect such that the peak positive strain of specimen 1 at measuring point 4 (protection direction) was only 0.27 times that at measuring point 9 (non-protected direction). Numerical simulations indicated shaped jet formation, damage-reduction and charge penetration process and obtained the force law of cement target plate. Experimental results revealed that application of charge in tunnel controlled blasting achieved a clear controlling effect on contour line excavation. Compared with ordinary smooth blasting method, all technical indicators of the developed method were improved such that half hole mark rate was increased by about 33% and the amount of over-under break was decreased by about two times. Research results are of certain significance for the stability of surrounding reserved rocks and formation of roadway in blasting engineering and the developed method was found to be applicable to mining, shaft excavation and other projects.

This study proposes a fractal damage calculation method that understands the blasting damage laws at the macroscopic, mesoscopic, and microscopic scales of rock. The findings indicated that the binary graph derived from the Moments algorithm can represent minute cracks and exhibit less noise within the image. This makes the algorithm suitable for identifying and extracting macroscopic damage. A three-dimensional (3D) reconstruction technique offers visualization of the macroscopic rock damage following an explosion. The extent of this damage is quantitatively assessed using the box dimension. In addition, a multifractal method is introduced to comprehensively evaluate the macroscopic and mesoscopic damage to rock post-blasting. The multifractal dimension calculations analysis reveals that the mesoscopic damage to rock following blasting is a significant factor in the overall blasting damage. The box dimension presents a straightforward, macroscopic evaluation method for assessing 3D macroscopic fractures. On the other hand, the multifractal dimension can more accurately evaluate the macroscopic cracks and mesoscopic damage resulting from blasting. Both methods emphasize different aspects and are equally effective for assessing blasting damage.HighlightsThis study proposes a fractal damage calculation method that understands the blasting damage laws at the macroscopic, mesoscopic, and microscopic scales of rock.The box dimension is a straightforward macroscopic evaluation method for assessing 3D macroscopic fractures.The multifractal dimension more accurately evaluates the macroscopic cracks and mesoscopic damage from blasting.After ordinary charge initiations, blasting damage exhibited a bimodal distribution along the borehole's axis, peaking in the charging section.

To increase the efficiency of deep-hole blasting driving in mine rock tunnels, an innovative pattern of wedge cutting blasting with hole-inner delay was proposed. First, the blasting mechanisms of conventional and innovative wedge cutting patterns were theoretically investigated. The results showed that the resistance from large upper rock blocks and the clamping action from the surrounding rock were the major challenges of conventional cutting methods. For the innovative cutting pattern, under the conversion of the spatial distribution and release sequence of blasting energy, the first blasting of the upper charge can strengthen the breaking of the upper rock mass and create a new free surface, which provides favorable conditions for the delayed blasting of the bottom charge. Second, finite element models of two cutting patterns were established and solved, and the simulation results visually revealed the propagation of a stress wave. Critically, the stress strength in the upper cavity increased by 66–83% under the action of the upper charge, which was conducive to the breaking of the upper rock mass and the generation of a new free surface. Therefore, the rock mass in the bottom cavity can be readily broken and discharged. Ultimately, field applications were executed in a rock tunnel. Compared with a conventional cutting pattern, the proposed innovative cutting pattern can prominently increase the cycle advance and hole utilization and greatly reduce the unit consumption of explosives and detonators. This research confirms the usability of the innovative wedge cutting pattern with hole-inner delay in deep-hole blasting driving of rock tunnels.

During tunnel construction by the drilling and blasting method, the blasting stress waves may affect the mechanical response of existing tunnel lining structure. Based on the similarity theory, a mechanical response of existing tunnel lining structure by blasting model test is designed. The similar material of surrounding rock, explosives, and tunnel lining structure are determined by the similarity of physical mechanical parameters. This study investigates the mechanical response of existing tunnel lining concrete and reinforcing steel‌ by the action of adjacent tunnel blasting. The experimental results reveal the maximum strain distribution and stress peak value of existing tunnel lining concrete and reinforcing steel‌ affected by blasting load. Meanwhile, the equations are established between the peak particle velocity (PPV) and the strain (or stress) in tunnel lining concrete and reinforcing steel‌ affected by adjacent tunnel blasting as well. These Eqs. ( 13 ) and ( 14 ) can be used to predict the maximum stress value of existing tunnel lining concrete and reinforcing steel‌ by the action of blasting load. Simultaneously, these equations have been validated and adjusted by an actual engineering project field test. Thus, evaluating the stress states of tunnel lining caused by adjacent tunnel blasting is more effective. This finding is of great significance for evaluating the stress state of existing tunnel lining structure, as well as providing theoretical guidance and reference for the design of blasting parameters on adjacent tunnel construction.

Drill and blast method is widely applied in deep rock engineering, and the in-situ stress poses a great challenge to blasting excavation. The failure mechanism of rock under coupled dynamic and static loads and the effect of in-situ stress on blasting effects are major concerns when dealing with deep rock blasting excavation. In this study, lab-scale crater blasting experiments on sandstone specimens under various equal biaxial compressive stresses were conducted to investigate the effects of in-situ stress on blasting effects and the mechanism of in-situ stress affecting rock blasting. The initiation and propagation of crack network, morphological characteristics of blasting crater, and distribution characteristics of blasting fragments under biaxial in-situ stress were studied. Besides, the quantitative relationships between biaxial in-situ stress and blasting crater parameters (diameter, area, and volume) were analyzed. The experimental results show that the biaxial static stress inhibits the formation of radial cracks and promotes the formation of circumferential cracks, resulting in the time delay of initial crack formation and the change of initial crack type from radial crack to circumferential crack. With increasing biaxial static stress, the diameter, area and volume of blasting crater, and the size and quantity of blasting fragments gradually increase. Meanwhile, blasting craters are all circular under the various biaxial static stresses. Biaxial static stress has significant influences on the evolution of flaky failure zone, while the effect on the block failure zone and transition failure zone is relatively small. Finally, the mechanisms of the effect of biaxial in-situ stress on the initiation and propagation of blast-generated cracks, blasting crater morphology, and blasting fragments’ distribution were analyzed theoretically.HighlightsCrater blasting experiments on hard stone under various biaxial in-situ stresses were conducted.The effects of static stress on cracks, blasting crater, and blasting fragments are investigated.Quantitative relationships between in-situ stress and blasting crater parameters are examined.Mechanism analysis of biaxial in-situ stress affecting blasting.