In response to the high-quality requirements for large-diameter deep-hole blasting, and the traditional stemming material being too long and prone to “blowout”, a new type of blasting hole stemming material was proposed using early strength cement mortar and a bag-like structure. Static mechanical tests and blockage model tests under impact loads were conducted on cement slurry with different admixture contents and ages, and the self-shrinkage performance, compressive strength, and passive confinement pressure of the cement mortar under impact loads were analyzed to determine the dynamic mechanical properties of the early strength cement mortar under passive confinement. The stress characteristics of the stemming material in the blasting hole under the pressure of the blasting gas were also analyzed to provide a reasonable stemming length for large-diameter deep-hole blasting. The results showed that the self-shrinkage of the test piece increased with the increase of admixture content. The compressive strength of the test piece increased with the increase of age and decreased with the increase of admixture content. With the increase of admixture content and age, the expansion pressure increased, resulting in an increase in passive confinement pressure. When the admixture content was 4%, and the age was 16 hours, the expansion pressure reached its peak at each measuring point. Additionally, with the increase of admixture content, the porosity of the slurry increased, the axial compressibility of the blocking material increased, and the acting time of the blasting gas pressure in the blasting hole was prolonged, which improved the stemming quality. Comprehensive on-site test results have shown that the stemming length, reasonably selected based on the derived theoretical formula and combined with on-site production, ensures safe production during the mining period, and achieves good results in deep-hole blasting.

With the widespread use of mixed emulsion explosives, there exists the situation that the stemming materials penetrate into emulsion explosives in open-pit blasting construction, which indirectly changes the stemming length and reduces the blasting effect. To study the influence of stemming on mixed emulsion explosives, stemming simulation tests, numerical simulation tests and field blasting tests were carried out successively. Firstly, four kinds of PVC pipes with common hole diameters were used to simulate the blasting holes, and the rock chips were used to simulate the stemming materials. They were used to systematically study the infiltration of rock chips into the explosives on top of the explosive column during the filling process of stemming. Secondly, the numerical simulations of single-hole blasting were conducted with the LS-DYNA software, and the influence of the stemming mixture at the top of the explosive column on the explosive power was investigated by observing the changes of stress values at the measurement points. Finally, the stemming filling process was improved by setting physical isolation during the charging process based on the bench blasting in the Jinduicheng open pit mine. And the effect of stemming on the mixed emulsion was analyzed by comparing the blasting effect before and after the physical isolation. The results show that the phenomenon of explosive overflow appears on the top of the explosive column in the explosive charging process. Then, the rock chips gradually infiltrate into the emulsion explosive due to the influence of gravity after the charging is completed, and the infiltration length of rock chips increases with the increase of hole diameter in the same time. The numerical simulation results show that the stresses of different monitoring points have decreased, and the infiltration of stemming reduces the explosive power of the top explosive. The fragmentation analysis of the top rock after improvements shows that the main fragment size distribution of rocks decreases from 20~40 cm to 0~20 cm, and the proportion of rocks over 60 cm decrease from 6.13% to 1.81%, compared with the conventional charging process. In summary, the stemming has a significant impact on the power of emulsion explosive and blasting effect, and it can effectively improve the blasting effect by taking physical isolation to separate the stemming and explosive.

The impact vibration caused by blasting demolition of tall buildings (structures) may affect the service status of adjacent subway tunnels. In order to demolish a 24 story frame structure building only 6.5 meters away from the subway tunnel, on-site tests and analysis of blasting vibrations and dynamic strains were first conducted. And then, a three-dimensional finite element calculation model was established for analyzing the dynamic response of the subway tunnel structure by ANSYS/LS-DYNA, which can reasonably describe the impact of the collapsed part on the ground during the blasting demolition of the building. Finally, the vibration response characteristics and dynamic stress changes of the tunnel structure under the impact of building collapse were simulated and compared with the field measured data. The research results show that the peak particle vibration velocity (8.61 mm/s) in the subway tunnel caused by the drilling and blasting of the load-bearing columns is greater than the peak particle vibration velocity (4.95 mm/s) caused by the impact of the building on the ground. The main frequency of the blasting vibration and the collapse impact vibration are about 100 Hz and 2 Hz, respectively. The vibration velocity of the subway tunnel under the action of the collapse impact load is equivalent to the structural vibration caused by an earthquake with an intensity of Level Ⅲ (3.82~8.19 mm/s). The low-frequency collapse impact vibration can cause relatively obvious additional dynamic stress to the subway tunnel. The dynamic compressive stress generated in the circumferential direction of the tunnel is about 4 MPa, and the dynamic tensile stress generated in the axial and tangential directions is about 0.4 MPa. The existing cracks may expand, or delamination may occur when the internal damages or construction defects are generated in the tunnel structure under the impact of dynamic tension and compression cycles. The safety allowable particle vibration velocity value of 10~12 cm/s when f<10 Hz required in the current blasting safety regulation (GB6722—2014) is dangerously high, and it should be adjusted in combination with the frequency and dynamic strain characteristics.

In order to investigate the dynamic response and stability of a steep slope under blasting vibrations from multiple blasts, the displacement, stress, maximum shear strain, safety factor and sensitivity of the steep slope were analyzed by field monitoring, numerical simulation and mathematical methods based on the an open-pit mine in Inner Mongolia. The data fitting results show that the radial vibration velocity has the highest correlation coefficient, with all the coefficients of three directions greater than 0.8. The relative error of the prediction results is larger in the near-blasting area, while smaller in the far area. After a single blast, the horizontal displacement increases rapidly and reaches the maximum value on the right side of the blast hole at 0.05 s. In the vertical direction, the stress increases gradually from top to bottom and the bottom is prone to stress concentration. The overall stress distribution of the slope gradually increases from the slope surface to the slope interior. After multiple blasts, the displacement and horizontal stress of the slope generally continues to increase with the increase of blasting times. The peak value of vertical stress and acceleration are generally oscillating with the increase of blasting times. For a period after the blasting, the acceleration is still not 0, and it takes a long time for the blasting energy to completely dissipate. Multiple blasting vibration will continue to reduce the safety factor of the slope to a certain extent. With the increase of blasting times, the change rate of the safety factor of the slope will gradually increase. Based on the gray correlation coupling analysis of safety factor and orthogonal tests, the sensitivity of each factor is as follows: charge per delay (X₅) > total explosive charge (X₆) > hole spacing (X₃) > blast distance (X₂) > blasting vibration duration (X₄) > hole number (X₁). It is indicated that in actual construction, it is necessary to control the charge per delay and total charge in order to ensure safe production.

In order to study the blasting vibration prediction and control measures of excavation in urban area under complex environment, the response law of peak particle vibration velocity and main vibration frequency is analyzed based on field blasting tests, and the blasting vibration prediction method is proposed based on the above two factors. The vibration reduction effect of hole by hole initiation and vibration reduction ditch is discussed, so that to obtain the optimal vibration reduction range of the ditch. And the control measures of blasting vibration are also formulated. The results show that the prediction formula of the peak particle vibration velocity and main vibration frequency is realized by considering the actual maximum single-hole charge and the actual total charge. The predicted value is smaller than that solely based on the maximum single-hole charge, and the prediction accuracy is increased by 3.2%. In the aspect of blasting vibration control, the blasting vibration is characterized by low vibration velocity, high frequency and short duration. Among all the measures, the effect of the vibration reduction ditch is remarkable. Considering the peak particle velocity, signal frequency band energy distribution and instantaneous input energy response law, the vibration reduction effect is the best within 1~6 m radius on the side of the ditch opposite to the blast source, and the maximum vibration reduction ratio can reach 77.5% within 1 m radius. For similar projects, the proposed blasting vibration prediction formula can be used for pre-assessment. When the distance of the building from the explosion zone is less than 10 m, it is recommended to implement vibration reduction ditch.

In order to successfully demolish a high pier reinforced concrete aqueduct by blasting between the 75^#~84^# piers of Dongfeng Canal in Yichang City and reduce the impact on the surrounding complex environment, a bidirectional collapse design was adopted. In the design scheme, the aqueducts between the 75^#~76^# piers collapse in a northerly direction perpendicular to the aqueduct trend, and the aqueducts 77^#~84^# piers collapse westward along the aqueduct trend. More precisely, an initiation network of electronic and non-electric detonators with delays of 50 ms and 150 ms was adopted using the 75^# pier as the initiation point. Moreover, the harmful effects of blasting on the environment were controlled by using lifting holes as blast holes, excavating vibration reduction ditches, hanging nets and covering protection layer, storing water in the trench body, and covering soil protection. The results show that the aqueduct collapsed with a 4-minute delay after initiation, and the collapsed pier body was basically decomposed into blocks with intact aqueduct body, with most fragments scattered along the trend within 10 m of the central axis of the aqueduct, and only a few small pieces flying farther than 10 m. The adopted protective measures can effectively control the blasting flying rocks and vibration, and no damage has been found to the inverted siphon of temporary water delivery pipeline and the road pavement. The project was carried out successfully despite the delay in collapse. The possible reasons for the delayed collapse include no incision on outside of the structural column, the delay time interval between pier columns is small, and the blasting incision is small.

In the teaching of demolition blasting, the structure modeling period and the cost of single experiment are both too excessive, and the experiment cannot be repeated in a short time. In addition, the experiment is transient, irreversible, and dangerous, which is not conducive to close observation and learning. Aiming at the difficult problems of experimental teaching in blasting demolition engineering, a platform of virtual simulation experiment is established for teaching design schemes. Firstly, through the two interactive operation links of “toppling scheme selection” and “cut design”, the learners can master the basis for the selection of toppling scheme and the design method of blasting cut, and understand the design content of blasting cut such as cut shape, orientation window and positioning window. It is easy by the platform for the learners to understand the stress conditions for cut design according to the mechanical principle of chimney toppling. They also should be familiar with the knowledge of tension zone, compression zone and neutral axis, and master the calculation formula of the extreme stress of the cut section and the application of strength conditions. Secondly, the platform system can make the learners participate in the design of powder factor, blast hole parameters and initiation network through “blasting parameter design”, and correctly select the detonators inside and outside hole. Then, through the interactive learning of “safety check” and “arrangement of shock absorption measures”, the learners can master the data collection steps, the safety check methods and measures to control the negative blasting effects. Finally, the learners can experience the on-site blasting operation process by the “blasting site” module, and gradually establish their understanding of the blasting operation process by participating in the design and organizing each construction step. In addition, the experimental system has a knowledge introduction for each module, which is convenient for learners to learn independently. The construction of the virtual simulation experiment platform not only optimizes the teaching methods, but also improves the teaching quality, and enriches the characteristics and innovative ideas of the experiment teaching of engineering blasting.

In order to control the forming effect of excavation profile and reduce the disturbance of preserving rock mass caused by blasting, the foundation pit blasting at the Yunnan bank of the large arch bridge across Jinsha river, whose total depth is about 51 m and one-time excavation depth is about 20 m, is taken as the engineering background. Reinforced loose blasting with hole-by-hole initiation was applied to the main blasting holes and smooth blasting was used for the contour holes. A kind of deep hole smooth blasting technology which can be applied to foundation pit excavation of the deep and steep arch bridge is presented. In addition, the action process of gas, the expansion pressure at the hole wall and the damage range of the smooth blasting hole were theoretically calculated and analyzed. The blasting results show that a flat excavation profile, with more than 90% half-hole ratio of relatively intact rock mass and less reserved hole marks of relatively cracked rock mass whose overbreak and underbreak can still be controlled, can be formed by using the deep hole smooth blasting technology, which greatly reduces the stress concentration on the rock wall surface. The crushing zone will not be formed near the charge section in the smooth blasting and the maximum damage range of the reserved rock mass was about 49cm, which fully ensured the rock wall stability and construction safety. In the process of smooth blasting construction, engineering measures were also taken to ensure the reliability, safety and economy, including slowly tilting the excavation surface at the bottom of the bench to the free surface, tying the explosive charge with cotton rope for traction, and setting detonators inside and outside the hole every 5~7 smooth blast holes.

In modern blasting engineering research, the matching model of explosive and rock provides a scientific basis for revealing the internal mechanism of blasting process and predicting the economic benefits of blasting system, which has become an irreplaceable important tool. However, due to the diversity and complexity of soil-rock medium and the uncertainty of explosion process, the interaction between explosive and rock is more complex and uncertain, and it is difficult to study the matching of explosive and rock from their interaction process. Earlier studies mainly relied on empirical formulas and field tests for calculation and summary, which often had high eigenvalues and harsh application environment. However, the feature of machine learning is that it only considers the beginning and the result, and does not care about the middle process, which ensures its universality in the study of explosive-rock matching model. The XGBoost algorithm, together with multi-threading, data compression and fragmentation method, has the advantages of high efficiency in the case of largedata amount, and is suitable for training of a large amount of field data. In view of this, a field test was carried out in a mine in Guizhou province, and XGBoost algorithm was used to establish a matching system between explosives and rocks. The network was trained through successful examples, and the trained neural network was applied to practical projects. The results show that the performance of the explosives selected by the matching system based on this method is similar to that of the industrial explosives used at present, and the error is within±10%, which has a high reliability, and further verifies the rationality of the explosiverock matching system based on XGBoost algorithm.

The peak particle velocity (PPV) of blasting vibration is an important index to measure the impact of blasting vibration on surrounding environment and structures. In order to improve the reliability of PPV prediction, a model based on extreme gradient boosting optimized by the sparrow search algorithm was proposed, and a corresponding blasting vibration prediction system was built using the App Designer of MATLAB. The maximum charge per delay, distance from blast center to measuring point, and elevation difference between measuring point and blast center were selected as the input parameters of 36 sets of training data and 5 sets of test data for the model to predict PPV. The results show that the proposed SSA-XGBoost model has a smaller average relative error compared with the GA-BPNN model and BPNN model, and it has a higher prediction accuracy and better stability proved by the Taylor graph.