In order to realize the blasting demolition of 62.8 m high brick structure chimney in complex environment, various demolition options which fully consider the structure of the chimney and the surrounding environment were compared in the case of insufficient space for collapse on the east, west and north sides. After analysis, one-way and two-way folding blasting options were initially selected to blast and demolish the chimney. The circular angle of the upper and lower notch was designed as 220°. The lower notch was set as 2 m high at 0.5 m from the bottom of the chimney, while 30 m from the bottom of the chimney located the upper notch which parameters need to be simulated and optimized. ANSYS/LS-DYNA finite element analysis software was used to compare the collapse effect of the preliminary scheme, and it was calculated that the one-way folding blasting did not meet the demolition requirements, so the two-way folding blasting was selected. Then the chimney collapse process was simulated with the upper cut height of 1m, 1.5 m and 2 m and the delay times of 0.5 s, 1 s, 1.5 s, 2 s and 2.5 s between the upper and the lower cut. After analyzing the collapse process and the distribution range of the blast pile of the chimney under different working conditions, it was determined that the best folding effect with a small collapse space happened when the upper cut height was 1m and the delay time was 1 s. Furthermore, safety measures which were related to blasting vibration and flyrock protection were designed. The blasting effect showed that the chimney collapsed smoothly according to the designed direction during the blasting process, and no damage occurred to the surrounding buildings (structures). The overall blasting demolition effect was good enough to meet the expected goal. It can provide a reference for related scholars and demolition projects.

The demolition blasting of the tailrace outlet cofferdam of Baihetan hydropower station has obvious characteristics of tight construction schedule, heavy task, complex rock conditions, close proximity to protective objects and high requirements for slag washing by water flow. In view of the important and difficult points in the construction, a phased, partitioned and layered blasting demolition scheme was adopted, and thus the single cofferdam was divided into two phases, three layers and eight zones. By reserving an economic cofferdam and demolishing the part above water in advance, the difficulties of huge engineering quantity and tight construction schedule were overcome. The method of drilling with large-diameter drills and protecting the hole with casing effectively reduced the occurrence of hole collapse under complex geological conditions, improved the construction efficiency and ensured the blasting effect. The design of high powder factor, low single shot, inter-hole segmentation and intra-hole delay not only met the requirements of safety control of vibration velocity, but also ensured that the rock fragmentation after blasting can be washed away by water flow. The engineering application results showed that the peak vibration velocity of blasting under the most unfavorable conditions was 11.85 cm/s, which was less than the allowable safety control standard of 12 cm/s for structural concrete. The measured peak pressure of surge wave was 0.12 MPa, which was also under the allowable value of 0.4 MPa for hydraulic steel gates. The fragmentation after blasting was controlled mostly within 40 cm, and the boulder yield was controlled within 5%. The research results can provide reference for similar projects.

In order to analyze the failure characteristics and strain evolution law of reinforced concrete columns after blasting under different amount of explosives per unit area and section stresses, blasting tests of 12 reinforced concrete columns were carried out by using a self-developed test system with uniaxial inertial dynamic loading model, which is based on the theory of elastic mechanics. When the upper section stress of the reinforced concrete columns was 0 MPa, the corresponding amounts of explosives per unit area were 0.11 kg/m², 0.23 kg/m², 0.27 kg/m², respectively. When the upper section stress was 2 MPa, the corresponding amounts of explosives per unit area were 0.13 kg/m², 0.18 kg/m², 0.23 kg/m², respectively. When the upper section stress was 3 MPa, the corresponding amounts of explosives per unit area were 0.18 kg/m², 0.23 kg/m², 0.32 kg/m², respectively. When the upper cross-sectional stress was 4 MPa, the corresponding amounts of explosives per unit area were 0.13 kg/m², 0.18 kg/m², 0.23 kg/m², respectively. In addition, numerical simulation software was used to analyze the impact of different section stresses on blasting effect. The longitudinal central axis crushing distance is defined to describe the crushing range of the column after blasting, and the central axis crushing distance and strain evolution law are analyzed under different influencing factors through theoretical deduction, field experiment and numerical simulation. The analysis results show that with the increase of section stress, the greater the coupling tangential stress close to the central axis, and the coupling tangential tensile stress which is perpendicular to the loading direction is relatively reduced. When the amount of explosive per unit area is less than 0.15 kg/m², the crushing range of the central axis of the column decreases with the increase of the section stress. When the amount of explosive per unit area is more than 0.15 kg/m², with the increase of section stress, the crushing range continues to increase. The peak of tangential tensile strain shows an upward trend, and the absolute value of the peak radial compressive strain gradually decreases. When the section stress is fixed, the crushing range of the column increases with the increase of the amount of explosive per unit area, but the growth rate decreases with the increase of the amount of explosive per unit area. Meanwhile, the peak of the tangential tensile strain of the column increases, and the absolute value of the peak radial compressive strain also shows an upward trend. With the increase of section stress, the crushing range in the column damage cloud is increasing, and the crack tends to extend axially with the load, which further verifies the correctness of the test conclusions.

To reveal the propagation characteristics of blasting vibrations induced by blasting demolition of a reinforced concrete support beam in a deep foundation support system, the vibration velocities and frequencies in the horizontal and vertical directions of the support system and the response spectrum characteristic of the enclosure structure of the foundation pit are analyzed based on the monitored vibration data. The vibration test lines were laid in the same and the upper layer to the support beam. The results show that the vibration velocity decays rapidly with the increase of distance. The peak vibration velocity at the blasting layer is 5~7 times than that of the upper layer within 50 m of the blasting area. However, the peak vibration velocity of the blasting layer gradually attenuates to 1~2 times than that of the upper layer outside 50 m of blasting area. Besides, there are obvious differences among the components of vibration velocities in three directions in the blasting layer. The radial component has the largest peak value, which is 2~5 times of the vertical component. On the contrary, the three components of vibration velocities in the non-blasting layer are close to each other. Meanwhile, it is high frequency vibration in the support beam, and the vibration frequency of the blasting layer is slightly smaller than that of the non-blasting layer, and both of them have a steep increase phenomenon in the supporting structure of the foundation pit. When the support beam is demolished by blasting, the short-period response spectrum of the enclosure structure of the foundation pit is obviously beyond the designed spectrum, and the blasting vibrations will have a certain influence on the enclosure structure. The related results can provide references for the design of blasting demolition of support beams, vibration control, and the dynamic response analysis of enclosure structure of a deep foundation pit.

In order to select the shaped charge structure with low residual height and small fragmentation after blasting of concrete base, numerical simulation method is used to study the motion characteristics of jet flows formed by 60° and 120° conical liners and explosive formed projectiles (EFP) formed by curved liners with curvature radius of 10.8 cm as well as the vertical penetration process and damage effect on concrete bases under the same explosive charge, outer diameter and shaped charge liner thickness. The results show that: Different shaped charge penetrators have different penetration modes to concrete bases. The head part of the jet flow formed by the 60° conical liner penetrates the concrete base first, and then the pestle part expands the hole. For the 120° conical liner, the pestle body and the jet flow penetrate the concrete base together, while the curved liner mainly penetrates the concrete base by the formed projectile; the crushing capacity of the shaped charge is related to the diameter of penetration hole. The larger the hole diameter is, the stronger the crushing capacity is. The penetration hole diameters of 60° liner, 120° liner and EFP liner are 4.3 cm, 5.2 cm and 7.0 cm, respectively. In addition, the number and width of cracks formed within the penetration depth show an increasing trend; the residual height of the concrete base after blasting is related to the distance between the transverse through cracks and the bottom, while the formation of transverse cracks is related to multiple factors such as penetrator parameters, charge quantity and so on; for the concrete base with a limited size, a shaped charge liner with a large cone angle has a better comprehensive effect with respect to crushing range and degree. Although the penetration ability of EFP liner is the weakest and the residual height of the concrete base after blasting is large, its crushing ability within the penetration depth is the strongest. The study of blasting effect of different shaped charge penetrators on a concrete base can provide a reference for exploring damage mechanism and selecting destruction mode.

A waste fireworks and firecrackers destruction project in Nantong city required the destruction process to be safe and efficient. On the basis of fully understanding the characteristics of the fireworks and firecrackers to be destroyed, the principles of destruction were clarified, and the destruction plan was carefully designed in combination with the specific characteristics of the project. In the open offshore area, a 20 m×20 m site with a depth of 2 m and a maintenance slope of about 5 m was first pre-set as the destruction site. The entering and exiting roads were then arranged reasonably so as to improve the unloading efficiency. According to the traffic conditions between the storage and the destruction site, the transportation route and time were determined. At the same time, in order to ensure the safety of the transportation process, the vehicle speed, loading and unloading, placing and other technical requirements were strictly regulated. According to the size of the destruction site and the location of fireworks to be destroyed, the minimum discharge angle was calculated as 12°. Combined with the maximum height of the fireworks liftoff, the discharge area, escape area and scattered area were determined in the process of destruction, based on which the safety warning range of the destruction was set as 120 m. The joint control measures of warning personnel and UAV were adopted to monitor the destruction process in real time to ensure that the fire hazard was controlled in the initial stage. The destruction was thorough, safe and accident-free with good results.

Field detection of surrounding rock damage range is cumbersome. In order to obtain the surrounding rock damage range simply and accurately, a major underground cavern project to be built is taken as the research background. Theoretical analysis and numerical simulation are adopted according to the blasting design scheme to establish the cumulative damage calculation model of multi-stage delay blasting with different charges. By using equivalent blasting load method and LS-DYNA complete restart technology, the blasting vibration data and the cumulative damage range of surrounding rock under multi-stage delay blasting loads are obtained. The cumulative damage effect of surrounding rock of the underground cavern is analyzed and the correlation between blasting vibrations and the cumulative damage range of surrounding rock is studied. The results show that the induced damage of surrounding rock of the underground cavern is mainly caused by blasting of the second circle holes and the surrounding hole, and the damage range of surrounding rock of the cavern vault (2.21 m) is significantly larger than that of the surrounding rock of the arch waist (2.05 m). The peak value of the blasting vibration curve is within the delay time range of cutting holes, which is not consistent with the blasting stage that causes the damage of surrounding rock. Therefore, the correlation between the peak particle vibration velocity and the damage range of the surrounding rock should be studied within the delay time which has great influence on the damage of surrounding rock. The quantitative relationship between the cumulative damage range of surrounding rock and blasting charge, blasting center distance and peak particle vibration velocity is established, and the functional relationship between the cumulative damage range of surrounding rock can be deduced from the peak particle vibration velocity at any blasting center distance. It provides a basis for controlling the blasting damage of surrounding rock and has practical significance for guiding the safety of blasting construction on site.

In-situ collapse blasting demolition technology is a new blasting demolition technology which can break through the condition of serious shortage of collapse space for towering chimneys. The difficulty of this technology is to set up efficient operation platforms at multiple locations at hundreds of meters to quickly complete drilling, charging, stemming and networking, thus forming multiple ring blasting cuts. According to the requirements, a variable diameter hanging basket as a construction platform is developed. The overall design idea of the new operation platform is as follows: The core function of the platform is defined based on the analysis of the operation process, and the variable section basket platform with a sliding plate is selected by comprehensively considering various factors such as efficiency, reliability, adaptability and cost. A parametric model is established to determine the optimal values of the length and included angle of the fixed section and the sliding plate of the hanging basket for different chimney dimensions, which is according to the adaptability of the platform to the overall dimension of the chimney. The technical schemes of the telescopic structure are compared and selected, and finally the steel wire rope traction scheme together with the resistance reduction scheme by tetrafluoroethylene plate is selected. On the basis of the above technical scheme, the structural scheme, safety guarantee scheme, adaptive design scheme, installation, disassembly and using scheme of the platform are determined. In order to verify the reliability of the structural design, the stress analysis of the structure under various working conditions is carried out by using the finite element software. Meanwhile, a special test frame is set up, and a series of tests including functional test, load test and reliability test are carried out on the first test prototype to verify the safety and functional reliability of the platform structure. The test results show that all the functions of the platform reach the design expectations, and the structural safety and functional reliability meet the requirements. The platform can meet the needs of in-situ collapse of towering chimneys by blasting demolition, and can also be used as a construction platform for the demolition of other high-rise structures with variable cross-sections.

The dynamic response of the lining structure of an existing tunnel during the blasting construction of a new tunnel is studied based on the Bogongao No.1 tunnel project which belongs to one of the level 1 risk tunnels of Ganzhou-Shenzhen high-speed railway. The numerical model of the test section is established by using ANSYS/LSDYNA finite element software. By comparing the field measured with the model calculated vibration velocities, the reliability of the numerical simulation is verified with the inversed surrounding rock mass parameters. Furthermore, based on the parameters of the test section, a numerical model of the intersection of the two tunnels is further constructed, which is used to analyze the vibration attenuation law of the existing tunnel lining structure in the intersection, and put forward vibration reduction measures under the worst cases at the intersection. According to the research results, the largest vibration velocity appears at the vault of the existing tunnel and the smallest vibration velocity is at the floor. Within 30 m from the front and back of the intersection, the vibration velocity at the vault is about 2.0~2.3 times that at the side wall closer to the blast. For the whole section of the existing tunnel, the controlled vibration velocity of 1.6 cm/s. However, for the side wall, the early warning value of vibration velocity should be 0.8 cm/s. When the cut holes are bottom initiated, most of the explosion energy is transmitted to the unexcavated area, which contributes to a higher attenuation rate of vibration velocity from the excavated area of the new tunnel than from the unexcavated area. The blasting scheme of the test section is no longer applicable to the cross affected section. On the premise of considering both the work efficiency and blasting effect, the vibration velocity of the secondary lining in the existing tunnel can be controlled within the safe range after the footage is shortened to 1.0 m and the cut hole charge is reduced to 9.86 kg.

In order to study the crushing energy dissipation characteristics of graphite ore rock under impact loads, ϕ 50 mm diameter split Hopkinson pressure bar (SHPB) test device is used to conduct impact compression tests. The crushing energy dissipation law of the graphite ore rock samples is analyzed under different loading rates with five different impact pressures from 0.2 MPa to 0.6 MPa with a 0.1 MPa interval. The test results show that the dynamic compressive strength of the samples have a strong third-order polynomial relationship with the average strain rate under impact loads. The graphite ore rock has dynamic hardening under impact loads, and its dynamic compressive strength increases nonlinearly with the increase of strain rate, which shows an obvious strain rate effect. In addition, there is an obvious logarithmic relationship between the crushing dissipation energy and the incident energy. With the increase of incident energy, the crushing dissipation energy also increases. However, the proportion of the crushing energy gradually decreases from 0.38 to 0.11. The crushing energy dissipation density of the samples has an obvious strain rate effect, and its value increases with the increase of strain rate. Besides, the average particle size of the broken samples is strongly correlated with the energy dissipation density of the samples. As the energy dissipation density increases, the crushing degree of the sample becomes more severe. Therefore, the average particle size of the crushing fragments can be used to quantitatively describe the crushing degree of the samples.