In the blasting demolition of large-volume reinforced concrete bridges in China, the traditional method of manual drilling of 40 mm small-diameter holes for blasting of bridge pier columns is time-consuming, labor-intensive, difficult to ensure drilling accuracy, and has high construction costs. Based on the experience of previous studies, a new method of large-diameter drilling for bridge demolition has been proposed, which includes technical measures for blast hole diameter, hole layout, powder factor, initiation network, and safety protection. To verify the effectiveness of this new method, the blasting demolition project of Ronghui 2 bridge of Chongqing Lijiatuo compound line bridge south diversion project was selected. According to the structural loading of the bridge and the environmental conditions, delayed initiation technology was used, and explosives were detonated at a certain height above the bridge pier, which led to the bridge sequentially collapsing in place from the center to both ends, achieving the goal of one-time completion of the demolition. In this method, water-mill drilling was used to dig holes into the bridge piers, with a hole diameter of 70 mm and crosswise drilling layout, and nonel millisecond delay detonators were used inside the holes, while electronic detonators were used outside for ignition. Multiple layers of protection were provided by bamboo boards, rubber mats and flexible wire mesh. After ignition, the blasting sound was muffled, and the bridge completely collapsed and disintegrated according to the design requirements, while the impact of flying rocks, blasting vibrations, collapse ground vibrations, and explosion shock waves were all controlled within the allowable range.

In order to develop a kind of packaged emulsion explosive with full appearance and long storage period, the formulation of the packaged emulsion explosive with the best natural storage performance was selected as the reference object. The corresponding emulsion matrix was prepared by testing different kinds and proportions of emulsifiers, and the corresponding packaged emulsion explosive was prepared by physical sensitization and chemical sensitization. The storage stability of each emulsion explosive was evaluated by means of high-low temperature cycle tests and water solubility tests. The results show that the stability of the emulsion explosive prepared by polymer emulsifier LZ2832 is better than that prepared by polymer emulsifier EPE-3002. Among the composite emulsifiers, the stability is best when the ratio of emulsifier Span80 to emulsifier LZ2832 is 1∶9, which can be subjected to at least 40 high-low temperature cyclic tests. It is expected that this packaged emulsion explosive product can be stored naturally for more than 24 months. In explosive sensitization, hollow glass microspheres with a matrix mass of 1.2% are first physically sensitized. In addition, accelerant #2 with 0.2% matrix mass and a sensitizer with 0.3% matrix mass are used for chemical sensitization when the temperature dropped to 50~55 ℃. The aftereffect of explosive sensitization is obvious, and the final density is controlled at 1.05 to 1.10 g/cm³. The results of batch production tests on the production line are consistent with the experimental results, and the full and elastic packaged emulsion explosive product with a long storage period has been successfully developed. The explosive has remained stable in natural storage for 12 months with the detonation velocity more than 4500 m/s, the brisance more than 16 mm, and the detonation distance more than 6 cm.

The inlet cofferdam of the expansion engineering of Wuqiangxi hydropower station consists of the reserved rock barrier, concrete, soil and stones. The rock barrier is a bedding slope with relatively developed soft interlayers, which results in a complicated geological condition and blasting demolition environment for the cofferdam. In the process of demolishing the bedding rock barrier, it is impossible to break the rock once in a large area according to the economic section of a conventional cofferdam due to the large engineering quantity of the underwater blasting excavation, high requirement of fragmentation, long construction time and high risk. Under the condition of ensuring the stability of the cofferdam, the method of vertical stratification, horizontal zoning and loosening bench blasting was adopted to implement land excavation as much as possible. For the underwater blasting, according to the geological conditions of rock barrier, the mechanical characteristics of rock mass, the water depth (20~37 m) and the fragmentation requirement, the powder factor of 0.9~1.1 kg/m³ and maximum charge per delay of 60 kg was adopted. Electronic detonators were used for blast hole initiation and a series of safety measures such as bubble curtains and flexible protective nets were set. The field monitoring results show that the effect of blasting vibration and water percussive wave on structures such as inlet gate has been effectively controlled, and the efficiency of underwater slag removal and transfer has been improved.

The peak vibration velocities and distributions of main frequencies induced by the tunnel blasting operations of Wuhan Metro Line 5 when it was passing through the air defense chamber, Beijing-Guangzhou railway, Yellow Crane Tower and Sacred Stupa were analyzed based on the field monitoring data. Furthermore, FLAC3D software was used to analyze the vibration velocity attenuation law, displacement, and stress response law of the air defense chamber structure under the influence of upper bench blasting. The field monitoring results were in good agreement with the numerical simulation results. The results showed that the air defense chamber and Sacred Stupa were affected the most by blasting with the vibration velocity close to the limit value. While the impact of blasting on the reinforced concrete structure of Yellow Crane Tower was small. The blasting vibration of the existing railway was less than 0.9 cm/s, lower than the control value of 2 cm/s. With the advance of tunnel working face, the impact of blasting vibration on the railway will get smaller. The maximum peak vibration velocity of each measuring point appears in the vertical direction, and the corresponding main frequency is mainly located in the low and medium frequency region. In addition, the vibration energy mainly concentrated in the frequency range of 20~65 Hz. The attenuation of peak vibration velocity (PPV) at each part of the civil air defense chamber is different with the maximum value appears near y=4 m, and the PPV attenuates faster in the excavated area. The displacement of the air defense structure is within the control range, and the maximum displacement and principal stress are concentrated at the arch foot B which is closer to the blasting source. Finally, the safety control value of the peak vibration velocity of the civil air defense structure is obtained by regression of peak vibration velocity and maximum principal stress.

To improve stemming effectiveness for tunnel excavation and blasting, a stemming device was designed utilizing the expansion characteristics of aluminum tubes under explosive action. The expansion-induced circumferential strain of the stemming device colliding with the steel tube was then measured using a dynamic strain gauge. The simulated explosive stemming devices were subjected to uniaxial compression deformation tests using a universal testing machine. The stemming effects were evaluated by recording the blasting process of cement pillars through high-speed photography. Results showed that the peak circumferential strain of the steel tube under the impact of the stemming device reached 0.02, indicating that the expansion impact force of the device on the blast hole wall was substantial which helped the device adhere to the wall. The compressive strength of the stemming device after adhesion to the blast hole wall was between 4.1 MPa and 5.5 MPa and its shear strength ranged from 0.49 MPa to 0.66 MPa, far greater than the conventional stemming material's shear strength of 0.09 MPa. In practical use, the stemming device together with the stemming material could effectively prevent its movement. When the traditional stemming material was used for stemming cement pillars, punching phenomenon appeared while no damage was observed after blasting. However, when the stemming device was used instead, there was no punching, and the stemming device only shattered after creating cracks at the collar of the blast hole, resulting in the cement pillar being split into three parts. Therefore, the stemming device significantly improved the stemming effects, and helped increase rock-breaking efficacy of the explosive gas while also enhancing the throwing effect, which is of great significance in improving blasting effects for cut holes.

Ground surface settlement caused by explosion-induced liquefaction of saturated sand foundation is an important subject in the seismic safety evaluation and explosion compaction of dam foundation. In this paper, the characteristics of ground surface settlement caused by liquefaction under contained explosions are studied for layered saturated sand foundation with roller compaction. Based on the existing empirical prediction models of explosion-induced liquefaction and surface settlement, the calculation formula of liquefaction volume is derived, and the rapid prediction model of surface settlement area is established and verified for reliability. Based on the above model, the characteristics of the explosion-induced liquefaction zone of saturated sand foundation and the resulted surface settlement funnel are investigated by changing the control factors such as compactness, explosive amount and burial depth, and the influence of stratified ground compaction on the characteristics of the surface settlement funnel is also discussed. The results show that the explosion liquefaction zone of saturated sand foundation has three types from small to large, including ellipsoid type, funnel type and pot bottom type. From small to large, there are two types of surface settlement area: inverted cone type and butterfly type. The liquefaction and settlement zones increase with the increase of explosive amount and the decrease of burial depth and compactness. For the layered saturated sand foundation with rolling compaction, the explosion-induced liquefaction and the resulted surface settlement are not only affected by the amount of explosive, buried depth and density, but also determined by the relative size of delamination thickness compared with the initiation depth, which further affects the range of surface settlement area.

In order to solve the problem of blasting demolition of tall reinforced concrete water towers in restricted space, a vertical in-situ blasting demolition technology was developed. The impact failure mechanism, collapse process and touchdown vibration of the water tower were analyzed comprehensively by means of high-speed photography, vibration monitoring and numerical simulation. It was found that the collapse process of the tower by vertical in-situ blasting demolition is similar to free fall motion with an acceleration of 9.4 m/s² calculated by regression analysis, which was slightly smaller than the gravity acceleration. By using the “separated” finite element model, the collapse process of the water tower could be approximately simulated and the impact time of each section cylinder could be accurately captured. In general, cumulative damage by multiple impacts is the main characteristic of the complex failure process of the water tower, which can be simulated by the No.159 concrete material model. The main frequency band of the vibration is mainly concentrated in the range of 5~60 Hz. The high frequency part of the vibration signal attenuates rapidly, and the energy is mainly concentrated in the low frequency part. Moreover, the total energy of the vibration signal decreases significantly with the increase of distance. The test results show that the successive vertical collapse of the tower and the simultaneous blasting on the top water tank can control not only the collapse range of the tower, but also the touchdown vibration and blasting dusts.

Smooth blasting is of great significance to roadway stability and safety. The conventional smooth blasting method has some disadvantages when applied to the full-section blasting of a small section roadway in hard rock. Due to the selection of unreasonable charge quantity of the contour hole, hole spacing and decoupling coefficient, the phenomenon of backbreak or underbreak occurs after blasting. This approach can also lead to increased support work, decreased efficiency, and problems such as sidewall collapse and roof caving. To achieve a one-time full-section smooth blasting of the tunnel and reduce damage to the surrounding rock, an optimized smooth blasting method was developed. Six large-diameter empty holes with a diameter of 70 mm were designed at the periphery of the tunnel using the stress concentration effect of empty holes. The distance between the contour holes was reduced from 544~600 mm to 400 mm and evenly distributed around the tunnel contour. The contour holes were charged with the air decking structure and spaced at intervals of 0.4 m. The optimized smooth blasting method was applied in a test of a hard rock tunnel in the middle roadway of Heilangou Gold Mine at a depth of 500 m. Results show that compared with the traditional smooth blasting method, the optimized smooth blasting is more remarkable in technical, economic and safety aspects. The average footage increased by 0.03 m, the average half-hole rate increased by 34%, the explosive consumption decreased by 0.42 kg/m³, and the blasting operation cost decreased by 7.82 yuan/m³. The tunnel walls were smooth, and the roof stability was better, effectively reducing the disturbance to the surrounding rock, providing valuable experience for deep hard rock mining.

The dislocation and overbreak of tunnel inverted arch are serious when traditional blasting excavation technology is used. This is because traditional blasting technology does not adopt the smooth blasting method, and the angle of the perimeter holes is too large when drilled by manual rock drilling rigs. By therefore analyzing the traditional blasting excavation technique of invert, the cause of serious studiedthe smooth blasting technology for inverted arch is proposed based on the smooth blasting theory and a large quantity of engineering practice. Water decking charge structure is adopted in the perimeter holes, which can be adjusted according to the inverted arch shape. The spacing between the perimeter holes is 30~50 cm, and the thickness of the smooth blasting layer is greater than the perimeter hole spacing by 10~30 cm. Additionally, a drilling counterforce support is used to reduce the angle of the perimeter holes which can ensure each blast hole to be drilled to the design depth. After comparing the blasting effects of the proposed smooth blasting technology and traditional blasting technology for the inverted arch by field tests, the contour overbreak by the smooth blasting technology is far less than that of traditional blasting technology, and the cost of every 12 m tunnel excavation is reduced by 35.14%.

Based on the actual production in jilangde open pit coal mine, the application of air interval charging blasting technology was clarified, defining two test significance: one is “reducing cost and increasing efficiency”, the other is “controlling blasting fragmentation”. Three groups of orthogonal tests are used to evaluate the application effect of air interval blasting technology. The photo photography method is used to identify the fragmentation distribution after blasting. Firstly, the matlab program is optimized with reference to relevant literature to process the fragmentation image into fragmentation distribution data. Secondly, the data is imported into Origin software to generate fragmentation distribution curve to evaluate the blasting effect. The test results show that the fragment size distribution of 17.3% interval blasting is close to continuous charging blasting. Conclusions 1: The air interval height has no positive correlation with the final effect., There is a reasonable interval height which is in line with the purpose of reducing cost and increasing efficiency of enterprises. The fragmentation grading evaluation method is used to analyze the uniformity of blasting effects of different charges. Firstly, the fragmentation distribution data is imported into Origin software to fit the blasting fragmentation grading curve. Secondly, five fragmentation evaluation indexes are summarized with reference to relevant literature. The analysis results are the uniformity of blasting block: continuous charge > interval 17.3% > interval 11.5% Conclusion 2: The charging amount can be reduced through the control of central air interval charging technology, so that the blasting effect is close to the traditional continuous charging, which can achieve the purpose of controlling blasting fragmentation.