Partition Prevention And Control Of Rock Burst At The Headgate Of Ultra-thick Coal Seam

Many serious rock burst accidents have happened at the headgate of ultra-thick coal seam in China in recent years.The mechanism of rock burst occurrence is necessary to be carefully studied in order to early warning and prevention of the rock burst harzard.This thesis investigates the partition prevention and control of rock burst at the headgate of ultra-thick coal seam,through on-site investigation,case study,theoretical analysis,numerical simulation,laboratory experiments and engineering practice.Firstly,the dynamic evolution characteristics of plastic region in surrounding rock were revealed.The headgate was divided into 3 zones,namely head zone,dynamic evolution zone and stable zone.The mechanical model of rock burst at each zone was built separately.A mechanical discrimination method for rock burst at different zones was put forward.Secondly,the mechanism of rock burst at different zones at the headgate of ultra-thick coal seam was revealed.At the head zone,the rock burst was induced due to the superposition of disturbing stress and tectonic stress exceeding the critical impact stress.At the evolution zone,the rock burst happened when the local stress concentration exceeded the critical impact stress in the process of stress adjustment in the surrounding rock.At the stable zone,the rock burst occurred due to the unstable creep of surrounding rock.Thirdly,a risk assessment method for the rock burst was proposed,based on three indexes,including the comprehensive index of elastic energy,the stress ratio index and the velocity index of impact energy.All the three indexes were quantified using fuzzy mathematics.Thus,a comprehensive evaluation index system of rock burst risks at the headgate of ultra-thick coal seam was set up.Fourthly,a multi-parameter monitoring and early warning method for rock burst at different zones at the headgate of extra thick coal seam was proposed.A comprehensive indicator system for monitoring and early warning of rock burst was established,with the indicators included vibration of surrounding rock,stress dynamics of surrounding rock,support force of bolt and cable,and drilling cuttings of coal.A hazard identification procedure was built accordingly.Then a multi-parameter partition monitoring and pre-warning system for rock burst at the headgate of ultra-thick coal seam was proposed.The multi-parameters include ground sound,borehole stress,bolt(cable)stress and drilling cuttings.Thus,a multi-parameter monitoring system for rock burst prevention in coal mines was developed.Last but not least,the partition prevention and control methods for rock burst at the headgate of ultra-thick coal seam was studied and implied.The comprehensive rock burst prevention measurements,such as retain coal pillar section for rockburst prevention,rockburst risk assessment,multi-parameter monitoring and early warning of rock burst,and pressure release.The results obtained from this thesis were successfully applied and verified in Yima Mine and Binchang Mine,which achieved a good economic and social benefit.