Aiming at the problem of reasonable spacing-burden ratio in wide hole spacing blasting technology,laboratory blasting experiments of PMMA plates with the spacing-burden ratios of 1.7,2.5,3.5 and 4.5 were carried out based on related rock fragmentation mechanism at home and abroad.Meanwhile,a blasting calculation module was developed to study the crack propagation process and the response law of displacement based on the principle of near-field dynamics of conventional modes.The results show that the radial cracks present the character of branching to the corner of the free face and finally form the main cracks of a funnel shape,affected by the reflected tensile stress wave.Under the condition of fixed minimum resistance line,the stress reduction area gradually increases with the increase of the spacing-burden ratio,and the radial cutthrough cracks between the blastholes in the same row disappeared.An excessive spacing-burden ratio will further cause the disappearance of the cutthrough cracks between two rows of holes,and finally lead to the occurrence of individual hole blasting.The displacement results further confirm the above rule,and the rock ridge left by the front row of holes is just broken by the rear row of holes when the spacing-burden ratio is small.This breaking effect gradually decreases with the increase of the spacing-burden ratio.It is suggested that the spacing-burden ratio should be appropriately adjusted according to the mechanical properties of rock mass,geological conditions and blasting purposes to reduce explosive consumption and boulder yield in practical projects.

Structural plane is one of the key factors controlling the local stability of rock mass engineering.It is a prerequisite for rock mass stability analysis to find out the occurrence and combination of structural planes.Geological survey is often used at present.However,a high-cost supplementary survey is often needed when there are omissions due to the limitation of this survey means.Therefore,the surface vibration response law of the structural plane model was studied by laboratory tests.The study shows that the amplitude of the particle in front of the structural plane increases for the single structural plane model.For a block model cut by two structural planes,the amplitude-amplification effect exists only in front of the structural plane far from the power input side.Furthermore,the rock mass models with different structural plane dip angles were simulated respectively.The results show that,when the angle θ between the structural plane and the ground in the direction of the explosion source is less than 90°,the particle amplitude in the incident area of the vibration wave in front of the structural plane has an obvious amplification effect,and the particle amplitude behind the structural plane significantly attenuates.With the decrease of the angle θ between the structural plane and the boundary plane,the increase rate of the peak vibration velocity of the particle in front of the structural plane gradually increases,and the amplitude of the wave amplifies 2.8 times when θ=20°.

The seismic wave signal acquisition will result in the mixed noise in the measured signal due to the monitoring environment,test system and other factors,and the existence of noise will lead to the distortion of the time-frequency analysis results of the signal Hilbert-Huang Transform.There are two reasons.One is that the empirical mode decomposition(EMD) algorithm will obtain the intrinsic mode function(IMF) component with modal confusion phenomenon when processing the blasting seismic wave signal containing noise; The other reason is that because the Hilbert transform is constrained by the Bedrosian theorem,which will produce negative instantaneous frequencies when dealing with modal confusion components.These lead to huge analytical errors.In order to obtain real blasting vibration properties,HHT should be improved.Complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN) can be obtained by adding adaptive noise signal to EMD.Then normalized Hilbert transform is performed on the IMF obtained by CEEMDAN,and an improved normalized Hilbert transform(INHT) is obtained.Through the above two steps,the CEEMDAN-INHT time-frequency analysis algorithm can be established.In order to verify that the algorithm can effectively improve the time-frequency analysis accuracy of the noise-containing blasting seismic wave vibration signal,a comparative study on the time-frequency analysis of the HHT and CEEMDAN-INHT noise-containing simulated vibration signals is carried out.Finally,CEEMDAN-INHT is used in the time-frequency analysis of blasting seismic wave signals in an underground cavern,and it is found that the algorithm can effectively overcome the inherent mode confusion of EMD,and at the same time obtain the time-frequency-energy characteristic parameters reflecting the real blasting vibration attributes.It is of practical significance to carry out resonance analysis of blasting excavation in caverns from the perspective of frequency and energy,and to realize blasting seismic wave hazard control.

In order to explore the blast-induced crack propagation behavior in rock mass with two vertical prefabricated defects,a series of blasting experiments of models with double vertical cracks were carried out based on digital laser caustics.The evolution process of blast-induced crack is shown and the effect of single-hole charge on the crack propagation behavior(crack propagation length,stress intensity factor,propagation velocity,and initiation time,et al) in rock mass with defects was explored.The results show that the crack propagation length,propagation velocity,crack initiation toughness and stress intensity factor at the end of the double vertical cracks increase with the increase of single-hole charge.For crack Ju,the effect of single-hole charge on crack propagation velocity is small,and the limit velocity of crack propagation is about 0.38 times of the shear wave velocity.For cracks Dl and Dr,the initiation time decreases,but the peak stress intensity factor increases with the increase of single hole charge.Besides,the stress intensity factor and propagation length of crack Dr increases significantly compared with crack Dl.The crack Dl starts to crack earlier than the crack Dr when the energy of the blasting stress wave acting on both ends of defect B is enough to cause the crack to propagate on both sides.The increase of charge in a single hole can increase the propagation velocity of crack Dr,but has little effect on the propagation velocity of crack Dl.

The distribution characteristics of blasting pile is an important index indicator to evaluate blasting effect.In view of the inadequacy of the current direct and indirect methods of measuring fragment size of the blast pile,a spatial distribution measurement method for adaptive stratification of the blast pile is proposed.It uses the GA-LSSVM model to predict the shape parameters α and β of the Weibull function and sets multiple prediction points to predict the three-dimensional blasting pile morphology.By converting and fusing the parameters of the Kuz-Ram fragment prediction model,a distance prediction model of blast pile stratification is established and applied to the Weibull-GA-LSSVM model to achieve an automatic stratification of the blast pile.Through field application,the stratification design is continuously optimized for the best stratification position to realize the adaptive stratification.The results show that:(1)the Weibull-GA-LSSVM model can accurately predict the morphology of the blast pile with a good stability that the average relative error of the prediction results of the maximum forward distance of the blast pile is only 5.6% and the relative error of the prediction results of the looseness coefficient is mostly around 9%.(2)The Kuz-Ram-based blast pile stratification model can reasonably output the layer distance and number before blast,which ensures the shoveling efficiency after blast.(3) The optimal layer distance formula is derived to achieve the adaptive stratification of the blast pile,and the measurement accuracy of the fragment size distribution of the blast pile is significantly improved,which is closer to the overall fragment size distribution.

The primary support is the main load-bearing structure in the tunnel construction stage,the response rule and safety control of the primary support under dynamic disturbance are of great significance to ensure the safe and rapid construction.Figuring out the dynamic response characteristics and the safety control of the primary support is an important issue for the blasting excavation of a soft rock tunnel with reserved core soil.A three-dimensional finite-element numerical model was established by ANSYS/LSDYNA for the Linchang tunnel blasting excavation,and the reliability of the numerical model was verified by the field vibration monitoring data.The stress distribution characteristics of the primary tunnel support under the simultaneous action of two blast sources was studied combined with the construction characters of the reserved core soil method.The attenuation law of blasting vibration was obtained by using Sadovsky empirical formula.The safety criterion of blasting vibration velocity for the primary tunnel support under the simultaneous blasting excavation of both sides of the lower bench was proposed by taking stress as the control standard.The results show that the maximum vibration velocity appears at the arch foot of the primary support rather than at the tunnel floor or vault,which is different from the full section method and bench blasting method.Meanwhile,the propagation path of the blasting stress wave is dramatically affected at the un-backfilled area of the tunnel invert.The vibration velocity of the primary tunnel support is larger and attenuates faster on the left arch foot versus right arch foot.The maximum tensile stress and shear stress appear on the left arch foot of the tunnel under simultaneous blasting with 7.544 MPa and 2.78 MPa,respectively,which exceed the allowable value of the specification.According to the established linear stress-vibration velocity relationship,a blasting vibration safety criterion of primary tunnel support is proposed based on the ultimate strength.In addition,the safety vibration velocity threshold of the primary support in Linchang tunnel is 10 cm/s.

In open-pit bench blasting,blasting TBlasting toe rocks is an important indicator to measure the blasting effect in open-pit bench blasting,and it is most directly influenced by the blasting parameters have the most direct influence on the formation of blasting toes.In order to find outresearch the influence of ultra-deepsubdrilling on the smoothness flatness of bench in deep-hole bench blasting,statistical analysis of the relationship between damage variables and wave velocity in rock mass was conducted based on the basic theories of rock damage mechanics.based on the basic theories of rock damage mechanics and through statistical analysis of the relationship between damage variables in engineering and wave velocity in rocks,Tthe threshold values of damage variable,Dd for critical damage variable damage state of of rock mass is determined as Dd that is was 0.2,and the damage threshold Dt of for rock breaking mass in critical broken state is was were defined as 0.2 and 0.8,respectively .based on the basic theories of rock damage mechanics and through statistical analysis of the relationship between damage variables in engineering and wave velocity in rocks.Furthermore,Based on the dynamic damage model of rock with comprehensive consideration of the damage effect of tension and compression,the damage range of bench blasting under different conditions of with different subdrilling conditionsultra-deep was simulated by using the dynamic finite element analysis program LS-DYNA based on the dynamic damage model of rock mass with a comprehensive consideration of tension and compression effect.Meanwhile;based on the threshold of critical damage variable,the fluctuations distribution image of the bench surface after blasting was drawn to determine the optimal ultra-deep of subdrilling hole based on Dt the threshold of critical damage variable,and the image is was used for the quantitative analysis,so as to ensure that the rock mass of upper bench was fully damaged without affecting the construction of the lower bench surface.Finally,combined with the actual situation of deep-hole bench blasting in Ezhou Airport,the influence mechanism of ultra-deepsubdrilling on blasting toes is was verified in the deep-hole bench blasting of Ezhou Airport,and an optimal method for determining the optimal ultra-deepsubdrilling value for deep-hole bench blasting is was concluded.

In deep hole bench blasting,the classification of rock mass under different geological conditions according to its blastability is the premise for determining and optimizing blasting parameters.It is of great significance to improve blasting efficiency and effect and reduce blasting costs.Combined with the actual blasting excavation of Changtan open-pit coal mine,relevant indexes of rock mass blastability classification were obtained through on-site single-hole blasting crater tests,rock mass acoustic wave tests and laboratory rock mechanical tests.Furthermore,the blastability of stripped rock mass in Changtan open-pit coal mine was classified and evaluated based on the combination weighting(CWM) and cloud model(CM).The results show that the blastability of gray-green coarse sandstone at the 1130 platform is grade Ⅲ(medium).The blastability of yellow-green medium sandstone at the 1115 platform is grade Ⅱ(more difficult to be broken by blasting).The blastability of purple-red sandy mudstone at the 1100 platform is grade Ⅰ(difficult to be broken by blasting).The blastability of purple mudstone at the 1145 platform is grade Ⅲ(medium).

Charge structure has an important impact on deep hole blasting effect with a large diameter in thick and large ore bodies.The current charge structure(24.2% air deck length) used in Bangzhong mine of Zhongkai Mining has a serious problem of post-blast impact damage,resulting in blockage,collapse or even scrapping of the latter row of holes,which seriously affects productivity.However,blindly increasing the air deck length ratio has the risk of increasing the boulder yield.Based on the actual explosives and rock parameters of the mine,a study on charging structure optimization was carried out by using the numerical simulation software LSDYNA.The commonly used air spacers were selected as the deck materials.Then,12 charging structure solutions were designed for numerical simulation with respect to the air deck length ratio,and the relationships between the charging structure and the evaluation indexes(such as the back impact effect,boulder yield,peak particle velocity of free surface and peak effective stress) were obtained.The results show that the peak particle velocity of the free surface and the peak effective stress gradually decrease with the increase of the air deck length ratio.The back impact effect is obvious and the back row of holes may collapse when the air deck length ratio is less than or equal to 30.5%.There is a risk that the boulder yield increases when the air deck length ratio is greater than or equal to 45.3%.The optimal air deck length ratio is 44.2%.The deep hole blasting tests show that the boulder yield of the optimized charge structure is 7.1%,and the back impact effect has been effectively controlled.

Shaped charge blasting technology plays an important role in goaf retaining roadway engineering,and the charge structure is always a hot and difficult issue in current discussions.At present,there is no clear indicator of the pre-splitting charge length of goaf-retaining roof.Taking the track groove of No.2-11031 working face of the Mengjin Coal Mine as the research background,an isometric charge pre-splitting technology is proposed.Firstly,a three-dimensional directional shaped charge blasting model is established by LS-DYNA numerical simulation software to determine the optimal charge structure.By changing the axial cylinder length and taking the crack propagation length and stress decay rate as the analysis indexes,the numerical simulation shows that the radial slit distance is about 40 cm,and the axial slit distance is about 80 cm per meter when the axial uncoupling coefficient is between 1.25 and 1.7.Additionally,the slit distance is respectively increased by 25% and 12.5% compared with the axial uncoupling coefficient between 2 and 3.Furthermore,the energy utilization is the most reasonable as the stress attenuation rates are all less than 1 when the axial uncoupling coefficients are between 1.25 and 3.Finally,a roof directional blasting experiment with an axial uncoupling coefficient α=1.25~2 was carried out on the track groove of No.2-11031 working face of the Mengjin Coal Mine.After the pre-split blasting,the middle line of the two holes was drilled and peeping.It is found that the cracks along the cutting seam direction between the two holes have been completely connected,the cracks are smooth,and the field application effect is good.Considering economy and safety,the uncoupling coefficient α=1.7 is the best.The results show that the isometric charging structure can replace the traditional three-stage charging structure.

Smooth blasting in tunnel construction needs decked charge in the peripheral holes.However,this charging method has certain limitations and risk of misfire due to the usage of detonating cord together with detonator.So,it is an urgent problem to improve the effect of smooth blasting and ensure tunnel excavation efficiency at the same time.Related research was conducted by field tests,and a new initiation technology of “Shaped device+digital electronic detonator” has been proposed,which was applied to a plateau tunnel.The experimental results show that,compared with the original technology,the powder factor by using the new technology has been reduced by 0.2 kg/m3,the half-hole rate is increased by 5%,and the average charge time is reduced from the original 1.3 h to 1.0 h.The tunnel excavation cycle footage is stabilized,and the cost of consumables is greatly reduced,and it is expected to be widely used in tunnel smooth blasting.

The smooth blasting technology is the main means to control the over excavation and under excavation of tunnels at present.In order to explore the influence of the charge structure and charge amount of peripheral holes on the blasting effect,a series of single hole blasting tests were conducted in the silty shale section of Wulong Tunnel.The results show that the best blasting effect for detonating cord initiation can be achieved when a decked peripheral hole is charged with 0.1+0.075 5 kg of explosive.At this time,the residual rate of peripheral holes is 96%,and the average linear overbreak is 15.3 cm.On the other hand,the best blasting effect for detonator initiation happens when the charge amount of a peripheral hole is 0.45 kg,with the residual rate of peripheral holes as 90% and the average linear overbreak as 18.4cm.When a continuous charging structure is adopted for the peripheral holes,the best blasting effect appears as the charging amount is 0.3/0.45 kg.In this case,the residual rate of surrounding holes is 32% and the average linear over excavation amount is 24 cm.The decking charge structure of the peripheral holes can effectively improve the blasting effect,which ensures the residual rate of peripheral holes is more than 50% and reduces the tunnel over-excavation.By comparison,the blasting effect,in the order from best to worst,is ranked as detonating cord with decking,detonator with decking and continuous charge,respectively.And their residual rates of peripheral holes are more than 90%,more than 70%,and less than 50%,respectively.It is proved that both the detonating cord with decking charge structure and the detonator with decking charge structure can be used for surrounding holes to control tunnel over-excavation.

In order to solve the problems of large displacement,high boulder yield and low shovel loading efficiency in the front row of Husab mine blasting operations,a series of buffer blasting trials were designed and conducted.The project has successively completed the buffer blasting tests in 5 large blocks,and each section has 360 000 tons to 530 000 tons of ores,15~21 rows of holes,and 5~40 meters wide buffer materials on the free surface.The muck pile shape,shovel productivity,fragmentation and floor elevation deviation were measured and compared with the non-buffer blasting results in the same period.The test results show that there are forward pounce and uplift phenomenon to the blasting pile under the impact of explosion.Meanwhile,the muck pile surface presents a shape with unequal heights,and the maximum height difference varies from 4.06 m to 5.85 m.The productivity of a hydraulic shovel is 2722 t/h in the buffer blasting blocks,which is 4.69% higher than that in the non-buffer blasting blocks in the same period.Moreover,the results of fragmentation analysis reveal that the buffer blasting is better than non-buffer blasting on the fragmentation performance,and the buffer blasting has the advantage in reducing boulders.Finally,the test results show that the buffer blasting has certain advantages in floor elevation control.It is the first time to promote buffer blasting technology to the blasting of large sections with multiple rows of holes(15 to 21 rows),which is not only in line with the objective needs of large-scale mine production,but also an inevitable trend as large-scale equipment is used.

Most of the buildings in the mountain city area are built on leaning the mountains,with the characteristics of uneven terrain,scattered architectural layoutscattered layout of buildings and complex surrounding environment.In a certain area of Chongqing,there are were 10 frame-shear wall structure illegal buildings with a frame-shear structure that need to be demolished.Due to the requirements of construction safety and progress,single incision directional blasting demolition is was determinedadopted.Combined withBased on related the practice experience of blasting demolition project,according to the plane position,spatial distribution characteristics and surrounding environment of 10 illegal buildings,thean corresponding overall blasting scheme is was put forward according to the plane positionlayout,spatial distribution characteristics and surrounding environment of the 10 illegal buildings.And optimizing construction organization,tThe blasting demolition task of this building group is was completed safely and efficiently in three times within 15 days under an optimizding construction organization.In view of the environmental factors such as high and steep rock slopes,valleys and scarps that which affect the collapse of the building and the blasting effect,the directional collapse of the buildings can bewere reliably guaranteed by optimizing the blasting incisions,reserving buffer layers,and rationally designing blasting parameters.Through the rational reasonable design of the partition sections and delay times of firing circuitthe initiation network,and efficient organization of the circuit connection operations,the athe reliable delay initiation of large-scale industrial electronic detonator network is was realized.Finally,the collapse accumulation range and blasting harmful effects of building arewere effectively controlled.The collapse of eEach building is was fully disintegrated,the blasting heap piles fragments arewere concentrated,and all kinds of surrounding protection objects are were safe.The engineering practice results show that the initiation network of industrial electronic detonators initiation network can meet the needs of multi-unit and multi-level large-scale initiation network,which provides an important reference for similar projects.

Aiming at the blasting demolition of the buildings embedded with a 43 m high steel structure boiler frame,the five boiler frames of No.2~No.6 boiler rooms were demolished by one-time directional blasting method and collapsed from north to south by span to east according to the order of No.2~No.6 boiler rooms.The reinforced concrete support columns were drilled and blasted,and the steel support columns were cut by a shaped energy cutter.Three cuts for the first-row of support columns of No.2 and No.3 boilers were set with a cut heigh of 6 m.Similarly,three 4m high cuts and two 3 m high cuts were set for the second-row and the third-row of support columns,respectively.The cut heights of the first-row and second-row of support columns of No.4~No.6 boilers were set as 6 m and 3.5 m,respectively.Additionally,the steel plates with a thickness less than 14 mm were cut by the SGPQ-15(180 g/m) cutter,and the steel plates with a thickness of 16mm and 20 mm were cut by the SGPQ-19(280 g/m) cutter.The total charge was 30.288 kg.During the explosion,the coal hopper room,boiler building roof and steel structure boiler frame overturned according to the designed direction.The frame of No.2 boiler sank at the moment of detonation,and the lower seat of No.5 column in the boiler room was placed after 0.25 seconds.Subsequently,the factory collapsed span by span from north to south and tilted towards the east with a detonation interval of 0.25 seconds.The collapse of the two stairwells were lagged significantly under the support of shear walls,and the stairwells toppled eastward under the impact of boiler overturning.The column between the upper and lower blasting cuts was compressed and collapsed during the tilting process of the column on the east side of the boiler room towards the east.The column was 16 m away from the chimney,and the upper part of the middle staircase,boiler,and shear wall were tilted forward.The main body was 14 m away from the chimney,and the closest distance of collapsed object to the chimney was 6 m.Both of the blasting flying stones and blasting vibration(0.28 cm/s) did not exceed the standard,and the blasting demolition did not cause any damage to surrounding buildings and facilities.

An equal proportion separated common node model was established by ANSYS/LS-DYNA finite element software to simulate the collapse process of a frame structure with a small height-width ratio demolished by blasting,and the stress characteristics of reinforced concrete columns of the structure were analyzed.It is found that the actual engineering and simulation results are highly consistent in terms of collapse time,collapse process and blast muck pile range,which shows that the numerical simulation is reliable.Additionally,during the collapse process,the plastic hinge was generated at the beam-column joints after each row of columns reached the section resistance moment,and the upper structure rotated with the plastic hinge as the fixed axis.There was a backward reaction force on the rear column,which resulted in an obvious recoiling in the forward leaning process.In the early stage of collapse,the stress of the reinforcing bar and the concrete element is stressed together.The stress of the reinforcing bar element with its co-node suddenly changed after the failure of the concrete element,and then it continuously changed in the state of tension and compression until the collapse ended.The reinforced bar at the blasting cut has certain hindrances to the free fall of the upper structure.

Aiming at the blasting demolition problems of a 180 m reinforced concrete chimney in Wuhan Iron and Steel plant,which contains a herringbone large volume lining and an adjacent gas pipe,the feasibility of the optimization scheme of “digging large arched guide window and raising blasting incision” was demonstrated by the ANSYS/LS-DYNA finite element software.The calculation results show that the collapse and accumulation speed of the inner lining is obviously greater than the closing speed of the blasting incision after it is generated.Meanwhile,the chimney may not be topple over under the influence of the accumulation body by using a general directional dumping scheme.However,the chimney will collapse by raising the height of blasting incision to 5.6 m and digging a large arched guide window which is 6.09 m wide and 8 m high.In addition,to ensure a good effect of blasting demolition,the auxiliary measures of mechanically removing the lining around the blasting incision and covering the surface of the blasting incision and gas pipeline with flexible protective layers composed of safety nets,barbed wires,geogrids and other composite materials were put forward.The actual demolition blasting results show that the chimney collapse process is smooth after the incision detonation,and the numerical simulation results are in good agreement with the actual situation.At the same time,the gap between the chimney root cylinder wall and the ground is filled with the accumulated objects after the collapse,and there is no damage to the adjacent gas pipe.Besides,the excavation of the oversized arched guide window not only realizes the relief of the accumulation materials,but also greatly reduces the workload of charging and protection.

In order to carry out the controlled blasting of two 200 m reinforced concrete bridges(an old continuous beam bridge and a new arched bridge) under complex environment,the piers of the two bridges,the webs of the continuous beam and the double-curved arch foot of the arch bridge were selected as the blasting locations,and the main bearing parts of the bridges were destroyed.Furthermore,deep hole blasting method and shallow hole blasting method were adopted for the pier and main beam respectively to improve the construction safety and efficiency.Specifically,large-diameter vertical holes facing the pier from the bridge were adopted for the blasting of the pier to overcome the influence of pier arc face on the calculation of minimum resistance line and reduce the drilling workload.Additionally,the two bridges were detonated span by span in the same direction from south to north,with an equal delay interval between two adjacent spans.At the same time,the detonation time of the new bridge is 50 ms later than that of the old bridge.To reduce the damage of blasting vibrations and ground touch vibrations,millisecond delay controlled blasting was adopted,and the direction of the minimum resistance line was deviated from the near shore protection object.Meanwhile,in order to control the flying stone,sandbags were piled on the abutment,and the blasting objects were bounded with wire meshes and covered with multilayer bamboo basketries.After detonation,the bridge collapsed span by span as expected,the vibrations and flying rocks were controlled well.

In order to investigate the dynamic response,damage evolution and failure of concrete tunnel structure by underwater explosion load,laboratory tests and numerical calculations are adopted in this paper.Firstly,a 40∶1 specimen was designed according to the East Lake underwater tunnel.An explosion test of the underwater box concrete tunnel model was then carried out.The dynamic response rule of the concrete specimens under different emulsion explosive equivalent was compared by monitoring the strains.Meanwhile,the failure forms of the scaled model of the box tunnel caused by the underwater blasting load were investigated by measuring the size of the failure range and the length of crack propagation.Furthermore,a 1∶1 modeling simulation analysis of the test was carried out using the S-ALE algorithm in ANSYS/LSDYNA.It is found that the simulation results were basically consistent with the experimental results by comparing the experimental data and failure patterns.At the same time,the complete propagation process of the underwater explosion shock wave and the deformation law of the specimen structure were obtained by further analysis of the simulation results.Finally,the dynamic response mechanism of the box tunnel specimens under explosion load was revealed through statistical analysis of strain and displacement data at the measuring points.The results show that the transverse strain of the box concrete tunnel structure is much larger than the longitudinal strain.The failure location of the tunnel is mainly concentrated in the area near the explosion source and the structural angle position.It is verified that the S-ALE algorithm can simulate the dynamic response and damage evolution of the structure by underwater explosion accurately.

The blockage of a fine ore bin is a common problem during the process of the beneficiation and smelting of non-ferrous metal mine due to its inherent structure,the properties of fine ore and environmental factors.The treatment methods such as air gun and manual knocking are inefficient and labor-intensive,which cannot meet the production requirements.It is a feasible way to dredge the blockage of the fine ore bin by controlled blasting.The key to handling the blockage by blasting is to determine the explosive charge amount under the condition of ensuring safety.According to the blockage position and degree,two kinds of charge calculation formulas were used by analyzing the reason for the fine ore bin blockage,the characteristics of the blockage body and the principle of blasting dredging.One method is refer to the empirical formula of condensate disassembly blasting.The charge amount for viscous plugging is designed and calculated according to the slagging thickness.The calculations indicate that the charge for the upper part with a larger diameter is 0.59 kg,while the charge for the lower conical feeding port with a smaller diameter is 0.07 kg.The other method is according to the calculation principle of volume charge and the characteristics of the clogging body of the fine ore bin.The calculations indicate that the charge for the upper part with a larger diameter is 0.49~0.98 kg,while the charge for the lower part with a smaller diameter is 0.15~0.30 kg.The safety charge amount is determined through calculating the safety pressure by the Faupel correction formula and shock wave calculation.As a result,the charge amount for the upper part and the lower part are determined as 0.6 kg and 0.15 kg,respectively.During the implementation process,15 blocked fine ore bins were treated by charge amounts not exceeding 0.6 kg and 0.15 kg,all of which were safely dredged as expected.The practice shows that the calculated charge amount is reasonable,and the safety measures are effective.

For the purpose of studyingTo study the influence of hydration rate of static explosives on the mechanical behavior and damage mechanism of coal ore body,numerical simulations of ore body mechanical damage were carried out using a stress-damage coupling model under different hydration rates.The impact of hydration rate on the evolution of stress field and damage zone in the ore body was analyzed,and the mechanism of the effect of drilling arrangement model on hydration rate was revealed.The research results indicate that the development of the damage zone in static blasting can be divided into four stages:compaction stage,micro-damage formation stage,damage zone development stage,and damage zone connection stage.Among them,the stages of damage zone development and connection stages show the most significant stress effects.The stress field and damage zone increaseincreases with the increase in of hydration rate.Specifically,and the influence of hydration rate on the stress field and damage zonesuch kind of influence is relatively small during the initial rapid energy release phase,but becomes significantly different in the later stages.Besides,Tthe borehole arrangement model affects the mechanism of hydration rate.withUnder the single-hole mechanical model,the hydration rate promotes expansion pressure differences,while However,the under the double hole mechanical model,hydration rate promotes stress superimposition forunder the double hole mechanical model.The guided hole arrangement model has the most significant effect,where the initial hydration rate accelerates stress transfer and the later hydration rate promotes stress superimposition,leading to the expansion and connection of the damage zone under the combined effects of time and stress dimensions.In the numerical simulation and field tests scheme of this study,the hydration rate of the static blasting agent was 1.8 MPa/min,the blast orehole diameter was 113 mm,the borehole spacing was 1000 mm,and the reasonable ratio of borehole spacing to diameter(η) was 9.The guided hole arrangement model can effectively fractures the ore body and generatees a large number ofmany damage zones.This research provides a reference basis for improving the fracturing effect and construction arrangement of static blasting technology.

Aluminum powder is the most used metal fuel in explosives industry.The nano aluminum powder has a much higher specific surface area,reaction reactivity and completeness compared with the micron aluminum powder.Therefore,the application of nano aluminum powder in explosives will undoubtedly improve the explosive power and the ammunition damage efficiency.This article has systematically reviewed the effects of nano aluminum powder on the detonation performance,safety performance,process performance and other explosive properties.As for the detonation performance,the nano aluminum powder can improve almost all detonation parameters of the mixed explosive,including the detonation velocity and heat,the peak value of shock wave overpressure of air explosion,the total energy of underwater explosion,the peak value of explosion pressure and the rise rate of explosion pressure of the fuel-air explosives,the metal acceleration ability,arson ability,work ability,and brisance,et al.However,some incorrect conclusions are often drawn by some researchers due to the low effective aluminum contents of the nano aluminum powder.In terms of safety performance,the introduction of nano aluminum powder increases the impact sensitivity,friction sensitivity,shock wave sensitivity and thermal sensitivity of mixed explosives,which significantly reduces the ignition energy of explosives and promotes the thermal decomposition of common explosives(such as TNT,RDX,HMX,CL-20,NG,etc.).Therefore,the introduction of nano explosives has a negative influence on the safety performance of mixed explosives.In terms of process performance,the nano aluminum powder increases the viscosity of the cast explosive system.However,it reduces the density of the explosive column in the pressed explosive system.Therefore,the introduction of nano-aluminum explosive deteriorates the process performance of the mixed explosive.It is pointed out that it is easy to oxidize in various stages from preparation to storage due to the large specific surface area and high reaction activity of nano aluminum powder,which results in a sharp decrease in the effective aluminum content of nano aluminum powder.This is an important reason why some researchers get wrong conclusions.Therefore,it is necessary to study the preparation methods and storage conditions to make full use of nano aluminum powder in explosives.

Aiming at the problems of high boulder yield,high explosive consumption and poor blasting effect in an open-pit mine with complex lithology in Xinjiang,59 blasting tests for the optimal inter-hole and inter-row delays in rock masses with different blastabilities were carried out on four levels(between 445 m and 595 m) at the east side of the mine.The optimal delays between holes and rows were determined by the shape of blasting pile,ore rock fragmentation and powder factor.The test results show that the blasting pile is flat and the fragmentation is uniform for benches of mudstone with some fine sands when the delays between holes and rows are 5.9 ms/m and 14 ms/m,respectively.For sandstone with part of mudstone lithologic,when the delays between holes and rows are taken as 2.7 ms/m and 14.2 ms/m respectively,the blasting pile shape and fragmentation are reasonable and the boulder yield is low.The test results are applied to the field production of the mine,and the average powder factor and boulder yield are 4.03% and 1.8%,respectively,which are lower than those of previous years.The research shows that reasonable selecting of delay time between holes and rows for complex geological conditions can obtain flat blasting pile and the uniform block size,which can effectively reduce the powder factor,and save costs.The delay time determined in this test can provide important field data for selecting the delay time of mudstone and sandstone mixed bench blasting under the same geological conditions in Zhundong area.

A monitoring method based on the characteristics of weak grating sensors is proposed for long-term monitoring of the uneven settlement and horizontal displacement of segments in shield subway tunnels during the operation period.The cable type weak grating sensor is fixed on the wall of the shield tunnel in a diamond patten after prestretching.By monitoring the deformation of the weak grating sensor,the tunnel deformations corresponding to different tunnel structure modes can be distinguished and calculated to meet the real-time and precision requirements for engineering.According to the similarity ratio principle,a 1∶5 tunnel displacement model is designed and manufactured to simulate the local expansion,settlement and horizontal displacement of the tunnel segments.The grating sensors are also fixed on the wall surface of the tunnel model.Sensitivity tests of the weak grating sensors are first conducted before displacement monitoring.Then,the weak grating monitoring results with different diamond layout angles are compared.The following step is to monitor the vertical settlement and horizontal displacement of the tunnel model,which are compared with the actual displacement values.The results show that the strain of weak grating with the diamond layout is larger than that with a linear layout under the same settlement condition,which means the sensitivity of the diamond layout method to settlement change is better than that of traditional linear layout.Furthermore,10°~20° is the optimal angle interval of the diamond layout for weak grating,for the monitoring result error is low.Additionally,the inversion equation of weak grating wavelength change and segment displacement is established based on the test data of diamond layout with an angle of 15°.

The explosion of premixed gas in a closed vessel is very complicated.In order to study the effect of ignition position on the explosion characteristics of methane/air premixed gas,the central ignition explosion experiment with 10 vol.% methane concentration in a 1 m3 closed spherical explosive vessel was carried out under an initial pressure of 101 kPa and an initial temperature of 300 K.Besides,the effect of different ignition positions(center ignition,0.5R ignition,R ignition) on the explosion characteristics of methane/air premix in the vessel was studied by LES turbulence model and Zimont combustion model of the Fluent numerical simulation software.It includes flame structure evolution,explosion temperature,explosion pressure and explosion pressure rise rate.The results show that the flame expands around until the wall and profile of the vessel gradually change from the initial “left thin and right thick” to the “left raised sharp angle” and gradually stretch from the “circular arc” to the “sharp shape” to the left when the flame is ignited at the center,0.5R and R.And then,there is a temperature gradient in the temperature field at different ignition positions.The heating law is continuously released from the energy of the ignition center,and the temperature continuously accumulates and rises.Furthermore,the variation trend of explosion pressure under different ignition positions is basically the same.The final maximum explosion pressure is stable at about 766 kPa due to the wall insulation.Finally,the rise rate of the maximum explosion pressure in the center ignition is the highest,which is 94.5% and 141.8% higher than that in 0.5R ignition and R ignition,respectively.

Boulder yield is an important index to evaluate the blasting quality in the blasting process of an open pit mine.Since a high boulder yield will not only greatly reduce the mining efficiency,but also increase the cost of secondary rock breaking,so fragments size statistics is an important work in open pit mining.Aiming at the problem that the statistics of fragment size is complex and not accurate enough,a statistical model of boulder yield was built by deep learning based on the takes the image data of blasting piles collected in the Unugetushan copper and molybdenum mine.Firstly,the annotated data set was initially segmented into an initial effect diagram of the mine rock contour based on the U-net image segmentation model.And then,the annotated data for training was optimized and the Resu-net model was improved on the basis of the residual learning module,which resulted in the final segmentation effect map of mine rock contour.Finally,the fragment size information of the blasting pile was obtained through the minimum external rectangle method combined with OpenCV image processing technology.The results show that the segmentation accuracy of U-net+Resu-net fragment size optimization model proposed in this study is 97.84% with an accurate image data segmentation.The statistics of fragment size in an inclined blasting pile is realized by OpenCV technology combined with the camera monocular imaging principle.In addition,the developed interactive interface is simple to operate and can quickly calculate the boulder yield.

In order to analyze the general rules and causes of civil explosive accidents in China,statistical analysis was carried on the occurrence time,regional distribution,accident grade and other dimensions of nationwide civil explosive accidents from 2006 to 2023.Using analytic hierarchy process(AHP),a hierarchical structure model is constructed.It includes four first-level indicators(human,machine,environment and system) and 11 second-level indicators(safety awareness,technical training,supervision intensity,safety education,standardized operation,production equipment,production process,weather and climate,storage conditions,safety management system and emergency management system).Through analysis,the weight of each index is obtained,and then the importance of the influencing factors on explosion accidents is sorted.The results show that the number of explosion accidents has decreased year by year,and the safety situation is improved.The explosion accident time is concentrated in the second and third quarters of each year,and the space distribution is across all provinces with a staggered characteristic of “North-South and high-low”.Generally,the ordinary accidents and large accidents are the main accident levels.Based on the analytic hierarchy process(AHP),it is learned that human is the most important factor to cause the accidents in the first-level indexes.Meanwhile,the standardized operation,production process,supervision intensity and safety management system are the more important factors in the second-level indexes.Finally,according to the importance of the factors affecting the accidents,preventive measures such as strict standardization of operation,increasing safety input,strengthening supervision and improving safety management system are proposed.

In order to study the development track and hot spot changing trends of blasting technology in open-pit mining,1116 valid journal articles were retrieved as a sample from the China National Knowledge Infrastructure(CNKI) database by selecting “open-pit mining” and “blasting” as the search criteria.According the visual analysis reports from CNKI and utilizing the visual knowledge graph tool CiteSpace,a comprehensive and in-depth study has been conducted on the state of the art,distribution characteristics,research hotspots,and cutting-edge trends in the field of open-pit mining blasting research in China.The research findings indicate that the study of open-pit mining blasting has undergone three distinct stages:the establishment and development of open-pit mining blasting theory(pre—2010),the phase of modern technology application and innovation(2010—2015),and the stage of green,intelligent,and precision development(2015—present).The disciplinary distribution primarily focuses on mining engineering and general industrial technology and equipment.The prominent journals for publication include Blasting,Engineering Blasting,and other journals in the field of mining engineering.The majority of authors and institutions are affiliated with mining-related universities,enterprises and research institutes.The research topics encompass various aspects,including the development and application of blasting design software,optimization of blasting parameters(such as blast hole pattern,powder factor and charge structure),deep-hole blasting,bench blasting,cast blasting,pre-splitting blasting,control and monitoring of blasting vibration,numerical simulation,and application of artificial intelligence algorithms,analysis of factors affecting blasting quality and evaluation of blasting effects.The future of open-pit mining blasting will continue to evolve towards automation,intelligence,precision and environmental friendliness.Through technological innovation and interdisciplinary integration,the industry aims to provide more efficient,safer and sustainable blasting solutions for the mining sector.