The pillar blasting stope project of 425 m medium stage in Lilou Iron Mine of Minmetals Mining was presented.Based on the stress wave theory,the propagation of blasting stress wave in total tailing cemented backfill and its interaction with medium interface were analyzed.According to the different failure criteria and mechanism of backfill,such as impact-compression-shear,shear and reflective tension,the particle vibration velocity threshold of backfill were studied.The research shows that the cementing surface between the pillar and the 1∶8 ratio backfill is prone to shear failure due to blast stress wave,and the cemented backfill is prone to compression-shear failure.Under the action of refracted and reflected stress wave,the cementing surface between the 1∶8 ratio and 1∶20 ratio backfill is prone to tensile failure,and the spall fracture of the 1∶8 ratio backfill adjacent to the 1∶20 ratio backfill may occur.The specific particle vibration velocity threshold of the backfill is summarized below:The particle vibration velocity threshold of shear failure on the cemented surface between the pillar and the 1∶8 ratio backfill is 27.6 cm/s;the particle vibration velocity threshold of compression-shear failure of 1∶8 ratio backfill adjacent to pillar is 172 cm/s;the particle vibration velocity threshold of tensile failure on the cementing surface between the 1∶8 ratio and 1∶20 ratio backfill is 12.6 cm/s.the particle vibration velocity threshold of spall fracture of the 1∶8 ratio backfill adjacent to the 1∶20 ratio backfill is 52.6 cm/s.

The research on the dynamic response of steel tower frame structure on reef sand foundation under explosion loading has important practical significance for our national defense and reef engineering construction.In this work,the acceleration dynamic response signals of steel tower frame structure for different reef sand foundation types,explosive charges,distances to blasting center and other working conditions were tested through model tests.Combined with dimensional formula and π theorem,the acceleration dynamic response calculation formula of the steel tower frame structure model is obtained.Then this formula is fitted by using the data collected from the tests to determine the related parameters.Finally,the acceleration dynamic response empirical formula of steel tower frame model on reef sand foundation is obtained.

Based on the theoretical analysis,the frequency domain expression of equivalent blast load of group holes is derived,which is substituted into the expression of amplitude spectrum of blasting vibration velocity in cohesive rock mass.The expression of amplitude spectrum of rock mass vibration velocity excited by simultaneous blasting of group holes is obtained.As to open-pit bench deep hole blasting,four hole blasting with square layout is taken as the research object.The influence factors of rock mass vibration frequency and attenuation mechanism of main frequency are studied.The results show that with the increase of blast center distance,blast hole spacing and single hole charge,the frequency spectrum structure shifts from high frequency to low frequency,at the same time the increase of pitch or blast hole spacing blasting,blasting vibration main frequency attenuation obviously,and the rise time and fall time of explosion load directly influence the proportion of blasting vibration spectrum.Comparing the attenuation law of the main frequency of blasting vibration under three typical rock parameters,it is found that the main frequency is in direct proportion to the elastic modulus of rock mass and the longitudinal wave velocity,while the attenuation speed of the main frequency is inversely proportional to the elastic modulus and longitudinal wave velocity of the rock mass.The vibration frequency excited by blasting in Jinping marble is relatively small,and the main frequency attenuation speed is the fastest.

Bench blasting effect evaluation is an important link in the process of blasting production,which directly affects the efficiency of subsequent construction.In order to understand the effect of bench blasting,the grey clustering evaluation model was established and optimized by using the trigonometric whiten weight function of mixed center point.According to the characteristics of bench blasting,the boulder rate,loosening coefficient,root ratio,back crack distance,vibration velocity and flying distance were selected as the evaluation indices affecting bench blasting effect.Combining the analytic hierarchy process and the CRITIC method,subjective weights and objective weights of the evaluation indices were assigned respectively,which overcomed the subjectivity of traditional index weight assignment and the sensitivity of data difference.An optimal combination weighting method based on the sum of squares of deviations was proposed,and the optimal combination weighting grey clustering evaluation model for bench blasting effect evaluation was established.The effectiveness and practicability of the model were tested by four deep hole bench blasts of Hongshuitai earthwork leveling project.In addition,the evaluation grade of bench blasting effect was analyzed,and hole-by-hole blasting with a spacing of 3.5 m was determined as the optimal bench blasting scheme.

Boulders and bedrock intrusion in shield tunneling has become an important factor affecting tunneling efficiency and leading to the increase of tunneling cost.Combined with the engineering practice of hard rock blasting of open shield tunnel under complex urban environment,the design and selection method of hard rock blasting parameters of shield tunnel and safety protection measures were introduced in detail.In addition,the rationality of the blasting parameters was verified by numerical simulation using LS-DYNA dynamic finite element software.The blasting results show that there are some blasting craters with scattered cracks in the tunnel face after blasting,which provides good working conditions for shield tunneling and effectively improves the tunneling efficiency.Compared with the common mining method and the ground drilling method,loosening blasting can reduce the overbreak phenomenon of the tunnel with less influence on the surrounding structures.It can also realize the goal of safe,efficient and continuous excavating of shield tunneling,which can reference for the design and construction of similar projects.

In order to study the safety of buried pipelines under blast load,ANSYS/LS-DYNA is used to establish the coupled model of explosives,geotechnical bodies,and buried pipelines,so as to study the dynamic response of buried pipelines under blast load.By monitoring the pipeline blast surface-back blast surface specific unit stress and velocity time curve,it is found that 1/4 from both ends of the pipeline blast surface and there is a stress concentration,back blast surface has a local stress amplification effect,and the axial vibration velocity of the pipeline reaches the maximum at 10~21 ms;by changing the pipe wall thickness with 4 mm,6 mm and 9 mm,the pipeline meet -back blast surface of the axial effective stress,velocity,and the pipeline annular vibration wave energy are decreasing with the increase in pipe wall thickness.When the pipe thickness ratio i<0.0525,he explosive energy attenuates the fastest.When 0.0525≤i≤0.05375,attenuation index η,β,κ values are 26.7%.And when i≥0.06,the pipeline annular monitoring unit of the attenuation index law change tends to be consistent.

As the deep mining environment becomes increasingly complex,the problems of high ground stress and passing through fracture zones were analyzed and studied in order to achieve safe and efficient deep mining blasting construction.The implicit and explicit coupling analysis program in the finite element analysis software ANSYS-LS/DYNA was used to simulate the fractured rock mass under bidirectional equal pressure and bidirectional unequal pressure.Then,this program was used to study blasting excavation in the special condition of fractured rock mass with weak plane under high ground stress.The research results show that during the blasting mining process of deep fractured rock mass,the tensile stress of the unit gradually decreases with the increase of the confining pressure,but the compressive stress of the unit does not increase significantly in an isobaric in-situ stress field in all directions.At the same time,the compressive stress of the element near the right side of the crack reaches the peak value of the survey line,and the compressive stress increases with the confining pressure.In anisotropic stress field environment,the tensile stress of the survey line in the hole and crack area reaches its peak value when the lateral pressure coefficient is 1.33.Therefore,in the process of deep mining and blasting,attention should be paid to the in-situ stress field in the fracture zone including cracks,which has a significant impact on the safe and efficient implementation of blasting excavation.

Large diameter deep hole blasting has been used for ore caving mining in Zhangzhuang iron mine.To effectively control the blasting impact on the integrity of the high-stage slope,the mine introduced a smooth blasting technology based on the engineering characteristic of the mine and the application of existing controlled blasting technology when a new middle section increased to 90 m high.According to different linear charge densities,a blasting industrial test was carried out after fixing the blasting parameters such as the hole diameter,charging diameter and hole spacing.By using the goaf scanning technology,the boundary shape of the goaf was drawn after mining of the whole stope.And then,the actual effect of blasting tests in each group was analyzed.Finally,the main smooth blasting parameters suitable for the high-stage slope were determined as follows:the hole diameter was 165 mm,the charging diameter was 70 mm,the decoupling coefficient was 2.36,and the linear charging density was 2 kg/m.This technology has been widely used in the other stopes of Zhangzhuang iron mine.

The hole layout design of medium-length hole blasting in underground mine directly affects the blasting efficiency and production cost.Previous research has proposed the optimization algorithm based on the single source & shortest path which greatly improved the efficiency of hole layout design optimization.However,the proposed methods still cannot fully meet the demands of actual application.In this paper,the correlation between the hole layout and the medium-length-hole blasting parameters was analyzed.The bottom distance between the holes was taken as one of the main control parameters.Based on dynamic programming of the shortest path from multiple sources and Floyd algorithm,an algorithm model for optimal layout design of fan-shaped medium-length hole blasting was established.The proposed model solved the problem of the hole layout optimization of fan-shaped blasting hole design with preset specific hole parameters.On this basis,the optimal design program module of medium-length-hole blasting was re-developed using the AutoCAD platform which was successfully applied to an iron mine.

In open-pit mine blasting,blasting delay time has an important influence on the shape of the blasting pile.The study on the variation law of blasting pile shape characteristics with changing delay time can optimize the blasting design scheme,facilitate the subsequent procedures such as shovel loading,transportation and crushing,and improve the mine production efficiency.The shape of the blasting pile in mine production is mainly evaluated by the height and shape characteristics of the blasting pile.The ideality of the blasting effect can be evaluated by analyzing whether the shape of the blasting pile meets the production requirements of shovel loading equipment.Taking a bench blasting project of an open-pit mine,the UAV tilt photogrammetry technology was used to obtain mine blasting pile tilt image data,and built a blasting pile model with smart 3D.The contour curve of blasting pile model was extracted,and the shape characteristics of blasting pile under different delay time were studied.The evaluation index of blasting pile under the delay time with 23 ms between holes and 50 ms delay between rows was better than those of other groups,which was more suitable for blasting production in the mine.Through MATLAB software,the Weibull function was selected to fit the shape of the explosive heap,and the value range of parameter α of Weibull function was 1.0297~1.2194,and the value range of β was 1.1754~1.8040.

Blasting technology was used to ensure the stability of a cutting slope in Lianyungang in order to prevent geological disasters.The construction site of the blasting area was narrow and the transportation of stone was limited.This condition led to the application of the technical scheme of buffer blasting with hole by hole initiation based on related rock fragmentation mechanism.The thickness of the buffer body was 3.5 m,and the initiation delay interval was 50ms.The single-hole explosive charge in the front and rear rows were 130 kg and 100kg,respectively,with a powder factor of 0.45 kg/m3.The safety of surrounding buildings could be ensured by checking the blasting vibrations.The results show that the blasting parameters are reasonable for a good blast effect,which can reduce the boulder yield and the blast vibration effect.

According to the surrounding environment and structural characteristics of a frame tube structure building to be demolished,the blasting demolition scheme of “inward folding” was adopted.The finite element analysis software ABAQUS was used to analyze the stability of the pre-demolished building structure and determine the pretreatment scheme combined with the stress distribution.The results show that the moment applied to the column was obvious,and the reinforcement was in elastic working state under the maximum tensile stress;the internal stress of the frame structure was reasonable.Bending deformation presented a trend towards the center,and the structure was in a stable state.In the blasting scheme,high blasting point was selected.In addition,blasting cuts were arranged in layers 1,2,4 and 5,and the cuts were gradually increased from top to bottom.Various blasting parameters and delay times were set according to the positions of 20 single-layer columns,and the blasting network consisted of 11 half second delay detonators and 3 millisecond delay detonators.In order to ensure the collapse direction and control the ground vibrations,the delay times of columns at individual positions were adjusted.Combined with effective safety protection and vibration reduction measures,the blasting effect had met the design expectation.The study can be used as reference for similar projects.

Taking a blasting demolition project of a 70 m building with a 8.0 m×8.6 m span between stand columns as an example,the impact vibration of the collapsed building on the ground was calculated and analyzed theoretically to ensure the safety of the buildings under construction.The blasting demolition control technologies including double incision accelerating the disintegration of the building in the air and block delay were used to carry out the demolition project.A blasting vibration tester was used for real-time monitoring,and the collapse shape was analyzed by a high-definition camera.The safety and effectiveness of the demolition control technology were then verified.The high-definition photos and vibration monitoring data showed that the potential energy conversion of the long-span building was fast,which could cause recoil easily.Although the damping ditch can significantly reduce the collapse vibration,it had no effects on the blasting vibration.While the floor height where measuring points were arranged had certain amplification effect on the blasting vibration velocity,it basically had no effect on the collapse vibration.

In order to further investigate the collapse process of the demolition blasting of a multi-section load-bearing column frame structure and analyze the stress of the reinforced concrete columns of the structure,the ANSYS/LS-DYNA finite element software was used to establish a separated reinforced concrete frame structure model with joint nodes.The collapse process of demolition blasting was numerically simulated and compared with engineering practice.The results show that the collapse process of the frame structure obtained by numerical simulation is consistent with the engineering practice.That is,it is divided into four stages:blasting incision formation,semi-free fall,incision closure,and touching ground.In the event of touching ground,a “plastic hinge” is formed at the joints of the columns on the first and second floors to ensure the smooth collapse of the structure.Because the failure strength of the steel bar is much higher than that of concrete,the superstructure is independently supported by the steel bars after the concrete elements co-jointed with the steel bar elements fail.

Due to the complex surrounding environment and limited collapse space for the demolition of a 210-meter-high chimney in a plant area,the accuracy and safety of the directional blasting must be ensured.According to theoretical calculation and engineering experience,a regular trapezoidal blasting incision was selected.The incision height was 4.5 m,the incision center angle was 216,the unit explosive consumption of the outer wall of the chimney was 2.3 kg/m3,and the unit explosive consumption of the inner wall was 1.45 g/m3.Measures by optimizing excavation technology,blasting parameters,and the blasting network were used to control secondary blasting hazards.The negative effects of blasting were controlled by adopting safety measures such as mixed material suspension cover protection and damping dikes.Finally,the blasting achieved good results.The surrounding buildings(structures) were not damaged during the blasting process,and the monitored vibration peak was 0.27 cm/s.

Portable explosive loader is a new type of small charging device for mixed emulsion explosive.In order to make it more suitable for blasting application,an application research of charging and blasting on site was carried out by equipment optimization and field tests.The results showed that the portable explosive loader was lighter and more mobile by optimizing the skeleton material and structural style.Furthermore,the production formula of mixed emulsion explosive was adjusted according to the working principle of the equipment.At the same time,terminal sensitization tests under high and low temperatures on the equipment were carried out.It was shown that the sensitization speed was fast and stable,and the after-effect was not obvious.The detonation speed of the field mixed emulsion explosive after sensitization was 4460 m/s which met the requirements.Combined with a newly developed 60 m  20 drug pipeline,a field charging and blasting test was carried out in a cement sandstone mine with narrow working faces and developed fractures.During the thickened formula charging,the maximum pressure was lower than 3 MPa,and no pipe plugging and leakage occurred.The blasting effect was favourable.

Aiming at the problem of insufficient supply of emulsion explosive on pre-splitting blasting,a new charging structure model was explored,that is,an axially continuous and radially uncoupled charge with granulated ANFO.The feasibility of the charging structure is verified theoretically.At the same time,LS-DYNA software numerical simulation was used to establish a 1∶1 model comparing with the actual hole size of the mine,and the difference between the uncoupled charge structure and the traditional emulsion cartridge was compared and analyzed.It is concluded that the axial continuous charge of granulated ANFO has advantages in protecting hole wall and crack propagation.The diameter of PVC pipe suitable for lithology of Laibetang mine was determined to be 40 mm,and the optimal hole spacing was 1.8 m,which was verified in field practice.

In the excavation of small-spaced tunnels,tunnel blasting has a great impact on the stability of the interlaid rock wall,and the construction of the cross passage will further aggravate the vibration damage of the interlaid rock wall.In order to study the vibration response of the interlaid rock wall under blasting,we monitored the vibration velocity of the interlaid rock wall caused by blasting with non-electric detonator in the small-distance tunnel project of Great Wall station of the new-built Beijing-Zhang Jiakou high-speed railway,and then analyzed the attenuation law of the seismic wave in the interlaid rock wall.At the same time,the vibration reduction tests of blasting with electronic detonator have been carried out to study the reasonable delay time of tunnel blasting hole.Through experimental research,some conclusions have been obtained.Firstly,the vibration of the end of the interlaid rock wall has obvious amplification effect due to the influence of vertical and horizontal tunnel segmentation.Secondly,the regression analysis of blasting vibration data by Sadovsky′s formula shows that Kfront<Kbehind,αfront<αbehind,which means that the influence of blasting vibration on surrounding rocks behind the tunnel face is larger than that in front of the tunnel face.Thirdly,the time-frequency analysis of the blasting vibration signal is carried out using the HHT method,and the result shows that vibration energy of the small-spaced tunnel is concentrated in the range of 50~200 Hz.Both the cutting holes and caving holes blasting contribute most of vibration energy to the rock behind the tunnel face.Finally,we set the time delay between cut holes and caving holes as 15 ms and 20 ms respectively in the hole with digital electronic detonator.This blasting scheme can make the blasting vibration energy distribution more distributed and reduce the peak value of vibration velocity by 50%~70%.

In a 2 m×2 m×2 m water tank,two detonation methods were used to conduct underwater explosion experiments on 2.5 g,5 g and 10 g cylindrical TNT charges.The pressure-time history curves with corresponding responses of shock wave and bubble pulsation under different working conditions were obtained.The experimental results showed that when the main charge was detonated by an electric detonator,the explosive was not completely detonated,and the peak pressure of the shock wave was less than the theoretical value calculated by the empirical formula,with the average error of 25.92% among them.After the main charge detonated by an electric detonator and a booster grain,the explosive was completely detonated,and the average error between of the peak shock pressure obtained from the experiment and the empirical formula was reduced to 4.37%,which was relatively stable overall.Comparing the data of the two detonation methods,it is found that when the explosive is not fully detonated,the bubble pulsation period and the maximum bubble expansion radius are reduced,and the peak wave pressure,shock wave energy and bubble energy are decreased obviously,but the effect on the peak pressure of bubble pulsation is not obvious.

Blasting engineering projects in complex urban environment is getting more prevalent.The urban environment construction,especially the establishment of civilized and health city,increasingly requires noise reduction and dust control.For this purpose,field experiments were carried out based on common noise and dust reduction measures in order to discuss the feasible reduction methods for dust,noise and vibrations.The field experiments included:spraying water before blast,covering colored strips and covering medium on single detonators.It is concluded that the best dust control was achieved by coverage of striped color cloth on blasting area,and the average rate of dust removal was more than 41.2%.When the surface detonator was covered with water,sand and gravel,the noise and vibration reduction effect was the best,with an average noise reduction rate of 21.2% and a vibration reduction rate of 35.2%.

It is urgent to study and solve the problem of gas safety in comprehensive pipe gallery.In order to explore the gas explosion load characteristics in the utility tunnel,the methane-air mixed gas enclosed explosion experiment was conducted in a small size pipeline of 0.11 m×0.11 m×6 m.The propagation rule of explosive waves with methane concentration between 7.5% and 13.5% at different ignition energies(electrode ignition-2 J;chemical ignition-5 J) was studied.The results showed that the overpressure peak of gas explosion increased first and then decreased with the increase of concentration(reaching the peak value at 10.5%).In addition,with the increase of ignition energy,the overpressure peak generally increased.SIMTEC numerical analysis software was used to simulate the experiment.Meanwhile,the Large Eddy Simulation and the modified Eddy Dissipation Concept model were adopted,which could well verify the most dangerous case of gas explosion in pipeline(methane-air full combustion explosion).

As an important safety protection facility of converter transformer valve hall,the explosion-resistant door should meets high quality requirements.Therefore,it is of great practical value to study the anti-shock performance of the explosion-resistant door of the valve hall.The anti-shnock performance of the explosion-resistant door filled with foam aluminum and nothing filled was studied and verified experimentally under the shock wave condition of 300 kPa and 1000 kPa,respectively.The anti-shock performance of the two different doors was evaluated through the amount of deformation,whose maximum values turned out to be 2 mm and 3 mm.The experimental results show that the explosion-resistant door with aluminum foam filling has better anti-shorck performance under higher loadings.

Numerical computation is an important way to study weapon effects and damage assessments.Its function is mainly reflected in three aspects:guiding test designs,optimizing schemes,and expanding test results as a supplementary means of theoretical and experimental researches.According to the basic characteristics of foreign software and the development status of domestic software for numerical computation of weapon effects,the outstanding advantages of foreign commercial software are strong research and development ability,convenient operation,high calculation accuracy and reliability,rich pre-processing and post-processing software,and parallel computing.On the whole,the numerical computation research in China is still restricted by others.Meanwhile,the developments of basic data,solution scale,computing ability and secondary development are relatively lagging behind.In order to overcome the bottlenecks,the secondary development technique based on open source numerical calculation software package is an effective way to rapidly narrow the gap with the mature foreign software.