| Rockburst is a serious dynamic disaster encountered in coal mining.At present,tunnelling rockburst accounts for about 90%of coal mine impact accidents,and with the increase of mining depth,the damage degree of tunnelling rockburst becomes more and more serious,the stability of tunnelling surrounding rock is difficult to control when disturbed or superimposed impact dynamic load under high ground stress conditions,resulting in serious deformation of tunnelling support and damage.Aiming at the current support technology and equipment can not meet support requirements of impact dangerous tunnelling,a theoretical model of tunnelling anti-impact support is established from the point of view of the system of tunnelling support and surrounding rock.The interaction between support and surrounding rock under static and dynamic loads is studied.The anti-impact support theory considering the residual area of surrounding rock are proposed.According to the theory,tunnelling anti-impact hydraulic support with function of inducing energy absorption is developed,which provides a new reliable equipment and new technology for combined control of tunnelling support and surrounding rock.The main research contents and conclusions are as follows:(1)Theory of tunnelling anti-impact supportBased on the instability theory of disturbance response,the mechanical model of tunnelling support-surrounding rock(residual zone+elastic-plastic zone)system is established.The theory of anti-impact support considering residual zone is put forward,and the differential equation analytical solution of support-surrounding rock elasticplastic medium system is obtained.The influence factors of supporting effect of tunnelling surrounding rock support system under rockburst are analyzed.(2)Support mechanical parameters of supportThe dynamic model of surrounding rock-support in rock burst tunnelling is analyzed.The dynamic response of rock mass at the support end is discussed by dynamic response differential equation,and frequency characteristics of surrounding rock are analyzed.Based on research of tunnelling support parameters,the wave differential equation of discrete viscoelastic medium and analytical solution are obtained,and then free vibration attenuation curve of surrounding rock is analyzed.It is obtained that as time increases,the vibration displacement of surrounding rock will gradually decrease.Therefore,it is proposed that the support parameters of tunnelling anti-impact hydraulic support need reasonable support strength,supporting displacement,supporting stiffness,supporting frequency,supporting speed and supporting energy.(3)Anti-impact performance of anti-impact memberBy means of experiment and theoretical analysis,the pre-folded inducing anti-impact member of tunnelling anti-impact hydraulic support is innovatively designed,and six mechanical properties of anti-impact member,such as variable resistance,variable displacement,variable stiffness,variable frequency,variable speed and variable energy absorption,are obtained under static load and impact load.Based on anti-impact index,anti-impact performance of pre-folded induced anti-impact structure is studied.The results show that the pre-folded inductive anti-impact member with 156 degrees pre-folded,quadrilateral cross-section pre-folded inductive anti-impact member and 8 mm thick pre-folded inductive anti-impact member have excellent anti-impact performance.(4)Anti-impact performance of anti-impact hydraulic support and columnAn innovative design of anti-impact hydraulic support column with combination of anti-impact member and pressure-limiting relief valve is presented.Considering viscosity,elasticity,plasticity and inertia,the six mechanical properties of column are verified by the static-dynamic combined loading hydraulic impact test system.Based on mechanism and theory of tunnelling rockburst,the anti-impact performance of hydraulic support is analyzed.Six anti-impact function indexes are obtained,including variable resistance,variable displacement,variable stiffness,variable frequency,variable speed and variable energy absorption.(5)Support surrounding rock interactionAccording to the specific supporting parameters and surrounding rock properties of Gengcun Coal Mine,the interaction between surrounding rock and supporting system of tunnelling is studied,and the control effect of external load of surrounding rock-supporting system of tunnelling is obtained.The distribution of stress-strain and displacement field of hydraulic support with different supporting strength under static pressure is analyzed by numerical simulation.It is found that the maximum stress of U-shaped support with row spacing of 0.8m is greater than that of 3.2m,and the convergence displacement of roof and floor and the convergence position of two sides are also found.A hydraulic support support system with a shift ratio to 3.2m row spacing is designed.The effects of vertical impact and oblique impact on the stress,strain and deformation of the whole system are compared and analyzed when the tunnelling surrounding rock-support system is subjected to impact.It is found that when the support system is subjected to vertical impact,the maximum stress is less than oblique impact,and the distance from tunnelling is greater than oblique impact.When the surrounding rock support is impacted,the convergent deformation of the tunnelling is also the vertical impact deformation smaller than the oblique impact.(6)Field application of supportThrough on-site study of tunnelling anti-impact hydraulic support support,according to the monitoring results of 13230 working face and tunnelling support in Gengcun Coal Mine,it is found that the tunnelling anti-impact hydraulic support can withstand 107J energy impact,the support is intact,the whole support system is complete,and surrounding rock-support system mainly composed of anti-impact hydraulic support has good supporting effect.The paper has 110 figures,26 tables and 130 references... |
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