Research On Mechanism Of Coal Pillar Instability And Rockburst In Roadway Backfilling Mining Technology

The roadway backfilling mining technology is an effective approach to mining the corner residual coal resource and the quality coal resource under buildings,railways,rivers,which is an important part of coal green mining system.In roadway backfilling mining technology,the rockburst accident caused by dynamic instability of coal pillar poses a serious threat to safety mining.This paper has a systematic study on the instability mechanism of coal pillar and rockburst accident in roadway backfilling mining technology by the method of experimental test,theoretical analysis,numerical simulation and field measurement.The innovative results are as follows:(1)By setting several levels of displacement loading rates,the burst tendency tests of coal rock in different loading rates is carried out with DDL500 electronic universal testing machine and MTS815.02 electro-hydraulic servo testing system.Thus,the change rule of coal rock burst tendency in different loading rates is obtained.(2)The mechanism of layer-crack plate of coal pillar is obtained with the fracture mechanics theory.Based on the energy mechanism of coal pillar instability,the layer-crack plate of coal pillar and the roadway roof are treated as energy dissipation body and energy release body,respectively;then the double-block mechanical model is established with energy dissipation body and energy release body.By analyzing the energy balance relationship of double-block,the dynamic instability mechanism of coal pillar can be obtained,based on the fold catastrophe model.(3)By analyzing the basic characteristics of overlying strata deformation in roadway backfilling mining technology,the mechanical model of bearing system in roadway backfilling mining is established.Based on the energy variation principle,the elastic solution expression of coal pillar deformation is deduced in roadway backfilling mining technology.Based on the elastic-viscoelastic correspondence principle,combining with the burgers rheological constitutive model,the viscoelastic solution expression of coal pillar deformation is deduced in roadway backfilling mining technology.By analyzing the compressive mechanical property of backfilling body,the time formula required for coal pillar and backfilling body to play the joint bearing function in roadway backfilling mining technology is obtained.(4)In order to evaluate the rockburst danger of coal pillar,the energy density criterion is programmed with FISH language in FLAC3 D numerical analysis sofeware.The numerical simulation model is established with four kinds of scheme,namely sequential mining scheme,one roadway interval mining scheme,two roadways interval mining scheme and three roadways interval mining scheme.The influence rule of driving order of backfilling roadway on coal pillar stability is obtained,by analyzing the change rule of vertical stress and energy density factor of coal pillar in different driving orders in roadway backfilling mining technology.(5)According to the mining and geological situation of field trial area,the burst risk of working face is obtained,based on comprehensive index method.The numerical calculating model is established in FLAC3 D numerical analysis sofeware,and the energy density criterion is introduced to evaluate the rockburst danger of coal pillar of backfilling roadway.The main cause of rockburst accident in roadway backfilling mining technology is obtained,and the prevention measure is put forward.The results can be treated as an important basis for the prevention and treatment of coal pillar instability and rockburst in roadway backfilling mining technology.