To carry out deep coal mining safely and efficiently, the dynamic mechanical characteristics and fracture mechanism of coal rock in deep earth were investigated under the ‘three high and one disturbance’ environment. A dynamic impact test of coal rock was carried out using the self-improved ϕ 50 mm high temperature synchronous split Hopkinson pressure bar (SHPB) test equipment at temperatures between 25~200℃. A ZWT viscoelastic constitutive model was also improved to establish a dynamic constitutive equation considering the temperature effect. The influence of high temperature on crack development law and the dynamic strength of coal rock was investigated based on the coupling of the finite difference and discrete element methods. The results show four stages to the dynamic stress-strain curve of coal rock under high-temperature impact: compaction, elastic, crack propagation, and softening failure. The dynamic compressive strength and dynamic elastic modulus of coal rock significantly decrease as temperature increases. In contrast, the failure strain increases, and the absorbed energy varies in a W-shaped pattern. The fractal dimension increases linearly as the particle size decreases. The degree and complexity of the fragmentation mechanism increase as the compressive strength decreases. Although the improved dynamic constitutive model based on ZWT could adequately express the stress-strain relationship following a high-temperature impact, it does not apply to the compaction stage. According to the simulation and test results, water and adsorbed gas actively escape in the coal rock at 150℃. The coal matrix is also heated and expanded, which induces cracks. There are apparent mesoscopic cracks initially and gradually developed through cracks, mainly shear ones. The crack development of coal rock under dynamic compression at 100℃ develops through the impact surface, and the high temperature deteriorates the strength of coal rock.

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.

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.

Numerical simulation is a vital tool for studying the dynamic characteristics of rock, with the accurate determination of models and parameters being the key to ensuring the reliability of simulation results. Among the 34 parameters of the RHT model, 19 parameters can be obtained through experimental and theoretical calculations, but the remaining 15 are challenging to determine. Nineteen basic parameters of anhydrite were obtained through experimental analysis and theoretical calculation to identify the model parameters suitable for anhydrite. Furthermore, the LS-DYNA performed SHPB simulation tests on the 15 challenging parameters. The sensitivity of stress-strain curves to these parameters was compared, and the values were optimized. Parameters with high sensitivity were identified through orthogonal testing. Finally, simulation results were compared with laboratory test results. The findings indicate that RHT parameters B, , n, D₁, n_f, P_comp and N have minimal impact on the stress strain curve, while parameters A, , , Q₀, , ξ, and A_f significantly influence the curve. Furthermore, the parameters with a significant impact on the stress-strain curve were determined by orthogonal tests, and the RHT model parameters fitting the SHPB impact test curve were obtained. Under varying loading strain rates, the dynamic stress-strain curves and failure patterns of anhydrite simulation tests were consistent with laboratory tests, verifying the suitability of the model parameters for anhydrite.

On-site double-hole slitting blasting experiments were conducted to study the effect of controlling fracture damage by double-hole slitting blasting. A test double hole slitting blasting model was constructed using ANSYS/LS-DYNA software, and its crack propagation and changes in gas unit pressure on the hole wall were compared and analyzed. The on-site results indicate that an intersecting fracture surface is formed between the two blast holes in the direction of the cutting seam after the explosion, and the half-hole residue is more obvious. Besides, the cracks will still develop towards the cutting direction by changing the cutting angle to 157°, and the guiding effect of the cutting seam is not affected by the change in angle. Meanwhile, the fracturing effect of adding empty holes between blast holes is better than that of non-empty hole slot blasting, which indicates that the existence of empty holes can effectively improve the directional fracture effect of slot blasting. The model results of the crack propagation and damage are consistent with the on-site results. By comparing and analyzing the double hole slit blasting and ordinary smooth blasting models, the superposition effect of stress waves causes the development of cracks between the holes to deflect, which forms a crack void between the two holes. Though analyzing the peak pressure of gas units around the hole wall at 0°~90°, it is found that the time when the pressure peak reaches the slit direction is earlier than that in the non-slit direction. More importantly, the pressure peak decreased significantly, and then the curve gradually tended to flatten during the slit blasting range of 0°~15°. The larger the angle, the smaller the peak change. The slit tube effectively controls the distribution of explosion energy during the explosion process, which forms stress concentration at the slit, with the maximum stress peak being about four times higher than that in the vertical direction.

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.

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.

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.

This study presents a comprehensive approach to solve the problem of low ore recovery caused by the difficulty in separating small-particle size ore from soil after blasting in a limestone building stone mine. Firstly, a correlation model between blasting fragmentation and dynamic damage of rock mass was established based on field measurement data and numerical simulation results, which can determine dynamic damage thresholds corresponding to various rock particle sizes. Secondly, the numerical simulation test of bench blasting in a three-dimensional fractured rock mass was carried out by using different air-decked charging stages and borehole distribution parameters, which can improve the particle size yield of 0.3~0.9 m and control the bulk ratio to obtain the best blasting parameters. Finally, the field blasting tests were conducted to optimize the charge structure and borehole distribution parameters based on numerical simulation results. The results show a negative exponential function relationship between the blasting block size and the dynamic damage value of the limestone. Specifically, the dynamic damage thresholds corresponding to the blasting size of 0.3 m and 0.9 m are 0.793 and 0.286, respectively. Using only an air-decked charging structure alone can increase the particle size ratio of 0.3~0.9 m and significantly raise the bulk rate. Conversely, combining an air-decked charging structure with a reduced hole spacing markedly enhances the particle size ratio of 0.3~0.9 m while maintaining a stable bulk rate. Optimal blasting results are achieved using a two-stage air interval charging structure and a strategic reduction in hole distribution parameters. The field application results show a 20.09 percentage point increase in the 0.3~0.9 m particle size ratio, with the bulk rate remaining virtually unchanged. Additionally, the unit consumption of explosives decreased by 10.29%.

Researching controlled blasting technology for hazardous rock bodies in complex environments holds significant theoretical importance and provides valuable reference points for enhancing highway construction efficiency and mitigating potential risks. This study focuses on the Gulin-Jinsha highway construction project, aiming to eliminate the dangers posed by hazardous rock bodies during construction. Six scanning stations were established using 3D laser scanning technology to create a high-precision 3D Digital Terrain Model (DTM) of the hazardous rock bodies. Additionally, four object detection lines were deployed using a high-density electrical method to achieve 3D visualization of the geological features in the hazardous rock area. A fracturing test was conducted based on the high-precision 3D model. The designed depth of the shell hole was 70% of the height of the hazardous rock body, with fracturing pipes connected in series and each pipe carrying a total charge of 720 g. The results demonstrated that the constructed high-precision 3D model accurately reflects the morphological characteristics of the hazardous rock body, providing reliable information for the blasting design. The fracturing pipes showed effective fracturing performance, facilitating the removal of the hazardous rock body during subsequent stages. This method offers a viable reference for similar projects, showcasing the potential for efficient and safe removal of hazardous rock bodies in complex environments.