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

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

In view of the problem that mining and crushing of magnetite ore require huge energy consumption,the split Hopkinson pressure bar(SHPB) is used to test and analyze the dynamic mechanical properties and energy dissipation characteristics of magnetite ore during crushing process under different strain rates.Meanwhile,the complete dynamic failure process of the sample is simulated by ANSYS/LSDYNA software.The results show that the dynamic compressive strength of the magnetite ore samples has a significant strain rate correlation,and increases from 126.77 MPa to 220.62 MPa when the strain rate ranges from 43.94 s-1 to 147.75 s-1.Besides,The analysis of energy transfer law shows that the increase trend of reflected energy become more obvious with the increase of incident energy,and the maximum proportion accounts for about 22% of the total incident energy.However,The increase trend of transmission energy become weaker,and the proportion of transmission energy decreases from 78% at low incident energy to 38% at high incident energy.At the same time,the dissipated energy used for specimen crushing increases gradually,which has a linear relationship with the incident energy.The failure mode changes from the splitting failure at low and medium strain rates to crushing failure at a high strain rate.In terms of the crushing scale,most of the fragments at low and medium strain rates are large,while the fragments at high strain rates are small and mostly finegrained and needle shaped.Numerical simulation results indicate that the initial failure is caused by the "cross" shaped reflected tensile waves on the incident end of the specimen.The results of this study can provide a reference for judging the difficulty of dynamic crushing of magnetite ore and improving the efficiency of rock breaking by impact.

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

Understanding the classification of rock mass blastability is an important basis for determining reasonable blasting parameters and improving engineering efficiency.Combined with the practice of bench blasting in Weijiamao mining area,the protodyakonov coefficient and the tensile strength of rock samples are obtained according to the engineering geological data of the mining area,on the basis of site investigation and sampling.The density and acoustic wave velocity of the rock samples on the exposed step surface are measured and analyzed by wax sealing density tests and acoustic wave tests.According to the four indexes obtained,the rock mass blastability in the mining area is studied based on the principle of weighted cluster analysis.The research shows that there are coarse sandstone,medium sandstone,fine sandstone,sandy conglomerate and argillaceous sandstone in the Wejiamao mining area.The density of the marl sandstone is the highest,which is 2.75 g/cm3.The density of the coarse sandstone is the lowest,2.01 g/cm3,while the density of the sandy conglomerate,fine sandstone and medium sandstone lies between the marl sandstone and the coarse sandstone.In the acoustic wave test,the longitudinal wave velocity of the rock in the 1064 platform is the highest,which is 2.615 km/s,while that in the 1096 platform is the lowest,which is 2.029 km/s.According to the distribution of the rock samples at the corresponding platform,the blastability of the rock mass in Weijiamao mining area gradually decreases from 1112 platform to 1064 platform.Among them,the 1112 platform is mainly sandy conglomerate with a medium blastability.The 1096 platform is mainly coarse sandstone with an easy blastability.The 1080 platform is medium sandstone with a medium blastability.The 1064 platform is mainly composed of fine sandstone with a difficult blastability.

The safety control standard of buildings subjected to blast vibrations should not ignore the influence of the cyclic blasts.It is suggested that the critical peak vibration velocity which makes each part in elastic deformation stage is taken as the safety control standard and damage law of brickconcrete buildings or structures under frequent blast vibrations based on the cumulative damage theory and numerical simulations.According to the specific material parameters and model conditions,the critical peak vibration velocity of an intact brickconcrete structure is 0.67 cm/s,and tensile damage occurs in the stress concentration parts.It is therefore recommended that for buildings with weak antivibration ability,such as brickconcrete structures,the range of the safety control standard under frequent blast vibrations can be determined by multiplying the lower limit value set by the most unfavorable frequency in the current blasting safety regulations for general civil buildings by a reduction factor,which can be 0.45~0.55.When determining the safety control standard of damaged structures under frequent blast vibrations,the actual damage situation of the buildings should be comprehensively considered.The vibration safety control standard is taken as the smaller value between the critical peak vibration velocity which does not lead to crack propagation and the critical peak vibration velocity which ensures that all parts of the structure are in elastic deformation stage.\blasting vibration; brickconcrete structure; safety control standards; cumulative damage; numerical simulation

Since continuous charge structure is adopted in the bench blasting of Heigou openpit mining area,the boulder yield is high and the secondary crushing workload is large,which seriously affects the operation efficiency of the mine′s subsequent production and loading shovel loading process.In order to optimize the openpit blasting charge structure,the 2DBench module for openpit mining in the blasting simulation software JKSimBlast is used.Taking the length and the position of the commonly used air decking as the research objects and the boulder yield as the evaluation index,25 groups of experiments with two factors and five levels are designed with the hole depth of 17.5 m and the charge length of 10 m.The simulation results show that with the same air deck length,the boulder yield decreases first and then increases with the deck position moving down,and thus there is an optimal deck position.With the same deck position,the boulder yield decreases first and then increases with the increase of the air deck length.Furthermore,the optimal air deck length is determined as 2 m and the optimal deck position is 11.5 m from the orifice.Finally,field industrial tests with the optimized structure are carried out in 5 different blasting areas.The blasting muck pile photos before and after optimization in area 3 is selected as the reference group.By comparison,the results show that the optimized charge structure reduces the boulder yield by an average of 9.24% and effectively improves the blasting effect,which provides a useful reference for the selection and optimization of the charge structure in open pit mines.

Aiming at the problem of high boulder yield under different thicknesses of frozen soil in high latitude and alpine region,blasting crater tests were carried out at low temperatures in winter in Unugtushan coppermolybdenum mine.According to the test results,the relationship between the charge parameters and the blasting crater parameters is determined by using the Livingston blasting crater theory.Simultaneously,the deformation energy coefficient of the frozen soil layer is calculated,and the blasting crater characteristic curves of different frozen soil thicknesses are analyzed.When the charging amount is 4 kg,the critical depth of the frozen soil is 1.3 m,the optimal depth is 0.84 m,and the deformation energy coefficient is 1.06.When the charging amount is 8kg,the critical depth of the frozen soil is 1.7 m,the optimal depth is 1.2 m,and the deformation energy coefficient is 1.05.When the charging amount is 12kg,the above parameters are 2.2 m,1.34 m and 0.95,respectively.According to the similarity law,the optimal charging parameters which are suitable for the frozen soil area on the site are derived,the blasting effect under multiple blasting parameters of different frozen soil thicknesses is compared and analyzed.In addition,the blasting effect is optimized by the principle of “subregions and stages”.For weak frozen soil,the blasting effect can be improved with shorter stemming length and longer charge length.For strong frozen soil area,auxiliary holes are added around the main blasting holes to reduce the boulder yield.Furthermore,the optimization scheme of blasting parameters which is suitable for the change of frozen soil layer thickness in Alpine region is summarized.As a result,the blasting effect is significantly improved,which greatly reduces the boulder yield after blasting of the frozen soil layer and improves the ore supply rate.

There was a special working face with an ultrahigh bench and a large resistance at the 410 platform of a mine in Qingyuan city,which required onetime blasting.This working face had a bench height of 30m,a length of 80 m,and a face angle of 45°~80°.Due to the large bench height,small face angle,and the different face angles of the upper and lower parts,it was difficult to conduct the blasting construction.Before blasting design,the RTK measuring instrument and total station were used to measure the topography of the detailed working face,and then calculate the slope angle of each position of the face according to the topographic map.According to the rock properties,the construction experience and the drilling rig type,the powder factor and blast hole diameter were determined.Based on the above results,the toe burden,drilling angle,depth and spacing of the first row of blast holes were then deigned.Similarly,the burden,drilling angle,depth,spacing of the following rows of holes were also determined.After the hole parameters were determined,the charging structure was designed according to the burden of each row of holes,the rock volume of each hole,powder factor,and the principle of uniform blasting action.Finally,the initiation network was designed by the software of 3Dmine based on the direction of rock movement and the earthquakeproof requirements of the protected objects.During the construction process,the key links such as hole layout,hole depth measurement,drilling,charging,and network connection were strictly controlled,and positive results were obtained after blasting.

While excavating the rock mass by drilling and blasting method,it is bound to cause a certain degree of damage to the surrounding rock.Therefore,it has an important guiding role for the tunnel support design and longterm stability to make clear the damage characteristics of the surrounding rock during tunnel blasting excavation.Taking the blasting excavation of the Longnan Tunnel of the GanzhouShenzhen Highspeed Railway under Class Ⅲ surrounding rock as an example,the crosshole ultrasonic detection method was used to detect the acoustic wave velocity of the surrounding rock in different parts of the same crosssection of the tunnel,and the distribution characteristics of the acoustic wave reduction rate were analyzed.Based on the analysis,the damage depth of the surrounding rock in different parts of the tunnel was determined,and the relationship between the damage degree and the damage depth of the surrounding rock was revealed.Based on LSDYNA numerical simulation software,the damage evolution and distribution characteristics of the surrounding rock under 8 cyclic bench blasting under the same working conditions are simulated,which are basically consistent with the damage distribution characteristics evaluated by the acoustic wave test.The analysis results show that the surrounding rock at the foot of the arch at the upper bench has the greatest degree of damage,but with the shallowest damage depth.The maximum depth of damage to the surrounding rock is located at the bottom of the inversion arch.Based on the damage distribution characteristics,and according to the engineering analogy and relevant standards,the length of the initial supporting bolts of the grade Ⅲ surrounding rock of Longnan Tunnel should be 3.5~4 m.

As a discontinuous and anisotropic heterogeneous structure,rock mass is randomly distributed with joints,cracks,faults and other structural planes.The existence of structural planes has an important influence on blasting effect.In order to explore the influence of the angles and locations of structural planes on bench blasting effect,LSDyna numerical simulation and field experiments were conducted based on Beskuduk open pit coal mine.The numerical simulation results show that when the dip of the structural plane is less than 30 degrees,the peak stress is less affected.When the dip of the structural plane is greater than 30 degrees,the initial peak value of the explosion stress wave increases with the increase of the angle.In addition,the position of a weak interlayer in a bench affects the energy release.Compared to the situation that the weak interlayers are located in the upper area of the bench,the blasting effect when the weak interlayers are located in the middle and lower areas,the energy release is more obvious with a worse blasting effect,therefore a specific blast method is needed to solve the problem.The field practice shows that with the increase of the structural plane angle,the boulder yield presents a decreasing trend.For the situation that the weak interlayers are located in the middle and lower part of the bench,the method of increasing the subdrilling to 0.5 m and adding 3~5 m depth to the inclined holes can effectively reduce the boulder yield,improve the blasting effect and the shovel loading efficiency.

In order to study the reasonable smooth blasting parameters such as smooth blasting range,hole spacing,line charge concentration and charge structure in a fault fracture zone,empirical formula is first used for calculation.Then the blasting effect is compared by field blasts to analyze the influencing factors of smooth blasting in a fault fracture zone,so that to improve the blasting parameters and charging structure.Research results and field applications show that the smooth blasting effect is relatively good when the charge column size is  60 mm×400 mm with an uncoupled charge structure,the hole spacing is 1.2~1.5 m,the smooth blasting range is 2.5~3.0 m,the linear charge concentration is 1.2~1.4 kg/m,and the air deck length is 0.6~0.8 m.When the charge column size is  60 mm×600 mm with an uncoupled charge structure,the hole spacing is 1.2~1.5 m,the smooth blasting range is 2.5~3.0 m,the linear charge concentration is 0.7~1.0 kg/m,the stemming length is 1m,,the air deck length under the stemming is 3.0~4.0 m and the normal air deck length is 1.5~2.0 m,the smooth blasting effect is the most ideal with a smooth and stable slope.Moreover,the latter scheme has a better economic return than the former one.The selection of blasting parameters,charge structure and charge column for this smooth blasting technology can provide reference for similar projects.

The blasting fragment size of a mine is required to be less than 0.4 m.However,this area has a geological structure consisting of both hard and soft layers,which makes the traditional blasting method easy to produce boulders,and the blasting quality difficult to meet the requirements.In order to conquer the problem and save the construction cost,blasting tests on square hole layout with both deep and shallow holes were carried out with the middle shallow hole depths of 0 m,4 m,5 m,6 m and 7 m.Firstly,ANSYS/LSDYNA finite element software was used to carry out numerical simulations with a limestone model with RHT constitutive relation in the upper part and a marl model with HJC constitutive relation in the lower part,forming a hardsoft interlayer structure.Then,numerical tests were conducted to initially obtain more optimal middle hole depths,and the distribution characteristics of rock mass damage and the distribution law of blast effective stress under different test conditions were analyzed.Since ANSYS/LSDYNA does not take the effect of detonation gas into account,the middle shallow hole depths of 4 m and 5 m were selected for onsite blast tests in order to obtain more accurate experimental conclusions and not to excessively increase explosive consumption.The research results show that it is effective to reduce the blasting boulder yield by square hole layout combining deep and shallow holes.When the depth of the middle shallow hole is 5m,the curvature coefficient Cc and the boulder yield can be reduced.Before the technology optimization,the average boulder yield was about 64.4%,and the rate of fragments larger than 0.4m have been reduced to about 38.1% after the technology improvement,making the blast fragmentation to a favorable level.So,the scheme of 5 m shallow holes has a better effect of reducing boulder yield than the original blasting scheme and the scheme of 4 m middle shallow hole.

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

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

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

In order to study the blasting technology of the insitu collapse of a cooling tower,the incision was analyzed by finite element software.Furthermore,a highdefinition camera was used to collect the deformation data of the cylinder body and lambdoid stand columns.Then detailed analysis was carried out for the deformation time of the cylinder,the collapse speed,the change of the incision closure,and the collapse range after the distortion and deformation of the cylinder.The practice results show that the incisions for the insitu collapse of the cooling tower cannot be designed as four equal parts as convention.It is easy for four equally distributed parts to cause the bottom part not to collapse.The perimeter of the fourth area(the last initiated part) is slightly larger than that of the first area by a quarter.The inhole delay times in the four areas are MS4,MS8,MS8 and HS3,respectively,and the outhole delay time is MS2.Through the finite element simulation,it takes 1 second to generate the collapse trend of the cylinder,3 seconds to close the incisions of the cylinder,and 6.8 s for the cylinder to squeeze,twist in the air and touch the ground.The deformation of each area must be completed within a reasonable time.By image analysis and calculation after the explosion,the above simulated times are the same as the actual times.90% of the insitu collapsed cylinder is within the pool,and the upper ring beam is thrown out of the pool by about 6 meters,which does not affect the surrounding hydrogen production station,circulating water pump room,steel gate and other facilities.After measurement,the peak vibration velocity the natural gas pipe is only 2.095 cm/s,indicating no impact on the buried gas pipe 23 meters away.The research shows that the insitu collapse blasting technology can effectively control the collapse touchdown vibrations and the collapse throw distance of the cylinder.

Nayong Weima stone arch bridge and the new simply supported beam bridge have a 41°diagonal crossing in the horizontal direction,with a total length of 68 m.It passes 28.5 m below the fifth span of the new bridge,and is only 0.8 m away from the #4 column of the new bridge.In order to ensure the successful blasting demolition of the old stone arch bridge,the insitu buffer collapse control blasting technology is adopted to ensure the safety of the adjacent new bridge.Considering the damage to the surrounding environment caused by the blasting demolition of the stone arch bridge,especially the damage to 4# column and the pier foundation,the horn blasting notches is used based on the structural characteristics of the stone arch bridge and the analysis of blasting and collapse vibrations.At the same time,the blasting notch of the EastWest arch foot is moved to the second abdominal arch,and the crushing notch close to #4 column is added.For the initiation network,the sequence of "west to east and south to north" is adopted.Other methods include adjusting the resistance line of the blast hole close to the #4 column and taking different powder factors for different blasting notches,etc.All those measures are taken to make the stone arch bridge tends to collapse to the south with a minimum collapse size and reduce the impact of blasting on the surrounding environment.Furthermore,the reliability and safety of the blasting demolition of the stone arch bridge are ensured by the safety protection measures such as stacking of slag and soft soil to cushion dikes and setting up protective shelving.According to the collapse vibration formula,the vibration velocity of the bridge deck corresponding to the #4 column of the new bridge is calculated to be 3.9~5.2 cm/s,which is close to the maximum vibration velocity of 3.879 cm/s measured by the vibration meter.It is verified that the design idea of the blasting demolition of the stone arch bridge and the selection of the relevant parameters are scientific and reasonable.The blasting demolition has achieved ideal results,which could provide reference for similar blasting demolition projects.

Rock foundation excavation plays an important role in the entire project of hydraulic structures.The key and difficult point of the blasting excavation is how to reduce the damage of the rock mass on the foundation surface under the premise of ensuring the excavation of the structural foundation to the specified elevation.In this paper,ANSYS/LSDYNA finite element software is used to numerically simulate the blasting damage of the rock mass 40 m underwater.The blasting and excavation simulation of composite energy dissipation structure,flexible cushion and traditional charge structure is carried out in a 24.5 cm×24.5 cm×30 cm rock mass model,respectively.Fluidstructure coupling algorithm is used in the simulation process,and 0.4 MPa water pressure is added to simulate the 40 m water depth environment.The simulation results found that the damage depth of the basement,the energy transfer of the retained bedrock and the damage degree of the retained bedrock can be reduced by 38.89%,30.52%,and 30.90% respectively by using the composite energy dispassion blasting technology under the same conditions.The results also show that the energy dissipation structure can effectively control the damage form and scope of the rock mass retained on the foundation surface,which can be applied to the protection of foundation surface of underwater rock excavation.

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

The stability calculation is the key to prevent and control the geological disaster of dangerous rock collapse,which is of great practical and prediction significance.However,the quasistatic method cannot depict the influence of factors as the shape and geometric size of the dangerous rock mass,the frequency and initial phase on the actual blasting vibration load.Based on conventional pseudostatic analysis and the slice method,a blasting dynamic stability analysis method considering size effect is established.This calculation program is compiled by using MATLAB.The results indicate that the calculated minimum stability coefficients of dangerous rock mass vary periodically with the initial phase of the blasting seismic waves.For a given calculation with specific parameters,the coefficients are proximate to those calculated by conventional quasistatic analysis.The relative difference of these two calculations is between 5.1% and 8.2%,which indicates the calculation method and program are reasonable and effective.When the number of slices is 1,the calculated results of the program are equivalent to those calculated by traditional quasistatic method.The method proposed in this study provides a reference for dynamic stability analysis and evaluation for dangerous rock mass.

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

In order to study the influence of blasting vibration on the stability of permanent slopes in an openpit mine,this paper takes three pits in the KamoyaKazibizi mine as the research object,and compares the effects of blasting vibrations on the stability of the slopes with different rock characteristics.By collating the measured blasting vibration data,the maximum charge per delay and the distances from the measuring points to the center of the blast source,the blast vibration attenuation law and curve are obtained by regression analysis with a power function,which can be used to predict future blasting vibrations.In order to obtain the influence of the distance from the measuring point to the center of the blast source and the maximum charge per delay on the vibration velocity,the distance and charge are taken as the influence factor,and the blasting vibration velocity is taken as the dependent variable.Based on the vibration velocity calculated according to the fitted blasting vibration formula of each pit,nine groups of experimental schemes are designed.Using SPSS software to carry out variance analysis,it is concluded that the distance between the measuring point and the center of the blast source is highly sensitive to the blasting vibration velocity,and has a greater impact on the mine slope vibration.Therefore,for the soft rock slopes of Kazibizi mine and East No.2 mine,2~3 rows of holes are reserved as a nonblasting area,and mechanical excavation is used to trim the slopes.For the medium hard rock slope of South No.2 mine,presplit blasting is used to reduce the impact of blasting vibration on the slope stability.The research results have reference and application value for other openpit coppercobalt mines in Congo.

Prefabricated piers are widely used in the field of bridge construction and are often affected by accidental explosions or terrorist attacks.In order to study the influence law of the damage factors of prefabricated bridge piers under explosion load,a numerical model of the prefabricated bridge piers under nearfield explosion load has been established by ANSYS.Based on the residual bearing capacity of bridge piers,the damage parameter D is proposed as the antiexplosion index.The influence of five damage factors,including the explosive equivalent,the distance from the explosion center,the initial prestress,the number of segments and the setting of shear keys,on the damage degree of bridge piers is analyzed.On this basis,grey correlation analysis method is used to measure the degrees of correlation and contribution among the damage factors.The results show that the comprehensive reduction rates of failure parameter D are 32.1% and 29.6% by increasing the initial prestress and setting shear keys between segments,which can effectively reduce the damage of the piers and have a good correlation with the blast resistance of prefabricated piers.However,increasing the shear key height and segment number to 12% and 7.2% has a small effect on pier damage.The order from largest to smallest of the five factors in the correlation degree on the damage of the fabricated bridge piers under blast loading is:TNT equivalent,blast center distance,initial tensile prestress,shear key setting and segment number.In the antiexplosion design of prefabricated bridge piers,the factors of large correlations such as increasing the initial tensile prestress and setting shear keys can be given priority.The grey correlation analysis method has certain reference value for the analysis of damage factors of prefabricated bridge piers under explosive load.

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

In order to analyze the dynamic response of the shield segments during the blasting excavation of a connecting channel,onsite vibration monitoring has been conducted based on the shield interval project of Qingdao Metro Line 8.The measured blasting vibration data show that the cut holes have the strongest impact on the shield segment vibrations.Then,based on the onsite charge of the cut holes,the MIDASGTS NX simulation software is used to establish a threedimensional model to analyze the vibrations and stresses of the shield segments with 8 different blasting distances from the exit and entry of the connecting channel.Compared with the entry blasting,the impact of the exit blasting on the vibrations of the adjacent shield tunnel is more intense under the same blasting distance,and the peak vibration velocity is 2.9~3.4 times that of the entry blasting.On the other hand,the growing rate of the peak vibration velocity also increases with the decrease of the distance.When the allowable vibration velocity is 20 cm·s-1,the blasting distance should be greater than 5.0 m at the exit and greater than 1.25 m at the entry.The rocks that have not been excavated are excavated with nonblasting methods.The stress concentration is the most obvious in the opening segments,but the position where the maximum principal stress is generated shifts from the bottom of the rectangular opening through the intersection of transverse and longitudinal seams on the side of the rectangular opening to the top corners of both sides of the upper part of the rectangular opening with the decrease of spacing.Cutting the segments at the intersection of the connecting channel and the shield tunnel will form an incomplete opening structure,which will weaken the maximum principal stress on its inner side under the blasting load,but will cause a small range of stress concentration on its outer side,making it the weakest position of the shield tunnel lining structure.

Field tests of blast vibrations were conducted based on the concept of interference between blastinduced seismic waves for the purpose of reducing blasting vibration intensity and controlling blasting vibration hazards.Three different blast schemes were realized by using electronic detonators,and nonel detonators were used for the fourth blast scheme as comparison.Monitoring points were arranged at the locations of 15 m,30 m,45 m and 60 m away from the working face.By studying variation law of the blasting vibration velocity,the optimal delay intervals between holes and rows were selected as those of the third scheme based on the characteristics of accurate timing of electronic detonators.In the third scheme,the cut holes were initiated every two holes from top to bottom with an interhole delay of 8 ms.The slashing holes were arranged symmetrically along the center of the working face,and initiated hole by hole with an interhole delay of 16 ms and interrow delay of 100 ms.In addition,the roof holes and bottom holes were initiated with a delay interval of 100ms.This scheme was used to obtain a vibration reduction effect by wave destruction interference.The test results show that the blast parameters are the key to reduce the blast vibration intensity.With the same distance to the blast source,the peak particle velocity when electronic detonators are used is much smaller than that when nonel detonators are used.At the same time,the dominant frequency of electronic detonators is higher than that of the nonel detonators.This engineering technology has achieved significant vibration reduction effect in the blasting construction of the flood discharge tunnel of Luoning pumpedstorage power station in Henan Province.

At present,there are some problems such as inadequate implementation of safety management measures and heavy burden of supervision departments in the special storage for civil explosives in commercial blasting operation units.Thus,the damage and economic burden to the blasting operation unit caused by explosion accidents of civil explosives storage are analyzed and illustrated by case studies.Combined with the new requirements of “fundamentally eliminate hidden dangers of accidents” in the “14th FiveYear Plan for the Safety Development of the Civil Explosives Industry” for the civil explosives industry,it is considered feasible to cancel the commercial blasting operation units owning or renting civil explosive storages that have passed the safety evaluation,from the perspective of the intrinsic safety of the civil explosive industry.Therefore,it is suggested that the Ministry of Public Security to modify or cancel the requirement of the item of 6.2.2.1 "a)(having or renting a civil explosive storage that has passed the safety evaluation) when revising the standard of the Qualification and management requirements for unit of blasting operation(GA990—2012).This measure can improve the safety production management system of the civil explosive industry,reduce the burden of the safety supervision department and the economic burden of the commercial blasting operation units,which is more conducive to the improvement of the intrinsic safety level of the civil explosive industry.

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