In order to further study the propagation characteristics of surge wave induced by underwater blasting loads, the multi-physical field coupling simulation method powered by the dynamic analysis software COMSOL was adopted to establish a transient solution model based on the second water source project-diversion project of Guilin City. The isosurface, peak stress and vibration velocity of surge wave under explosion load were studied and evaluated based on field monitoring results. The results show that the surge wave produced by underwater blasting essentially propagates around the center of the blast center, and the surge isosurface evolves from regular round to irregular ellipsoid with time. The surge waves decay rapidly during propagation, and with the increase of water medium velocity threshold, the influence range of surge wave action region is small. In addition, the stress of the surge wave has superposition effect under the condition of delayed blasting, and thus there are multiple peaks. When the distance to blast center increases from 28 m to 108 m, the attenuation rate of the peak vibration velocity of the surge wave reaches 96.3%, which has little effect on the structure. Meanwhile, the time of the peak velocity of the surge wave increases gradually with the increase of the distance to blast center.

Distortion phenomenon would occur in time-frequency analysis when Hilbert-Huang Transform (HHT) is used to process the blasting seismic signal mixed with noise. In order to improve the analysis performance for noisy blasting seismic signals, the factors affecting the accuracy of time-frequency analysis of HHT were improved through an improved algorithm. Firstly, the empirical mode decomposition (EMD) was improved by the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to suppress the low-frequency trend terms. Furthermore, the multiscale permutation entropy (MPE) code was added to control the high-frequency noise. Finally, the normalized Hilbert transform (NHT) was performed on the IMFs obtained by CEEMDAN·MPE. Through the above three steps, the problem of insufficient precision in the time-frequency analysis of noisy blasting seismic signals by the traditional HHT can be improved. In order to verify the accuracy of the CEEMDAN·MPE-NHT algorithm, a comparative study on the HHT and CEEMDAN·MPE-NHT algorithm was carried out, and the CEEMDAN·MPE-NHT algorithm was used for underwater drilling blasting seismic signals. The results show that the time-frequency spectrum of the IMF decomposed by CEEMDAN·MPE and processed by NHT has a greatly improved high resolution compared with HHT in both time and frequency domain. The research results can be used for identifying and controlling the hazards of blasting seismic waves.

In order to ensure the construction quality of large section shaft horsehead gate and reduce the damage caused by blasting, an advance crack zone blasting technology is put forward. According to the section design and engineering geological conditions, the section of Matoumen excavation, the gates at-199.5 m and-258.2 m of a certain underground mine are divided into upper layer, middle layer, and lower layer excavation zones. The construction sequence is: upper layer→middle layer→lower layer. Firstly, the advanced fracturing holes should be constructed along the excavation contour lines of each layer. The hole depth is equal to the driving depth of the horsehead gate. They are charged with decks and detonated before the main blasting area, which can achieve mutual penetration between holes. The "shock absorption ditch" shall be formed along the excavation contour lines of the horsehead gate, which can reduce the effect of blasting seismic wave propagation. Besides, each construction area of the horsehead gate is equipped with hole by hole millisecond delay detonations with an interval of 5~20 ms, which can achieve the interference and offset of the vibrations from the subsequent blasting and reduce the blasting impact on the large cross-section horsehead gate. It has been validated that the half-wall hole rate of the excavation contour line is higher than 95%. It can not only meet the requirements of controlling the quality of roof forming for the excavation of large cross-section gate in broken rock mass, but also reduce the cost of support and shotcrete.

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.

The reasonable selection of the incision angle is an important factor for the success of blasting demolition of a typical reinforced concrete chimney. In order to determine the selection range of incision angle, the isolation method was adopted to establish a theoretical model according to the force and failure characteristics of the residual section. The solution formula of any angle position on the residual section was derived, and a revision coefficient k was defined to express the influence of the cylinder at the upper part of the unnotched section. Furthermore, the stress and bending moment conditions of the dumping cylinder were established, and the selection range of the incision angle was obtained by combining the solution formula and the damping conditions. The case study shows that with the increase of the incision angle, the maximum tensile stress, the maximum compressive stress and the bending moment generated by the upper cylinder of the incision tend to increase, while the resistance moment of the residual section tends to decrease. The upper limit of the selection of the incision angle can be obtained when the maximum tensile stress reaches to the material strength limit, and the lower limit can be determined when the two bending moments are equal. Changing the incision angle would have a greater effect on stress than changing the incision height. Under the condition that the actual incision height is 4.5 m in the engineering case, the selection range of incision angle based on the established theoretical model is 198°~237.6°, and the actual incision angle is 216° within the theoretical selection range, which further verifies the reliability of the theoretical model. More extensive application and guide engineering practice are expected.

Experiments of vented explosion were conducted in a 1 m³ vessel under the conditions of top ignition for premixed methane-air gas with a concentration from 7% to 13% to investigate the influence law of methane concentration on flame evolution and internal overpressure during the vented explosion process. The explosion venting mechanism was analyzed by analyzing the pressure-time curve and the flame evolution image. The results prove that concentration has a significant impact on the explosion venting characteristics of the methane-air premixed gas. The overpressure inside the container presents a double-peak phenomenon with a specific methane concentration. The first pressure peak P₁ can appear at each concentration, while the second pressure peak P₂ only occurs when the concentration is 9%. P₁ increases first and then decreases with the increase of concentration, while the trend of the timing of the peak is the opposite. However, both reach the extreme value at the methane concentration of 10%. This is mainly formed by the combined effects of initial flame propagation, external explosion, Helmholtz oscillation and Taylor instability, etc. The phenomenon that P₂ is much higher than P₁ is mainly formed by the mutual promotion of flame and sound pressure and the thermoacoustic coupling effect triggered by disturbance. The flame downward propagation velocity increases first and then decreases with the concentration, and reaches the maximum value when the methane concentration is 10%, and the combustion velocity is generally faster in the slightly rich combustion state.

At present, mining method is widely used in tunnel construction. The influence of blasting vibration on surrounding rock and supporting structure in tunnel and its disaster control are always hot issues. In order to study the propagation law of blasting vibration inside a tunnel, the vibration signals of simultaneous detonation and detonation at three benches were monitored on site based on the engineering background of a tunnel with soft surrounding rock. The nonlinear regression of Sadovski formula and Fourier transform method were used to analyze and study the test data. The results show that for the same section of the tunnel, the vault has the characteristics of large vibration velocity, high vibration frequency and slow attenuation rate. When 100 ms delay blasting is used between the three steps, the blasting energy can be discretely distributed in time and space, and the vibration superposition effect can be significantly weakened. A single hole blasting test was set in the middle of the cut area, and the single hole vibration waveform was obtained by setting the delay between the test hole and the entire blast as 100 ms. Based on the principle of linear superposition, the delay time was optimized by investigating vibration waveforms synthesized by cut blasting. The results show that when the delay time between holes is 4~7 ms, the peak vibration velocity caused by cut blasting decreases sharply, and the effect of interference is obvious. After the delay time exceeds 7 ms, the peak vibration velocity has no significant difference.

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.

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.

To study the complex mechanical movement and accumulation process of broken blocks in the process of underwater rock bench blasting, a fluid-solid coupling numerical calculation method based on FLUENT-EDEM was adopted. Firstly, the parallel bond and Hertz-Mindlin contact model were introduced between the particles, and the parameters of the parallel bond were calibrated by comparing the results of Brazilian splitting experiment and numerical calculation. Furthermore, the underwater bench blasting model was established, and the mechanical action mechanism of water on rock mass breaking and movement was analyzed. Finally, the whole ejection process of particles from a submerged step block was studied, and characteristics of the block velocity, block stacking and flow field were discussed. The results show that the accumulation and stratification of block particles are related to their initial velocity and height, and the horizontal movement distance of the block particles in the middle step is the biggest under the explosion load action. Meanwhile, the block particles in the upper blocking part mainly roll and cover the middle block particle layer under the action of gravity and buoyancy, which are less affected by the explosion load. Additionally, the explosion energy is mainly used to break the rock at the initial detonation stage, and the water has no obvious flow velocity. With the bulging and throwing movement of block particles, the fluid streamline velocity near the front surface of the bench is largest. When the block particles start to roll and slide, the streamline is mainly affected by the movement form of the particles. Therefore, the fluid-solid coupling model by Fluent-EDEM can accurately simulate the block motion in the underwater bench blasting, which can provide a new research method for underwater rock blasting engineering.