Research On Multi-index Linkage Prevention And Control Technology For Blasting Vibration Disasters In Large-section Tunnel

With the continuous advancement of China’s social economy,the Belt and Road Initiative,and new infrastructure construction,the number of large-section construction projects is increasing.Drilling and blasting method is still the most commonly used construction in hard rock excavation such as highway,railway,and underground space in China,but vibration disaster prevention and control in drilling and blasting method construction is always a technical problem that restricts the safety and high efficiency of large section.Vibration leads to cracking or even collapse of newly poured concrete falling off supporting structures,which buries a major potential safety hazard in later operation and maintenance.However,the existing vibration reduction theory only pays attention to the control of amplitude strength and main frequency,but does not control the vibration time and the maximum charge of single-stage initiation.The prevention and control effect of vibration disaster is not good.Therefore,based on the high-speed Bayue Mountain from Tongliang in Chongqing to Anyue Expressway in Sichuan,this paper adopts the combination of theoretical indoor experiment,numerical simulation,and a field experiment to research multi-index linkage prevention and control technology of large-section vibration disaster.The main research work is as follows:(1)Based on the propagation law of vibration wave,the formation of vibration wave is discussed and the dynamic response characteristics of supporting structure under load are classified;Combined with the propagation law of elastic waves,the mechanism of superposition enhancement and interference cancellation of vibration waves is discussed,and the calculation of delayed initiation interval of large cross-section group holes is carried out.(2)The transversely isotropic damage constitutive model of slate under triaxial compression and dynamic impact load is established.Based on the TAJW-2000 microcomputer controlled electro-hydraulic servo triaxial test system and split Hopkinson pressure bar system,the static and dynamic experiments of slate specimens are carried out,which provide basic data for determining numerical simulation parameters,preserving rock mass damage and designing field parameters.(3)Based on the vibration reduction mechanism of millisecond delay initiation,the multi-index prevention and control technology of large cross-section multi-stage wedge cut hole reduction layout and vibration safety criterion are put forward,which comprehensively considers the influence of four factors: maximum charge,vibration velocity and time of single-stage initiation,and the optimization parameters of hole layout number realize the safe and efficient crossing of the large cross-section.(4)Using ANSYS/LS-DYNA finite element software,the numerical model of the large cross-section upper step is established,the effect and damage characteristics of the excavation cross-section are discussed,and the dynamic response law of primary support structure and secondary lining structure under load is discussed;The site experiment of the multi-stage wedge cut on the large cross-section is carried out,and the feasibility of the scheme is comprehensively evaluated by combining the excavation effect and vibration monitoring results,and the safe distance between the supporting structure and the excavation section is determined.