The high-quality development of engineering blasting lies in promoting the application research with refinement, innovation of process, equipment and apparatus.Aiming at the demand of precision blasting, the theoretical research process control, safety management and intelligent construction should be deepened.Precision represents the times characteristics of science and technology, and it is a reflection of cognition and practice.Meanwhile, Precision includes all aspects.However, its core should reflect the overall planning of precision and process control.The overall planning of precision should highlight the combination of demand and process control of length, capacity and weight etc.The process control should focus on the rationality of the fineness of the key links.In this paper, the concept of precision and fineness is expounded that precision based on overall accuracy is the key to scientific digitization and intelligentization, so as to realize the specialization, time-domain and systematization of data in a fast, good and economical way, and lay the application logic foundation for data manage data management.Based on overall planning of key processes, refinement is to establish a reasonable matching control logic of people, materials and things.Furthermore, with a complete process means of loop connection and closed-loop control, process elements would be accumulated for intelligentization.Precision, digitalization and intelligentization connects the past with the future, mutual cause and effect, unity of opposites.

This paper sorts out the influencing factors on damage effectiveness of shaped charge and summarizes the latest achievements of SC based on a large amount of relevant references.The basic concept and general structure of shaped charge were given.The action mechanism of the five main factors affecting the armor breaking efficiency of shaped charge, such as explosive charge, charge liner, shell, detonation wave front control and operation condition, is discussed in detail.Some recent research work and relevant findings about damage effectiveness of shaped charge both at home and abroad were reviewed.All influencing factors are divided into interior and external categories.The chart of influencing factors on damage effectiveness of shaped charge was drawn.Hot technologies of shaped charge design were summarized.The results have some reference value for shaped charge designers.

Changjiu Shenshan limestone mine is the largest sand aggregate field in the world.The blasting fragmentation directly affects production efficiency of the mine.Combined with production practice, 11 blast tests were carried out in two mining areas where rock joints are developed.Based on Kuz-Ram blasting fragmentation prediction model, the average fragmentation after blasts was calculated.It is found that there is a great difference between the predicted value and the measured value.The results show that joint development degree and rock properties are the main factors affecting fragmentation distribution.The calculation of rock coefficient A in the modified Kuz-Ram model seriously affects the prediction results.It is suggested that the influence of rock density should not be considered in the calculating of the rock coefficient A.Through the analysis of data from four field verification blasting tests, it shows that the accuracy of the average fragmentation prediction value is significantly improved based on the Kuz-Ram model and the rock coefficient obtained by the proposed correction method.The relative errors are all below 10%, and the prediction accuracy is greatly improved.The research results can provide a technical support for the adjustment of blasting parameters in mining.

In the process of ocean development, blasting excavation of underwater coral reef limestone is often involved.In order to study the fracture characteristics of coral reef limestone after underwater drilling and blasting, four types of coral reef limestone were used to simulate single hole blasting tests under three water depth conditions.The failure zone around the hole, radial crack and fragmentation distribution of reef limestone specimens under different water depth were analyzed.The results show that no obvious failure zone around the hole is observed in coral limestone and coral gravel limestone specimens.For the biological gravel limestone, obvious cavity can be observed on the surface around the blast hole.The number and width of apparent cracks of the specimen after blasting decreases with the increase of the water pressure.The boulder yield increases with the increase of water depth, and the block size distribution of underwater drilling and blasting of coral reef limestone conforms to the swebrec distribution.

According to the field situation of Biesikuduke open-pit coal mine, the propagation law of blasting seismic wave in multi-step slope was analyzed.The blasting vibration tests were carried out on the step slope of the mining area.Four vibration test points were selected from near to far on the upper platform of the blasting area, and seven times blasting vibration tests were carried.Finally, five sets of valid data were obtained, and the five groups of vibration data results were fitted by the Sadovski formula regression fitting.As a result, the correlation coefficient R of the fitting results in axial, radial and vertical directions are all greater than 0.8, which indicates that the linear correlation is good.Meanwhile, it also shows that the vibration propagation formula has a good applicability to the slope vibration attenuation law under this geological condition.Furthermore, with the increase of the distance from the blast center, the slope particle vibration velocity decreases continuously.Among the three directions, the peak vibration velocity of the horizontal radial direction, horizontal tangential direction and the vertical direction is largest, second and smallest, respectively.Therefore, The impact of the distance from the blast center on the blasting vibration velocity is much greater than that of the elevation.By using this formula to develop the blasting vibration prediction software, the vibration peak value of measuring point position can be predicted, the maximum single-stage detonating charge and the vibration safe distance can be checked through the given parameters, which provide the data basis for solving the non-working slope stability.

In allusion to the issue of the blasting vibration signal containing which a lot of high-frequency noise due to the complex blasting construction environment, a noise reduction method based on Fourier decomposition(FDM) combined wavelet packet threshold method is proposed.Firstly, based on Fourier decomposition theory, blasting vibration signals were decomposed into several Fourier intrinsic band frequency functions(FIBFs).Then, the correlation coefficients between the decomposed modal components and the original signal were calculated respectively, and the dominant modal components were screened out by the correlation coefficient method, the dominant modal components were reconstructed subsequently.Finally, the wavelet packet threshold method was used to further denoise the reconstructed signal, and the final pure blasting vibration signal was obtained.The results show that the new method has the advantages of both Fourier decomposition and wavelet packet analysis.Compared with the existing common methods, the combined denoising method of Fourier decomposition and wavelet packet analysis has the highest signal-to-noise ratio(10.3940) and the minimum root mean square difference(0.0889).The obtained time-history curve is smoothing and the denoising effect is better.It provides a new way to denoise similar blasting vibration signal.

In order to study the deceleration effect of explosive reactive armor(ERA) on long rod type tungsten steel armor piercing projectile, the long rod armor piercing projectile model was designed by using LS-DYNA finite element software, and the numerical model of long rod armor piercing projectile penetrating explosive reaction armor with different speeds and angles of attack was established and the penetration process and speed of each part of the armor-piercing projectile were analyzed.The results show that the explosive reactive armor has obvious deceleration effect on the long rod penetrator, which is related to the attack angle between the axis of the penetrator and the normal of the reaction armor.The larger the angle of attack is, the better the deceleration effect is, and the stronger the protection performance of the explosive reaction armor is; the deceleration effect of the projectile body in the process of penetration has hysteresis, and the farther away from the warhead, the slower the starting time of deceleration.A new type of explosive reaction armor piercing projectile with two-stage warhead is designed, which can provide useful reference for the designers of anti-Armor Weapon System in the aspect of structure optimization.

In order to obtain an accurate and feasible explosive reactive armor(ERA) detonation calculating method of pre-warhead jet after penetrating seeker., First the processes of jet formation and passinginterference through the equivalent interference of seeker arewas calculated by the using ALE method.Afterward, a SPH model reconstruction method was proposed, and the head jet after penetrating seeker interference was transformed into a three-dimensional SPH calculation model.Using the SPH model, a studyresearch of the front warhead penetrating seeker detonating reactive armor was carried out.Furthermore, Then using the SPH model reconstruction method, the head jet after penetration of seeker is translated into 3D SPH calculation model, the pre-warhead jet detonation to ERA is performed by using SPH method.And the feasibility of the simulation results is was verified by an ERA detonation experiment.The results show that this calculation method can accurately predict the initiation ability of jet to ERA after penetrating the seeker.The clear material interface process of ERA detonation is got.Meanwhile, the process of detonating reactive armor with clear material interface was obtained.More importantly, it was found that The the ERA which is was detonated by the generated the precursor wave generated when the jet penetratesd the cover plate, andwhich proved .Tthe detonation theory of precursor wave ERA detonation is was proved.

On the background of the extension of Nam Ngum 1 Hydropower Station in Laos, the blast vibration tracking of the existed buildings and equipment was implemented.The vibration characteristics of presplitting blast-holes and main blast-holes were compared by analyzing the statistical data.Besides, the smoothed particle hydrodynamics(SPH) numerical technique was used to study the causes of the vibration differences induced by presplitting blast-holes and main blast-holes from the views of charging structures, initiation modes and burden sizes.Results indicate that the peak particle velocity(PPV) induced by presplitting blast-holes is generally higher than that induced by main blast-holes.The charging structures, initiation modes and burden sizes all play a significant role on the explosion loading characteristics as well as the evolution and distribution of the nearfield blast damage, which further affects the transmission and distribution of explosion energy.The explosives in presplitting blast-holes are generally decoupled charging with the rock mass and laterally initiated by the detonating cord.Moreover, the burden of presplitting blast-holes is always larger than that of main blast-holes.The peak blasting pressure on presplitting blast-hole walls is lower than that on main blast-hole walls.For the presplitting blast-holes, the crush zone and the number of cracks adjacent to the blast-hole, as well as the damage degree of the rock mass along the resistance direction, are all relative smaller.Thus, less explosion energy is consumed by rock fragmentation and throwing, allowing more energy to be converted into vibration energy.Consequently, the vibration induced by presplitting blast-holes is relative larger than that induced by main blast-holes.

Taking the construction project of south extension of Shunhe Expressway, Yingxiong Mountain overpass to South Ring Expressway, in Jinan city as an example, dynamic response of step blasting in rear tunnel to advance tunnel with the field blasting vibration monitoring and simulation with ANSYS/LS-DYNA, the dynamic response of the excavated tunnel to the up-step blasting of the excavating tunnel with small distance was analyzed.The results show that the X horizontal radial velocity is the largest and is close to the combined velocity in the three-direction velocity of the excavated tunnel.The vibration velocity of the excavated tunnel decreases from the back of working face to the entrance of the tunnel, and the parameters of blasting scheme should be adjusted according to the data of X horizontal radial in the field monitoring was proposed.According to the construction conditions of Jinan tunnel, the construction method of CD method is adopted, and good blasting effect is achieved by controlling the actual blasting charge of single section, hole depth, small leading pipe and composite lining supporting methods, which can provide some reference for other projects.

In order to ascertain the impact of vibration on the villagers′ houses caused by bench blasting in south mining area of Tianjiacun south stope in Baima Iron Mine, combined with location of the houses, current situation of open-pit, geology and geomorphology characteristics, and the heterogeneity of rock and soil mass, the blasting vibration measurement was studied with the L20 series intelligent blasting vibration measuring instrument.After that, the least square method was used to carry out regression analysis on the data to obtain the corresponding values K, α values and the attenuation law of blasting vibration velocity in each direction, respectively.It can be seen that the validation results reflect the reliability of regression values of K and α.Furthermore, the vibration velocity of 1525 m, 1540 m and 1555 m Benches in south stope of Tianjiacun village from July 2019 to October 2020 were calculated in reverse.Among them, the maximum vibration velocity is 0.33 cm/s located in the Z direction, which provided a basis for evaluating the impact of blasting vibration on the houses.The results show that the blasting vibration velocities of the measuring points are no more than the permittable safety blasting vibration range of “earth cave, adobe house, stone house” and “general civil buildings” in 《blasting safety regulations(GB672—2014)》.However, it is necessary to consider the long-term impact of blasting vibration on adobe house, as well as the decoration, exterior wall tiles, plaster layer, and other non-load-bearing structures of brick-concrete buildings, and take the field investigation as the criterion.However, it does not affect the safety of the load-bearing structure of brick-concrete buildings.In addition, combined with the design data, the blasting vibration velocity in the future is predicted, the maximum value is 0.54 cm/s in the Z direction, which exceeds the safety vibration standard of “earth cave, adobe house, stone house”(0.45 cm/s, f≤10 Hz).However, it is still lower than the safety allowable blasting vibration standard of “general civil buildings”(2.0 cm/s, f≤10 Hz).Finally, some suggestions are proposed, such as reducing single hole charge and promoting the application of digital electronic detonator.

The stability of open pit slope is greatly affected by blasting vibration.In order to further analyze and study the stability characteristics of open pit slope under blasting vibration, the static stability of open pit slope is analyzedand the displacement, stress and static safety factor of slope under static conditions are obtained.On the basis of static calculation, the dynamic response characteristics of the slope under blasting vibration are calculated, and then the response characteristics such as displacement, stress and dynamic safety coefficient of the slope under blasting load are obtained, which can be used to analyze the stable state of the slope under blasting action.By using ANSYS finite element software, strength reduction method is used to analyze the stable state of the open slope under static and dynamic load.The safety factor under the dead weight of the slope is 1.66, which is in a stable state.The safety coefficients of the slope under different blasting loads are 1.46, 1.5, 1.56 and 1.62 respectively, decreaseingby 2.4%~12% under the static condition.Through the relation between safety factor and horizontal radial vibration velocity, it is deduced that the safety vibration velocity of the south side slope is 10.64 cm/s and the critical vibration velocity is 13.16 cm/s.

Blasting in deep mines is inevitably affected by initial ground stress.In order to explore the rock breaking law of combined holes under high ground stress, the combined rock breaking mechanism of initial stress and combined hole explosion stress was analyzed, and the numerical simulation research on rock fragmentation by combined hole blasting under different stresses was carried out.The results show that the suppression or promotion of the initial stress on the blasting effect depends on the comparison between the initial stress and elastic limit of the rock.When the initial stress is less than the elastic limit of the rock, the effect is inhibited, and when the initial stress is greater than the elastic limit of the rock, the promoting effect is shown.When loading different initial stresses(the rock peak stress is 90.58 MPa), the number of failure units and the crack propagation length of the combined hole are accord with the trend of “decreasing first and then increasing”, and the stress value at the inflection point is 25 MPa, 27.6% peak stress of the rock, which is consistent with the elastic limit stress value in the whole stress-strain curve of the rock.By extracting and analyzing the effective stress and vibration velocity at the measuring point, it can be seen that the coupling stress at the measuring point increases linearly with the increase of the initial stress(20~50 MPa), indicating that the initial stress plays a dominant role under the coupling action of the initial stress and the explosion stress.In the combined hole scheme, the advance cracking blasting creates a new free surface for the front row holes, and the vibration velocity monitoring at the monitoring point shows that the combined hole blasting plan has a good shock absorption effect.

Field testing and numerical analysis were used to study the influence of boulder deep-hole blasting on the vibration of adjacent shaft.The results show that:vibration holes can effectively reduce damage on the retaining pile of foundation pit by boulder blasting;Isolation holes can guarantee the explosion integrity.The blasting vibration speed of shaft can be effectively controlled by increasing blasting area, reducing the distance between holes and reducing the amount of one blasting.Taking the 5 partitions of boulder as an example, the blasting vibration velocity can be controlled within 2 cm/s as the hole spacing was adjusted to 0.5 m×0.4 m and the explosive diameter was adjusted to 32 mm.As a result, the safety of adjacent structures was ensured, and the boulder blasting effect met the requirements of shield tunneling.

In order to study a deep hole blasting dispose technology for blind goaf with large volume, large roof thickness and limited space, the 49-590 large-scale goaf in Dabaoshan open-pit mine was taken as an engineering example in this research.The goaf parameters were obtained by a 3D laser scanning system C-ALS and 3D solid modeling technology.The minimum safety thickness the roof was calculated to determine the best time for goaf treatment by using traditional mechanical method, limit analysis method and theory of elastic thin sheet with small deformation.By integrating the detection parameters of the goaf and the calculation results of the minimum safety thickness the roof, a reasonable blasting caving scheme for the goaf was adopted.The cut area was set in the thinnest part of the roof and the local powder factor was increased.Meanwhile, the bottom-charging hole was designed in the cut area to obtain the blasting compensation space.Thus, the goaf was effectively blasted.Using the volume balance method to evaluate the blasting effect, the roof was completely collapsed, and an expected effect was achieved.

The phenomenon of recoiling is easy to occur in the demolition of framed buildings by directional blasting, which poses a great threat to the protection target of the rear side protection.Combined with the design and construction practice of directional blasting demolition of frame structure buildings in complex urban environment, the method of controlling the recoiling of frame structure buildings is analyzed and discussed, and the rationality of the method is verified by numerical simulation with LS-DYNA dynamic finite element software.Practical results show that the scheme of raising the blasting incision to the second floor and not drilling and blasting the columns behind the incision can effectively prevent or reduce the recoil phenomenon of the frame structure building.After the blasting, the columns of the first floor and the rear side of the building are maintainedand broke off at the junction of the first and second floors.The front column of the first floor was broken off by the impact of the collapse of the building.The height of the blasting pile of the building is not significantly different from that of the 1st floor blasting.The blasting effect is good, and the front bottomcolumn can be used as a buffer layer to greatly consume the kinetic energy of the collapse impact of the building, weaken the vibration effect of the ground contact, and reduce the impact of the collapse vibration on the surrounding environment.

The No.4 Building of Yuandong Garden, Longchuan County, Heyuan City, a 22-story building with frame structure is an illegal building to be demolished by blasting.There is a three-story villa 5 m away from the building, whose fence is only 0.5 m away from the building.Therefore, it is necessary to prevent the building from generating backward sliding at bottom.According to the surrounding conditions, the directional collapse blasting demolition method was adopted, and the trapezoidal blasting cut with 13.5 in height was selected.In order to determine the best delay time, ANSYS/LS-DYNA was used to simulate the delay time of 300 ms, 500 ms and 800 ms, and the simulation results showed that 300 ms was the best one.During the detonation, multiple advanced digital cameras, drones camera, high-definition cameras, etc.were used to capture the entire process of building blasting movement and disintegration from different positions and angles.Comparing the numerical simulation and actual blasting results, it was found that they were very close to each other in collapse posture, movement track of observation point, degree of disintegration, shape and range of blasting pile.The accuracy and reliability of the numerical simulation results meet the engineering requirements.

A complex reinforced concrete structure building including an annex building(length-to-width ratio=1), an office building(length-to-width ratio=2.9) and two residential buildings(length-to-width ratio=1.4) were required to collapse longitudinally by demolition blasting.The office building with large length and width was sheared into two parts step by step from the middle part under the action of gravity by means of delayed blasting between the rows of columns in the annex building.In this case, the center of gravity of the building was easier to move out of the outside of the building.At the same time, high-speed cameras were used to study the failure time and process of the structure and prove the feasibility of this method.When half-second delay detonators were used for the columns, the reasonable delay time between the last row of columns and the adjacent row of columns was about 200~300 ms.The highest point of the incision corresponds to the position of the last row of columns should be weakened by blasting to improve the reliability of collapse.In actual blasting, it was found that it′s necessary to increase the height of the blasting cut of the first exploded building due to the upward shift of the height of the center of gravity after the annex building blasting, and the form of flat cut was adopted.The countermeasures for flying rocks caused by air ejection in the basement were proposed to provide reference for similar blasting projects in the future.

Due to the limitation of the size of the site, the demolition blasting of the tall chimney needs to be collapsed.In order to further study the optimal delayed initiation time of the upper and lower blasting cuts in the two-way folding directional dumping blasting demolition of a 100 m reinforced concrete chimney in a complex environment, a common node separation model is established with LS-DYNA and Hypermesh, and the steel joints and concrete joints are directly produced as unit bodies.At the same time, the numerical simulation results are compared and analyzed with the actual project.Through the simulation analysis of the collapse process and results under different delay time of the upper and lower cuts of the chimney, 1 s, 1.5 s, 2 s, 2.5 s and 3 s, the collapse degree of the chimney, and the explosion range and after analyzing and comparing the speed of chimney touching the ground, it is determined that the optimal delay time of the upper and lower cuts is 2.5 s.The result of numerical simulation calculation is highly consistent with the actual project.

In order to compare the effect of different pretreatment methods on the blasting demolition effect of reinforced concrete water towers, two water towers with similar structures(1 # water tower and 2 # water tower) were demolished by directional blasting.The blasting cut angle of 1# water tower is 198°, the cross-sectional area of the remaining support body is 0.68 m2, the blasting cut height is 1.5 m, the angle of the directional window is 45°, and the symmetrical door is excavated by blasting method.The blasting cut angle of 2# water tower is 200°, the cross-section area of the remaining support body is 0.70 m2, the blasting cut height is 1.2 m, the angle of the directional window is 63.5°, and the symmetrical door is excavated by mechanical method.After the initiation of the two water towers, 1# water tower collapsed smoothly in the predetermined direction, however, as to 2# water tower, the concrete in the cut was completely stripped and flew out, the reinforcement was exposed, and the water tower failed to collapse.The analysis shows that the remaining support body has a large cross-section area and a small compressive stress per unit area after the blasting cut is formed, which is not conducive to the smooth collapse of the reinforced concrete water tower.The angle of the directional window has no direct relationship with the collapse of the reinforced concrete water tower.The height of blasting cut is the key factor affecting the collapse of reinforced concrete water tower.In blasting construction, the strength, stiffness and stable bearing capacity of reinforcement in water tower should be considered, and the reasonable blasting cut height should be considered.

Based on the blasting demolition case of longitudinal concrete cofferdam of Wenzhai hydro-junction project, the project schedule, surrounding environment of blasting area and blasting scheme were studied in this paper, the cofferdam was successfully demolished by blasting with a combination of variable linear density charge and the initiation network of industrial electronic detonator.The cross section of the demolition body is narrow in the upper part and wide in the lower part.The fan-shaped arrangement vertical ultra-deep hole is drilled, and the variable linear density charge is adopted in the hole.In addition, the linear density length and linear charge density of each section are controlled by decreasing the loose blasting action index(n=0.4~0.6) and the powder factor(0.5~0.75 kg/m3).According to the protection requirements of the surrounding buildings and ecological environment, the maximum single blasting charge quantity is derived for demolition blasting.Through blasting monitoring, the harmful effects of blasting are controlled in safety.The quality of demolition body meets the design requirements.

One wedge gate valve of venting steel pipe of a reservoir diversion tunnel in Hubei Provence failed to work properly, which caused a great safety threat to the operation of the reservoir.Therefore, effective measures should be taken to empty the reservoir in order to complete the rush repair of gate valves before the flood.According to the engineering characteristics and emergency needs, shaped charge blasting technique was selected to cut the vent steel pipe.and annular cutting and local rectangular cutting were designed and compared.According to the material and shape of shaped charge cutter, ANSYS/LS-DYNA and field tests were used to simulate and analyze the shaped charge cutting effect, where the fluidic velocity after penetrating the steel plate was taken as the evaluation index.Then the optimal blasting height of the cutter(top width=6 mm, bottom width=30 mm, height=25 mm, and liner angle=90°) was determined to be 13~17 mm.The practice showed that the steel pipe with a thickness of 14~16 mm can be cut successfully using the shaped charge cutter with a linear charge density of 380 g/m.Besides, the detonation mode, installation and blasting cutting effect of shaped charge cutter in practical engineering were introduced in detail, which provides a successful example for the similar engineering.

“Flying pipe” and handling and operation of “gas-filled tube” are potential security issues, which bring difficult problems of blasting security management to public security organs.In order to solve these problems, a method of combining the optimized design of cracking pipe structure with the field explosion test was adopted.As a result, after "design-test-improvement" repeated research, a new type of fracturing pipe, a technology of inflation process in hole and a terminal management and control information system were successfully developed.According to the preliminary application study, the vibration value produced by carbon dioxide expansion blasting is only 1/20~1/15 of that produced by the same explosive blasting.

Pressure and flame sensors and laser schlieren system were installed in a mesoscale shock tube to study the flow field evolution near the gas explosion barriers within a confined space.Those Barriers with a blocking rate of 21.56% were set at the glass window.By changing the number of barriers, the flame propagation, pressure change, shock wave movement and flow field change under different working conditions were compared to analyze the influence of barriers on the evolution of gas explosion flow field in confined space.The experimental results show that the excitation effect of barriers on gas explosion cannot be ignored.The maximum explosion overpressure increases by 32.3% and the maximum flame propagation speed increased by 115.4% when a single obstacle is added.In addition, the excitation effect of barriers on gas explosion is positively correlated with the number of barriers and mainly in the area around the barriers.The main mechanism of the excitation effect is that the presence of barriers increases the turbulence intensity near them, which induces the flame tensile deformation, increases the flame front area, and accelerates the chemical reaction.

In view of the high hit accuracy of modern weapons and ammunition, it is of great significance to study the damage of H-beam steel columns under close explosive loads, for H-shaped steel columns are important load-bearing components of most steel structure workshops.According to the similarity law, scale transformation was applied to a H-shaped steel column of a typical steel structure factory building.Using the LS-DYNA finite element software, the fluid-solid coupling method was used to simulate the impact of close explosion loads from 9 charges at different scaled distances on the similarity model of the H-shaped steel column.By comparing the bearing capacity of the H-shaped steel column before and after the explosion loading, a steel column damage index was determined.The results show that in the interval between 0.100 m·kg-1/3 and 0.400 m·kg-1/3, the maximum and minimum damage index are 0.533 and 0.095, respectively.Besides, the damage index generally decreases with the increase of the scaled distance.When the scaled distance is 0.100 m·kg-1/3, the energy dissipated in the shear part of the steel column web is significantly increased.This results in a general rebellion trend phenomenon in the interval between 0.100 m·kg-1/3 and 0.125 m·kg-1/3, and the damage index increases as the scaled distance increases.

In order to study the protection performance of the cladding on a bridge pier under explosion loading, a numerical model of reinforced concrete slab under explosion was established with ANSYS/LS-DYNA and its validity was verified.Using this numerical model, the response and failure modes of a hollow rectangular section pier with and without cladding under explosion loading were analyzed and compared.The propagation process of stress wave, the failure mode of pier and the displacement of the pier surface opposite to explosion were observed.Meanwhile, the influence of the thickness of the cladding, the density and thickness of the core layer on the protective effect to the pier under explosion were further discussed.The results show that the damage degree of the pier under explosion can be significantly reduced by the attached cladding.When the thickness of the cladding increased from 1 cm to 3 cm and the thickness of the core layer increased from 10 cm to 30 cm, the displacement of the pier surface opposite to explosion decreased obviously.Within certain limits, the protection effectiveness increased with core density.This study can facilitate the application of lightweight cladding on pier protection against explosion.

In order to study the environmental characteristics and verify the theoretical research results on the inbound and outbound vibrations of a metro train, an acceleration variation model was built was established based on the measured vibration data In time domain, the peak ground accelerations, acceleration amplitude variation and the duration of the vibration were analyzed.In addition, the frequency distribution of train vibration energy and the characteristics of acceleration vibration level were analyzed in frequency domain.The results show that the outbound vibration peak of the train tends to be larger than the inbound vibration peak.Besides, the track vibration mitigation measures have attenuated the high frequency contents of the vertical vibration component, while the horizontal high frequency component is retained, so that the vertical and horizontal vibration peaks are close to each other when the train is running at a low speed.Furthermore, the acceleration vibration levels of different measuring points are different at varying frequencies.However, the acceleration level curves of the inbound and outbound vibrations are very similar for the same measurement location.After comparison, analysis results based on the measured data are consistent with those of theoretical research.

Safety is related to the sustainable development of blasting enterprises.In order to study the transformation path and optimization and upgrading of safety management of blasting companies under the condition of precision blasting, in view of the new changes of management objectives, methods and objects, the “three high” characteristics of systematic safety management were analyzed:safety is highly dependent on technology;A high level of government and social participation; Safety responsibility is highly subdivided.The results show that the establishment of comprehensive evaluation standard system of precision blasting is an effective means to realize the transformation from controlled management to systematic management.It is necessary to pay attention to the selection and stability of standards, and pay more attention to the research and development of standards.Meanwhile, the condition construction of elaborate construction should adopt excellent equipment and technology, and pay more attention to the construction of enterprise culture with trust and responsibility as the core.Especially, the psychological counseling and humanistic care of front-line workers should not be neglected.Since he safety management scope of systematic management is wider, it is necessary to establish a multi-agent precision blasting organization and implementation mode to highlight the basic role of technical elements and break through the single subject of the company.Besides, many links of the systematization of responsibility implementation should be emphasized, as the organization and leadership, construction technology, comprehensive coordination and emergency rescue.