Broken coal and rock(BCR)are an important component medium of the caving zone in the goaf(or gob),as well as the main filling material of fault fracture zone and collapse column.The compaction seepage characteristics ...Broken coal and rock(BCR)are an important component medium of the caving zone in the goaf(or gob),as well as the main filling material of fault fracture zone and collapse column.The compaction seepage characteristics of BCR directly affect the safe and efficient mining of coal mines.Thus,numerous laboratory studies have focused on the compaction seepage characteristics of BCR.This paper first outlines the engineering problems involved in the BCR during coal mining including the air leakage,the spontaneous combustion,the gas drainage,and the un-derground reservoirs in the goaf.Water inrush related to tectonics such as faults and collapse columns and surface subsidence related to coal gangue filling and mining also involve the compaction seepage characteristics of BCR.Based on the field problems of BCR,many attempts have been made to mimic field environments in laboratory tests.The experimental equipment(cavity size and shape,acoustic emission,CT,etc.)and experimental design for the BCR were firstly reviewed.The main objects of laboratory analysis can be divided into compression tests and seepage test.During the compaction test,the main research focuses on the bearing deformation characteristics(stress-strain curve),pore evolution characteristics,and re-crushing characteristics of BCR.The seepage test mainly uses gas or water as the main medium to study the evolution characteristics of permeability under different compaction stress conditions.In the laboratory tests,factors such as the type of coal and rock mass,particle size,particle shape,water pressure,temperature,and stress path are usually considered.The lateral compression test of BCR can be divided into three stages,including the self-adjustment stage,the broken stage,and the elastic stage or stable stage.At each stage,stress,deformation,porosity,energy,particle size and breakage rate all have their own characteristics.Seepage test regarding the water permeability experiment of BCR is actually belong to variable mass seepage.While the experimental test still focuses on the influence of stress on the pore structure of BCR in terms of gas permeability.Finally,future laboratory tests focus on the BCR related coal mining including scaling up,long term loading and water immersion,mining stress path matching were discussed.展开更多
Concerning the issue of mine pressure behaviors occurred in fully mechanized caving mining of thick coal seams beneath hard stratum in Datong Mining Area, combined with thin and thick plate theory, the paper utilizes ...Concerning the issue of mine pressure behaviors occurred in fully mechanized caving mining of thick coal seams beneath hard stratum in Datong Mining Area, combined with thin and thick plate theory, the paper utilizes theoretical analysis, similar experiments, numerical simulations and field tests to study the influence of remaining coal pillars in Jurassic system goaf on hard stratum fractures, as well as mine pressure behaviors under their coupling effects. The paper concludes the solution formula of initial fault displacement in hard stratum caused by remaining coal pillars. Experiments prove that coupling effects can enhance mine pressure behaviors on working faces. When inter-layer inferior key strata fractures, mine pressure phenomenon such as significant roof weighting steps and increasing resistance in support.When inter-layer superior key strata fractures, the scope of overlying strata extends to Jurassic system goaf, dual-system stopes cut through, and remaining coal pillars lose stability. As a result, the bottom inferior key strata also lose stability. It causes huge impacts on working face, and the second mine pressure behaviors. These phenomena provide evidence for research on other similar mine strata pressure behaviors occurred in dual-system mines with remaining coal pillars.展开更多
基金support for this work is provided by the National Key R&D Program of China(2023YFC3012101)the National Natural Science Foundation of China(52104155)+1 种基金the Natural Science Foundation of Beijing(8212032)the Fundamental Research Funds for the Central Universities(2023ZKPYNY03).
文摘Broken coal and rock(BCR)are an important component medium of the caving zone in the goaf(or gob),as well as the main filling material of fault fracture zone and collapse column.The compaction seepage characteristics of BCR directly affect the safe and efficient mining of coal mines.Thus,numerous laboratory studies have focused on the compaction seepage characteristics of BCR.This paper first outlines the engineering problems involved in the BCR during coal mining including the air leakage,the spontaneous combustion,the gas drainage,and the un-derground reservoirs in the goaf.Water inrush related to tectonics such as faults and collapse columns and surface subsidence related to coal gangue filling and mining also involve the compaction seepage characteristics of BCR.Based on the field problems of BCR,many attempts have been made to mimic field environments in laboratory tests.The experimental equipment(cavity size and shape,acoustic emission,CT,etc.)and experimental design for the BCR were firstly reviewed.The main objects of laboratory analysis can be divided into compression tests and seepage test.During the compaction test,the main research focuses on the bearing deformation characteristics(stress-strain curve),pore evolution characteristics,and re-crushing characteristics of BCR.The seepage test mainly uses gas or water as the main medium to study the evolution characteristics of permeability under different compaction stress conditions.In the laboratory tests,factors such as the type of coal and rock mass,particle size,particle shape,water pressure,temperature,and stress path are usually considered.The lateral compression test of BCR can be divided into three stages,including the self-adjustment stage,the broken stage,and the elastic stage or stable stage.At each stage,stress,deformation,porosity,energy,particle size and breakage rate all have their own characteristics.Seepage test regarding the water permeability experiment of BCR is actually belong to variable mass seepage.While the experimental test still focuses on the influence of stress on the pore structure of BCR in terms of gas permeability.Finally,future laboratory tests focus on the BCR related coal mining including scaling up,long term loading and water immersion,mining stress path matching were discussed.
基金provided by the National Natural Science Foundation of China(No.51104191)the National Natural Science Foundation of China(No.51374258)the Program for Changjiang Scholars and Innovative Research Team in University of China(No.IRT13043)
文摘Concerning the issue of mine pressure behaviors occurred in fully mechanized caving mining of thick coal seams beneath hard stratum in Datong Mining Area, combined with thin and thick plate theory, the paper utilizes theoretical analysis, similar experiments, numerical simulations and field tests to study the influence of remaining coal pillars in Jurassic system goaf on hard stratum fractures, as well as mine pressure behaviors under their coupling effects. The paper concludes the solution formula of initial fault displacement in hard stratum caused by remaining coal pillars. Experiments prove that coupling effects can enhance mine pressure behaviors on working faces. When inter-layer inferior key strata fractures, mine pressure phenomenon such as significant roof weighting steps and increasing resistance in support.When inter-layer superior key strata fractures, the scope of overlying strata extends to Jurassic system goaf, dual-system stopes cut through, and remaining coal pillars lose stability. As a result, the bottom inferior key strata also lose stability. It causes huge impacts on working face, and the second mine pressure behaviors. These phenomena provide evidence for research on other similar mine strata pressure behaviors occurred in dual-system mines with remaining coal pillars.
