Research On Dynamic Response Characteristics And Directional Fracture Control Methods Of Tunnel Blasting

In tunnel boring construction,drilling and blasting method is widely used for economic and convenient reasons,but the vibration effect generated by blasting often affects the stability of surrounding rock,which may lead to engineering accidents,so it is of great scientific significance to study the characteristics of dynamic response of tunnel surrounding rock under the action of blasting and control methods for safe construction.In this thesis,through numerical simulation and field monitoring methods,relevant research is carried out,and a slit tube structure with freely adjustable slit direction is developed independently based on the research of slit pack,which reduces the disturbance caused by blasting construction to the tunnel surrounding rock,obtains a better blasting contour line and improves the blasting effect.The main research contents of this thesis are:(1)Based on the combination of immune algorithm and neural network(IA-BP)intelligent algorithm,a dynamic parameter inversion method based on tunnel blasting vibration velocity is established based on the principle of orthogonal experiment.The constitutive parameters of rocks are quickly and accurately inverted,and the calculated experimental values are compared with the inversion values of IA-BP algorithm to verify the rationality of IA-BP algorithm.This solves the problem of difficult to accurately calibrate dynamic parameters in practical engineering and lays the foundation for subsequent numerical simulation analysis;(2)Conduct on-site blasting vibration monitoring experiments on engineering sites,use the TC-4850 vibration meter to measure a large amount of on-site vibration velocity data,fit the vibration velocity data of 10 groups under different blasting center distances and explosive quantities,and use the least squares method to obtain the attenuation formula of the surrounding rock vibration velocity.Analyze the dynamic response characteristics of the tunnel surrounding rock and the propagation law of blasting seismic waves,and substitute the on-site measured data into the trained neural network,Obtain the actual surrounding rock parameters of the on-site engineering and verify their accuracy through numerical simulation,in order to determine the basic parameters of the surrounding rock in the Johnson Holmquist constitutive model(JH-2 model);(3)Based on the actual engineering blasting scheme,the finite element software ANSYS/LS-DYNA is used to numerically model the tunnel as a whole and its palm faces,calculate the peak vibration velocity at each monitoring section under the blasting action,and analyze the stress wave propagation law and the microscopic fracture behavior of the rocks on the palm faces,based on which the blasting profile damage distribution is analyzed to provide a reference for the subsequent application of directional fracture technology.to provide reference for the subsequent application of directional fracture technology;(4)To establish a numerical model of the slit pack,analyze its fracture expansion process and stress changes,and explain the advantages of the slit pack in directional fracture control,and on this basis,propose a new slit tube structure developed independently,which can freely adjust the direction of the slit opening to cope with complex engineering conditions,and conduct numerical simulation analysis of this structure,and highlight the advantages of the structure compared with the blasting effect of ordinary slit pack.This structure is used for the purpose of blasting directional fracture and reducing damage to the surrounding rock.