To investigate the dynamic mechanical characterization of non-pure and non-intact ice materials under impact loads, a modified split Hopkinson pressure bar (SHPB) was used. Rapid loading, rod end cooling and waveform shaping techniques were used to ensure the stability of the ice material and achieve dynamic stress balance during loading. The impact mechanical properties of complete ice (pure water, containing 2.5%, 3.5%, 4.5% salt, containing 2.0%, 4.5%, 8.5% coconut) and spliced ice (splicing interface inclination 30°, 60°) at freezing temperature of −10 ℃ were studied. The strain rate ranges from 150−250 s⁻¹. The failure process was recorded by using the high-speed camera triggered simultaneously with the pressure rod. The correlation between the stress and strain of the sample, along with the failure process, was determined by analyzing the time history curve of sample. The failure mode of the spliced ice sample was analyzed by combining the Mohr-Coulomb strength criterion. The results show that the pure water ice exhibits the highest compressive strength, followed by the ice with coconut shreds, and both of them show a positive strain rate effect. However, the compressive strength of the ice with salt addition decreases significantly due to its loose structure and the strain rate effect is not obvious. The dynamic compressive strength of ice samples added with coconut fiber increases firstly and then decreases with the increase of coconut fiber content. Ice samples with high coconut fiber content are prone to “double peak” phenomenon due to the binding effect of coconut fiber on broken ice with small particle size. The splicing plane affects the crack growth, resulting in lower compressive strength than the intact ice sample, and affects the failure mode as well. The ice with small interface inclination is mainly damaged by interface slip, while the ice with large interface inclination is mainly damaged by whole ice, which is similar to the intact ice. The research results provide theoretical basis and method reference for the dynamic mechanical properties of non-pure and non-intact ice materials under impact loads.

Tunnel blasting is prone to inducing disasters such as rock collapse, and parameters such as pulse width and amplitude of the blasting stress wave directly affect the degree of tensile damage of the tunnel surrounding rock. In order to investigate and quantitatively analyse the effects of pulse width and amplitude on the dynamic mechanical properties of water-saturated red sandstone, a dynamic Brazilian splitting test was carried out on dry/water-saturated red sandstone by using a split Hopkinson pressure bar system, a high-speed video camera, and digital imaging technology. The results show that the water-saturated condition can weaken the strength of red sandstone, with tensile strength weakening rates of 91.16 %, 94.00 %, 94.86 % and 95.09 % for bullet impacts of 200 mm, 300 mm, 400 mm and 500 mm length, respectively; the damage mode of red sandstone is dominated by the expansion of tensile cracks, and the increase of the pulse width of the incident stress wave can promote the initiation and expansion of tensile cracks; moisture inhibits the absorption of energy in red sandstone, and the absorbed energy per unit volume increases with the increase of the pulse width of the stress wave; the percentage of non-tensile energy consumption of water-saturated red sandstone is higher than 80 % under the conditions of impact speed greater than 8 m/s under each pulse width, and the energy consumption rate of red sandstone decreases to less than 5 % when the impact speed is greater than 10 m/s, and the free water in cracks can produce a force that can inhibit the expansion of cracks, and the absorbed energy is used for shear damage.

Before uncovering coal in crosscut of high gas or outburst mine, it is necessary to design drainage boreholes and display the position of boreholes on the interaction surface of roadway and coal seam.In order to solve the problem that common AutoCAD and other drawing softwares can not efficiently meet the needs of a large number of calculations, combined with the relevant provisions of coal mine gas drainage and based on Matlab software programming, utilized Hungarian algorithm and simulated annealing algorithm, the automatic optimization design software of drilling parameters of crosscut uncovering coal gas drainage is developed.The results show that: ①the automatic optimization design software can be used to solve the problems of automatic optimization design and scheme comparison of drilling parameters based on any coal seam, roadway spatial position and extraction input conditions, which greatly improves the calculational efficiency and accuracy; ②The image drawing function realized by programming can realize the three-dimensional display of drilling track; ③On the basis of drilling parameters, the parameters of drilling layout are designed and verified synchronously to realize the closed-loop control of design and verification; ④The function of arbitrary hole filling parameters greatly improves the practicability of the automatic optimization design software and solves the problem of hole filling parameter design.The application of automatic optimization design of gas drainage borehole parameters in crosscut uncovering can obtain the optimal drainage borehole parameters, greatly improve the work efficiency of field technicians in coal mine, and provide important support for intelligent mining in coal mines.

The process of coal adsorption and desorption of gas is accompanied by obvious thermal effects, and its variation pattern is of great value for the research of gas hazard prediction techniques such as coal and gas outburst prediction. Using self-designed multiparameter coal adsorption and desorption heat effect test system, we conducted pressure, temperature and heat flow test experiments for CO₂, N₂ and CH₄ gas adsorption and desorption of bituminous coal at 0. 5 MPa, 0. 8 MPa and 1. 1 MPa, and analyzed the characteristics of heat flow changes of bituminous coal during the adsorption and desorption process. The study showed that: (1) during the whole process of adsorption and desorption of bituminous coal specimens, the change of heat flow density on the coal wall is divided into five processes: ①in the evacuation stage, the heat flow increases rapidly and then decreases slowly to 0; ②in the inflation stage, the heat flow is positively correlated with the inflation rate; ③in the adsorption stage, the heat flow is first fast up and then fast down and finally decreases slowly; ④in the deflation stage, the heat flow is positively correlated with the pressure relief rate; ⑤in the desorption stage, it is divided into two stages: the stage of fast down and slow rise. (2) The maximum heat flux values of N₂, CH₄, and CO₂ three gases increase sequentially; for the same gas, the maximum heat flux values under the three gas pressures will increase with the increase of pressure. (3) The theoretical values of heat in the process of adsorption and desorption are always larger than the experimental values, but the overall trend is consistent. (4) The heat flux parameter has the characteristics of inflow and outflow direction vector, which is superior to the temperature index. The heat flux is consistent with the heat transfer change law, which can well characterize the change law of thermal effect of adsorption and desorption of bituminous coal, and provide reference for the research of new index of coal and gas outburst prediction.