Research on key parameters of pipeline transportation of waste rock treatment in underground residual space

Abstract

As the key link of coal gangue slurry filling, slurry pipeline transportation is an important guarantee to realize the slurry mixing and safe transportation of gangue from solid powder. To realize the underground excavation gangue of the Huangling No. 2 coal mine without raising the ground, the slurry filling technology is proposed to transport the slurry made by gangue through the pipeline and fill it into the goaf. The phase composition and microstructure characteristics of underground excavation gangue in the Huangling No. 2 coal mine were analyzed by X-ray diffraction and an electron microscope scanning test, the slurry-forming properties of gangue powder with different particle sizes and gradations were studied, and the influence of gangue slurry concentration on its rheological properties was analyzed. The experimental results show that the gangue powder crushed using a cage crusher can be made into stable slurry when the particle grading size is the natural crushing gradation with the upper limit of particle size less than 3 mm. The viscosity of the slurry is positively correlated with the concentration. When the concentration is below 70%, the increase in viscosity is small, and when the concentration is above 70%, the increase in viscosity is significant. It is determined that the concentration of the Huangling No. 2 coal mine slurry is 70%. Based on the determination of slurry preparation parameters, the simulation analysis of slurry pipeline transportation was carried out, the influence of design velocity on the velocity distribution of the pipeline section and the variation law of slurry concentration was explored, and the design velocity of the project is determined to be 1.5 m/s. The engineering practice shows that the slurry preparation parameters are reasonable. The crushing and pulping of gangue under the ground and the safe transportation of a 6 km pipeline are realized, which provides a reference for similar engineering projects.

Numerical Study of Gangue Slurry Deposition Behavior in Pipelines Considering Viscosity Change

“…The pipe simulation model is the same as the actual grouting pipe, with an inner diameter of 178 mm. The actual length of the pipe is too long, so a unit pipe model with a length of 2 m is defined in combination with the available experimental data [13,17,21]…”

“…The clogging of the grouting pipeline will cause economic losses and delay the progress of the filling project. Moreover, it even affects settlement management, which will bring more significant safety hazards [10,[14][15][16][17]. Therefore, it is necessary to study the flow state of gangue slurry in grouting pipes to avoid the phenomenon of gangue slurry clogging in the grouting pipeline.…”

Study on the diffusion and deposition law of pore slurry in gangue filling zone based on CFD-DEM coupling

“…The motion of the particles is governed by the Newtonian equations of motion describing the translational and rotational motion of a spherical particle (motion with six degrees of freedom in three dimensions). The particle i in space realizes the contact collision, rotation and other motions in space through the contact with other particles j, the solid wall and its own gravity [25], and the advection control equation of the particles under the force in the DEM can be expressed as Eq (6).…”

“…They determined experimentally and numerically that grouting pressure and time affect rock mass elastic modulus, studying modification effects of high viscosity slurries [5]. Wenzhe Gu analyzed the phase composition and microstructure characteristics of gangue to study its rheological properties affected by concentration, proposing a technique to make gangue into slurry and transport it through pipelines to fill goafs [6]. Huazhe Jiao explored pore structure shear evolution and bottom flow slurry dehydration behavior using high-precision CT scanning and 3D reconstruction techniques, revealing thickening mechanisms [7][8][9][10].…”

Research and engineering practice on space characteristics of gangue slurry filling

“…However, the large volume of gangue and the relatively low comprehensive utilization rate [8][9][10], as well as the high cost and limitations of traditional backfilling mining techniques, such as the mutual influence of mining and backfilling processes and the impact of backfilling on working face productivity [11][12][13], make existing gangue utilization methods and approaches inadequate for efficient, green, and large-scale disposal of coal gangue. Based on this, some scholars have integrated the advantages and disadvantages of traditional solid backfilling, paste backfilling, and high-water backfilling techniques [14][15][16]. They proposed a new type of coal gangue slurry backfilling technology by combining caving zone grouting technology, long-distance pipeline transportation technology, and yellow mud grouting technology [17][18][19].…”