Spatio-temporal evolution characteristics of whole strata movement and deformation during coal seam mining under thick loose layers

ZHANG Pingsong; XU Shiang; WU Haibo; LI Shenglin; FU Xianjie; GUO Liquan; LU Haifeng

doi:10.13225/j.cnki.jccs.2024.1614

Abstract：Underground mining of coal resources induces movement and deformation in the overlying strata,significantly impacting the operation and maintenance of industrial square structures,mining area planning,and mine safety production.Revealing the differences in movement and deformation among bedrock,loose layers,and the surface,as well as their ver-tical deformation transfer characteristics,holds important practical significance for safe mining and subsidence control in mining areas.The Xinji mining area in the Huainan-Huaibei coalfield is selected as the research area.A distributed optic-al fiber sensing(DOFS)system was employed to construct a full-strata monitoring system.By combining three-dimen-sional physical similarity model tests with in-situ engineering measurements,strain characterization data were used to in-vestigate the vertical movement process,deformation distribution,and evolutionary characteristics of the entire strata dur-ing coal seam mining.The research reveals that the movement and deformation of bedrock,loose layers,and the surface exhibit non-integrated and discontinuous characteristics,with internal deformation in bedrock and loose layers displaying typical segmentation.The temporal deformation patterns vary significantly,the bedrock follows a"rapid-gradual-stable"subsidence pattern with fast deformation transfer;the loose layers display a"gradual-rapid-gradual-stable"response gov-erned by aquifer-aquitard interactions;while the surface subsidence shows a"slow-gradual-stable"subsidence pattern with non-uniform velocity.Further analysis indicates that the deformation transfer rate in the bedrock section is 4.8 times that of the loose layer section,while the deformation transfer time in the bedrock section is only 0.27 times that of the loose layer section.Field monitoring results show that in the total strata subsidence composition,the bedrock section contributes 78.4％,whereas the loose layer section contributes 21.6％.During coal seam extraction,the overlying strata are influenced by both layered sedimentary structures and dewatering effects.Tensile deformation within the strata is mainly concen-trated in the bed separation zones above the goaf and near the goaf boundaries,while compressive deformation is concen-trated in the abutment pressure-affected zones ahead of the coal wall.The findings enhance the understanding of the de-formation transfer mechanism in overburden strata under thick loose layers during coal mining.They provide data support and scientific guidance for transitioning from passive subsidence control to active subsidence and damage mitigation dur-ing mining operations.