Three-dimensional pore structure and seepage evolution law of soil-rock mixture filled in fault fracture zones
Fault fracture zones are often encountered in the construction of mine tunnels;the filling medium in fault fracture zones is complex in composition,has poor continuity,and is easily disturbed;water and mud sudden accidents are very likely to occur when the tunnels pass through them.This study focuses on the seepage disaster problem of fault fracture zone filling media.Based on the independently designed fault fracture zone erosion seepage experimental device,similar material permeability experiments on factors such as aggregate Talbot grading,porosity ratio,and the gravel position were carried out,and the computed tomography(CT)reconstruction technology was used to explore the spatial distribution state and structural characteristics of the mesoscopic pores inside the fault filling soil-rock mixture.The research results show that the primary and secondary factors that affect the permeability coefficient of soil-rock mixture filling fault fracture zone are porosity>gravel position>aggregate Talbot gradation>Hurst index>binder content;The larger the aggregate Talbot gradation,that is,the greater the stone content in the soil-rock mixture,the greater the permeability coefficient of the soil-rock mixture filled in the fault fracture zone.The smaller the porosity ratio when the soil-rock mixture is sampled,the more cement content in the binder,and the smaller the permeability coefficient of the soil-rock mixture.There is an excellent exponential relationship between the stone content of the soil-rock mixture and the permeability coefficient;the porosity ratio is in direct proportion to the permeability coefficient.By conducting triaxial seepage experiments and using CT scanning of the pore structure of the filling soil-rock mixture,it was found that during the seepage process,the migration of fine particles blocked and divided some larger pores,and differentiated them into smaller pores.In the sample with a rock content of 70%,the erosion effect of the fluid on fine particles was more obvious.The results of this study provide a theoretical basis for disaster prevention and control in fault fracture zones.
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