With the continuous development of precision step blasting technology in open pit mines, the disadvantages of traditional layout methods in layout precision and construction efficiency are becoming more and more prominent. In order to improve the precision and efficiency of hole layout, the theory of hole layout is combined with RTK line lofting technology. According to the designed values of the chassis resistance line, hole spacing and row spacing, the RTK line lofting method is used to measure the size of the chassis resistance line and determine the line coordinates and layout direction of the first row of holes. Then, each row of holes can be laid out for construction by setting parameters such as mileage, mileage increment, deviation and deviation direction in the RTK manual book. Finally, a single person can achieve high-precision and high-efficiency hole laying while recording the hole position and measuring the design hole depth. This paper introduces a construction method of RTK line lofting and hole layout in detail, applies it to the actual construction, and gets a good effect. Applying this method provides a new idea for the precision, standardization and high efficiency of the open-pit bench blasting construction, improves the construction efficiency and precision while saving workforce, and reduces the cost of open-pit blasting.

Abstract: A patented technology for bus current acquisition of electronic detonators is introduced, which uses a low-cost hardware solution to achieve high-precision and wide-range current acquisition. This technology is designed to monitor and acquire data related to the working current, communication current, charging current, and detonator bus current load for electronic detonators, thus enabling these devices' status monitoring, data communication, and bus protection. This system focuses on the innovative, low-cost circuit design concept and the methods employed to ensure high-precision, high-resolution, and wide-range current acquisition. The typical working current of the electronic detonator control module ranges between 10~30 uA, and data is transmitted to the detonation controller via a current carrier. The communication current typically falls within the 0.5~2 mA range, and the ignition energy storage capacitor is charged through the bus with a peak charging current of 1~2 mA. The detonation controller determines the working status of the electronic control module by acquiring bus current data, which includes communication and charging status, to determine the module's working condition. In the current acquisition method discussed, low-side resistors are used to sample the current, replacing a differential comparator with three low-cost operational amplifiers. Furthermore, a 12 bit AD converter integrated into the MCU replaces an external 16-bit AD converter, which reduces hardware costs by over 80%. By segmenting the current collection, the system maintains the required accuracy for small current sampling and expands the current sampling range by 30 times, covering the rated current of the bus. The absence of an external AD conversion module significantly improves the sampling efficiency.

The dynamic compression mechanical characteristics of the surrounding rock mass of the shale formation tunnel in western Hubei province need detailed exploration. A Split Hopkinson Pressure Bar (SHPB) and a highspeed camera were employed to conduct impact tests on shale samples at five different bedding angles (the angle between the direction of impact loading and the normal of the bedding planes of the specimen, including 0°, 30°, 45°, 60°, and 90°). Meanwhile, the research team also studied the influence mechanism of bedding angles, impact pressure, and strain rate on the dynamic compression mechanical characteristics and failure mode of shale with different dynamic loading strain rates under different impact pressures. The research results indicate that the dynamic compressive strength of shale has an approximately U-shaped pattern with increasing bedding angles under different impact pressures and strain rates. Among them, the shale with bedding angles of 0° and 90° has relatively higher compressive strength, while the shale with a bedding angle of 60° has the most minor compressive strength. Furthermore, the dynamic compressive strength of shale with different bedding angles increases as the impact pressure and strain rate increase. The macroscopic failure modes of shale are mainly divided into tensile failure, shear failure, and mixed failure. Significantly, the macroscopic failure modes of samples with bedding angles of 0° and 90° under different strain rates are mainly tensile failure. The primary macroscopic failure mode of the sample shows a transition process of shear failure mixed failure tensile failure' as the strain rate increases when the bedding angle is 30°. The primary macroscopic failure mode of the specimen evolves from shear failure to mixed failure as the strain rate increases when the bedding angle is 45° and 60°. The energy absorption ratio of shale samples first increases and then decreases as the bedding angle increases under the same impact pressure. Additionally, the energy absorption ratio and the degree of sample damage are simultaneously maximum as the bedding angle is 60°. The degree of fragmentation of shale samples with different bedding angles increases, and the energy absorption ratio gradually tends to be consistent as the impact pressure and strain rate increase.

To address the instability problem of shallow-buried tunnel with unsymmetrical pressure under blasting, the potential energy equation of surrounding rock was derived by considering both blasting damage and water weakening effect. Using the cusp catastrophe theory and its calculation method, a catastrophe instability criterion of surrounding rock mass in a shallow-buried tunnel with unsymmetrical pressure under blasting was established. Then, the effects of water weakening, blasting damage and unsymmetrical pressure on the instability of the surrounding rock mass were discussed. Taking Dayangan tunnel in the national high-speed G5615 (Tianbao-Malipo section) as an example, a catastrophe criterion k of surrounding rock mass under different working conditions was calculated according to the physical and mechanical parameters of surrounding rock and the results of the field acoustic wave test. Meanwhile, a shallow-buried tunnel's surrounding rock stability state with unsymmetrical pressure was determined. The results show that the necessary condition for abrupt instability in shallow-buried tunnels with biased pressure under blasting is the abrupt failure criterion k<1, indicating a potential state of abrupt instability. The degree of bias pressure is the critical internal factor affecting tunnel instability surrounding rock mass. Additionally, the greater the degree of bias pressure, the more prone the tunnel is to sudden instability. The practical evaluation results are consistent with the field observations, verifying the practicability and validity of the criterion.

To study the influence of rock fracture characteristics with different inclination angles, the notched semi-disk bending (NSCB) specimens were prepared based on the 3D printing technology for experiments on typeI static fracture characteristics of rock mass. Specifically, the straight-cut groove half-disc bending specimens (NSCB) with crack angles were prepared by 3D printing technology to investigate the influence of different pre-fabricated crack angles on rock fracture characteristics. Furthermore, the printed specimens were placed in dry ice and subjected to quasi-static three-point bending tests when their surface temperature reached-30℃ after the solidification and baking treatments. The experiment revealed the influence of pre-fabricated crack angles on fracture toughness, initiation angle, and fracture energy. The results show that the average fracture toughness of NSCB specimens containing fissures is smaller than that of standard NSCB specimens. The fracture toughness of specimens is positively correlated with the fissure inclination angle. For NSCB specimens containing fissures, the initiation angle increases with the increase of the fissure inclination angle when β is between 0° and 90°, and the crack propagation path shows a distinct ‘deflection’ phenomenon. The fissure inclination angle significantly impacts the complexity of the NSCB specimen propagation path. The crack propagation path becomes more complex when the fissure inclination angle and fractal dimension increase. From the perspective of fracture energy, the fracture energy increases with the increase of the fissure inclination angle.

To explore the attenuation law of blasting stress waves in concrete under different charging structures, the strain values at different positions of the experimental models were tested by a 16-channel dynamic strain gauge based on similarity theory. Meanwhile, the attenuation law of axial and radial blast stress waves in concrete under different charge structures was obtained by calculating the peak stress. The results show that the blasting stress wave exhibits a power exponential decay as the distance between the blasting centers increases. The initial pressure and maximum pressure on the borehole wall of the coupled charge structure are the highest, and the detonation wave acts on the medium for a short time. The uncoupled charge structure reduces the initial pressure on the borehole wall and prolongs the time of detonation pressure action. The coupled charging structure consumes much energy in the crushing zone, and the energy transfer is uneven. The stress wave attenuation of the uncoupled charging structure during blasting is slow, and the energy transfer is uniform.

In order to study the gas diffusion-transport law and the influence of ventilation on the gas concentration of high gas tunnel after blasting, an optimization blasting scheme under gas conditions was carried out, and a gas diffusion-transport characteristic near the working face was investigated under both ventilated and unventilated conditions in a project. The study shows that the residual rate of the blast hole and the utilization rate of the blast hole are above 90%, and the over-excavation control effect is better with an expected blasting footage of 1.2 m and an uncoupling coefficient of 0.76. Under the condition of unventilated condition by numerical simulation, the gas accumulation near the arch top and the arch waist at the tunnel's working face is severe as the gas concentration is close to 30%. Meanwhile, the gas concentration is higher in the area 7 m away from the working surface, and the gas concentration gradient is smaller in the area beyond 7 m after the gas state is stabilized. The gas concentration can be reduced to the safe range around 30 days after ventilation. However, gas accumulation quickly occurs at the arch foot and the arch waist on the other side of the air duct, especially the gas accumulation at the arch foot is more prominent, and the gas concentration is close to 20%. There is a ventilation blind area at the arch foot of the same side of the air duct, and the gas accumulates in a small range as the concentration is about 5%. The monitoring and prevention of the above areas should be strengthened. The field measured gas concentration distribution and gas influence range are consistent with the simulation results, and the research results can provide a reference for similar gas tunnel blasting construction and ventilation optimization.

For the blasting and demolition project of a 130 m multi-tube sleeve chimney, the LS-DYNA finite element software was used to simulate the blasting incision by unit failure using a separated common-node model. The collapse process of the multi-tube sleeve chimney was numerically simulated, analyzed and compared with the actual blasting effect. The results show that the effective stress is mainly concentrated on the edge of the remaining part of the support when the blasting notch is forming. However, the notch closure stage of the falling speed is different due to the length and slenderness ratio and the nature of the material of the outer chimney and the inner sleeve are different. The simulation shows that the external chimney and the steel inner tube would be collisional at the notch closure stage as the internal and external detonation simultaneously. Choosing the detonation method with a delay of two seconds between internal and external components will achieve the ideal collapse effect.

Researching blasting similar simulation materials for ultra-deep shaft surrounding rock and conducting physical model tests are the basis for studying the dynamic response law of ultra-deep shaft surrounding rock under blasting. This paper used the monzonitic granite in Xiling subsidiary shaft of Sanshandao gold mine as the simulation object to prepare similar granite materials. The iron ore powder and barite powder were selected as fine aggregates, the quartz sand was selected as coarse aggregate, the rosin alcohol solution was selected as binding material, and the gypsum was selected as adjusting material. The orthogonal design method was used to prepare the simulation materials. The mechanical parameters of similar materials with different proportions were determined, and the sensitivity analysis of each influencing factor and the blasting test of the simulated materials were carried out. The results show that the selected proportion can meet the requirements of indoor blasting model tests based on the specimen's density, unaxial compressive strength and elastic modulus. The proportion of fine aggregate in the total aggregate significantly affects the density of the simulated materials. The binder concentration significantly affects the compressive strength, tensile strength, elastic modulus and cohesion of the simulated materials. The proportion of gypsum significantly affects the internal friction angle of the simulated materials. The peak strain value in the model test block under high confining pressure is more significant as a whole, and the attenuation rate of the peak strain gradually decreases with the distance increase.

Since the problems of significant rock clamping effect and ore depletion were caused by deep hole blasting in steeply inclined thin veins, a combination of on-site investigation, PMMA (organic glass) blasting model experiment and numerical simulation was used to explore the mechanism and a quantitative characterization method of rock clamping effect by taking a gold mine in Gansu Province as the engineering background. Firstly, to analyze the distribution pattern of blasting cracks under different mining conditions of thin ore veins, a PMMA blasting model experiment was conducted. The results show that reducing the mining width of the thin ore veins reduces the radius of blasting crushing and fracture areas around the blast hole and suppresses the development of blasting cracks. Furthermore, different blasting conditions of thin ore vein mining were simulated. The results show that as the mining width of thin ore veins decreases, the blasting energy reflected and superimposed at the blasting-free surface decreases, and the volume of blasting rock decreases accordingly. Meanwhile, more blasting energy is dissipated as kinetic energy, which could not be effectively used to break the rock. Finally, a quantitative characterization method for the clamping coefficient of thin ore vein blasting was proposed based on the analysis of blasting energy. A clamping coefficient was defined by the ratio of the total energy peak at the center point of the blasting free surface under semi-infinite and narrow amplitude working conditions, and this index characterized the size of the clamping effect. As a result, a prediction model for the blasting clamping coefficient was established through the mining width and rock mechanics parameters. The study of this paper can provide a theoretical basis and technical support for the optimization design of deep hole blasting parameters in steeply inclined thin ore veins.