The Research On Permeability Characteristics Of Collapse Column Fillings And Its Application In Engineering

Water inrush from coal mine is one of the main disasters faced by safe mining of coal mine,and water inrush accidents caused by collapse column occur from time to time.Once water inrush accidents happen to collapse column,it will cause major casualties,economic losses and negative social impact,and seriously threaten safe mining of coal mine.Although scholars at home and abroad have done a lot of research on collapse columns for a long time,few studies have focused on the seepage and mechanical properties of collapse columns.Therefore,it is of great significance to study the seepage and mechanical properties of collapse columns for engineering applications.This paper takes the collapse column fillings as the research object,according to the geological environment characteristics of collapse column interstitial material,the effects of water content,consolidation time and consolidation pressure on the permeability and mechanical properties were studied by laboratory experiment.FLAC3D numerical simulation technology was used to comprehensively analyze the water inrush risk of coal mine with collapse column filler under the fluid-solid coupling effect,providing reference value for engineering application.The following conclusions are obtained:?1?The consolidation pressure and size of traditional geotechnical consolidation tester can not meet the test requirement.The purpose of this study is to study the effects of different water content,consolidation time and consolidation pressure on the permeability and mechanical properties of the collapse column.According to the theory of taibo gradation,the experimental material of collapse column interstitial material was proportioned through the lever high pressure consolidation instrument test device independently designed and developed,and the remolded sample of collapse column interstitial material was prepared.It lays a foundation for the research of laboratory test and numerical simulation.?2?The permeability of the reshaped specimen filled with collapse column is between 3.90×10^-16m² to 41.56×10^-16m².The permeability increased with the increase of water content,and first increased and then decreased with the increase of consolidation time and consolidation pressure.Uniaxial compressive strength ranged between 0.52MPa to 1.17MPa.Uniaxial compressive strength increases first and then decreases with the increase of water content,consolidation action time and consolidation pressure.The correlation between permeability,uniaxial compressive strength and porosity is poor,and the porosity is between 8%and 21%.?3?In the context of actual engineering,based on the test data,the collapse column filler content to assign different sectional parameters,three-dimensional calculation model is setted up,using FLAC3D numerical simulation software,the coal seam and is not a collapse column filler content condition under the action of fluid-structure interaction of numerical calculation,analysis of pore water pressure,seepage vector change rule and characteristics of the plastic zone,revealing the mechanism of collapse column water bursting.?4?The numerical simulation shows that before water inrush,the internal and external pore water pressure of the collapse column goes through three stages:slow rise,gentle stability and rapid decline.When it is 21.7m away from the collapse column,the leading plastic failure zone of the coal seam working face is connected with the plastic zone of the collapse column,forming a water diversion channel,which may cause water inrush from the collapse column.Therefore,in order to ensure the safe production of coal mine,determine the water inrush position of collapse column and guide the practical engineering application,under the conditions of this paper,the limit safe mining interval of 6.7m should be reserved for the working face.