Mineral resources are abundant in cold and high-altitude areas in China.However,these areas are characterized by low temperature,low atmospheric pressure,freeze-thaw cycle and fragile ecology,which lead to the existing mining theory and technology can′t meet the problem of the safe and efficient mining of mineral resources.Therefore,through a large number of literature research,the difficulties of blasting construction in alpine and high altitude areas are summarized,which are mainly divided into three aspects:plateau,frozen soil and ecological environment.In response to the plateau problem,measures of strengthening safety management are proposed to ensure the safety of construction personnel.The important measures such as adding antifreeze to finished explosives and adding anti-caking agents to granular ammonium nitrate to ensure the performance of explosive,and improving the reliability of detonation transmission by pressure relief treatment of detonating detonators.Aiming at the problem of frozen soil,deep hole blasting is used.The important measures such as adjusting the charging structure and construction organization to improve the effect of frozen soil blasting,and using over-drilling,dredging,and hole protection to solve the problem of difficult drilling.As for the issue of ecological environment,the principle of prevention first,protection first,development and protection equally important is adopted to avoid blasting excavation damage to the ecological environment around the construction site and reduce the thermal thawing of frozen soil to protect the ecological environment.In addition,the application of detonating tube detonator,electronic detonator and field mixed explosive technology in cold and high-altitude area is introduced in detail.The slow pressure relief of detonator can effectively reduce the generation of blind gun.The construction efficiency of electronic detonator is about 3 times higher than that of detonating tube detonator,which can carry out network detection and guarantee the quasi-explosion rate.The technology of field mixed charge explosive has the advantages of reducing labor intensity,improving work efficiency,enlarging blasting scale and improving blasting effect.Finally,the research direction and development trend of field mixed explosive blasting technology,tunnelling electronic detonator and mine regreening technology in cold and high-altitude areas in the future are prospected.

The spatial morphology of blasting crack is the theoretical basis for a blasting design.The blasting hole of underground ultra-deep hole blasting is under the action of confining pressure,and there is no blasting free surface.Under such condition,the spatical morphology of blasting crack needs to be further studied.In order to study the influence of confining pressure on the spatial morphology of blasting crack,large scale 4000 kN true triaxial loading equipment and permitted detonating cord of coal mine are used to provide confining static load and explosive dynamic load respectively.For this study,a 300 mm×300 mm×300 mm size cement mortar cube test block is used,the equivalent explosive content is 3 g,the first,and the second and the third principal stress of the test block under confining pressure is 8.50 MPa,7.00 MPa and 5.75 MPa,respectively.The spatical morphology difference of blasting crack with and without confining pressure is compared and analyzed.It is found that the spatial morphology of the blasting crack under confining pressure is very different from that under a blasting free surface condition.Under the condition of surrounding blasting free surface,the test block was broken into fragments by blasting.The mass proportion within the range of the fragmentary size L<100 mm and 100 mm≤L<200 mm accounts for 30% and 70% of the total mass of the test block respectively,among which the mass of the large size 150 mm≤L<200 mm accounts for 55.32%.However,the quantity was small and they were all generated on the surface of the test block.Under confining pressure,a symmetrical macroscopic fracture surface which is on the hole sealing device is formed perpendicular to the direction of the second principal stress.Meanwhile,more cracks appear on other surfaces of the test block.After the test block is cut,microcracks appear on the hole wall,and obvious cracks appear on the hole wall in the pre-perforated direction.

In deep borehole parallel cut blasting,the length of the blast hole stemming is an important factor to determining the blasting effect.Too long or too short filling will weaken the cut blasting effect.In order to improve the blasting effect of deep borehole parallel cut blasting,based on the theory of rock fragmentation under the combined action of shock wave and explosion gas,by analyzing the relationship between the movement process of the stemming rushing out of the blast hole and the time required for rock fragmentation,the reasonable stemming in the cut is obtained.The calculation formula for the upper and lower limits of the length can determine the reasonable range of the stemming length.Three groups of model tests are carried out to analyze the blasting funnel,blasting pile quality and fragmentation produced by the test.The test shows that the stemming length of the experimental group with the best blasting effect in the model test is 20 mm,which is in the range of 19.86 mm to 22.07 mm of the reasonable stemming length calculated in theory.The reasonableness of the formula for calculating the reasonable stemming length range is verified.In view of the situation that the blasting gas passes through the empty hole due to the excessively long stemming,it is proposed to properly block the upper and lower ends of the empty hole in deep borehole parallel cut blasting to reduce this effect.

Decoupled charge blasting can effectively reduce the peak pressure of the hole wall,thus reducing the range of crushing zone and improving the blasting effect.Air and water are two common coupling media used in practice.Taking granodiorite as an example,the blast loading of these two charge structures is analyzed based on isentropic adiabatic expansion theory and elastic theory.Theoretical calculation results shows that when the charge diameter is 70 mm and the blast hole diameter is 115 mm,the quasi-static pressure load and the peak pressure of hole wall produced by water-coupled charge structure are 5.63 times and 2.15 times of those produced by air-coupled charge structure,respectively,which is beneficial to strengthen the blasting crushing and throwing of rock mass.Moreover,a water-coupled bench cast blasting technology is proposed,which adopts a comprehensive method to optimize the distribution of unit consumption of explosive,blasthole inclination angle and initiation delay.Meanwhile,the process of crushing rock with this technology is illustrated.The engineering application of water-coupled bench cast blasting technology used in the excavation of slope rock mass at Yebatan hydropower station proves that this technology can evidently improve the throwing rate of rock mass to 47.8%,and the average size of rock mass after blasting is 327.3 mm.Additionally,the blasting dust is controlled.The effects mentioned above all help to speed up the construction progress.Application of related technologies can provide reference for similar projects.

Joint has significant influence on propagation and attenuation of blasting vibration,and relevant research is of great significance for blasting vibration control.In this paper,cement gypsum material was used to make rock similarity model specimen,mica sheet was used to simulate filling joints,single detonator was used as the detonation source to generate blasting vibration signal,and TC-4850 was used to monitor the blasting vibration velocity of incident and exiting waves.The mechanical properties of the selected cement gypsum material were tested,including uniaxial compressive strength,tensile strength,elastic modulus,Poisson ratio,cohesive,internal friction angle.The similarity ratio between the mechanical parameters and limestone was about 20.The conditions set in the test include:1~3 joints as three joint quantity conditions and 20°,40°,60° joint angles as three joint dip angle conditions.Based on the vibration data of incident wave and outgoing wave,the changes of blasting vibration intensity and attenuation rate under different conditions were compared and analyzed.The experimental results show that compared with the blasting vibration velocity data of the complete model,the blasting vibration amplifies in the incident wave region in front of the joint,and the blasting vibration attenuation increases in the outgoing wave region behind the joint.The attenuation of blasting vibration velocity increases with the increase of the number of joints,but the increase is small.However,the attenuation of blasting vibration velocity decreases with the increase of the joint inclination angle,and the variation amplitude is significant.The variation of blasting vibration velocity in horizontal axial direction and vertical direction has the same law and the same change amplitude.

The delay time identification of blasting network is easily affected by the mode confusion of EMD,and the IMF with false components is obtained.However,the Hilbert transform is constrained by the Bedrosian theorem.When dealing with such components,it will produce negative instantaneous frequency,resulting in huge identification error.CEEMD-MPE-NHT blasting network delay time analysis algorithm was proposed to solve the problems of traditional HHT blasting network delay time analysis.In this algorithm,EMD mode confusion suppression is achieved by improving EMD and obtaining the complementary set empirical mode factory-Multiscale Permutation entropy(CEEMD-MPE) algorithm.The IMF obtained by CEEMD-MPE is transformed by normalized Hilbert transform to remove the constraint of Bedrosian theorem on Hilbert transform.The envelope of the IMF component with the largest energy content is solved,and the time interval corresponding to the envelope peak value is the actual delay time of the blasting network.By analyzing the difference between the actual delay time and the theoretical delay time,it can be judged whether the detonator is in normal service condition.Further,through the interference reduction method,the most reasonable delay time of the project is 54.51~59.75ms.The research results show that the blasting network delay time analysis based on CEEMD-MPE-NHT has important practical significance for blasting safety control.

A 60 L combustion bomb was used to study the influence of coal dust concentration on the explosion flow field of dusty methane in tank-shaped space.Four pressure sensors were arranged and located on the upper,lower,left and right of a section of the bomb,which were named PU,PL,PD and PR,respectively.According the explosion pressure and the flame image captured by the laser schlieren system,the variation tendency of the explosion pressure and flame structure were analyzed.A total of 6 sets of working conditions were designed in the test.The methane-air premixed gas with a concentration of 9.5% was selected for the test.The coal dust with various concentration(0 g/m3,5 g/m3,10 g/m3,15 g/m3,20 g/m3 and 25 g/m3) was added to the gas for the test.In case of methane explosion,the variation of explosion pressure can be divided into four stages,pressure rise stage,pressure decrease stage,secondary rise stage and continuous decline stage.The peak pressure of PU sensor is the largest and the rise rate of the pressure is the fastest.When the oxygen concentration keeps constant,the peak pressure of dusty methane explosion presents the reverse-V type variation tendency with the increase of coal dust concentration.When the coal dust concentration is 15 g/m3,the maximum explosion pressure is 598.697 kPa.The evolution process of explosion flame structure can be divided into three stages,laminar flow stage,cellular instability stage and turbulent flow stage.The disturbance in the flow field leads to the folds of the flame front and the increase of the coal dust concentration,which increases the influence of coal dust particles on the flame disturbance and accelerates the evolution process of the flame structure.

In order to effectively solve the difficulty of setting up real experiments in the “Blasting Safety” course,the construction and practical research of integrated experimental teaching system are carried out based on virtual simulation technology and related patented technology.Taking the “design and implementation for blasting safety during roadway excavation” in the blasting safety project as an example,a experimental teaching platform for blasting safety during roadway excavation based on virtual simulation is developed,which can realize the whole process of blasting plan design,blasting construction and blasting hazard monitoring.Meanwhile,a virtual simulation system for emergency rescue of blasting fume poisoning accident during roadway excavation has been developed,which can realize the animation demonstration of blasting fume poisoning accidents,and interactively complete the two practical operations of self-rescue and mutual rescue of workers and rescue of rescuers in a virtual environment.Then the simulation model of rock tunnel excavation and blasting and the simulated electric detonator for teaching have been developed,which can complete four practical operations of blast hole arrangement,detonator detection,detonation network connection and network continuity detection.Based on above work,the teaching content of fusion experiment is designed.The research and exploration online experiment has the characteristics of heuristic,inquiry,multi-way and multi scheme; The comprehensive design offline experiment has the characteristics of interaction,team and design.The comprehensive design offline experiment has the characteristics of interaction,team and design.Teaching practice shows that online virtual simulation experiment not only greatly enriches the form of experimental teaching and enhances the interest of experimental courses,but also breaks through the limitations of time and region for experimental courses,and students can complete experimental tasks through the network anytime and anywhere.The offline physical simulation experiment not only cultivates the teamwork spirit of the students,but also deepens the students' understanding and application of the theoretical knowledge learned in the classroom,and their hands-on operation ability can be simultaneously improved.Combining the experimental teaching system,a hybrid teaching mode of combining virtual and real and complementing each other is constructed,which provides ideas and references for solving the difficult problems of blasting experimental courses.

As the characteristics of fragile surface and easy relaxation,it is rare that the columnar jointed basalt is the base rock of the 300 m high arch dam abutment.During the construction of bedrock surface on the columnar jointed basalt rock,some problems often occur,such as destruction of the pre-crack surface of slope,serious pre-excavation of the pre-crack surface,low half-hole ratio of pre-crack surface and rock mass disturbance.In order to solve the stability problem of the broken rock mass excavation and reduce the pre-splitting blast damage to the foundation surface stability,a blasting type was determined by comparison test of the pre-splitting blasting and smooth blasting according to the physical and mechanical characteristics of the columnar jointed basalt on the left bank of Baihetan Hydropower Station.Meanwhile,The parameters of charge line density and hole row spacing of pre-split blasting were optimized.The results show that the comprehensive effect of pre-splitting blasting is better than smooth blasting.The damage of surrounding rock mass was monitored by arranging geophysical monitoring instruments before and after explosion.The blasting parameters of 0.6 m spacing of pre-splitting blasting hole and 240 g/m linear density are obtained,which can minimize the disturbance to the bedrock surface of columnar jointed basalt and achieve the best blasting effect.It provides theoretical and practical reference for foundation excavation of high arch dam with strongly unloaded rock mass.

In the process of open-pit mining,blasting effect is the key to the production benefit of the mine.There are some prominent problems in the external ramp of Beskuduk open-pit coal mine,such as excessive toe rock,high bulk rate,low blasting and loading rate.This paper aims to adjust the optimum hole network parameters by engineering tests based on the existing construction technology and mechanical equipment conditions of Beskuduk mine.Five groups of blasting tests were carried out at +1240~+1228 west outer ramp,+1240~+1228 east outer ramp,+1216~+1204 west outer ramp and +1144~+1132 west outer ramp,respectively.Each group of test plan was repeated three times,and the average value of the three tests was taken as the final analysis basis.The results show that compared with other test plan groups,it is found that test plan #5 has the best blasting effect on the outer ramps,with the toe rock rate of 3.83%,the bulk rate of 4.22%,the blasting rate of 97.76%,the powder factor of 0.54 kg/m3 and the loading rate of 6.0 car /h.In addition,test plan #5 gives full play to the reasonable cooperation of mechanical equipment and personnel,reduces the generation of toe rocks and bulk rate to a large extent,and improves blasting and loading rates.Through the comparison between before and after improvement,it is found that the optimized scheme greatly improves the poor blasting effect of the outer ramp,and reduces the blasting and excavation cost of Beskuduk mine to a certain extent.

The design and construction of traditional blasting for open-pit mines are mostly implemented based on the experience of blasting operators or engineering analogy method,which lead to typical problems such as large design deviation,low drilling accuracy and large blasting boulder yield.In order to improve consistency in blasting engineering design and construction,reduce waste of labor,materials,and machinery,and improve bench blasting effectiveness,a set of intelligent blasting design optimization system software was developed.It involves modules of bench blasting design,statistical analysis of fragmentation distribution of blasting pile,blasting vibration analysis and prediction,comprehensive evaluation of blasting effect,and so on.Using the software,the original data of blasting object is extracted based on high-precision GPS measurement technology,and the design results are then exported to the construction site.Taking the open-pit limestone mining of a cement plant in Guizhou as an example,GPS is used to collect the topographic data of the current mining area,and the intelligent design of bench blasting was carried out combining with the actual situation of the site.Then,the design data was accurately fed back to the construction site through GPS technology to guide the site construction.The results show that the intelligent design software has strong adaptive ability,and the intelligent design based on GPS can improve the accuracy of design and drilling,reduce the bulk rate by 33%,improve the blasting effect significantly,realize the fine management of design and construction,and achieve the purpose of safe,economic and efficient mining.

After entering deep mining of Sanxin Gold and copper mine in Hubei Province,a fan-shaped medium-deep hole blasting is adopted to excavate the top and bottom pillars.Due to the changes of hole layout and physical and mechanical rock properties,the fan-shaped medium-deep hole blasting has many problems,such as high bulk rate and serious shrinkage.To simulate the process of medium-deep hole blasting with different hole network parameters,the ANSYS/LS-DYNA numerical simulation software is used.Based on the actual physical and mechanical properties of on-site rock and the actual explosive material parameters,the numerical calculation models of three different hole bottom distances(1.4 m,1.6 m and 1.8 m) and three different row distances(1.6 m,1.8 m and 2.1 m) were established.By analyzing the effective stress cloud at the critical moment during the hole blasting process,the rock low-stress area of fan-shaped medium-deep hole blasting is concentrated on the upper and middle positions of the center lines of the two holes.By comparing the Von Mises effective stress peak on the monitoring unit at the key model position with the maximum dynamic tensile strength of rock material,it is determined that the effective stress peak is most close to the maximum dynamic tensile strength when the hole bottom distance is 2.1 m and the row spacing is 1.4 m.Therefore,these parameters are the optimal hole network parameters of fan-shaped medium-deep hole blasting of Sanxin Gold and copper mine.The field application test proves that a better hole bottom spacing and row spacing design can effectively reduce the problems of high bulk rate and serious hole shrinkage in fan-shaped medium-deep hole blasting under the same single explosive consumption.The research results can provide a guidance for subsequent mining work,and it has certain reference value for underground metal mine mining with similar problems.

The full face excavation of hard rock tunnel has high requirements for controlling the volume of cutting cavity,the smoothness of tunnel face and the under-excavation of bottom.Based on the full face excavation of class Ⅲ hard rock of Zhaishan tunnel,the optimization blasting parameters of cutting holes was put forward by using the methods of field test,problem analysis and empirical formula.From the perspective of expanding the volume of cutting cavity,four pairs of compound-term short cutting holes were added in the main cutting area from top to bottom,the depth of the long cutting holes was expanded to 3.8 m,and the distances between the bottom of the compound-term long and short cutting holes were reduced to 0.3 m.Considering powder factor of rock blasting and rock breaking volume,the maximum single hole charge of the long cutting holes was determined to be 3.0kg.The results show that after blasting excavation,the hard rock face is smooth,the bottom is flat and the sizes of rocks are reasonable by using the optimized cutting parameters.The powder factor of the overall cutting blasting is decreased by about 4.5%.

With the permission of surrounding rock conditions,adopting the full-face smooth blasting technology can accelerate construction progress and improve construction efficiency in large section tunnel blasting excavation.Meanwhile,the rationality of blasting technical parameters will directly determine the blasting effect of full section excavation.According to the engineering geological conditions and drilling machinery characteristics of Huangbaishan long and large tunnel of Jiangxi-Shenzhen high-speed railway,a full-face smooth blasting technology scheme of large-section tunnel is proposed.Furthermore,the drilling and blasting parameters of tunnel are determined according to the engineering analogy and the empirical formula calculation.Field blasting tests show that the contour of the tunnel excavation section is relatively smooth,the powder factor decreases from 1.16 kg/m3 to 1.07 kg/m3,the utilization rate of blastholes increases from 83.5% to 91.2%,and the peripheral hole mark rate increases from 73.6% to 87.4%,which efficiently improves tunnel excavation process and reduces construction costs.

Studying the blasting effect with different coupling coefficient of blast hole can meet the needs of high-efficient rock-breaking in existing coal mine roadway driving.By exploring the extent of the rock's explosive and fracture zone,the blasting effect is simulated under the hole diameter of 32 mm,35 mm,42 mm with the explosive cartridge diameter of respectively 27 mm,29 mm,35 mm and 42 mm using the nonlinear dynamic simulation software.Meanwhile,the blasting process of charge with different coupling coefficients and the effective stress peaks at different positions away from the hole center are obtained.The effective stress peaks and subsequent stress changes of rock at different time points are visualized,and the peak stresses at the same point under various conditions are compared.The results show that the stress peak decreases rapidly with the increase of the distance from the hole center,and the attenuation degree of the peak effective stress peak of the coupled charge is smaller than that of the uncoupled charge at both near and far.The effective stress of rock mass around coupled charge is much larger than that of uncoupled charge,and the peak value of effective stress increases with the diameter of borehole.The effective stress peak attenuation of coupled charge is slower than that of uncoupled charge.The uncoupling coefficient has a greater effect on the effective stress peak than the explosive diameter.And through the obtained radius of crack circle,the power of unit explosive is quantitatively calculated and compared,and the simulated power of unit explosive is 447.02 mm2 when 42 mm hole coupling charge is adopted,which is more suitable for the construction site.

In order to further study the influence of blasting cut height on the collapse effect of frame structure with small height-width ratio,ANSYS/LS-DYNA finite element software was used to establish the model of reinforced concrete frame structure with common joints.According to the collapse angle theory,the collapse angles were set as 20°,25°,30°,35°,35°(loose blasting) and 40° respectively.The collapse effect of the structure under six different blasting incisions was simulated,and the numerical simulation results were imported into the post-processing software LS-PREPOST for processing.The time interval was one second,and the vertical collapse speed of the structure was less than 200 mm/s as the completion time of the collapse,and the comparison was made with the actual engineering.The results show that with the increase of the blasting cut height,the accumulated energy is more,the recoil distance of the structure is also increased,and the growth rate is on the rise.The height of blasting pile is inversely proportional to the height of blasting cut and tends to be stable with the increase of cut height.For similar projects of blasting demolition of frame structures with small height-width ratio,excessive blasting cut height should be avoided as far as possible,and the appropriate elevation angle for blasting cut the should be between 30° and 35°.

In order to further clarify the damage characteristics of steel square pipe under localized lateral explosion.Using the finite element software LS-DYNA and the method of fluid-solid coupling and adding mass damping,distinguishing different burst distances within 10~20 cm,the impact of 160 g cylindrical explosives on a steel square tube with a cross-sectional area of 13.51 cm2 was studied.Analyzing the theoretical calculation value and numerical simulation value of the ultimate bearing capacity of steel square pipe,it is found that the difference between the theoretical calculation value and the numerical simulation value is 2.63%.Analyzing the experimental displacement value and numerical simulation displacement value of the center point of the explosion face of the steel square pipe,it is found that the errors are within a reasonable range,indicating that the model built is reasonable and credible.Analyzing the axial residual bearing capacity of the steel square pipe,it is found that with the increase of the burst distance,the axial residual bearing capacity of the square pipe increases in turn.Analyzing the energy absorption capacity of the pipe under the explosion load,it is found that the typical damage mode of the steel square pipe is that the central area of the explosion facing surface is obviously concave,and the steel pipe has no obvious deformation as a whole.The damage index,radial indent index and radial removal index were defined,it is found that the radial indentation index curve determines the overall change trend of the damage index curve,and the radial displacement index curve affects the local curvature of the damage index curve.The engineering algorithm for damage index of axial bearing capacity is proposed by fitting damage index.

Due to tool wear,the tunneling section of the shield machine in the hard rock stratum is under-excavation,and the length of the longitudinal under-excavation is about 2.5 m,resulting in the left and right line of the shield machine being stuck in the rock stratum at the same time.In order to get the shield out of trouble,the section of the upper half of the tunnel in the under excavated section is expanded by blasting.Before expanding the section,it is necessary to excavate a certain length of blasting on the front face of the shield machine,so as to create operation space for drilling and blasting construction(reverse blasting) in the under-excavated part.The first round blasting close to the tunnel face of the shield machine knife plate is the most difficult.Firstly,the distance between the cutter head and the blasting body is the smallest,so the damage to the cutter head caused by blasting impact should be avoided; The second is to consider the crushing damage to the cutter head caused by the increase of rock crushing volume after blasting.Therefore,short footage,less charge and zone blasting are adopted to reduce the damage of the aforementioned harmful effects on the cutter head.In the reverse excavation blasting,the cutting blasting with the largest impact force should be arranged far away from the shield shell,and measures such as non-coupling charge,symmetrical initiation and charge control should be adopted to finally blast the section of the under-excavation part into place,so that the shield machine can safely escape.Under the condition of hard rock(compressive strength greater than 150 MPa),in a narrow space with a width of 0.6 m(between shield shell and rock) and a hole depth of 2.8 m,the reverse excavation blasting can make the blasting rate reach more than 90%,which is inseparable from the use of cutting of annular empty hole(6 empty holes are arranged around the middle charging hole).This method can be used to solve the problem of shield machine being stuck under medium hard rock and hard rock conditions.

Single-use cracking tube is a new type of carbon dioxide expansion blasting equipment,which has the characteristics of safety and control,convenient construction,etc.Through theoretical calculation and hydrostatic test,the average pressure peak value of ZWD89 series of single-use cracking tube is 53.19 MPa,and the error is 12.48% from the theoretical calculation value of 47.29 MPa.The blasting energy of a single ZWD89-1500 type single-use cracking tube is equivalent to that of 264.24 g TNT explosive by using the formula of blasting energy of compressed gas and steam vessel.The field vibration test shows that the blasting vibration velocity peak value at 5 m in two working conditions is 2.5032 cm/s,and the peak value of blasting vibration basically shows a linear attenuation trend,which proves that the carbon dioxide expansion blasting technology is suitable for blasting engineering construction under harsh environment.The frequency spectrum analysis shows that the main frequency of carbon dioxide expansion blasting is mainly distributed within 50 Hz.With the increase of the number of blasting holes,the main frequency is gradually close to the low-frequency region,which needs to be paid attention to.

To study the boulder-blasting characteristics of single-base gun propellant,boulder blasting experiments of the single-base gun propellant and emulsion explosive were carried out,cement mortar blocks with 50 cm in diameter and height were employed to simulate the rock boulders,and powder factor was 0.05~0.25 kg/m3.The variation of fragmentation distribution,crushing energy,and energy efficiency with powder factor of boulder blasting experiments were analyzed.The results showed the boulder-blasting maximum fragmentation size decreased with the increasing powder factor,the energy efficiency barely changed with powder factor.The surface crack distribution and propagation of boulder blasting with single-base gun propellant and emulsion explosive were observed through high-speed photography,which revealed that the rock-breaking mode of single-base gun propellant was significantly different from that of emulsion explosive.The gas pressure raised rapidly with the combustion of single-base gun propellant in the borehole,which lead to the axial and circumferential tensile failure of the boulder.When the boulder was completely broken,the remaining propellant will no longer provide rock-breaking energy.

Aiming at the inherent endpoint effect of Empirical Mode Decomposition(EMD) of blasting seismic wave signal,an EMD endpoint effect suppression method based on Boundary Local Characteristic Scale and Adaptive Matching Extension(BLCS-AME) is proposed.In this method,the internal relationship between the global time parameters of the original signal and the local variation trend of the amplitude parameters of the signal at the endpoint are considered together to obtain the extended Boundary Local Characteristic Scale(BLCS).Then,taking BLCS as the research object,a set of time series with the highest matching degree with the BLCS are found in the original signal.Finally,the time series are translated to the endpoint of the original signal for EMD,and the BLCS-AME based EMD endpoint effect suppression processing can be realized.Through the comparative analysis of EMD endpoint effect suppression of simulated signals by various methods,it can be concluded that compared with conventional endpoint effect suppression methods,the BLCS-AME method has better inhibition ability to suppress EMD endpoint effect,and inherent mode function(IMF) with higher accuracy can be obtained,which can better reflect the internal attributes of signals.Finally,the method is applied to the actual blasting seismic wave signal EMD,it can be found that the method can effectively suppress the endpoint effect generated in the process of blasting seismic wave signal EMD,and it is beneficial to extract the detail characteristic parameters of blasting seismic wave signal and obtain the characteristic parameters reflecting the inherent properties of blasting seismic wave signal,which has important practical significance for blasting seismic hazard control.

Due to the complexity of mine environment,the error of monitoring sensors and the interference of magnetic field,the measured blasting vibration signal inevitably contains a lot of high-frequency noise.In order to remove the noise components,adaptive CEEMD algorithm was obtained by introducing the correlation root mean square error.This algorithm was used to fine decompose the blasting vibration signals,and obtain an intrinsic mode functions(IMF) with frequencies from large to small.Furthermore,the random MPE test was carried out for each IMF.In order to achieve the purpose of noise reduction,the IMF components with MPE value which was greater than 0.6 were removed.The results show that the algorithm has good fidelity and denoising effect.It eliminates the high frequency noise effectively and has little influence on the real information.Comparative analysis shows that the adaptive CEEMD-MPE algorithm is superior to the EMD-MPE and the EEMD-MPE algorithm,which verifies the effectiveness of the algorithm.

In order to study the influence of vacuum on ground vibration caused by explosion,the attenuation law of ground vibration caused by explosion after vacuum explosive vessel is studied.The attenuation law of explosion vibration is studied,and the influence of vacuum on the ground vibration effect after explosion is further analyzed.At the same time,the influence distance of different explosive amount in the explosion container is predicted to determine the explosion influence range for protection.Based on the experimental data,the attenuation law of vibration velocity with explosive amount and the distance between testing point and charge is analyzed,and the blasting vibration parameters K、α are obtained by using the Sadowski empirical formula and the least square method.Finally,the attenuation equation of explosion vibration velocity is obtained,and the vibration attenuation curves under comprehensive condition and vacuum are compared and analyzed.The results show that the vacuum degree has an effect on the vibration velocity attenuation under the 5 times specific distance of the explosive container.However,when the specific distance is greater than 5 times the specific distance,the vacuum degree of the explosive container has little effect on the vibration,and the distant foundation vibration does not change much at the same distance.In the case of the same charge quantity and distance between testing point and charge,the resultant velocity increases slowly with the increase of container pressure,that is,the vacuum has little effect on the vibration at a long distance.This is the first time in China to explore the law of ground explosion vibration under different vacuum degrees,and the safe distance is calculated numerically according to the specific allowable vibration velocity,which can be used as a reference for similar research.

In order to study the stress distribution and dynamic response of concrete dams under underwater explosion impact load,the numerical analysis model of dam structure explosion was established by using ANSYS / LS-DYNA software,including explosive,water medium,air medium,dam concrete and rock.The dam with a bottom width of 60 m and a height of 85 m was selected as the research object.Considering the influence of large deformation and high strain of concrete under explosion load,HJC(Holmquist Johnson cook) constitutive model was used to simulate the damage,failure and plastic deformation of the dam concrete.The possible failure modes and mechanisms under the conditions of two models with and without considering gravity were studied.The stress distribution of the dam after explosion was obtained by numerical simulation,and then four typical locations were selected to study its displacement-time history and pressure-time history.The research shows that the notch generated at the initial explosion is the starting point of shock wave diffusion,and the shock wave will be reflected by multiple times.The maximum stress at the initial explosion can exceed 50 MPa,and then vibrates between 10~30 MPa.The maximum peak pressures appear at the first reflection for all the typical positions,and the first reflection pressure can be used as the explosion impact load of the arc panel.The maximum von Mises stresses occur at the notches near the explosion source and the dam slope corners,which are prone to stress concentration.The displacements of the typical positions are negatively correlated with the distances from the explosive position.The displacements and pressures caused by gravity can resist the explosion responses,but there is no significant difference in the maximum von Mises stress.

In order to better deal with the fuzziness of language and randomness of quantitative analysis of evaluation grade in blasting effect evaluation,a cloud model evaluation method for open-pit mine blasting effect was established based on DEMATEL-SEWM.DEMATEL(Decision Laboratory Analysis Method) and SEWM(Structural Entropy Weight Method) are used to calculate the weight coefficient of blasting effect evaluation indexes,which objectively reflects the influence of the correlation among indexes and the difference degree of index weight judgment.The randomness and fuzziness of blasting effect evaluation are objectively described by using cloud model eigenvalues,such as Expected Value Ex,Entropy 、En and Excess Entropy He.Considering the influence of various index weights,the comprehensive membership degree of blasting effect is analyzed and the evaluation grade of blasting effect of open-pit mine is determined according to the principle of maximum membership degree,so as to better realize the quantitative visual representation of fuzzy randomness of qualitative concept in blasting effect evaluation.The model was applied to evaluate the blasting effect of an open-pit mine,and the results showed that the mixed weights of each index are 0.101,0.102,0.154,0.163,0.128,0.112,0.132,0.107,respectively.According to the weight,it can be known that the powder factor,the big block percentage and the vibration velocity have a great influence on the blasting effect.The cause degree of the powder factor is 1.2961 and the cause degrees of other indicators are negative.Therefore,the powder factor is the reason element which is the key factor to improve the blasting effect.The comprehensive membership degrees of the four blasting effects are 0.358,0.339,0.360 and 0.469,respectively.Meanwhile,the evaluation grades of the four evaluation results are all above good,which are consistent with the actual situation and verified the effectiveness and feasibility of the model in blasting effect evaluation.

In view of the influence of blasting vibration on railway safety in the mine room blasting of Ⅰ-1 orebody,a numerical model of the orebody and railway subgrade was established to evaluate the safety of existing railway subgrade and station.According to the location relationship of the mine room 1 and 2,the sections of 1-1,2-2 and 3-3 were set on the adjacent railway subgrade to monitor the dynamic response.Specifically,the vibration speed,the stress and the strain of each monitoring profile were calculated and analyzed.Analysis shows that the maximum vibration of the railway subgrade is caused by the blasting of mining room 1,the maximum vibration point is located under the railway subgrade of section 1-1,the maximum resultant velocity is 3.412 cm/s and the maximum three-direction velocity is on the Y direction which is 3.392 cm/s.More importantly,the maximum vibration of the station is caused by the blasting of the mining room 2,and the maximum resultant vibration velocity of the station is 0.02005 cm/s,which is the bottom vibration velocity of the railway subgrade.Meanwhile,the vibration velocity of the railway subgrade and station caused by mine room blasting is less than the allowable vibration velocity of blasting safety.During the blasting of mine room 1,the maximum stress occurs on section 1-1.More precisely,the maximum principal stress is 8108.17 Pa,the maximum value of the minimum principal stress is 12409.1 Pa,the maximum shear stress is 5955.34 Pa.However,all stress values do not cause damage to the subgrade.For another,during the blasting of mine room 2,the stress value of section 2-2 of subgrade is the largest.But the maximum stress values are all less than the stress values generated by the 1-1 section subgrade during the blasting of Mine room 1.Besides,the maximum shear strain value generated by the subgrade and station under the mine room blasting is 2.58×10-4ε.It is very small,because the station is far away.In this case,the subgrade and station will not produce obvious deformation.