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

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.

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

In 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).

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

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

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.

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

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

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