In order to explore the dynamic crack propagation law of beam members, bar defects with the heights of 22 mm, 28.5 mm and 35 mm were designed in a three-point bending beam, and then tested by the digital laser dynamic caustic line experiment system and the drop weight impact test system. The results show that the crack propagation rate and stress intensity factor are affected by the defect height in two stages in the drop weight impact experiment. In the first stage, the maximum growth rates of crack propagation have a trend of first rising and then stabilizing as 247.49 m/s, 292.49 m/s and 284.99 m/s with the increase of defect height, and the cracking stress intensity factor was respectively 1.480 MPa/m^3/2, 1.665 MPa/m^3/2 and 1.812 MPa/m^3/2, which increased with the increase of defect height. Meanwhile, the crack initiation and propagation rates respectively decreased by 634.42 m/s, 524.97 m/s and 377.67 m/s, the cracking stress intensity factors of K_Ⅰ type respectively decreased by 3.281 MPa/m^3/2, 3.192 MPa/m^3/2 and 2.876 MPa/m^3/2, and the cracking stress intensity factors of K_Ⅱ type respectively increased by 1.254 MPa/m^3/2, 1.319 MPa/m^3/2, and 1.398 MPa/m^3/2. Furthermore, the K_Ⅰ-K_Ⅱ composite stress intensity factor was transformed into a K_Ⅰ type stress intensity factor by deflection.

It is prone to occur dynamic disasters such as roof falling, sidewall slabbing and rock burst under dynamic disturbance of mechanical percussion drilling and explosive blasting in the roadway with hard rock. It is extremely meaningful to investigate the dynamic load effect on roadway deformation and failure mechanism. To understand the mechanical behavior of roadway surrounding rock under dynamic disturbance, a hard rock roadway was simplified as a hole in rock. And then, a series of impact tests were conducted on prismatic sandstone rock specimens with a hole by a modified split Hopkinson pressure bar testing system to explore the influence of hole size and shape on the dynamic mechanical properties, failure mode and energy dissipation characteristics. The results show that the existence of the hole has significant weakening effects on the dynamic strength, dynamic elastic modulus and peak strain. The dynamic mechanical properties of the rock decrease significantly with the increase of hole size. Among the specimens with different hole shapes, the dynamic strength and peak strain of the square-holed specimens are the largest, followed by the horseshoe-holed and the circle-holed specimens, but their elastic moduli show opposite results. In terms of rock failure modes, splitting tensile and tensile-shear failure occur respectively in intact specimens and pre-holed specimens under impact load. Additionally, the energy consumption density and fractal dimension of the horseshoe-holed specimens are the largest, which are 1.94 J/cm³ and 2.11 J/cm³, respectively. It indicates that the failure process is the most intense for the horseshoe-holed specimens, while the fragmentation degree of the circle and square holed specimens is not much different.

In channel dredging engineering, the underwater drilling and blasting technology is often used for underwater reefs higher than the designed bottom elevation. However, after drilling and blasting, there are still some rocks that cannot be completely removed and irregular and unstable underwater shallow points remaining. In actual construction, emulsified explosive is often used to remove such isolated stones. Compared with drilling and blasting, adobe blasting has small contact surface between explosive and rock face, large amount of explosive, low energy utilization rate, high explosive consumption, large noise and water shock wave, affecting ecological environment and so on. In order to analyze the influencing factors of shallow blasting, field monitoring research was carried out to compare the adobe blasting underwater and the drilling & blasting method. Under the same effect, the water hammer wave and seismic wave data of CO₂ adobe blasting, drilling CO₂ gas blasting and drilling emulsion explosive blasting were obtained. In this paper, taking the foundation groove, berthing excavation, reef blasting and reef clearing project of 18#~22#berth wharf in Fangchenggang as examples, the arrangement and amount of charge are formulated according to the property of rock strata, rock formation, water depth and shallow point thickness of the blasted rock top. The results show that the overpressure of CO₂ adobe explosion is 1.87~41.9 times that of CO₂ drilling gas explosion under the same cylinder condition. The overpressure of underwater drilling emulsion explosive blasting is 7.9~18.7 times of the water shock wave of CO₂ drilling gas explosion, and the vibration value is 3~10 times of the latter. Based on the research on the propagation law of underwater blast wave, this paper comprehensively analyzes the harmful effect of underwater shock wave.

To explore the mechanical mechanism of burn cut blasting with a large-diameter empty hole, the stress concentration effect of the large-diameter empty hole was studied by theoretical analysis and numerical simulation. Firstly, a mechanical model for the stress concentration effect of the empty hole was established. Furthermore, the empty hole's stress concentration effect was clarified based on the elasticity theory and wave dynamics. A numerical simulation under a typical working condition was then carried out, and finally the stress concentration effect of the empty hole was investigated based on the numerical results of stress wave propagation, rock damage, and the first principal stress. The results show that the stress concentration effect of the empty hole is mainly derived from the stress concentration around the cavity and the stress wave superposition effect. During the blasting process, the stress wave is reflected at the empty hole wall and superposed with the incident wave, which is mostly located in the vicinity of the empty hole and the region between the cut holes. The regions with high damage degree are mainly around the cut hole, near the empty hole, and within the triangle regions formed by adjacent cut holes and the empty hole, and the latter two regions correspond to the stress wave superposition regions. There is a significant stress concentration effect near the empty hole, and the closer the rock is to the empty hole, the more obvious the effect is.

Blasting is widely used in tunnel engineering as a large scale and high efficiency method of rock breakage, but it inevitably brings some bad effects to the adjacent structures and surrounding rocks, among which blasting vibration is the first. Electronic detonator initiation can realize the active control of blasting vibration intensity and spectrum due to its accurate delay, high reliability and safety, which is an effective means to reduce the seismic effect of blasting. In order to explore the influence of the location and number of electronic detonators on the frequency spectrum of blasting vibration, field tests and numerical calculations were combined. The main frequency characteristics of blasting vibration are summarized for five different initiation locations, including the bottom of the charge, the top of the charge, the middle of the charge, simultaneous initiation at the top and bottom of the charge, and simultaneous initiation at two points evenly distributed in the charge section. Based on the spectrum expression of blasting vibration in viscoelastic medium, the characteristics of blasting loads under different working conditions were analyzed from the perspective of superposition of blasting sources, which was used to reveal the influence of detonator arrangement on blasting vibration frequency spectrum. The results show that the initiation conditions are ranked as simultaneous initiation of two uniformly distributed points, middle initiation, simultaneous initiation at the top and bottom, top initiation and bottom initiation, in the order of vibration frequency from largest to smallest. Multiple detonators actually divide the whole charge into several segments, which is equivalent to superposition of multiple sub-explosive sources. Changing the location or number of detonators is essentially to detonate the entire charge in segments at the same time. The more segments, the length of sub-explosive source charge and the detonation process are shorter, which means the energy release rate of explosives and the blasting vibration frequency are higher, and the rise of explosion load is faster. In addition, with the increase of distance to blast source, the influence of detonator position on blasting vibration frequency converges.

The authenticity of fracture distribution model is one of the key factors during numerical simulation of blasting in jointed rock mass, which would obviously affect the numerical simulation results. It is hard to represent the complex three-dimensional joint distribution in the existing joint construction method. To explore a simple and feasible operation method for constructing the complex 3D joint model in LS-DYNA software, a K file of blasting numerical model was analyzed and reorganized by MATLAB software. Furthermore, a 3D refined numerical model for jointed rock mass was constructed by the 3D joint distribution law and the constitutive joint model parameters. Finally, a statistical analysis of the three-dimensional joint distribution law was carried out in an open-pit limestone mine, and the joints were reconstructed in the numerical model of a bench blasting. Consequently, a comparative study of the numerical simulation and the field blasting test for open-pit bench blasting was carried out. The results show that the error between the joints built in the numerical model and the actual joints is less than 13%. The joint surface changes the damage distribution of the rock mass. Compared with the intact rock mass, the damage rock mass range increases by 12.04%, and the proportion of fragments with the size of 0~100 mm decreases by 8.11%. The damage results obtained by blasting simulation are close to the field rock breaking effect, and the percentage error of fragments with the size of 0~100 mm is 4.16%. The analytical reconstruction method is feasible and easy to represent the complex three-dimensional joint distribution, and the numerical results are close to experimental results.

Due to the influence of complex environment of tunnel blasting and the electromagnetic interference of instruments, the measured blasting vibration signals mostly contain high-frequency noise, which makes it ineffective to analyze related laws by the raw blasting vibration data. In order to obtain the real blasting vibration characteristics, a signal smoothing and noise reduction model based on the optimal variational mode decomposition (OVMD) and the multi-scale permutation entropy (MPE) is adopted, which is verified by the simulated superposition signals and measured signals. Firstly, the signal is decomposed by OVMD to obtain the band-limited intrinsic mode functions (BIMF). Then, the high-frequency BIMFs larger than the threshold set by MPE are removed as noise. Finally, the remaining BIMFs components are reconstructed to obtain the noise-reduced signal. The results show that the OVMD-MPE model can accurately identify the signal frequency information, and the first two order components can effectively reflect the effective contents of the superimposed signal, which is suitable for high-precision data analysis and feature extraction. Compared with EEMD-MPE and CEEMDAN-MPE models, the OVMD-MPE model has better noise reduction performance. The noise reduction error ratio, root mean square error and smoothness are increased by 22.05%, 48% and 33.34%, respectively. The denoised curve is closer to the original signal and is more suitable for blasting signal analysis with different source distances. The blasting vibration signals measured during the construction of the right line of Shuangzishan Tunnel are concentrated in the middle and the low frequency bands below 200 Hz. The natural frequency of the lining structure is similar to the main frequency of the blasting signal, which means shock absorption measures need to be taken to ensure the construction safety of the tunnel project.

In order to explore the interaction mechanism between the structure of different sizes and the bubbles, an underwater explosion experiment of 2.5 g TNT was carried out at the bottom 15cm of the fixed square plates with side lengths of 20 cm, 40 cm and 70 cm. Through the observation of the experimental high-speed video and the pressure data measured by the sensor, it is found that when the size of the plate is too small, the bubble will contact with the air during the expansion process, and the bubble pulsation process will be terminated. In order to further explore the matching relationship between the explosion bubble and the target size, CEL algorithm in Abaqus software was used to establish the fixed square plate with Lagrange grid and the remaining part with Euler grid. The dynamic behavior and pressure data of the near-field underwater explosion bubble were numerically simulated. The feasibility of the simulation method is verified by comparing the simulation results with the bubble phenomenon captured in the experiment and the measured pressure time history curve. Taking the explosion depth divided by the maximum bubble radius as the specific depth and the side length of the board divided by the maximum bubble radius as the side length, a series of simulations were carried out with the side length of the board being 0.455 to 3.182 times the maximum theoretical bubble radius and the explosion distance being 0.455 to 1.136 times the maximum theoretical bubble radius. The simulation results show that with the decrease of plate size, the bubbles are more likely to collapse in advance. With dimensionless plate size and dimensionless explosion depth as variables, a boundary function is given to complete the bubble pulsation. The closer the distance between explosion distance and plate size, the earlier the end time of bubble pulsation.

The influence of charge shape on the dynamic response of underground structures was investigated. A dynamic finite element analysis program was used to establish a model consisting of air, soil, reinforced concrete pipe corridors, and explosives. The response of the underground pipe corridor under explosion load in soil was studied using a fluid-structure coupling algorithm. In tests, TNT is often arranged as a square group charge to detonate underground structures, while in practice, precision-guided bombs are cylindrical in shape. Comparing the response of cylindrical charges and block charges with equivalent sizes and detonation positions, it was found that when the proportional distance is less than 0.5 m/kg^1/3, the axial overpressure of cylindrical charges at the same proportional distance exceeds the radial overpressure by approximately 1.12~4.79 times its peak value. Additionally, when the proportional distance is less than 0.4 m/kg^1/3, the axial overpressure of cylindrical charges surpasses their radial counterparts. The radial overpressure generated by cylindrical charges is greater than that produced by group charges at equivalent proportional distances. Furthermore, blast shock waves propagate faster along the axial direction compared to radial propagation. Under top initiation conditions for both types of charges, one notable difference lies in vertical responses at the top part of structures. The vertical disturbance duration of the roof of the structure is longer, and the peak vertical acceleration of the roof is 15.6% higher in the top part of the large cabin and 12.2% higher in the top part of the small cabin, which has no great influence on the acceleration and displacement of the side wall. These findings demonstrate that charge shape indeed influences dynamic responses within structures.

In order to better study rock blasting mechanism better in layered rock strata, the dynamic tensile mechanical characteristics of the carboniferous shale surrounding rock mass around the Sujiayan tunnel were explored, which belongs to the north section of the Zhengwan high-speed railway project in western Hubei Province. To reveal the effects of impact angle and velocity on the dynamic tensile strength and corresponding failure mode of carbonaceous shale, dynamic Brazilian splitting tests were carried out under five impact angles (0°, 30°, 45°, 60° and 90°) by the split Hopkinson pressure bar (SHPB) device with a high-speed camera and the digital image correlation technology (DIC). At the same time, different impact velocities for every impact angle were also tested by three impact pressures (0.1 MPa, 0.2 MPa and 0.3 MPa). The results show that the dynamic tensile strength of the shale decreases first and then increases with the increase of impact angle under different impact velocities. The minimum value is reached when the impact angle is 30° and the maximum value is reached when the impact angle is 90°. The dynamic tensile strength of shale presents a significant anisotropy, and the degree of anisotropy decreases with the increase of impact velocity. With the increase of impact velocity, the dynamic tensile strength of shale increases correspondingly, and there is a significant linear relationship between the dynamic tensile strength and impact velocity. In addition, both impact angle and impact velocity have a great influence on the dynamic tensile failure mode of shale.