To study the energy evolution law and damage constitutive behavior of high-strength concrete based on the conventional triaxial compression tests of C60 and C70 high-strength concrete subjected to five different confining pressures, the failure characteristics of high-strength concrete are analyzed at different confining pressures, and the evolution of the input energy density, elastic strain energy density, and dissipation energy density with axial strain and confining pressure are quantified. Combined with a continuous damage theory and non-equilibrium statistical method, the ratio of dissipation energy density of concrete to dissipation energy density corresponding to peak stress is used as the mechanical parameter. Assuming that the mechanical parameter obeys the Weibull distribution laws, the statistical damage variable describing the damage characteristics of concrete were derived. According to the Lemaitre strain equivalent principle, the damage variable is introduced to the generalized Hooke law to establish the statistical damage constitutive model for high-strength concrete. The results show that: (1) the input energy density and dissipation energy density increases with the increase of axial strain, while the elastic strain energy density increases first and then decreases as a function of the axial strain and reaches the maximum value at the peak stress; (2) the input, elastic strain, and dissipated energy densities corresponding to the peak stress of the two high-strength concretes all increase as a function of confining pressure, and the elastic strain energy density corresponding to the peak stress increases linearly as a function of the confining pressure; (3) the statistical damage constitutive model results of C60 and C70 high-strength concrete are in good agreement with the test results, and the average relative standard deviations are only 3.64% and 3.99%. These outcomes verify the rationality and accuracy of the model.

The mechanical response characteristics of mudstone from the ingate roadway of the west ventilation shaft in Yuandian No. 2 coal mine, Huaibei City, Anhui Province, China to dynamic loads were quantified in single- and cyclic-impact compression tests, using the split-Hopkinson pressure bar test device. The dynamic stress–strain relationships and the failure characteristics of mudstone samples under different impact loads were analyzed systematically. Considering the “rate effect” of the mudstone dynamic strength, the dynamic strength criterion of mudstone was proposed, and the dynamic damage constitutive model of mudstone was established, based on the statistical damage theory. In response to single-impact loads, with increasing impact pressure, the mudstone peak stress and strain gradually increased, and the peak stress and average strain rate increased nonlinearly. In response to cyclic-impact loads, with an increasing number of impacts, the mudstone peak stress first increased and then decreased, and the peak strain increased gradually. With increasing impact pressure, the number of impacts to the samples’ failure decreased gradually. By parameter identification and comparative analysis of the test results, the proposed dynamic damage constitutive model of mudstone was validated. The model can be used for stability analysis of roadway-surrounding rock under dynamic loads.

In engineering, loose sandy (gravelly) strata are often filled with cement-based grout to form a mixed material with a certain strength and impermeability, so as to improve the mechanical properties of sandy (gravelly) strata. The tortuosity effect of sandy (gravelly) strata and the time-varying viscosity of slurry play a key role in penetration grouting projects. In order to better understand the influence of the above factors on the penetration and diffusion mechanism of power-law slurry, based on the capillary laminar flow model, this research obtained the seepage motion equation of power-law slurry, the time-varying constitutive equations of tortuosity and power-law fluid viscosity were introduced, and the spherical diffusion equation of penetration grouting considering both the tortuosity of porous media and time-varying slurry viscosity was established, which had already been verified by existing experiments. In addition, the time-varying factors of grouting pressure, the physical parameters of the injected soil layer, and slurry viscosity on penetration grouting diffusion law and the influencing factors were analyzed. The results show that considering the tortuosity of sandy (gravelly) strata and the time-varying of slurry viscosity at the same time, the error is smaller than the existing theoretical error, only 13~19%. The diffusion range of penetration grouting in the sandy (gravelly) strata is controlled by the tortuosity of sandy (gravelly) strata, the water–cement ratio of slurry, and grouting pressure. The tortuosity of sandy (gravelly) strata is inversely proportional to the diffusion radius of the slurry, and the water–cement ratio of slurry and grouting pressure are positively correlated with the diffusion radius. In sandy (gravelly) strata with a smaller particle size, the tortuosity effect of porous media dominates the slurry pressure attenuation. When the particle size is larger, the primary controlling factor of slurry pressure attenuation is the tortuosity effect of porous media in the initial stage and the time-varying viscosity of slurry in the later stage. The research results are of great significance to guide the penetration grouting of sandy (gravelly) strata.

To elucidate the distribution law of the multiphase coupling slag discharge flow field in gas-lift reverse circulation during drilling shaft sinking, a numerical analysis model of gas–liquid–solid multiphase coupling slag discharge was established by CFD–DEM (Coupling of computational fluid dynamics and discrete element method) method, taking the drilling of North Wind well in Taohutu Coal Mine as an example. This model presented the distribution of the multiphase flow field in the slag discharge pipe and at the bottom hole, and was validated through experimentation and theoretical analysis. Finally, the impact of factors, including bit rotation speed, gas injection rate, air duct submergence ratio, and mud viscosity on the slag discharge flow field was clarified. The results indicated that the migration of rock slag at the bottom of the well was characterized by “slip, convergence, suspension, adsorption, and lifting”. The slag flow in the discharge pipe exhibited the states of “high density, low flow rate” and “low density, high flow rate”, respectively. The multiphase fluid flow patterns in the well bottom and slag discharge pipe were horizontal and axial flows, respectively. The model test of the gas lift reversed circulation slag discharge and the theoretical model of the bottom hole fluid velocity distribution confirmed the accuracy of the multiphase coupling slag discharge flow field distribution model. The rotation speed of the drill bit had the most significant impact on the bottom hole flow field. Increasing the rotation speed of the drill bit can significantly enhance the tangential velocity of the bottom hole fluid, increase the pressure difference between the bottom hole and annular mud column, and improve the adsorption capacity of the slag suction port. These findings can provide valuable insights for gas lift reverse circulation well washing in western drilling shaft sinking.

This study aimed to clarify the mechanism of the effect of surface charge of clay particles on the separation pressure between adjacent frozen clay particles. A general mathematical model of separation pressure between adjacent spherical clay particles was given based on the extended colloidal stability (DLVO) theory; it was introduced into the frost heave process, and the functional expression of separation pressure and freezing temperature between clay particles was derived by using the relationship between the pore throat’s radius and freezing temperature, which was verified by the existing experimental results. Finally, the effects of the freezing temperature, mineral species and solution concentration on the freezing separation pressure and ice-lens growth were analyzed. Our results show that the surface distance of adjacent charged bodies is a single-valued function of their separation pressure, but the freezing temperature is the main factor affecting the separation pressure between adjacent frozen clay particles; the separation pressure between adjacent clay particles is proportional to its surface-charge density. For the same particle spacing, the separation pressures of kaolinite and illite are not much different, but they are both about one order of magnitude lower than montmorillonite; the separation pressure between clay particles is negatively correlated with the solution concentration. When the solution concentration is less than 0.1 mol$·$m⁻³, the effect of the solution concentration on the separation pressure between particles is negligible. The research results can provide a theoretical reference for improving the existing geotechnical frost heave theory.

Combined with the advanced drilling of the central return air shaft in Kekegai Coal Mine, the distribution law of slag discharge flow field by drilling method and the influencing factors of slag discharge effect are studied. Firstly, the numerical model of gas–liquid–solid coupling slag discharge is established by CFD-DEM (computational fluid dynamics coupled discrete element method). Then, the flow field distribution law of the site slag outlet layout model and the optimization model is compared and analyzed. Finally, the influence of drilling parameters on slag discharge effect is studied. The results show that the best arrangement of slag suction ports is: the number is two, the length-diameter ratio is 0.4, the area ratio is 1, and the total area ratio is 1.94%. The fluid movement at the bottom of the well is mainly tangential flow, while the fluid in the slag discharge pipe is mainly axial flow. The construction parameters of efficient slag discharge are put forward: bit rotation speed is 8.7 r/min, gas injection rate is 4200 m³/h, air duct sinking ratio is 0.84, and mud viscosity is 165 MPa·s. The research results can provide useful theoretical reference for large-scale sinking construction in deep wells.