Control And Analysis Of Roof Stability Of Coal Roadway Roof In Cucurbit Mine

The mining roadway of cucurbit mine is coal lane,and there is a hidden danger outside the anchorage area of the roof.It is of great significance to carry out the research on the roof support optimization to improve the safety of the roof and the speed of the driving.In this paper,the static and dynamic analysis of the roof stability mechanism is carried out with theoretical modeling and numerical calculation.The support scheme of high pre tight long anchorage is put forward,and the characteristics of the roadway pressure under the new support technology are mastered through the monitoring of the mine pressure tracking in the whole process of excavation and recovery.The main conclusions are as follows:(1)Combined with the geological conditions of cucurbit,the main features of the existing supporting equipment,the time used in each supporting process,and the direction of the roof support optimization of the cucurbits coal mine roadway are low density and single support form.(2)There is a self-stabile balance arch in the roof of the roadway,and the rock in the arch is the object of bolting support.The height of the self-stabile balance arch increases with the increase of roadway burial depth.Based on the self-stable equilibrium arch height,the analysis of the minimum anchorage thickness is carried out by the combined beam theory.When the deflection of the upper and lower two layers in the balanced arch is not consistent,the interface is a possible separation position.The balance arch height of the coal roadway in the cucurbit mine is 7.0m,and the anchorage layer thickness should exceed 3.5m.(3)The model of roadway layered roof is established,and the numerical simulation study of FLAC3 D software shows that:(1)the disturbance distance of the stress on the rear roof gradually increases with the speed of driving,the height of stress relief area decreases obviously,the change rate of stress in the unit area decreases,and the range of the area of the head-on stress concentration area has a shrinking trend,which is beneficial to the improvement of the stability in the head-on operation area.Of.But the driving speed can not affect the final stress state of the balance section.(2)when the heading distance is 5m,the roof of the empty top area reaches the self stabilizing limit and the lateral stress is minimum.(3)The timing of the support does not restrict the driving speed.Timely support and high stiffness support should be preferred,so as to fully utilize and improve the self bearing capacity of surrounding rock and prevent weakening of surrounding rock strength.(4)The influence of preload and length of anchor cable on supporting effect is explored by using FLAC3 D numerical simulation software,which provides basis for parameter design of roof support.According to the requirements of anchorage thickness and driving speed,a high pretension long anchorage support scheme using single length anchor,high prestress and thick anchorage layer is proposed.This technique has the advantages of large anchorage thickness,high strength,high pre tightening force,strong active support ability,single low density support and short support time.According to the engineering geological conditions and excavation support equipment of the coal roadway roof in the cucurbit mine,the supporting parameters suitable for the roof conditions of the coal roadway in the cucurbit mine are designed.(5)The roof abscission layer and fissure of the experimental roadway are all within 1.1m,and the separation layer and fracture are all developed in the shallow part of anchorage zone.The overall strength of roof anchorage layer is high,and the development of shallow separation layer leads to the small subsidence of roof and the rapid increase of bolt support resistance during tunneling.Shallow separation causes polarization of roof shallow integrity and discrete roof subsidence.The roof of the mined out area presents the collapse shape of bending convergence or anchoring blind area instability,and there is no difficulty in maintaining the roof due to the goaf.The indexes of the roadway in the whole process of mining and mining are good,and the rationality of the support scheme is verified successfully,which lays a good foundation for the popularization and application of the similar conditions and the further research and development of other conditions.