Experimental Study On Permeability And Water Inrush Behavior Of Karst Column Pillar Accompanied By Particle Migration

With the increase of mining depth,the water damage of the bottom plate has become one of the important factors that restrict the safe production of coal mines.As the main manifestation of the karst column pillar sudden water,the pore change characteristics inside the karst column pillar under particle migration are obvious.It is important to study the permeability characteristics and sudden water behavior of the karst column pillar during the recovery process to understand more comprehensively the mechanism of karst column pillar sudden water and prevent the occurrence of karst column pillar sudden water disaster.Therefore,this paper starts from the problem of trap-column burst water and takes the trap-column filling as the research object.Under the condition of considering particle migration,a combination of indoor test and theoretical analysis is used.In this paper,the infiltration characteristics and the behavior of the karst column pillar with particle migration are studied.In order to reveal the intrinsic nature of the karst column pillar sudden water accident,a set of seepage test system that can simulate the karst column pillar sudden water was improved.And the modified sample drawings of the main components were provided.Based on this system,pore penetration tests of trap pillar fills with different grading structures were carried out.The article simulates the bearing infiltration process of the karst column pillar fill under different burial depths in mining activities.Based on the description of the corresponding experimental phenomena,the relationship between migrating particles,bearing load,particle size ratio and rock skeleton and permeable pore space is analyzed.The paper concludes that migrating particles are an important cause of pore space differences in the fill.It is argued that the load fluctuation of the graded specimens generally occurs in the middle and late stages of the 10 KN load(there exists a peak load after compression density,near 35.3 KN).The mass of migrated particles decreases with increasing grade n values,and specimens with grade values n=0.3 vs.n=0.5 easily migrate more fine particles.The skeletal particle size of the specimens after infiltration showed a trend of rapid decrease followed by a slow increase in decrease.By controlling the bearing stage and adjusting the osmotic pressure,the water burst test of karst column pillar with different bearing permeability state under the effect of particle migration was carried out.The paper simulates the burst water behavior of the karst column pillar fill under different burial depths.In the process of describing the sudden water behavior of the corresponding state,the influencing elements of the water-conducting pore space of the filling and the destruction characteristics of the sudden water channel are analyzed.The results show that the large fluctuation phase under load of each group of specimens mostly occurs in61s~306s,and the specimens with the grading value n=0.7 and n=0.9 have better hydraulic bearing capacity and the pore dense interval under bearing load exists.In the process of controlling the infiltration state,the peak load collapse behavior of each group of specimens mostly occurs around 442 s and the change trend is similar.The siltation particles are mostly in the interval of 5~8 mm,and the area of the sudden water channel shows a trend of decreasing and then increasing with the grade n value.And the area of water breakout is mostly located on the outside of the cylinder wall,and the local center is occasionally seen.Based on the particle characteristics of the filler specimens before and after infiltration,combined with the scanning electron microscope system,the fine structure characteristics such as pores,cracks and particle splicing are commonly found on the particle surface of the filler from the perspective of fine view.The paper analyzed the effects of inter-particle extrusion fragmentation and water softening erosion on the migrating particles of the filler.On the basis of generalizing the hydrodynamic model of karst column pillar under particle migration,the relationship between solid rock skeleton deformation,high pressure water seepage and migrating particles is discussed.The paper concludes that particle migration is the intrinsic nature of the pore bursting behavior of the karst column pillar,and the permeable water pressure P and external load F only play a facilitating role.The paper investigates the infiltration characteristics and sudden water behavior of karst column pillars accompanied by particle migration,and gives suggestions for the management of sudden water accidents in karst column pillars under particle migration.