The impact vibration caused by blasting demolition of tall buildings(structures) may affect the service status of adjacent subway tunnels.In order to demolish a 24 story frame structure building only 6.5 meters away from the subway tunnel,on-site tests and analysis of blasting vibrations and dynamic strains were first conducted.And then,a three-dimensional finite element calculation model was established for analyzing the dynamic response of the subway tunnel structure by ANSYS/LS-DYNA,which can reasonably describe the impact of the collapsed part on the ground during the blasting demolition of the building.Finally,the vibration response characteristics and dynamic stress changes of the tunnel structure under the impact of building collapse were simulated and compared with the field measured data.The research results show that the peak particle vibration velocity(8.61 mm/s) in the subway tunnel caused by the drilling and blasting of the load-bearing columns is greater than the peak particle vibration velocity(4.95 mm/s) caused by the impact of the building on the ground.The main frequency of the blasting vibration and the collapse impact vibration are about 100 Hz and 2 Hz,respectively.The vibration velocity of the subway tunnel under the action of the collapse impact load is equivalent to the structural vibration caused by an earthquake with an intensity of Level Ⅲ(3.82~8.19 mm/s).The low-frequency collapse impact vibration can cause relatively obvious additional dynamic stress to the subway tunnel.The dynamic compressive stress generated in the circumferential direction of the tunnel is about 4 MPa,and the dynamic tensile stress generated in the axial and tangential directions is about 0.4 MPa.The existing cracks may expand,or delamination may occur when the internal damages or construction defects are generated in the tunnel structure under the impact of dynamic tension and compression cycles.The safety allowable particle vibration velocity value of 10~12 cm/s when f<10 Hz required in the current blasting safety regulation(GB6722-2014) is dangerously high,and it should be adjusted in combination with the frequency and dynamic strain characteristics.

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.

A kind of explosive stemming apparatus with detonating cord was placed in a simulated blast hole to evaluate its blocking effect,and then a uniaxial compression test was performed on it using a universal testing machine.The result showed that the compressive strength of the explosive stemming apparatus after being in contact with the blast hole wall was 26.5~35 MPa,and the shear strength was 3.07~3.4 MPa,which was much higher than the shear strength of conventional stemming materials(0.09 MPa).The explosive stemming apparatus was applied on cut blast in tunnel excavation together with optimizing the original blast hole layout.It turned out that the number of cut holes reduced by 35% compared to before optimization while maintaining the same excavation depth,and the hole spacing increased accordingly,which reduced the risk of piercing adjacent cut holes and effectively improved construction efficiency.Therefore,combining the explosive stemming apparatus with stemming material can greatly enhance the blocking effect and prevent premature gas escape.This effect can further extend the gas action duration in the blast hole,and improve the throwing effect of explosion gases by fully exerting the gas wedge rock breaking effect.

In response to the high-quality requirements for large-diameter deep-hole blasting,and the traditional stemming material being too long and prone to “blowout”,a new type of blasting hole stemming material was proposed using early strength cement mortar and a bag-like structure.Static mechanical tests and blockage model tests under impact loads were conducted on cement slurry with different admixture contents and ages,and the self-shrinkage performance,compressive strength,and passive confinement pressure of the cement mortar under impact loads were analyzed to determine the dynamic mechanical properties of the early strength cement mortar under passive confinement.The stress characteristics of the stemming material in the blasting hole under the pressure of the blasting gas were also analyzed to provide a reasonable stemming length for large-diameter deep-hole blasting.The results showed that the self-shrinkage of the test piece increased with the increase of admixture content.The compressive strength of the test piece increased with the increase of age and decreased with the increase of admixture content.With the increase of admixture content and age,the expansion pressure increased,resulting in an increase in passive confinement pressure.When the admixture content was 4%,and the age was 16 hours,the expansion pressure reached its peak at each measuring point.Additionally,with the increase of admixture content,the porosity of the slurry increased,the axial compressibility of the blocking material increased,and the acting time of the blasting gas pressure in the blasting hole was prolonged,which improved the stemming quality.Comprehensive on-site test results have shown that the stemming length,reasonably selected based on the derived theoretical formula and combined with on-site production,ensures safe production during the mining period,and achieves good results in deep-hole blasting.目(2021CX2034)

In modern blasting engineering research,the matching model of explosive and rock provides a scientific basis for revealing the internal mechanism of blasting process and predicting the economic benefits of blasting system,which has become an irreplaceable important tool.However,due to the diversity and complexity of soil-rock medium and the uncertainty of explosion process,the interaction between explosive and rock is more complex and uncertain,and it is difficult to study the matching of explosive and rock from their interaction process.Earlier studies mainly relied on empirical formulas and field tests for calculation and summary,which often had high eigenvalues and harsh application environment.However,the feature of machine learning is that it only considers the beginning and the result,and does not care about the middle process,which ensures its universality in the study of explosive-rock matching model.The XGBoost algorithm,together with multi-threading,data compression and fragmentation method,has the advantages of high efficiency in the case of largedata amount,and is suitable for training of a large amount of field data.In view of this,a field test was carried out in a mine in Guizhou province,and XGBoost algorithm was used to establish a matching system between explosives and rocks.The network was trained through successful examples,and the trained neural network was applied to practical projects.The results show that the performance of the explosives selected by the matching system based on this method is similar to that of the industrial explosives used at present,and the error is within ±10%,which has a high reliability,and further verifies the rationality of the explosive-rock matching system based on XGBoost algorithm.

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.

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.

When excavating a tunnel in a gently sloping strata,serious overcut and undercut problems occur in various parts of tunnel blasting construction due to the existence of horizontal weak interlayer.Based on the project of Baoanying tunnel of Chengdu-Kunming Railway which passes through horizontal sand-shale interlayers,LS-DYNA software is used to simulate the blasting effect with different layer thicknesses to propose reasonable blasting control parameters.And the reliability of the parameters is verified by field blasting tests.The main research results are as follows: (1)When blasting excavation in a horizontal rock layer,the damage range of rock mass along the horizontal direction is large with long cracks,especially at the junction of sandstone and shale.On the contrary,the damage range along the vertical direction,with a small explosive energy utilization rate.(2)The blasting effect of horizontal sand-shale interlayered surrounding rock is significantly affected by hole spacing and the thickness of soft shale.When the thickness of shale interlayer is thin,smaller hole spacing should be selected.With the increase of the shale interlayer thickness,the controllable cracks can be effectively generated by arranging the hole spacing and empty holes to achieve a better smooth blasting effect.(3)The optimal hole spacing of the surrounding rock blasting with different thickness of sand-shale interlayer is determined.When the shale thickness is 5 cm,10 cm,15 cm,20 cm and 30 cm,the optimal hole spacing is 42 cm,46 cm,50 cm and 54cm,respectively.At the same time,the position of the blast hole must be strictly controlled to reduce the blasting vibration as much as possible.

In the process of tunnel blasting excavation,the influence of ground stress and joints on the blasting effect of rock mass is significant,and they are two important factors that must be considered in the layout of tunnel blasting holes.The static and dynamic mechanical parameters of jointed slate were obtained by indoor experiments by taking the Tongan Expressway Bayue Mountain Tunnel as the engineering background.Based on the LS-PREPOST software,a three-dimensional numerical model of jointed rock mass tunnel blasting under different ground stresses(3 MPa,6 MPa,and 9 MPa) was established to analyze the distribution of effective stress at different locations after blasting.A method for the layout of blasting hole network in jointed rock mass tunnel under different ground stresses was proposed,and the method was verified based on on-site blasting experiments.The results show that ground stress has a restraining effect on crack propagation during jointed rock mass tunnel blasting,and the greater the ground stress,the more obvious the restraining effect.The explosion stress wave will undergo multiple refractions and reflections at the joint location,leading to serious over-excavation.When the hole spacing of the contour holes in the grade IV rock mass was set to 45 cm and the linear charge density was set to 0.375 kg/m,the average over-excavation value was controlled within 20 cm.The designed concrete volume of the research section was 15.1 m3,and the actual concrete consumption in the three on-site tests was 26.4 m3,23.7 m3,and 25.8 m3,with an average concrete excess consumption of 10.2 m3 and an average excess consumption rate of 67.5%,which were all controlled within 100%.

In order to study the deformation and damage of tunnel surrounding rocks under the coupling action of static and dynamic stresses,a tunnel model under the coupling action of ground stresses and blasting loads is established.Firstly,the JH2 constitutive parameters of surrounding rock are deduced based on the on-site monitoring data of Wenbishan tunnel and the wave velocity of the rock mass.According to the surrounding rock grade,combined with the known parameters and wave equation,a simple method to determine the JH2 constitutive parameters is given,and the damage model of the surrounding rock is established by embedding a subprogram into ABAQUS.In order to make the simulation model closer to the reality,this research first balances the ground stress,takes the soil state at this time as the initial stress state of the blasting simulation,then using the equivalent blasting load method to simulate the tunnel blasting,so as to realize the blasting simulation for large-scale geotechnical engineering under the coupling of static and dynamic stresses on a macro level.The simulation model not only considers the blasting effect on the working face,but also focuses on the impact of blasting on the surrounding rock of the tunnel.The results show that the initial ground stress plays a significant role in the damage and deformation of the surrounding rock during tunnel excavation.The existence of the initial ground stress induces damage propagation.The greater the ground stress is,the greater the damage is.The maximum damage depth of the arch bottom in vertical direction is 2.2 m.At the same footage,the smaller the ground stress is,the greater the deformation is.The maximum deformation of 11.7mm is produced at the arch crown near the excavation face.The horizontal convergence deformation of the surrounding rock is different.The upper part is away from the tunnel,and the lower part points to the tunnel.In addition,the surrounding rock at the boundary between the upper and lower benches is subject to shear load.The damage and deformation of the surrounding rock are closely related to the actual project.101001)

During open-pit bench blasting,the movement trajectory of rock in the bench area is an important factor affecting the accurate mining of open-pit mines,especially for unevenly mineralized ore bodies.In order to solve the difficult problem that the internal movement trajectory of rock during bench blasting in the Wushan Cu-Mo mine is not clear,a tracking algorithm with signal markers was used on bench blasting tests at the Wushan Cu-Mo mine in Manzhouli.Through on-site installation,positioning,monitoring and data analysis of intelligent beacons,the research results showed that: the first row of beacons had a long motion time and fast movement with an average speed of 5.89.8 m/s.The movement distance was between 18.4 m and 29.4 m.Due to constraints and obstruction of the rock mass in the front section of the bench,the motion time,movement speed and distance of the #2 monitoring beacon were significantly reduced,with an average speed of 1.8~4.8 m/s and a movement distance of 5.3~14.2 m.The movement distance and time of the #3 blast hole beacon was the smallest,and the inclination angle of the #3-3 beacon reached about 25°.The inclination angles of #6-1,#6-2 and #6-3 beacons were relatively gentle at about 2°~8°.From the depth perspective,the shallow beacons move forward horizontally during the forward rush period,and there was a significant downward trend in the latter half.The vertical motion distance of the deep beacons was significantly smaller than that of the shallow beacons.

In order to control the forming effect of excavation profile and reduce the disturbance of preserving rock mass caused by blasting,the foundation pit blasting at the Yunnan bank of the large arch bridge across Jinsha river,whose total depth is about 51 m and one-time excavation depth is about 20 m,is taken as the engineering background.Reinforced loose blasting with hole-by-hole initiation was applied to the main blasting holes and smooth blasting was used for the contour holes.A kind of deep hole smooth blasting technology which can be applied to foundation pit excavation of the deep and steep arch bridge is presented.In addition,the action process of gas,the expansion pressure at the hole wall and the damage range of the smooth blasting hole were theoretically calculated and analyzed.The blasting results show that a flat excavation profile,with more than 90% half-hole ratio of relatively intact rock mass and less reserved hole marks of relatively cracked rock mass whose overbreak and underbreak can still be controlled,can be formed by using the deep hole smooth blasting technology,which greatly reduces the stress concentration on the rock wall surface.The crushing zone will not be formed near the charge section in the smooth blasting and the maximum damage range of the reserved rock mass was about 49cm,which fully ensured the rock wall stability and construction safety.In the process of smooth blasting construction,engineering measures were also taken to ensure the reliability,safety and economy,including slowly tilting the excavation surface at the bottom of the bench to the free surface,tying the explosive charge with cotton rope for traction,and setting detonators inside and outside the hole every 5~7 smooth blast holes.

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.

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.

In the field of blasting work,stemming has a significant impact on the effectiveness and safety of blasting operations.To improve the blasting effect and reduce blasting costs,it is essential to determine the optimal length of stemming.This study uses a combination of explosion wave theory,theoretical mechanics,and LS-DYNA numerical simulation to analyze the impact of stemming length on blasting effect,which is then validated through field experiments.The study results indicate that when the blast hole depth is between 0.6 m and 1.4 m,the optimal stemming ratio is between 0.38 and 0.54,and with an increase in blast hole depth,the optimal ratio decreases.When the blast hole depth is between 1.6 m and 2.4 m,the optimal stemming ratio is between 0.36 and 0.38.If the blast hole depth exceeds 1.2 m,and the stemming length equals or exceeds half of the blast hole depth,a detrimental effect may occur.The radial uncoupling coefficient R exerts a significant effect on the optimal stemming length.When R is less than or equal to 1.8,the optimal stemming length decreases with an increase in R.However,when R is greater than 1.8,the optimal stemming length remains unchanged.Additionally,field experiments were conducted at the Wangcun Coal Mine Limited Liability Company 8107 return airway,including tests on 1.2 m and 2.2 m cut holes and a 2.0 m auxiliary hole.The optimal stemming lengths were found to be 50 cm,90 cm,and 80 cm,respectively,which aligns with the results of theoretical calculation and numerical simulation.钱七虎.地下工程建设安全面临的挑战与对策[J].岩石力学与工程学报,2012,31(10): 1945-1956.

A combined demolition method of directional tilting of main tower and in-situ collapse of bridge beam has been designed for the blasting demolition of a single-tower reinforced concrete cable-stayed bridge in complex environment.An "inverted step" cut with a height of 4 m was designed for the middle tower pillar,and the mechanical pre-processing method was used in the lower tower pillar to form two windows with a width of 1.3 m and a height of 4 m to reduce its strength.The loose blasting was used for the bridge beam at four locations where the cables were anchored on the beam.Decked charge was adopted for the blast holes deeper than 2.1 m and initiated by detonating cords,which effectively dispersed the explosive energy.The middle tower pillar,lower tower pillar and the beam were initiated as 3 stages with nonel detonators.A “rigid+flexible” composite protection method was proposed for the culvert crossing the bridge.Two sandbag damping walls were settled on the touchdown area of the bridge beam to form a "flexible" protection.Meanwhile,a welded steel skeleton and rubber cushion layer were arranged along the direction of the culvert to form the “rigid” protection.Grass curtains,bamboo fences,and steel wire layers were covered on the blasting area.After the blast,the tower toppled on the predetermined direction.And the main beam collapsed in place,divided into several sections which were then processed with mechanical methods.In this project,good blasting results have been achieved without causing flyrock accidents or impact damage to the culvert.

In order to successfully demolish a high pier reinforced concrete aqueduct by blasting between the 75#~84# piers of Dongfeng Canal in Yichang City and reduce the impact on the surrounding complex environment,a bidirectional collapse design was adopted.In the design scheme,the aqueducts between the 75#~76# piers collapse in a northerly direction perpendicular to the aqueduct trend,and the aqueducts 77#~84# piers collapse westward along the aqueduct trend.More precisely,an initiation network of electronic and non-electric detonators with delays of 50 ms and 150 ms was adopted using the 75# pier as the initiation point.Moreover,the harmful effects of blasting on the environment were controlled by using lifting holes as blast holes,excavating vibration reduction ditches,hanging nets and covering protection layer,storing water in the trench body,and covering soil protection.The results show that the aqueduct collapsed with a 4-minute delay after initiation,and the collapsed pier body was basically decomposed into blocks with intact aqueduct body,with most fragments scattered along the trend within 10 m of the central axis of the aqueduct,and only a few small pieces flying farther than 10 m.The adopted protective measures can effectively control the blasting flying rocks and vibration,and no damage has been found to the inverted siphon of temporary water delivery pipeline and the road pavement.The project was carried out successfully despite the delay in collapse.The possible reasons for the delayed collapse include no incision on outside of the structural column ,the delay time interval between pier columns is small,and the blasting incision is small.

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.

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.

The charge parameters are crucial factors affecting the damage effect of RC components under close-in explosion.The study of the influence law of different charge parameters on component damage is of guiding significance for improving warhead design and optimizing fire strike scheme.A cylindrical charge with a length to diameter ratio of 5.5 and a charge of 10 kg was used to carry out near explosion damage tests of the supporting column of a reinforced concrete single-storey stacked structure plant at a proportional distance of r=0.2 m kg-1/3,and a comparison test of spherical charge was set up.The experimental results show that the damage effect of a cylindrical charge is stronger than that of a spherical charge,and the reliability of the numerical simulation model is verified by the experimental data.The length to diameter ratio,blast height,charge amount and action distance of cylindrical charge are taken as the research factors,and three levels are determined for each factor.The simulation results of blast damage of reinforced concrete under 9 different charging parameters were designed and obtained by orthogonal simulation test method,and the influence law of cylindrical charging parameters on the damage effect of reinforced concrete columns was analyzed.The amount of the cylindrical charge has the greatest effect on the damage degree,the ratio of length to diameter has the second effect,and the blast height has the least effect on the damage degree.When 4.5≤L/D≤6.5,the damage effect on the component is greater.When the blast height is 1/4,1/2 and 3/4 column height respectively,the explosion at the 1/4 column height has the best damage effect on the support column.

To study the influence of different geo-stress levels on the propagation of explosive stress waves in natural environment such as mountains and dams,numerical simulation technology was used to simulate the explosion of concrete specimens under different geo-stress conditions.First,by applying different stresses to the boundary of the concrete specimens,the failure of specimens subjected to explosive load were observed.And then,the peak stress and particle velocity of the four preset measuring points on the specimen were obtained by changing the unilateral ground stress value and keeping the same explosion load on different models.Finally,the influence of geo-stress on the propagation of explosion stress wave was analyzed on different characteristic parameters of explosion wave,such as the peak stress and particle velocity.The results show that the influence of geo-stress on explosion stress wave is mainly manifested as “restraining propagation” and “promoting propagation” under high and low stress level,respectively.During the explosion process,the superposition coupling of explosion stress wave and in-situ stress increases the peak stress intensity of the measuring point.On the contrary,the high ground stress inhibits the displacement of the medium particles,thereby reducing the particle velocity.The research starts from the influence of different ground stress levels on the propagation of explosive stress waves,and creatively analyzes the inhibition of ground stress on stress waves.

In order to investigate the dynamic response and stability of a steep slope under blasting vibrations from multiple blasts,the displacement,stress,maximum shear strain,safety factor and sensitivity of the steep slope were analyzed by field monitoring,numerical simulation and mathematical methods based on the an open-pit mine in Inner Mongolia.The data fitting results show that the radial vibration velocity has the highest correlation coefficient,with all the coefficients of three directions greater than 0.8.The relative error of the prediction results is larger in the near-blasting area,while smaller in the far area.After a single blast,the horizontal displacement increases rapidly and reaches the maximum value on the right side of the blast hole at 0.05 s.In the vertical direction,the stress increases gradually from top to bottom and the bottom is prone to stress concentration.The overall stress distribution of the slope gradually increases from the slope surface to the slope interior.After multiple blasts,the displacement and horizontal stress of the slope generally continues to increase with the increase of blasting times.The peak value of vertical stress and acceleration are generally oscillating with the increase of blasting times.For a period after the blasting,the acceleration is still not 0,and it takes a long time for the blasting energy to completely dissipate.Multiple blasting vibration will continue to reduce the safety factor of the slope to a certain extent.With the increase of blasting times,the change rate of the safety factor of the slope will gradually increase.Based on the gray correlation coupling analysis of safety factor and orthogonal tests,the sensitivity of each factor is as follows: charge per delay(X5)>total explosive charge(X6)>hole spacing(X3)>blast distance(X2)>blasting vibration duration(X4)>hole number(X1).It is indicated that in actual construction,it is necessary to control the charge per delay and total charge in order to ensure safe production.

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.

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.

In view of the problem of noise and information loss in the CEEMDAN method in the denoising process of actual measurement blasting vibration signals,the clustering analysis method is considered to have good data processing ability.Based on the idea of decomposition-clustering-reconstruction,CEEMDAN-K-means algorithm for denoising of blasting vibration signals is proposed.Firstly,this method decomposes the blasting vibration signal by CEEMDAN method to obtain IMF components of different quantity levels.Then,the K-means clustering analysis algorithm is used to classify the IMF components into five different categories,and variance contribution rate verification is used.Finally,the IMF components of high frequency noise category are removed and the reconstructed pure blasting vibration signal is obtained.Taking the blasting vibration signals from an open-pit mine as example,the signal denoising performance of the CEEMDAN-K-means algorithm was evaluated by signal-to-noise ratio and root mean square error indexes.The research results show that compared with the CEEMDAN method and the EMD-wavelet threshold method,the CEEMDAN-K-means signal denoising method has the largest signal-to-noise ratio(20.06 dB),which is increased by 1.26 dB and 7.7 dB,respectively,and the smallest root mean square error(0.22 10-3),indicating that the method not only has good denoising effect,but also has good fidelity.Through the comparison and analysis of the denoising effect of different methods,it is known that on the basis of effectively retaining the real signal component,the CEEMDAN-K-means method can effectively remove the high-frequency components contained in the measured blasting vibration signal,and has practicality and effectiveness in the field of blasting vibration signal denoising.

The experimental signals collected in explosion experiments are always mixed with different degrees of noise interference.In order to accurately analyze the variation laws conveyed by these signals,four sets of explosion experiments were designed with different charge amounts and vacuum environments in the vacuum explosion vessel.Then,the collected impact load data were analyzed by applying both Fourier filtering algorithm and median-averaged filtering algorithm.By comparing the P-t curves processed by the two filtering algorithms with the original ones,it is found that the Fourier filtering algorithm is a global analysis of the signal,which can extract the frequency information of the function in the whole frequency domain,while the characteristics of the signal cannot be revealed in a local time range.Although the processing speed is faster,the error for the characteristic parameters is larger,and the effect of the filtering process directly applied to test signals of the blast impact is less satisfactory.The fit degree between the signals of explosion impact processed by the median-averaged filtering algorithm and the original ones is higher,and the varying details of the impact load with time in the blast container can be clearly reflected with a smaller error and a higher reliability.

The peak particle velocity(PPV) of blasting vibration is an important index to measure the impact of blasting vibration on surrounding environment and structures.In order to improve the reliability of PPV prediction,a model based on extreme gradient boosting optimized by the sparrow search algorithm was proposed,and a corresponding blasting vibration prediction system was built using the App Designer of MATLAB.The maximum charge per delay,distance from blast center to measuring point,and elevation difference between measuring point and blast center were selected as the input parameters of 36 sets of training data and 5 sets of test data for the model to predict PPV.The results show that the proposed SSA-XGBoost model has a smaller average relative error compared with the GA-BPNN model and BPNN model,and it has a higher prediction accuracy and better stability proved by the Taylor graph.

In order to study the blasting vibration prediction and control measures of excavation in urban area under complex environment,the response law of peak particle vibration velocity and main vibration frequency is analyzed based on field blasting tests,and the blasting vibration prediction method is proposed based on the above two factors.The vibration reduction effect of hole by hole initiation and vibration reduction ditch is discussed,so that to obtain the optimal vibration reduction range of the ditch.And the control measures of blasting vibration are also formulated.The results show that the prediction formula of the peak particle vibration velocity and main vibration frequency is realized by considering the actual maximum single-hole charge and the actual total charge.The predicted value is smaller than that solely based on the maximum single-hole charge,and the prediction accuracy is increased by 3.2%.In the aspect of blasting vibration control,the blasting vibration is characterized by low vibration velocity,high frequency and short duration.Among all the measures,the effect of the vibration reduction ditch is remarkable.Considering the peak particle velocity,signal frequency band energy distribution and instantaneous input energy response law,the vibration reduction effect is the best within 1~6 m radius on the side of the ditch opposite to the blast source,and the maximum vibration reduction ratio can reach 77.5% within 1 m radius.For similar projects,the proposed blasting vibration prediction formula can be used for pre-assessment.When the distance of the building from the explosion zone is less than 10 m,it is recommended to implement vibration reduction ditch.

To solve the problem of impact danger to the coal pillars in the bearing section of the coal mine caused by rock burst,the stability analysis of the coal pillars was carried out using a theoretical analysis method during the excavation and backfilling periods of the B4328 working face of the Xinglongzhuang coal mine.The reasonable width of the coal pillars was calculated.A numerical calculation model was established using Phase2 to determine the stress distribution of the coal pillars in different mining states.Based on the degree of stress concentration on both sides of the roadway and the floor,a large-diameter borehole pre-pressure relief plan was implemented,and reinforcement measures for the transportation roadway before backfilling were also developed.The research results show that the plastic zone width of the coal pillar on the excavation side after transportation is 4.71 m and 14.45 m on the goaf.It is believed that the coal pillars are only affected by the impact of single-sided mining and the redistribution of drilling stresses,and the 25 m coal pillars are in a relatively stable state.At the same time,the simulation calculation shows that the transportation excavation area is located in the position where the supporting pressure peak drops in the goaf but the value is still relatively high,and the impact danger of the outer side of the coal pillar is greater than the inner side.Therefore,it is necessary to strengthen the support and take pre-pressure relief measures for the elastic area of the coal pillar.Because the coal pillar is less disturbed during the excavation period,and the two sides are basically in a plastic state after pressure relief,the elastic zone starts to produce plastic deformation,the elastic energy is released slowly,and the impact risk is reduced.

The estimation of equivalent and depth of underwater explosions is an important task of the hydroacoustic monitoring in the International Monitoring System(IMS) of the Comprehensive Nuclear-Test-Ban Treaty(CTBT).In order to effectively estimate the equivalent and depth of underwater explosion in near and far-fields,the relationship between the ratio of the first and second periods of the bubble pulsation and the bubble radius and depth was fully used based on the semi empirical formula of bubble pulsation period.The analysis results of near-field underwater explosion show that the average estimated equivalent and depth are about 118 g and 7.96 m,76 g and 21.4 m,1.23 kg and 44 m for different actual TNT equivalent values and blasting depths of 100 g and 7 m,100 g and 25 m,1 kg and 50 m,respectively.These results show that the depth estimation is more accurate than the equivalent estimation.Furthermore,the proposed method failed for a small explosion equivalent of 100 g and a depth of 50 m,which indicates that the method is limited in explosion depth.Finally,this method was used to analyze the far-field underwater explosions recorded by IMS hydroacoustic stations,and the equivalent and depth estimation results were consistent with the references,which indicated that this method is also suitable for the far-field explosion estimation.

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.

In the teaching of demolition blasting,the structure modeling period and the cost of single experiment are both too excessive,and the experiment cannot be repeated in a short time.In addition,the experiment is transient,irreversible,and dangerous,which is not conducive to close observation and learning.Aiming at the difficult problems of experimental teaching in blasting demolition engineering,a platform of virtual simulation experiment is established for teaching design schemes.Firstly,through the two interactive operation links of “toppling scheme selection” and “cut design”,the learners can master the basis for the selection of toppling scheme and the design method of blasting cut,and understand the design content of blasting cut such as cut shape,orientation window and positioning window.It is easy by the platform for the learners to understand the stress conditions for cut design according to the mechanical principle of chimney toppling.They also should be familiar with the knowledge of tension zone,compression zone and neutral axis,and master the calculation formula of the extreme stress of the cut section and the application of strength conditions.Secondly,the platform system can make the learners participate in the design of powder factor,blast hole parameters and initiation network through “blasting parameter design”,and correctly select the detonators inside and outside hole.Then,through the interactive learning of “safety check” and “arrangement of shock absorption measures”,the learners can master the data collection steps,the safety check methods and measures to control the negative blasting effects.Finally,the learners can experience the on-site blasting operation process by the “blasting site” module,and gradually establish their understanding of the blasting operation process by participating in the design and organizing each construction step.In addition,the experimental system has a knowledge introduction for each module,which is convenient for learners to learn independently.The construction of the virtual simulation experiment platform not only optimizes the teaching methods,but also improves the teaching quality,and enriches the characteristics and innovative ideas of the experiment teaching of engineering blasting.

Electronic detonators are the main initiation method currently used in the field of explosives engineering.However,they cannot be used in classroom or experimental teaching due to their high risk and special control requirements.It is urgent to develop a safe,reliable and reusable simulation device.Based on the STC15 microcontroller technology,a kind of analog electronic detonator for teaching was designed and tested.The simulated electronic detonators can be manufactured by 3D printing technology an they have been successfully applied to detonator detection and detonation network simulation experiments.The analog electronic detonator is mainly composed of power circuits,detonator simulation circuits,and PCB boards.A pair of leads protruding from one end of the detonator are connected to the power supply.Then,the microcontroller control chip,the drive circuit and the acousto-optic simulator are powered by the power supply circuit.After being powered on,the microcontroller control chip can drive the acousto-optic simulator device according to the written program to simulate the operation of the electronic detonators.Thus,adjustable delay times have been implemented.In addition,the real blasting scene can be simulated,the internal structure can be visually observed,and series parallel stable operation can be realized.Through the experimental teaching,students can understand the structure and characteristics of electronic detonators,master the detonator performance detection method and detonation network connection method.The new analog electronic detonators can fully mobilize students′ enthusiasm of learning the “blasting safety” course,give full play to the subjective initiative,and effectively improve their practical ability.