In view of the devastating outcomes of fires and explosions, it is imperative to research the dynamic responses of concrete structures at high temperatures. For this purpose, the effects of the strain rate and high temperatures on the dynamic tension behavior and energy characteristics of high-strength concrete were investigated in this paper. Dynamic tests were conducted on high-strength concrete after exposure to the temperatures of 200, 400, and 600 °C by utilizing a 74 mm diameter split Hopkinson pressure bar (SHPB) apparatus. We found that the quasi-static and dynamic tensile strength of high-strength concrete gradually decreased and that the damage degree rose sharply with the rise of temperature. The dynamic tensile strength and specific energy absorption of high-strength concrete had a significant strain rate effect. The crack propagation law gradually changed from directly passing through the coarse aggregate to extending along the bonding surface between the coarse aggregate and the mortar matrix with the elevation of temperature. When designing the material ratio, materials with high-temperature resistance and high tensile strength should be added to strengthen the bond between the mortar and the aggregate and to change the failure mode of the structure to resist the softening effect of temperature.

The propagation law of blast stress waves in jointed rock masses is closely related to the characteristics of the joint filling medium. The water content and thickness of the filling medium affect the propagation characteristics of the blast stress wave in the joint surface. Based on similarity theory, mortar-red clay-mortar composite specimens with different moisture contents (36%, 39%, 42%, and 45%) and medium thicknesses (3 mm, 6 mm, and 9 mm) were prepared with red clay as the filling medium. The dynamic uniaxial compression test of the specimen under different strain rates was carried out by using a variable cross-section split Hopkinson compression bar with a diameter of 50 mm. The effects of strain rate, moisture content, and medium thickness on the stress wave propagation characteristics, dynamic stress-strain curve, peak stress, crushing energy consumption density, and crushing characteristics of mortar-red clay-mortar composite specimens were analyzed. The results show that the blocking effect of joints on stress waves increases significantly with increasing filling medium thickness and water content. With increasing strain rate, the peak stress and energy of the composite specimen increase and there is an obvious strain rate effect. With the increase in the thickness and moisture content of the filling medium, the peak stress, dynamic elastic modulus, energy consumption density per unit volume, and crushing degree of the specimen gradually decrease and the nonlinear deformation is more obvious. There is a good linear relationship between the peak stress and the thickness and moisture content of the filling medium. The existence of joints greatly weakens the damage effect of stress waves on the specimens behind the joints, and with the increase in the thickness and water content of the filling medium, the degree of damage to the specimens behind the joint surface decreases under the same impact pressure and the weakening effect becomes increasingly significant.

To acquire a satisfying cutting effect during medium-length hole blasting driving of rock tunnels, an improved wedge cutting blasting method with supplementary blasting of the center holes was proposed. Initially, the cavity forming mechanism of the improved cutting method was analyzed theoretically. The results suggested that cutting hole blasting could realize the ejection of rock within the range from free face to critical cutting depth, and hence reduce the restraining force of the center hole blasting, and the supplementary blasting of the center holes could further accomplish the expulsion of the residuary rock. Subsequently, simulation of the improved cutting method was implemented to exhibit the stress wave evolution and reveal the stress field distribution. The simulation results indicated that cutting hole blasting could cause the preliminary failure of the residuary rock, and center hole blasting could strengthen the stress field intensity in 1.8–2.5 m in order to aggravate the destruction of the residuary rock. Hence, the residuary rock could be broken into small fragments that were easy to expel out. Finally, a field application experiment was conducted in a coal mine rock tunnel. Using the improved wedge cutting method instead of the conventional wedge cutting method, the full-face blasting driving efficiency was obviously enhanced and the overall blasting driving expense was significantly reduced, which forcefully confirmed the engineering usefulness of the improved wedge cutting method in the medium-length hole blasting driving of rock tunnels.

During the process of coal mining, there is a violent appearance of mining stress when the initial weighting occurs. To guarantee the safety of the gob-side entry formed automatically by roof-cutting (EFARC) in an inclined coal seam, a study was conducted on the initial weighting mechanism and appearance characteristics through field monitoring and theoretical analysis. The findings reveal that, upon the initial breaking of the main roof in the non-pillar mining stope of an inclined coal seam, the deflection of the thin plate structure exhibits asymmetric distribution, with the maximum position situated in the middle-upper part of the thin plate. As the main roof thin plate reaches its limit interval, the tensile fracture first occurs in the middle-upper part of the coal wall in front and back of the stope. Once broken, the thin plate changes to a simply supported state. The analysis of field data reveals that the mine pressure in the non-pillar stope of EFARC shows an asymmetric weighting phenomenon. The periodic weighting interval at the ends of the working face increases, and the weighting intensity decreases. These results can serve as theoretical support for controlling mine pressure in non-pillar mining through EFARC in inclined coal seams and can serve as a basis for further investigations in this area.

Deep rock bears dynamic loads such as machinery, blasting and disturbance in the mining process. The dynamic fracture mechanism of deep rock is a necessary prerequisite for engineering design and analysis. To study the dynamic fracture mechanism of rock under high in situ stress, deep mudstone and sandstone were selected as research objects. The dynamic mechanical properties and energy dissipation of mudstone sandstone were assessed by using a 50 mm diameter separated Hopkinson test device. According to the similarity criterion, the similarity of strength was assumed as primary factor to prepare similar model materials. Then, dynamic mechanical tests of these similar materials were carried out under dynamic compression splitting and active confining pressure. The results show that materials similar to mudstone and sandstone mainly show axial fracture tensile failure and crushing failure. Both the average strain rate dynamic strength and peak strain of these similar materials increase with increasing impact pressure, and the dynamic strength of similar materials increases exponentially with increasing strain rate. This result is consistent with the regularity of original rock. The dynamic splitting of mudstone-like materials is dominated by the failure of intermediate cracks, and sandstone-like materials also show secondary cracks in addition to intermediate splitting cracks. The dynamic peak strength of mudstone-like materials increases with increasing active confining pressure, and the dynamic peak strength of sandstone-like materials increases nearly twofold under the action of active confining pressure.

Smooth surface blasting control technology is aimed at blasting the rock body until it is left with a smooth surface and to protect it from damage; the current air spaced axial uncoupled charge and air spaced radial uncoupled continuous charge are effective charging structures for smooth surface blasting. Reserved air spacing can effectively reduce the blast wave and the peak pressure of the explosive gas, improving the quasi-static pressure of the explosive gas under the action of rock surface blasting with fracture seam quality. In order to ensure the effect of surface blasting, small-diameter light surface holes are more often used; with the development of drilling machinery, the use of large-diameter light blast holes with an oversized uncoupled coefficient of loading structure effectively improves the efficiency of the construction and at the same time achieves better blasting results. However, according to the bursting assumption of obtaining the theory of light surface blasting in the application of large uncoupling coefficient loading, light surface blasting has certain limitations. In this regard, the bursting theory explores the air spacing uncoupling charge in line with the multi-faceted exponential expansion of the critical uncoupling coefficient and is in accordance with the following: the requirements of light surface blasting and the field loading structure; the derivation of the quasi-static pressure on the wall of the gunhole under the action of large uncoupling, uncoupling coefficient, and the parameters of the spacing between the gunholes; the establishment of the axial uncoupling coefficient and the radial uncoupling coefficient-equivalent relationship between the uncoupling coefficient and the theoretical relationship between the selection of the spacing between the holes; the uncoupling coefficient and the selection of the theoretical relationship between the spacing between the holes. This study reveals the mechanism by which different parameters of surface blasting can achieve good results in engineering practices. A slope in Guizhou is an example of sample calculations and the application of two different charging structures applied to field loading, which have achieved good surface blasting results.