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 gradeⅢ (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 gradeⅢ (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.