Aiming at the construction problems of a subway tunnel adjacent existing buildings in the section between Jialingjiang Road station and Xiangjiang Road station of Qingdao Metro Line 13, a new construction scheme of mechanical excavation combined with blasting is proposed. In the scheme, bench method is used with the upper bench in the weak stratum excavated by mechanical method, and the lower bench in the hard stratum excavated by blasting method. Furthermore, the vibration velocities of the adjacent buildings caused by the proposed scheme and the traditional full-section blasting scheme are analyzed and compared by using FLAC3D and blasting equivalent load method. The results show that, the peak vibration velocity of each monitoring point under the mechanical-blasting scheme decreases significantly compared with the full-section blasting with the maximum reduction rate of 61.1% which is within the allowable range and validates the new scheme. The construction parameters of the mechanical-blasting scheme are compared and selected based on the building settlement, plastic zone of surrounding rock mass, vibration velocity of the buildings, etc. Finally, the mechanical excavation advance of the upper bench is determined to as 0.5 m. Besides, the construction effect of the optimized parameters is monitored and evaluated. The mechanical-blasting construction scheme successfully solved the problems encountered in the project, and shortened the expected construction period by 3 months, which shows the rationality of the proposed construction scheme and parameters, as well as the validity of the calculation results.

At present, mining method is widely used in tunnel construction. The influence of blasting vibration on surrounding rock and supporting structure in tunnel and its disaster control are always hot issues. In order to study the propagation law of blasting vibration inside a tunnel, the vibration signals of simultaneous detonation and detonation at three benches were monitored on site based on the engineering background of a tunnel with soft surrounding rock. The nonlinear regression of Sadovski formula and Fourier transform method were used to analyze and study the test data. The results show that for the same section of the tunnel, the vault has the characteristics of large vibration velocity, high vibration frequency and slow attenuation rate. When 100 ms delay blasting is used between the three steps, the blasting energy can be discretely distributed in time and space, and the vibration superposition effect can be significantly weakened. A single hole blasting test was set in the middle of the cut area, and the single hole vibration waveform was obtained by setting the delay between the test hole and the entire blast as 100 ms. Based on the principle of linear superposition, the delay time was optimized by investigating vibration waveforms synthesized by cut blasting. The results show that when the delay time between holes is 4~7 ms, the peak vibration velocity caused by cut blasting decreases sharply, and the effect of interference is obvious. After the delay time exceeds 7 ms, the peak vibration velocity has no significant difference.

In order to ensure the construction quality of large section shaft horsehead gate and reduce the damage caused by blasting, an advance crack zone blasting technology is put forward. According to the section design and engineering geological conditions, the section of Matoumen excavation, the gates at-199.5 m and-258.2 m of a certain underground mine are divided into upper layer, middle layer, and lower layer excavation zones. The construction sequence is: upper layer→middle layer→lower layer. Firstly, the advanced fracturing holes should be constructed along the excavation contour lines of each layer. The hole depth is equal to the driving depth of the horsehead gate. They are charged with decks and detonated before the main blasting area, which can achieve mutual penetration between holes. The "shock absorption ditch" shall be formed along the excavation contour lines of the horsehead gate, which can reduce the effect of blasting seismic wave propagation. Besides, each construction area of the horsehead gate is equipped with hole by hole millisecond delay detonations with an interval of 5~20 ms, which can achieve the interference and offset of the vibrations from the subsequent blasting and reduce the blasting impact on the large cross-section horsehead gate. It has been validated that the half-wall hole rate of the excavation contour line is higher than 95%. It can not only meet the requirements of controlling the quality of roof forming for the excavation of large cross-section gate in broken rock mass, but also reduce the cost of support and shotcrete.

Perimeter blasting is very important to control engineering quality in the process of roadway construction, and it is a common way to use slotted pipe blasting to improve the perimeter blasting effect. However, the unreasonable setting of slotted pipe blasting parameters still weakens the directional destruction effect, including the greatly damaged contour, low hole retention rate, common phenomena of over-excavation and under-excavation. In order to improve the directionality of blasting damage, the slotted pipe blasting parameters should be optimized. The reasonable blasting parameters were determined with the study of explosive slotted pipe uncoupling and different initiation positions by numerical simulation using ANSYS/LSDYNA. According to the numerical simulation results, the balance between the protection of surrounding rock mass and directional failure can be achieved when the uncoupling coefficient between the explosive and slotted pipe is 1.12. Meanwhile, the integrity of the contour line is greatly improved when the initiation positions of two adjacent explosives are changed to make the meeting position of the explosive shock waves on the same horizontal plane that shifted to 3/4 of the position between two blast holes. It can be concluded that the damage to the retained rock mass can be greatly reduced as adopting uncoupled structure between slotted pipe and charge, and changing the meeting position of stress wave between blast holes by adjusting the detonation position of charge.

In order to solve the problem that excessive blasting vibration affects the safety of village buildings (structures) on the earth's surface during the mining process of an underground orebody, the inter-hole delays of 8 ms, 10 ms, 12 ms, 14ms and 18ms and inter-row delay of 100 ms were selected for tests in the #63113 ore room of the orebody III in the mine. By combining the actual situation of the site and the empirical formula, the natural vibration frequency of the brick-concrete buildings with 1 to 2 floors in the village was 7.63~13.23 Hz. The blasting vibration data was collected on site and HHT transformation was applied on the measured blasting vibration signals by MATLAB. The characteristics of the signals were then analyzed from the perspectives of time domain, frequency domain and energy. The highly adaptive EMD decomposition was used to decompose the original vibration signal into the IMF components which were transformed by 10-layer db8 wavelet transform and the proportion of energy in the total energy of the frequency band 7.8~15.7 Hz of level 9 was summarized. The three-dimensional Hilbert spectrum and marginal spectrum were obtained by Hilbert transformation of the reconstructed signal with the IMF components. Through EMD decomposition and wavelet transform research on the blasting vibration signals, it is concluded that the three-direction energy ratio corresponding to the 12 ms delay time at No.3 measuring point is reduced by 14.07%, 24.89% and 6.26%, respectively. The experiments show that the problem that the problem that the low frequency energy takes a large proportion in the total energy can be improved by optimizing the inter-hole delay, and the resonance effect can be effectively avoided. By comparing the Hilbert marginal spectrum and the three-dimensional Hilbert spectrum with different delay times, the main vibration frequency and the maximum instantaneous energy of the blasting with an inter-hole delay of 12 ms appear 200 ms after the detonation, concentrated in the range of 30~40 Hz which is higher than the natural vibration band of the buildings, and thus have the least influence on the structures.

Using traditional continuous charge blasting method in Zijin Mine is easy to produce powder near the crushing circle of the hole, resulting in substandard ore gradation and waste of resources. Therefore, in order to improve the ore gradation and increase the aggregate products, a blasting test was carried out under the conditions of 0 m, 1 m, 1.2 m, and 1.5 m in the middle of the air-decked charge blasting technology. Firstly, a limestone model using HJC constitutive relation was established to simulate the actual geological by ANSYS/LS-DYNA finite element software. And then, the damage distribution characteristics of rock mass under different spacing distance conditions were analyzed, and the relatively optimal air spacing charge length was obtained. Finally, the 1.2 m and 1.5 m middle air decking are selected to control the blasting powder rate. The field blasting tests and the comparison of rock gradations under different conditions show that it is effective to reduce the powder rate by adopting the intermediate air decked charge. When the air decking length is 1.5 m, the non-uniformity coefficient Cu and the blasting powder rate can be reduced. Before the technical transformation, the average powder ore rate is about 15.94%, and after the technical transformation, the powder ore rate below 4.75 mm can be reduced to about 9.37%, making the grading to a good level.

Reinforced concrete (RC) short beam is the key load-bearing component of buildings. In order to study its dynamic response and failure mechanism under impact load, drop hammer impact tests with different impact mass, impact velocity and impact energy were carried out by combining strain gauge sensor, high-speed photography and digital image technology (DIC). The results show that, the failure forms of the short RC beams under impact loads are arch collapse cracks and overall bending deformation, which are obviously different from those of shallow beams. The axial strain in the mid span of a short RC beam changes from tensile strain to compressive strain. With the increase of impact energy (18 061 J≤E≤49 831 J), the axial peak tensile strain and residual compressive strain in the mid span increase first and then decrease. The short RC beam is in the stage of elastic flexural deformation, elastic-plastic flexural deformation and punching shear failure mode in turn. The crack initiation and propagation process of the short RC beam under impact load is not unidirectional. And the fracture zone is formed by the multidirectional fracture propagation with multiple times, and then the plastic hinge is formed, resulting in the overall short beam failure. The deformation degree of the beam mainly depends on the impact speed rather than the impact energy. Specifically, the peak deflection and residual deflection in the middle span of the beam (26.81 mm≤w_p≤29.85 mm; 17.12 mm≤w_r≤21.66 mm) increase with the increase of the impact speed (5.53 m/s≤v≤7.13 m/s) under the same impact energy (30 000 J).

The reasonable selection of the incision angle is an important factor for the success of blasting demolition of a typical reinforced concrete chimney. In order to determine the selection range of incision angle, the isolation method was adopted to establish a theoretical model according to the force and failure characteristics of the residual section. The solution formula of any angle position on the residual section was derived, and a revision coefficient k was defined to express the influence of the cylinder at the upper part of the unnotched section. Furthermore, the stress and bending moment conditions of the dumping cylinder were established, and the selection range of the incision angle was obtained by combining the solution formula and the damping conditions. The case study shows that with the increase of the incision angle, the maximum tensile stress, the maximum compressive stress and the bending moment generated by the upper cylinder of the incision tend to increase, while the resistance moment of the residual section tends to decrease. The upper limit of the selection of the incision angle can be obtained when the maximum tensile stress reaches to the material strength limit, and the lower limit can be determined when the two bending moments are equal. Changing the incision angle would have a greater effect on stress than changing the incision height. Under the condition that the actual incision height is 4.5 m in the engineering case, the selection range of incision angle based on the established theoretical model is 198°~237.6°, and the actual incision angle is 216° within the theoretical selection range, which further verifies the reliability of the theoretical model. More extensive application and guide engineering practice are expected.

In order to further study the propagation characteristics of surge wave induced by underwater blasting loads, the multi-physical field coupling simulation method powered by the dynamic analysis software COMSOL was adopted to establish a transient solution model based on the second water source project-diversion project of Guilin City. The isosurface, peak stress and vibration velocity of surge wave under explosion load were studied and evaluated based on field monitoring results. The results show that the surge wave produced by underwater blasting essentially propagates around the center of the blast center, and the surge isosurface evolves from regular round to irregular ellipsoid with time. The surge waves decay rapidly during propagation, and with the increase of water medium velocity threshold, the influence range of surge wave action region is small. In addition, the stress of the surge wave has superposition effect under the condition of delayed blasting, and thus there are multiple peaks. When the distance to blast center increases from 28 m to 108 m, the attenuation rate of the peak vibration velocity of the surge wave reaches 96.3%, which has little effect on the structure. Meanwhile, the time of the peak velocity of the surge wave increases gradually with the increase of the distance to blast center.

In order to explore the interaction mechanism between the structure of different sizes and the bubbles, an underwater explosion experiment of 2.5 g TNT was carried out at the bottom 15cm of the fixed square plates with side lengths of 20 cm, 40 cm and 70 cm. Through the observation of the experimental high-speed video and the pressure data measured by the sensor, it is found that when the size of the plate is too small, the bubble will contact with the air during the expansion process, and the bubble pulsation process will be terminated. In order to further explore the matching relationship between the explosion bubble and the target size, CEL algorithm in Abaqus software was used to establish the fixed square plate with Lagrange grid and the remaining part with Euler grid. The dynamic behavior and pressure data of the near-field underwater explosion bubble were numerically simulated. The feasibility of the simulation method is verified by comparing the simulation results with the bubble phenomenon captured in the experiment and the measured pressure time history curve. Taking the explosion depth divided by the maximum bubble radius as the specific depth and the side length of the board divided by the maximum bubble radius as the side length, a series of simulations were carried out with the side length of the board being 0.455 to 3.182 times the maximum theoretical bubble radius and the explosion distance being 0.455 to 1.136 times the maximum theoretical bubble radius. The simulation results show that with the decrease of plate size, the bubbles are more likely to collapse in advance. With dimensionless plate size and dimensionless explosion depth as variables, a boundary function is given to complete the bubble pulsation. The closer the distance between explosion distance and plate size, the earlier the end time of bubble pulsation.