Study On Dynamic Response Of Deep Chamber Surrounding Rock Under Blasting Vibration

Blasting vibrations easily induce rockburst,landslide,roof collapse and other geological hazards during blasting in deep chamber,affecting project progress,increasing costs and sometimes causing casualties and property losses.Therefore,it is very important to analyze the dynamic propagation of blasting vibration and the dynamic response of the surrounding rock under the action of blasting vibration in the deep chamber drilling and blasting.It is very important for the analysis of chamber stability.In this paper,blasting excavation in deep underground laboratory in Jinping is taken as the engineering background,and the dynamic finite element program ANSYS/LS-DYNA is used to carry out numerical simulation to investigate the reason of the rock burst occurred in 7#and 8#laboratories.Completed the following work:(1)Firstly,the 3D modeling of 7#and 8#laboratory and 4#traffic tunnel in Jinping underground laboratory was carried out.The middle slot trenching and blasting vibration in 7#laboratory were simulated.The curve of the vibration velocity of the particle at the measuring point with time is obtained and compared with the measured vibration velocity curve.Both the waveform and the velocity peak agree well with each other.It is shown that the model built in this paper can reproduce the propagation of blasting vibration in excavation of 7#laboratory well,which can simulate and analyze the impact of blasting vibration in practical engineering so as to obtain the propagation law of stress wave generated by blasting in the rock burst area of 7#and 8#laboratories.(2)Numerical simulation of chamber blasting excavation under the presence or absence of initial stress is conducted,and the effect of initial stress on the response of rock burst zone in surrounding rock under blasting vibration is discussed.The results show that the initial geostress can increase the vibration response of the rock burst zone significantly.(3)Whether there are traffic holes in the chamber or not,whether the inner wall of the chamber is symmetrical or not,whether the middle trough in 8#laboratory is fully excavated and four different internal structure models are established under the three conditions considering the influence of chamber structure on the dynamic.response of the surrounding rock.The results show that the cavern structure has no significant influence on the particle velocity in the rock burst area.The asymmetry of the chamber structure causes the stress redistribution,but the stress state of rock mass in the rock burst area is basically unaffected.(4)The numerical simulation of blasting and excavation for the chamber model with different joint surfaces in surrounding rock is carried out to investigate the influence of the number of joint planes and joint planes on the propagation of explosive stress waves.The dynamic response of surrounding rock under blasting vibration is analyzed.The results show that the existence of joint surface will increase the disturbance of surrounding rock by blasting vibration,and the more the joint number is,the more obvious the stress concentration phenomenon is,which increases the possibility of rock burst.The results of quantitative analysis show that the deep jointed environment and the three joints contained in the surrounding rock of the rock burst zone are the main causes of the secondary rock burst induced by blasting vibration.