The shock load of underwater explosion usually includes shock wave load and bubble pulsation load. The structural damage caused by shock wave and bubble load is always a hot topic in ship design. It is generally believed that the impact of shock wave load on the structure is mainly local damage, while the impact of bubble pulsation load on the structure is mainly global damage. The actual damage process of underwater explosion load is often the result of the joint action of the two kinds of loads. However, it is difficult to quantify the contribution of the two kinds of elements to ship damage. In order to study the damage effects of two kinds of loads on ships, a variable section box girder was used to simulate the surface ship structure, and its response process under the impact of underwater explosion was experimentally studied. Both the influence of distance on shock wave and the conditions for utilizing bubble energy were considered in the design of the experiment. The results show that plastic hinge was formed in the box beam structure near water surface under the action of near-field explosion load, and the energy transferred by explosion load to the beam structure was mainly converted into the deformation energy of the plastic hinge. In addition, the dynamic strain response of the structure gradually decreased from the middle to the end of the box beam, and the residual plastic deformation mainly occurred near the middle of the structure. The continuous large opening mode on the upper surface of the box beam resulted in larger plastic deformation of the deck side plate and the upper part than that at the bottom of the hull.

A 110 m thin wall reinforced concrete cooling tower has been demolished by controlled blasting. Aiming at the characteristics of large height, thin wall and large bottom diameter of the cooling tower, the blasting scheme of “opening window, breaking steel bar and reserving supporting plate” was adopted. In the pre-demolition process, two simplified directional windows were set up along the edge of the blasting zone by optimizing the blasting incision of the cooling tower. In the blasting area, only the bottom and top of the herringbone column of the cooling tower were blasted, and the blasting incision was divided into 5 blasting areas using the non-electric millisecond delay initiation technology. In order to control the damage effect of blasting, laying buffer soil layer and steel plate in the collapse direction of the cooling tower for double protection effectively reduced the collapse touch vibration. The protective measures combined with mesh and geogrid covering at the blasting incision effectively controlled the flying stones without causing damage to the surrounding structures. The blasting effect shows that setting two simplified directional windows on the edge of the blasting incision not only cuts down the drilling and related workload, reduces the safety hazard and the difficulty of protection, but also improves the structural stability of the pre-treatment part and prevents the blasting incision from falling. Through the simplified design of the directional window, the cooling tower distorts and disintegrates fully in the collapse process, with a concentrated explosion pile and small ground vibration.

According to continuous blasting vibration monitoring results carried out on three monitoring points (bottom, middle, and top) at different vertical positions at the same horizontal distance from an underwater blasting project in a channel adjacent to high-rise buildings, the three-dimensional spatial patterns of blast vibration velocity, vibration frequency, and vibration energy were analyzed, and the elevation effect mechanism of blasting vibrations on high-rise buildings was explored. The analysis results show that: (1) Blasting vibration velocity is influenced by the combined action of the elliptical motion of Rayleigh wave, energy attenuation, and whiplash effect. It presents a significant three-dimensional spatial effect in the propagation among high-rise buildings, in which the vertical direction is dominated by Rayleigh wave elliptical motion and whiplash effect, showing a significant elevation amplification effect, while the horizontal and tangential directions are dominated by Rayleigh wave elliptical motion and energy attenuation, exhibiting an elevation attenuation effect. (2) The propagation of blasting vibration frequency in high-rise building is mainly affected by the vertical distance from the wall, showing an elevation attenuation effect in all three directions. (3) The distribution of vertical blasting vibration energy presents a significant elevation amplification effect from the bottom, middle to the top of the building. Specifically, the high-frequency energy proportion shows an elevation attenuation effect in the middle and top relative to the bottom, while the low-frequency energy proportion exhibits an elevation amplification effect in the middle and top relative to the bottom.

The building to be demolished was a framework-tube structure with high structural strength and good stability. It was located in a densely populated area with a complex surrounding environment. To determine a reasonable blasting demolition plan, the “three-dimensional gradual detonation” method was proposed, which was a way of detonation that achieves spatial delay by differentiating the delay time of adjacent blasting column holes in the horizontal and vertical planes of the blasting notch. Then, ANSYS/LSDYNA finite element software was used to simulate and analyze three different blasting schemes: V-shaped detonation, symmetrical detonation, and “three-dimensional gradual detonation” with a delay time of 0.50 s. By comparing the shape and range of blasting muck pile, and energy changes when the structure touches the ground, the blasting scheme “three-dimensional gradual detonation” with a delay time of 0.50 s was finally determined. The results showed that compared with symmetrical detonation, the “three-dimensional gradual detonation” reduced the kinetic energy when the structure touched the ground by 50% and increased the internal energy by 47%. Compared with V-shaped detonation, the kinetic energy when the structure touched the ground was reduced by 36%, and the internal energy was increased by 31%. The use of “three-dimensional gradual detonation” reduces the collapse vibration of the structure and completely disintegrates it, reducing the range of the blasting muck pile. When the delay time is 0.50 s, the width and length of the blasting muck pile and the collapse vibration of the structure are smaller than when the delay time is 0.25 s. The numerical simulation time for the upper part of the structure touching the ground was 3.8 s, while the actual time was 4.0 s. The final formation of the blasting muck pile was at 6.0 s, and the numerical simulation of the building collapse process and the range of the blasting muck pile was in basic agreement with the actual blasting effect.

Smooth blasting is the main method for controlling excavations in hard rock tunnels, but due to the complex mechanism and process of rock fragmentation by blasting, as well as the rough design of blast parameters, it is difficult to achieve a smooth excavation profile for the entire tunnel. This study focuses on the Level Ⅲ hard rock section of the Zhaishan tunnel, and through a large number of blasting tests and investigations, it was found that there were problems such as over-excavation and under-excavation, misfire, and secondary blasting construction around the tunnel profile after the original blasting plan was carried out. Based on relevant specifications and engineering experience, optimization measures were proposed for the blasting parameters, including reducing the spacing between contour holes, increasing the number of relief holes, using water bag as the charge decking and stemming, as well as reducing the amount of explosives loaded in each hole. The results showed that the optimization measures can improve the utilization of explosive energy, achieve uniform fragmentation of the rock mass, and control over-excavation and under-excavation of the tunnel perimeter rock mass. The blast parameter optimization also results in smooth and round tunnel profile with clear blast hole marks, which helps to improve the quality of excavation and accelerate the progress of tunnel construction.

Dynamic disturbance scattering such as blasting generates dynamic stress concentration which is an important factor resulting in instability and damage in underground structures. In this paper, a theoretical model of a deeply buried pipeline under plane P-wave incidence is developed based on the wave function expansion method. Fourier transforms and Duhamel integrals were introduced to solve the transient response around a deeply buried circular aqueduct, and the effect of wavelength on the transient response was analyzed. Considering that the ground stress is a non-negligible factor for the destabilization of deep structures, a numerical model was established with the help of LS-DYNA finite element software to analyze the dynamic response mechanism of deeply buried pipelines under the action of the initial stress. The results of the study show that the compressive stress concentration generated by short-wave incidence is greater, and the tensile stress concentration due to long-wave incidence is greater, and the tensile stress concentration is very easy to occur along the direction of incidence. The larger the lateral pressure coefficient, the more pronounced is the suppression of the dynamic response in the presence of initial stresses. In addition, the pipeline and the surrounding rock mass under the initial stress state will experience more drastic fluctuations in the stress state when subjected to dynamic loading. These research phenomena reveal that the dynamic response mechanism of underground pipelines and the impact of the in-situ stress environment, which can be used for the seismic optimization design of deep underground structures.

Taking the “6·13” major gas explosion accident in Shiyan as the research object, this work constructed an accident investigation technique integrating scene investigation, interview and inquiry, numerical calculation and theoretical analysis. During the scene investigation, it was found that a section of DN57 mm medium pressure natural gas pipeline remained in the river below the southeast corner of the market. The pipe was adjacent to the domestic sewage drainage outlet, and it was rusted and partially ruptured due to the long-term wet environment. Meanwhile, yellowish natural gas fume was first found in the river at the southeast corner by video monitoring, visits and inquiries from surrounding residents, which led to the result that the aforementioned pipeline was the leak point. In addition, some merchants were engaged in flame operations before the accident. Some sparks entered the river through the smoke exhaust pipe and ignited the premixed combustible gas accumulated in the river, which resulted in the explosion. A numerical model of the river was established by the ANSYS/FLUENT software, and the volume of the natural gas accumulated in the riverway was 600 m³, which explosive TNT equivalent was 225 kg. The gas volume and explosion equivalent are consistent with the data published in the accident investigation, which proves the feasibility of this analysis method.

With the widespread use of mixed emulsion explosives, there exists the situation that the stemming materials penetrate into emulsion explosives in open-pit blasting construction, which indirectly changes the stemming length and reduces the blasting effect. To study the influence of stemming on mixed emulsion explosives, stemming simulation tests, numerical simulation tests and field blasting tests were carried out successively. Firstly, four kinds of PVC pipes with common hole diameters were used to simulate the blasting holes, and the rock chips were used to simulate the stemming materials. They were used to systematically study the infiltration of rock chips into the explosives on top of the explosive column during the filling process of stemming. Secondly, the numerical simulations of single-hole blasting were conducted with the LS-DYNA software, and the influence of the stemming mixture at the top of the explosive column on the explosive power was investigated by observing the changes of stress values at the measurement points. Finally, the stemming filling process was improved by setting physical isolation during the charging process based on the bench blasting in the Jinduicheng open pit mine. And the effect of stemming on the mixed emulsion was analyzed by comparing the blasting effect before and after the physical isolation. The results show that the phenomenon of explosive overflow appears on the top of the explosive column in the explosive charging process. Then, the rock chips gradually infiltrate into the emulsion explosive due to the influence of gravity after the charging is completed, and the infiltration length of rock chips increases with the increase of hole diameter in the same time. The numerical simulation results show that the stresses of different monitoring points have decreased, and the infiltration of stemming reduces the explosive power of the top explosive. The fragmentation analysis of the top rock after improvements shows that the main fragment size distribution of rocks decreases from 20~40 cm to 0~20 cm, and the proportion of rocks over 60 cm decrease from 6.13% to 1.81%, compared with the conventional charging process. In summary, the stemming has a significant impact on the power of emulsion explosive and blasting effect, and it can effectively improve the blasting effect by taking physical isolation to separate the stemming and explosive.

The optimization of delay time is very important for controlling blasting vibrations and guaranteeing the technical-economic effect of blasting projects. The proposed improved linear superposition method can be used to in-depth discover the relationship between the particle peak velocity (PPV) of blasting vibration and delay time. Because blast vibrations actually belong to random process, which means merely using a one-time measured single-hole blasting vibration signal to simulate a multi-hole blast vibration waveform may not be reasonable. Similarly, it is also not enough to simulate a multi-hole blast vibration waveform corresponding to a certain delay time only once. A method involving random variables and statistical treatments is necessary. Firstly, Fourier series is used to represent a measured single-hole blast vibration waveform. This is necessary to formulize a piece of measured time-series data. Secondly, random variables are added to the coefficients and phases of the Fourier series expansion to generate a specified number of single-hole blasting vibration waveforms. Thirdly, Monte Carlo simulation is used to calculate the mean value of PPVs corresponding to each delay time between 0ms and 250 ms with an increment of 1 ms, and the change curve of the average PPV with delay time can be obtained. The results of example analysis show that if the civil house 531 m away from the explosion source is taken as the protection target and 0.45 cm/s is taken as the peak particle velocity control threshold, any delay time more than 7 ms can be selected to meet the safety standard, and when the delay time increases, the PPV decreases in general. To pick a specific delay time from the range determined by the above process, it is necessary to observe the relationship between the rock fragmentation effect and delay times. By investigating the fragmentation results of four blast tests, the total amount of boulder yield decreases first and then increases with the delay time per meter, and the minimum value appears when the delay time is 7 ms/m. That is, if the designed hole spacing is 6 m, and hole-by-hole initiation is adopted, the optimal delay time in terms of rock fragmentation is about 40ms. This delay time just falls into the range larger than 7 ms determined previous by the improved linear superposition method. Therefore, by comprehensively considering both the results of Monte Calo simulation of blasting vibration and the rock fragmentation tests, the optimal delay time of the mine can be finally selected as 40 ms.

As the main index to evaluate the blasting effect, the rock blasting fragmentation directly affects the subsequent construction objectives and construction costs of water conservancy and hydropower projects. In the process of quarry blasting, it is of great significance to improve the blasting efficiency and quality and meet the demand of good grading curve for the dam aggregates in the construction of water conservancy and hydropower projects. The influence of the number of free surfaces and the delay interval between holes on the rock blasting effect is studied by establishing a two-dimensional finite element numerical model. Firstly, the interaction of stress waves between holes and the reflection mechanism of explosion stress waves on free surfaces are explained theoretically. The conditions for the generation of blasting cracks are also analyzed. Then, with the help of ANSYS/LS-DYNA finite element software, RHT model is used to simulate the rock fracture process under different number of free surfaces and different delay times between holes, and WipFrag is used to analyze the rock grading under different blasting conditions. The numerical simulation results show that the influence of different number of free surfaces on blasting grading is obvious. Compared with no free surfaces, the maximum bulk yields of single free surface, two free surfaces and three free surfaces decreases by 25.9%, 46.5% and 61.8%, respectively. It can be seen that the more the number of free surfaces, the more cracks produced in the rock, the better the blasting fragmentation effect. Compared with simultaneous initiation, delayed blasting is beneficial to improve the rock fragmentation effect, but the interaction between stress waves and holes is not obvious in short delayed blasting.