The water jet nozzle is a penetrating drilling tool, which sends the pumped water to the nozzle through a high-pressure hose. It can work in a variety of working environments. When it dredges the blockage in the pipeline, its structural parameters will affect the jet flow field in the pipeline. Taking the self-propelled water jet nozzle as the research object, SolidWorks was used to establish the nozzle model with different parameter structures. Based on Fluent, the k-ε turbulence model was used to simulate the jet of nozzles with different nozzle sizes and arrangements in the pipeline. The distribution of the jet flow field and the change in velocity and displacement of nozzles with different parameters in the pipeline were compared, and then computational fluid dynamics (CFD) were used to process the simulation data for further research. The results show that when the inclination angle of the rear nozzle is 35°, the attenuation of the front jet velocity and the fluctuation of the wall fluid velocity are the smallest. When the nozzle aperture is increased from 2 mm to 3.5 mm, the vortex area inside the pipe is reduced, and the velocity attenuation of the front jet is also reduced, with the velocity attenuation rate decreasing by about 10%. This study provides a reference for the design and parameter optimization of self-propelled water jet nozzles.

In order to solve the ecological environment pollution caused by a large amount of coal gangue accumulation and the problems of poor conveying performance and low support strength of paste filling materials. Based on the standard slump test and uniaxial compressive strength test, the slump and compressive strength (post-coagulation) of gangue paste under different aggregate size aggregations were obtained through orthogonal experiments in this study. The results show that the slump of the gangue filling paste with four types of aggregate size gradations is negatively correlated with the mass fraction, and the slump of the filling paste with a coarser aggregate content is more obviously affected by the mass fraction The increase of fine aggregate content has a significant impact on the compressive strength of the filling paste, which shows a trend of first increasing and then decreasing. When the mixing ratio of coarse aggregate and fine aggregate is 5:5, the compressive strength of the paste reaches the best. In addition, different proportions of aggregate mixing cause the filling paste to form different skeleton structures, including the skeleton void structure at 7:3 or 6:4, the skeleton dense structure at 5:5, and the skeleton suspension structure at 4:6, which are decisive for the final performance of the paste. By analyzing the experimental results of the compressive strength and slump of the gangue filling paste, it was found that the relationship between the compressive strength and slump of the gangue filling paste is a power index function. Through data fitting, it was found that the regression coefficient of the fitting function is no less than 0.97, and the fitting effect is good for evaluating the strength of the filling paste under the aggregate size grading.

Because of the unclear understanding of the characteristics associated with coupled rock breaking using multiple water jets, a numerical model combining smoothed particle hydrodynamics (SPH) and the finite element method (FEM) was established to investigate the rock-breaking capacity of a high-pressure, double-stranded water jet structure. The effectiveness of this model was verified through field experiments. The study further examined the specific energy required for rock breaking using the high-pressure double water jets and analyzed the effects of jet pressure, nozzle diameter, jet impact angle, and impact point spacing on rock-breaking volume. The results demonstrate that the rock-breaking ability of a high-pressure double water jets is better than that of a single water jet. When the impact angle of the high-pressure double water jets was 15° and the distance between impact points was 2.0 d, the rock damage effect was the best. By comparing the specific energies for rock breaking of a single water jet and a double water jet, it was concluded that the best rock-breaking nozzle diameter is 1.6 mm. Furthermore, an orthogonal testing approach was employed to determine the main and secondary factors influencing the rock-breaking energy of the high-pressure double water jet. The order of significance was found to be jet pressure > impact angle > impact point spacing > nozzle diameter. These findings provide valuable guidance and reference for application in the coal mining industry.

To improve the cutting efficiency of abrasive water jet technology, a high-pressure water jet cutting system was developed to examine the cutting effects on granite and red sandstone under various process parameters. The results reveal that the average slit depth increases linearly with rising jet pressure, while the slit width shows a decreasing trend. In contrast, as the transverse speed increases, both the depth and width of the slit decline. The slit depth initially rises and then falls with an increase in jet target distance, peaking at a target distance of 5 mm, whereas the slit width consistently decreases. Furthermore, as the jet angle increases, the slot depth exhibits an oscillatory pattern of increase and decrease, with the maximum slot depth occurring at a jet angle of 10°. Conversely, the slit width first decreases and then increases with the jet angle, reaching its maximum at a jet angle of 20°. To clarify the relative importance of these parameters, an L16(4^4) orthogonal experimental design was utilized to conduct extensive experiments on granite and red sandstone. Through range analysis and variance analysis, the primary and secondary relationships among the factors affecting abrasive water jet cutting were established in the following order: transverse velocity > jet pressure > jet inclination > target distance. The optimal jet parameters identified were a jet pressure of 40 MPa, a target distance of 5 mm, a transverse velocity of 2 mm s⁻¹, and a jet inclination of 10°.

To address the demand for flow capacity expansion in filling mining systems, employing two parallel paste conveying pumps offers a cost-effective solution. However, as a viscoelastic-plastic fluid, filling paste is transported through pipelines under pulsed step excitation from paste pumps. Consequently, paste transportation exhibits distinct characteristics in both material properties and pumping mechanisms. The low efficiency of parallel pumping configurations constrains the practical adoption of dual-pump parallel systems. This study establishes a constitutive model based on the viscoelastic-plastic mechanism of filling paste. Using MATLAB/Simulink, a computational model simulating the constitutive behavior subjected to step-input excitation is developed. Two unbalanced pressure pulsation signals are generated to simulate parallel pump inputs, with systematic adjustments to frequency and phase differences for constitutive model loading. Analysis reveals that parallel pump operation achieves optimal flow continuity and pressure stability when synchronized at identical pulsation frequencies with a 90° phase difference. The findings substantially enhance pipeline transport efficiency while mitigating instantaneous impacts, providing critical theoretical guidance for parallel pump system design and operational control. This research establishes a foundation for effective implementation of dual-pump parallel conveying technology in mining applications.