Three-Dimensional Physical Similarity Simulation Experiments for a Transparent Shaft Coal Pocket Wall in Coal Mines

Abstract

To explore the variations of the loading, deformation, and loss and to determine the mechanical state, loss characteristics, and stability for the shaft coal pocket wall in coal mines under a dynamic-static load, this paper innovatively attempts to conduct a three-dimensional physical similarity test of a transparent material shaft coal pocket, as well as the experiments of loading and unloading coal in the shaft coal pocket using different bulk storage materials 80 times. Then, the deformation, pressure, the surrounding rock, and the flow pattern of the silo wall were discussed considering the existence of the warehouse wall support. The characteristics of shaft wall deformation and surrounding rock stress cracks during the unloading were analyzed with the help from multiple integrated test systems such as strain gauges, pressure sensors, borehole peeps, and other comprehensive test systems. The results indicated that different dispersion particles have a significant impact on the strain of the shaft wall. When using the coal particles as storage materials, the overpressure coefficient of the shaft wall is up to 1.95 times higher than using dry sand particles. The particle size and internal friction angle of the bulk particles impact significantly on the deformation of the wall, where the cohesive force among the dispersed particles produced by the compaction effect has a certain influence on the side pressure of the silo wall. During the unloading process, coal particles were easier to obtain an arching phenomenon than dry sand particles. In addition, the number of bulk arching could be significantly reduced under the conditions of the warehouse wall support. The “weak rock stratum” in the surrounding rock plays a major role in controlling the deformation and failure development of the shaft wall. The three-dimensional physical simulation experiment of the transparent shaft wall truly reproduces the field engineering practice, and the physical simulation results are verified by numerical simulation analysis.

Study on the Flow Trend of Particles in Shaft Coal Pocket of Coal Mine

“…Wu et al conducted a series of research on the shaft coal pocket wall in coal mine, and used to the practice (Wu et al, 2020(Wu et al, , 2021(Wu et al, , 2022Liu and Wu, 2017;Liu and Wen, 2021). Based on the analysis of the causes of the damage and collapse of the shaft coal pocket in coal mine, the team proposed the composite support scheme of "anchor cable net + inner sleeve double-layer reinforced concrete bunker wall", filled the collapse space behind the wall with concrete, specially treated the rock stratum in the aluminum mudstone section, and gave the effect evaluation.…”

“…Successfully completed the shaft coal pocket wall repair project of Ganhe coal mine (Liu and Wu, 2017); The mechanical model of shaft coal pocket wall of coal mine is established, and its deformation characteristics are studied; From the internal structure of loose particles in the shaft coal pocket of the coal mine, the bearing characteristics of the bunker wall are analyzed, and the unloading process of the shaft coal pocket of the coal mine is simulated combined with the numerical simulation experiment and three-dimensional physical similarity simulation experiment. It is proposed that there is a "three-dimensional conical shell" bearing structure in the unloading process of loose particles in the bunker (Wu et al, 2020(Wu et al, , 2021Liu and Wu, 2017;Liu and Wen, 2021); The concept of "weak rock stratum" is put forward for the shaft coal pocket project that longitudinally crosses multiple rock strata, and it is pointed out that the existence of this rock stratum is an important inducement for the failure of shaft coal pocket wall (Wu et al, 2022). Physical analogue simulation and numerical simulation experiment are important research methods in mining engineering (Qian et al, 2021).…”