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.

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.

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.

No matter violent & terrorist incidents or explosion accidents,parameters related to the explosion source,such as explosive equivalent,are always important for the post-explosion accident investigation.The characteristic trace of the medium under explosion load is an important basis for tracing the cause of an explosion accident and obtaining the corresponding explosion source parameters.After reviewing the typical research progress of explosive characteristic traces,including explosion crater,damage of surrounding buildings,and personnel damage degree,it is found that there are significant differences in the shape and size among the explosion craters created by near surface explosions,exposed surface explosions and explosions with certain depth.This research is based on an underground explosion accident in a gold mine in 2021,which was caused by that the dropped welding slag from the shaft ignited the underground combustible materials and explosive equipment.According to the sizes of three explosion craters formed at the accident site,the TNT equivalents are calculated as 654.17 kg,232.49 kg and 193.83 kg,respectively.Then,the particle vibration velocity and the shock wave overpressure of the shaft wall are calculated as 40 cm/s and 2129 Pa,according to the TNT equivalents.The calculation results are consistent with the damage degree of the cage and shaft wall.

Quartz sandstone samples were tested under cyclic impact loadings by the drop weight impact test equipment to study its mechanical properties and failure process under medium strain rates.Three specimens were selected at each impact height of 0.3~0.6 m,and each specimen was subjected to 8 cycles of impact with medium strain rates of 26.33 s-1,29.7 s-1,32.03 s-1 and 35.17 s-1,respectively.Then,the influence of cyclic loading times on the dynamic compressive strength,elastic modulus and energy efficiency of quartz sandstone were discussed.The results show that under different medium strain rates,the dynamic compressive strength of the specimens under the impact loading of the 8th cycle is about 13 MPa,which is lower than that of the first cycle.During the process,the resistance to deformation is weakened,and the elastic modulus is significantly reduced.The dynamic compressive strength of the specimens has a positively correlation with the elastic modulus.From the perspective of energy,the dissipated energy,energy efficiency and unit volume dissipated energy of the specimen are improved after 8 cycles of impact loading.The effect is most obvious when the impact energy is 70.27 J,the dissipated energy of rock is increased by 6 J,the energy efficiency is increased by 8.8%,and the unit volume dissipated energy is increased by 50%.For fracture fractal,the fracture morphology of rock under medium strain rates includes splitting failure,edge collapse failure,block failure and crushing failure.When the strain rate increases from 26.33 s-1 to 35.17 s-1,the characteristic value of the average particle size of the sample fragments decreases from 24.49 mm to 21.15 mm.The fractal dimension increases from 1.07 to 1.75 linearly.

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.

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.

In order to improve the efficiency of the directional cracking of hard rocks,starting from the mechanism of cracking from hard rocks to breaking rocks,based on the empty hole effect theory,the stress variation law of the empty hole wall under the 200 mm、250 mm、300 mm、400 mm hole spacing and the 20 mm、40 mm、90 mm、120 mm hole radius is studied,and the theoretical calculation and numerical simulation are compared and analyzed to verify.The results show that the existence of empty hole makes the stress concentration near the expansion hole,with the increase of empty hole spacing and the decrease of empty hole radius,the stress concentration of empty hole effect becomes weaker.The maximum tensile stress appears on the connection line of the empty hole and the expansion hole.The maximum pressure stress appears near the empty hole circle 70°.The stress intensity factor of type I rock on the inter-hole connection line corresponds to the law of stress variation.When the hole spacing reaches 400 mm,the stress intensity factor KI is smaller than the fracture toughness KIC of rock and the condition for formation of through cracks cannot be reached.According to the research results,set the parameters of the empty hole and in Shenzhen Tiegang-Shiyan reservoir Shiyan North clear water diversion tunnel to carry out the rock breaking test.The test results show that empty holes play a guiding role in the direction of crack propagation,which can cause the main crack to form on the connecting line between the empty hole and the expansion hole and is beneficial to improving the efficiency of the breaking rocks in hard rocks,which can provide reference for similar projects.

Shallow hole blasting is com in roadway or tunnel excavation,which has the disadvantages of more work cycles,less footage per cycle and low excavation speed.Meanwhile,deep-hole blasting which is widely used in mining engineering usually adopts continuous charge structure.This brings problems such as high charge quantity per delay,significant blast-induced harmful effect and high boulder yield.To overcome these problems,it is effective to adopt the in-hole sectional blasting technique.Firstly,key factors such as charging structure,charging materials,decking length,sectional delay and charging method are emphatically introduced based on the patents of in-hole sectional blasting in recent years.Then,taking the open-pit bench blasting of a mine adjacent to a railway as an example,the new two-deck charge blasting technology with rock powder barrier as the decking material was presented and compared with the traditional continuous charge blasting technology.After application of the new technique,the boulder yield was reduced by 54%,preventing secondary blasting.At the same time,the explosive usage was saved by 20%.The blasting vibration at the nearest monitoring point to the railway was reduced by 7.62%,and the flying rocks were all within the allowable range.The new technical scheme can also make the bench surface smoother after loading and transporting,which is more conducive to the subsequent stage of blasting operations.

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%.

Aiming at the problem that the blasting effect is not good due to poor or even no stemming of blast holes in underground coal mine,numerical simulation was used to analyze the mechanism of rock breaking and stemming mechanism.A 3 m×3 m two-dimensional concrete model with blast hole diameter of 0.04 m and hole depth of 1m was established using the finite element analysis software.In addition,the continuous emulsion explosive charge was set as 0.3 kg,and the stemming material was set as sand.For the explosive simulation,concrete and sand were modeled by Lagrange grid,and the air was modeled by Euler grid.ALE algorithm was used to simulate the explosion stress nephogram and damage cloud maps with a single hole stemming length of 0 mm,200 mm and 400 mm respectively under the blast load.The results show that the maximum stress around the hole with stemming is significantly higher than that without stemming.Meanwhile,the damage degree around the hole with stemming is more severe with smaller fragments than that without stemming.On the basis of analyzing the advantages and disadvantages of clay and water stemming structures commonly used in underground mines,a stemming structure by expansion-pipe water injection was designed,which can replace the clay and water stemming structure in underground coal mine blasting as a good field application.

The conclusions including:the Kuznetsov and kansake models are still applicable to the prediction of unit explosive consumption in bench blasting tunnel engineering,and the Kuznetsov model considers the influence of rock mass characteristics,which is more practical than the kansake model.In addition,the Kuznetsov model can predict the average blasting fragment as the basis of the distribution model of blasting fragment.Compared with the lower bench,the upper bench has higher single blasting consumption,higher content of fine particles and smaller fragments.The Kuz-Ram model has a good prediction effect for the small blasting fragments that below the average value.For the large blasting fragments that above the average value,the KCO model has a better prediction effect,and it has more accurate for the prediction of the largest blasting fragment.This paper analyzes the applicable conditions and scope of the prediction model for rock fragment,which provides a basis for the unit explosive consumption and fragment distribution of tunnel blasting.The methods for predicting the specific consumption of explosives and the fragmentation of rock mass during blasting originated from open-pit blasting.However,the stress state of the rock mass in stepped tunnels is different from that in open-pit mines,so it is unknown whether the above prediction methods are applicable to stepped tunnel blasting.Based on statistical data from the bench blasting in the Tianjiangli tunnel,several commonly used calculation methods in open-pit mines were used to predict the specific consumption of explosives and the distribution of fragments,and the predicted results were compared with the actual measurements.The results show that the Kuznetsov model and the Kansake model are still applicable to predicting the specific consumption of explosives in stepped tunnel blasting,and the Kuznetsov model takes into account the influence of rock mass characteristics,making it more practical than the Kansake model.In addition,the Kuznetsov model can predict the average value of the blasting fragmentation and serve as a basis for the fragmentation distribution model.The specific consumption of explosives is higher on the upper bench,resulting in a higher content of fine particles and smaller overall rock mass after blasting,while the specific consumption is lower on the lower step,resulting in a lower content of fine particles and a larger overall rock mass after blasting.The Kuz-Ram model is better in predicting the blasting fragmentation of small rock masses with a block size below the average value,while the KCO model is better for predicting the blasting fragmentation of large rock masses with a block size above the average value,and the KCO model can accurately predict the maximum blasting block.This article analyzes the applicable conditions and scope of the prediction models and provides a basis for the specific consumption and fragmentation distribution in tunnel blasting.

In order to comprehensively evaluate the effect of deep hole bench blasting in Weijiamao Coal Mine,considering the three objectives of blasting quality,safety and economy,eight parameters such as block rate,root rate,back crack distance,loose coefficient,unit consumption,long-meter blasting amount,vibration speed and flying distance were selected as evaluation indexes.Through UAV,high-speed photography,vibration monitoring and other technical means,the field monitoring of four production blasting flat plates in Weijiamao Coal Mine was carried out.In the meantime,the data analysis was carried out by Split-desktop,Motion studio and other software,and the quantitative indexes of the above parameters were obtained.The subjective and objective weights of evaluation indexes are obtained by using analytic hierarchy process and CRITIC method respectively,and then the combined weights of each index are determined based on the principle of maximum sum of squares of deviations.The grey clustering method is optimized by using the center point triangle whitening weight function,and the grey clustering evaluation model of blasting effect is established.The deep hole bench blasting effect of Weijiamao Coal Mine is comprehensively evaluated,and the order of blasting effect of four flat plates is obtained according to the comprehensive clustering coefficient.Finally,the main problems of the flat plate with the worst blasting effect are analyzed by comparing the index data.The results show that the combined weight of explosive unit consumption,bulk rate and base rate is greater than 0.15,which has a great influence on the blasting effect.The order of blasting effect of four flat plates is that 1080 flat plate>1064 flat plate>1096 flat plate > 1112 flat plate.The 1112 flat plate needs to be combined with geological conditions to optimize the bench blasting parameters for the problems of large back crack distance,high unit consumption,small blasting amount per meter and large flying distance.

The average lumpiness of ore rock is an important index to measure the blasting quality.The early research mainly relies on empirical formula summary,rock mechanics model calculation,which have shortcomings such as insufficient accuracy and strong subjectivity.Recently,,machine learning algorithm is applied for prediction,but still have problems such as empirical feature selection,insufficient model prediction stability,and poor generalization ability for the prediction of blasting material fragmentation.Aiming at above shortcomings,an extreme Gradient Boosting (xgboost) blasting fragmentation prediction model based on Feature Engineering is proposed.Taking Yuanjiacun Iron Mine in Taiyuan as the research area,engineering data are collected,Random Forest(RF) and Mutual Information (MI) are used for feature selection respectively,and the two feature subsets are integrated to obtain the best feature subset based on the value of MSE.XGBoost is used to predict the block size on the optimal feature subset,and the evaluation system is composed of two indexes:Mean Square Error (MSE)and Mean Absolute Error(MAE).The proposed method is compared with other traditional machine learning algorithms, and the results show that it is better than others.Furthermore,it can provide scientific guidance for the management and control of blasting.

The dynamic response characteristics such as deformation capacity,acceleration,and load transfer of high-rise frame structure buildings under the condition of single column failure in different parts were studied.Firstly,according to the Code for Design of Concrete Structure (GB50010),a 4×6 span 8-story reinforced concrete frame structure model was established by using PKPM design software.Secondly,based on the component removal method,the finite element software SAP2000 was used to calculate the dynamic response characteristics of the frame structure with the failure of different single columns at the first floor,including the center column,long side middle column,short side middle column and corner column.The results show that the plastic angle is less than 6 for all the four column failure conditions,and the structure will not collapse.When the central column fails,the structural stability is the worst,and the probability of continuous collapse is the highest,followed by that of the short side and long side middle columns,and the corner column has the least probability.Under the condition of center column failure,the dynamic impact of the load on the residual structure is the most significant,with a maximum negative acceleration of about 3 g,which is twice as high as that of the short side middle column and the long side middle column.After the failure of the columns,the loads will be redistributed.The axial force will be borne by the adjacent columns,while the stress form of the upper beam will also change from bending to tension,resulting in a catenary effect.In the scenario of the central column failure,the axial force of the adjacent columns will increase by nearly 20%.

In order to successfully demolish two brick chimneys and two reinforced concrete chimneys located in the same plant area where is a complex environment by blasting.The overall blasting scheme of “single cut,directional collapse” is determined to demolish the four chimneys at one time,by analyzing the surrounding environmental conditions and the structural characteristics.According to the engineering experience,it is determined that the bottom edge of the chimney cut is at the elevation of +0.5 m,the cut angle is 215°,the cut height,cut length and relevant blasting parameters are calculated by theoretical formula.The cut form is trapezoid like,and the initiation network uses the digital electronic detonator initiation system with higher accuracy to initiate in the way of parallel firing.Considering the different structural composition of the four chimneys,corresponding pretreatment schemes are formulated respectively.Through the safety check of the collapse reliability,blasting vibration and collapse vibration of the chimneys and the effective control of the flying debris and flying stones after blasting,the four chimneys collapse in the design direction and prevent harm to the surrounding protection targets.By using the finite element software LS-DYNA to simulate the collapse process of four chimneys,the results show that the simulated collapse process is almost the same as the actual process,and the collapse completion time is around 14 s.Moreover,by analyzing the displacement and velocity law of the top node,it can be judged that the chimney collapse effect is sufficient and the expected goal is achieved,which further shows a guiding significance of the numerical simulation for engineering practice and can provide reference for similar projects.

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 Yan Zhou power station bridge was built on the proposed structure site of the Yan Zhou hub project,which included construction of a new ship lock,power station,and spillway gate.Due to the progress of the engineering construction,the bridge was dismantled.The Yan Zhou power station bridge is a hyperbolic arch bridge with a total length of 180.0 m and a width of 8 m.It is located in the Pengshan tourist scenic area,surrounded by many famous historical sites and enterprise factories.The environment was complex,and the nearest distance from the bridge to the existing power station dam was 8 m.The reinforced concrete box girder bridge of the power station dam was adjacent and shared a bridge pier with it.Due to the working conditions on-site,blasting demolition was adopted.In order to ensure the reliable collapse and complete disassembly of the entire bridge,as well as the separation of steel bars and concrete,the components such as arch ribs,arch columns,and connecting beams were pulverized through throwing explosive devices,with a powder factor of 1.2~1.5 kg/m .Reinforced loose blasting was used to destroy the bridge piers,and the maximum explosive charge for a single pier was 480 kg.According to the principle of heavy left and light right,the entire bridge was collapsed toward the right bank direction like a domino.An inner-hole delay and out-hole relay initiation network was used.The MS12 detonator was used for the inner-hole delay,and the industrial electronic detonators were used in parallel out of the holes.The blasting order was from left bank to right bank,and then from pier to pier,to ensure that the bridge collapsed orderly and vertically,without causing crushing impact to the left bank bridge pier.A leaky PVC was pre-laid underwater along a 100m line near the left bank power station and water roller dam.An air compressor was used to press the air into the pipe to form an air bubble curtain,which effectively reduced the water shock wave overpressure,thereby reducing the impact of blasting vibration and water shock waves on surrounding buildings and structures.

Underwater blasting tests are dangerous and costly.The requirements for the related test equipment and site in laboratory are very strict.Each test must be approved in accordance with relevant procedures.In view of the current situation of cumbersome blasting test procedures and long waiting periods,a wave barrier curtain which can achieve satisfactory results with as few underwater blasting tests was designed by using collision and vibration simulation technology.In order to achieve this purpose,the protection of wave barriers made of different materials were simulated by the ANSYS LS-DYNA module.Data were collected at a position 5 m away from the explosion point with a pressure of 7.5 MPa,and the detonation wave reduction coefficients of the canvas wave blocking curtain and other five different materials were compared and analyzed.The simulation results showed that the wave resistance performance in order from high to low is:air bubble,porous aluminum plate,automobile tire,foamed plastic,asbestos cloth.Among them,under the equivalent working condition of 1 kg TNT,and at the location 5 m away from the explosion point with a pressure of 0.22 MPa,the air bubble′s pressure reduction rate reached 97%,and the protection effect was the best.

Explosive welding is an efficient,economical and practical technique that uses explosives as energy to achieve solid-state connection of the same or dissimilar materials.Because it can achieve large-area welding and combination of dissimilar materials,it is widely used in the preparation of layered metal composites.In order to explain the research development of explosive welding of dissimilar metal materials,the related concepts and basic principles of explosive welding are reviewed.Through the introduction of welding window theory,it is pointed out that choosing explosion welding parameters in the welding window surrounded by four boundaries can obtain relatively high-quality corrugation.Based on the research status at home and abroad,explosive welding interface is discussed in detail from three aspects:the structure and mechanical properties of the explosive welding interface,the influence of heat treatment on the interface structure,and the influencing factors of the bonding interface.Studies have found that defects such as cracks,adiabatic shear bands,and intermetallic compounds often appear at the interface junctions,which can be improved by heat treatment,use of intermediate layers,and gas shielded explosive welding.However,the formation mechanism and control methods still need further in-depth research.In addition,the current numerical simulation is mainly based on the SPH method.After comparative analysis,this method can effectively simulate the bonding interface and jet flow,but it also has the disadvantage of a single simulation process,and the formation mechanism of the interface wave is still unclear.Therefore,it is necessary to establish a scientific and perfect interface wave formation mechanism and a systematic and comprehensive numerical simulation process.With the continuous emergence of new materials,explosive welding technique will continue to play an important role in more fields.

At present,the model of the forming mechanism of the wavy metal interface during explosive welding can only give a quantitative or qualitative description of some aspects of the forming process,rather than fully explaining all the phenomena involved.In the study of explosive welding of the titanium-steel transition layer,the wavy interface was observed by scanning electron microscopy.When the scanning electron microscope was enlarged to 2000 times,the wavy interface turned out to be titanium drops forming island shape bonding interface in the copper.When the relative displacement of the two plates is large,the crest part of the interfacial wave will be pulled off and the "island" will be formed.The theoretical analysis and experimental study of explosive welding show that the Richtmyer-Meshkov instability mechanism can better explain the formation process of the wavy interface in explosive welding.In the process of explosive welding,near the collision point,a thin layer of melting zone will appear at the welding interface,and the material near the interface is in a quasi-fluid state.When the high pressure elastic-plastic stress wave arrives,the interface disturbance will be caused,and the disturbance caused by the previous stress wave will further develop under the action of a series of subsequent stress waves,forming a typical Richtmyer-Meshkov interface instability.Therefore,Richtmyer-Meshkov instability and freezing are responsible for the formation of various types of wavy interfaces observed in explosive welding.

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.

Using a closed explosion experimental system,the combustion performance of a new type of rock-splitting equipment′s loading agent was studied,providing guidance for the drug components and proportions in subsequent products.Different gradient components with a ratio of 9∶1 to 4∶6 were designed to mix the loading agents for the closed explosion experimental,and the p-t curve and dp/dt-t curve of all agents were analyzed.The drug ratio used in the explosive strength experiment was determined to be 7∶3 and 5.5∶4.5.The mixed drugs were subjected to the explosive strength experiment using two types of loading densities,0.12 g/cm3 and 0.2 g/cm3.The mixed drug was assumed as a single entity with a density of 1.5 g/cm3,referring to the method of treating the gunpowder burning speed.On this assumption basis,the Γ-ψ curve of the drug combustion and the corresponding parameters such as explosive strength and burning rate coefficient were obtained,among which the explosive power of the single + additive (7∶3) formula was the highest,reaching 564.87 kJ/kg.The explosive power of the dual+additive (7∶3) formula was slightly lower but still higher than that of the 5.5∶4.5 formula.The reason for the apparent incomplete combustion phenomenon observed in the experiment of the dual+additive (5.5∶4.5) formula was explained by analyzing the Γ-ψ curve of the drug.The analysis of the corresponding explosive strength and burning rate coefficient of the mixed drugs showed that the explosive force of the gunpowder on the overall drug is the dominant factor,and the increase in the ratio of the gunpowder will significantly improve the efficiency of the drug′s combustion.However,the effect of the change in loading density on the burning of the two types of gunpowder is inconsistent.The increase in loading density will cause a decrease in the burning efficiency of the monobasic formula,while the dual-base formula will exhibit an increase in burning efficiency.

In the process of blasting excavation of rear tunnel with mall clear distance and large section,it is very important to ensure the safety of front tunnel exposed to blasting vibrations.Based on the six-lane Xiaoyu Tunnel of Beijing-Qinhuangdao Expressway,a blasting vibration velocity distribution law of the longitudinal and transverse sections of the front tunnel was monitored and analyzed during the excavation of the rear tunnel.The blasting parameters of the rear tunnel were dynamically adjusted and optimized,and the safety control measures of blasting vibration were put forward according the monitoring results.The results showed that the vibration velocity on the radial direction of the side wall of the front tunnel was the largest when the rear tunnel was excavated,and it is mainly caused by cut hole blasting.The vertical vibration velocity is slightly lower than the transverse vibration velocity.However,there is little difference between them,and the blasting vibration energy is mainly concentrated in the frequency band of 30~100 Hz.For the vibration distribution on the longitudinal section of the front tunnel,the peak vibration velocity decays with distance,but the vibration velocity on the unexcavated direction is relatively higher,which is 1.2~1.6 times of the vibration velocity on the same excavated distance.For the vibration velocity distribution on the cross-section of the front tunnel,the vibration velocity on the front side is 5~10 times higher than that on the back side.Multi-stage cutting was adopted to optimize the distribution of the holes.12 different delays were adopted to reduce the charge per delay,and the delay interval was increased to 60 ms to control the blasting vibration.The field practice shows that the optimized blasting design can reduce the vibration velocity of the side wall of the front tunnel by about 50%.

The study of damage expansion process of the surrounding rock mass under blasting is of great significance to the blast resistance design of a chamber.In order to explore the damage propagation law of the surrounding rock mass around a chamber under the action of different blasting sources,a numerical calculation model including top explosion,vault side explosion,side wall explosion,bottom side explosion and bottom explosion was established by using the finite element simulation software ANSYS/LS-DYNA.The RHT model was used to analyze the damage propagation process of the chamber surrounding rock mass at different positions.On this basis,10 vibration velocity monitoring points were set equidistantly from the blast source to the chamber boundary in the model,and the vibration velocity attenuation law from the blast source center to the chamber boundary was studied.The results show the damage point first appears at the shortest distance from the blast source,and is then formed subsequently.The damage zone expands gradually along the boundary of the chamber and finally forms the damage zone.Compared with the decay law of the blasting vibration velocity,the blasting vibration wave is fully reflected in the surrounding rock mass,which makes the blasting vibration velocity appear an amplification effect.At the same time,the damage evolution from the blast source to the surrounding rock mass corresponds to the change law of the peak vibration velocity,which can be used to determine if damage happens.

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.

In order to study the influence of faults and internal karst on the propagation law of blasting seismic waves in open-pit mining,the change of seismic waves passing through faults and karst was analyzed.To collect the seismic data after blasting,monitoring points were arranged at the upper and lower walls of a large fault on the south slope and a karst cave at the +1014 m platform of the north slope of the Tangya limestone open pit mine.The Hilbert Huang transform method was used to process the original waveforms,and the changes of blasting seismic waves passing through the fault and the karst cave were analyzed by the time-spectrum energy spectrum,marginal spectrum,and instantaneous energy spectrum.The results showed that the energy attenuation of blasting seismic waves passing through the fault is very obvious.With the same vibration duration,the maximum instantaneous energy decreased from 1.7 10-5 at the front of the fault to 6.0 10-6 at the rear of the fault which was reduced to about 1/3 of the previous value.Among them,the energy at the rear of the fault in the frequency band of 60~80 Hz attenuated to 1/2 of that at front the fault.At the same time,the energy proportion of lower frequency band increased while the overall seismic wave energy decreased.The fault objectively hinders the propagation of blasting seismic waves.In addition,the energy change of blasting seismic wave was not obvious with the maximum instantaneous energy changed from 2.3 10-4 to 1.9 10-4 when it passed through the karst cave.However,the filtering effect of the high-frequency signal of seismic waves passing through the karst was obvious,and the energy distribution was more concentrated.The peak particle velocity on the rear part of the karst cave was slightly larger with an amplification coefficient of 1.10~2.53.The frequency band of energy generally developed to the low-frequency direction.Therefore,it is suggested to strengthen the support of rock mass above the karst.

In order to determine the degree of impact of blasting vibrations on main haulage roadways and surface buildings near an underground mine,and to control these effects,it is necessary to obtain field test data through industrial experimentation.The Blast-NET blasting monitoring instrument was first used to monitor the radial,tangential,and vertical vibration velocities and frequencies caused by the blasting.According to the Sadovsky formula,the K and α values related to geological conditions were calculated using single-factor regression analysis,and the actual blasting vibration velocity calculation formula was obtained.The reliability of the calculation formula was then verified through continuous vibration monitoring,and optimization experiments were conducted on three different blasting network configurations:row-by-row,segmented,and hole-by-hole.The research results showed that if the protection of surface buildings is considered,the minimum safe distance between the source of the explosion and the protected buildings is 250 meters,200 meters,and 125 meters respectively for row-by-row,segmented,and hole-by-hole blasting.If the protection of underground haulage roadways is considered,the minimum safe distance between the source of the explosion and the protected roadways is 30 meters,25 meters,and 25 meters respectively for row-by-row,segmented,and hole-by-hole blasting.Finally,it is concluded that when the predicted vibration velocity meets the requirements of row-by-row or segmented blasting,the mine can use nonel detonators for blasting.If the hole-by-hole blasting network is required,only digital electronic detonators or high-precision nonel detonators can be used.

When the local high voltage discharge occurs in the internal area of a converter transformer oil tank,the transformer oil in the discharge area will be vaporized instantly and explosion pressure wave will be generated.In order to study the propagation characteristics of the pressure wave in the transformer tank and elevated seat area in the above process,a three-dimensional geometric model was established and divided into polyhedral meshes according to the actual experimental situation.For numerical simulation,a fluent software was used.During the calculation,the actual discharge energy curve was loaded in the discharge area through the profile file,and the compressibility of gas and liquid was considered through the gas-liquid two-phase flow model.The results show that when the arc energy is 4.929 MJ and the duration is 58.6 ms,the peak pressures at the monitoring point on the top of the elevated seat,on the left and right top of the oil tank are 1.21 MPa,4.62 MPa and 3.79 MPa,respectively.The pressure peak in the elevated seat area decreases with the increase of the distance from the fault point.The simulated pressure peak and pressure variation trends obtained by simulation at different monitoring points display a satisfied consistence with the experimental results,which verifies the effectiveness of the simulation calculation model.By establishing and solving the arc fault discharge simulation model in the oil tank through numerical simulation,the detailed pressure variation curve and the pressure wave propagation law in the three-dimensional space can be obtained.It can greatly reduce the loss of manpower and material resources caused by the discharge experiment,and provide an effective theoretical basis for the prevention of arc explosion accident in the transformer oil tank.

It is an important content in the course of "Blasting Engineering" to master the dynamic mechanical response of rock (body) under the action of blasting dynamic load.Since students majoring in civil or mining engineering lack basic theories such as wave mechanics and rock dynamics,the teaching effect is poor when the knowledge of dynamic mechanical properties of rock is explained in class,which will affect the subsequent learning of rock breakage mechanism.Therefore,the Split Hopkinson Pressure Bar(SHPB) experiment of rock materials is applied to the practical teaching of “Blasting Engineering”.By measuring the dynamic compression strength of rock samples and observing the failure forms of specimens,students are guided to understand the dynamic mechanical response of rock materials under different strain rates.The finite element software LS-DYNA is also used to simulate the SHPB experiment,and the process of stress wave propagation and rock failure is reproduced to achieve the demonstration function of dynamic impact.Practice shows that this teaching method enables students to intuitively perceive the stress wave propagation,clearly understand the dynamic failure mechanism of rock,master the relationship between dynamic mechanical properties of rock materials and strain rate,and lay a foundation for further study of blasting engineering theory.