A Study on the Seepage Flow Characteristics and Disaster‐Causing Mechanism of Collapse Column

Abstract

Factors such as the hydrogeological conditions, the lithological characteristics of the columns’ components, and the lithological characteristics and stress conditions of the coal seam roof and floor are interrelated and jointly affect column collapse. In this study, the disaster-causing mechanism of column collapse was studied. Based on the system theory, a collapsed column is divided into the column and the surrounding fissure zone as two subsystems for analysis. And, the permeability coefficient of the broken rock under different conditions was measured by a self-designed equipment. The variations of the permeability coefficient for rock samples with different particle diameters, different axial pressures Pa, and different seepage velocities were further studied. Through phenomena analysis and experimental data processing, it was concluded that, under the same pressure state, smaller particle diameter meant smaller permeability coefficient; with the increase of axial pressure, the permeability coefficient decreased; and the larger the water flow velocity was, the smaller the permeability coefficient became. For particle diameter Φ = 2.5–5 mm or larger, the tiny particles formed by randomly washing and breaking in the water flow blocked some of the channels. For particle diameters smaller than Φ = 2.5–5 mm, the smaller permeability coefficient was attributed to the turbulence resulting from non-Darcy flow. The study on the permeability of the fractured rock mass clarified the mechanism of water inrush from the fissure zone of the collapsed column: the collapsed column itself was impermeable, and the permeability of the fissure zone around the collapsed column was related to the lithological characteristics of the rock within the fissure zone and the sequencing of rock strata. When mining coal in areas with collapsed columns, experiments on collapsed columns and fissure zones are prerequisites. This study has a certain referential value for coal mining in this region.

Mechanism Analysis of Delayed Water Inrush from Karst Collapse Column during Roadway Excavation Based on Seepage Transition Theory: A Case Study in PanEr Coal Mine

“…Once the mining or excavation affects the KCC connected with the Ordovician limestone aquifer with strong water yield, the high-pressure groundwater penetrates the filling and dramatically flows along the fracture channel. More than 5000 KCCs have been found in 45 mining areas in the Northern China coalfield, mainly distributed in Shandong, Hebei, Shanxi, Anhui, and Henan provinces [2][3][4]. In recent years, with the increase in excavation depth, the water inrush disasters caused by KCCs have become more and more serious.…”

Rock response characteristics in the area of the hidden collapse column induced by mining

“…Cao et al (2021) studied the karst collapse column above the coal seam in the southern coalfield of China and constructed a discrete element numerical model by analyzing the particle size distribution and mineral composition of the collapse column to reveal the evolution mechanism of the water conductivity channel. Li et al (2016) used the geological background of the Shuangliu mine as a prototype to study the formation of hydraulic conductivity channels and water inrush processes by examining the variation in rock resistivity. Feng et al (2018) used self-designed equipment to measure the permeability coefficients of fractured rock and clarified the mechanism of water inrush in the fracture zone of the collapse column.…”

“…Li et al (2016) used the geological background of the Shuangliu mine as a prototype to study the formation of hydraulic conductivity channels and water inrush processes by examining the variation in rock resistivity. Feng et al (2018) used self-designed equipment to measure the permeability coefficients of fractured rock and clarified the mechanism of water inrush in the fracture zone of the collapse column. Lin et al (2021) used the consolidation drainage method to remodel karst collapse columns and studied the variation in compressive strength, tensile strength, cohesive force, internal friction angle and permeability with consolidation pressure and water content and proposed the mechanism of hysteresis water inrush in karst collapse columns during the mining process.…”